Defence Infrastructure Organisation RAF Brize Norton

Transcription

1 Defence Infrastructure Organisation RAF Brize Norton C130 EGR Noise Assessment Technical Report AMEC Environment & Infrastructure UK Limited

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4 Document Revisions No. Details Date 1 Draft Report 12343i1 August Final Report 12352i1 August 2012

5 i Contents Glossary of Terms 1 1. Introduction Background Aim Scope of Works 6 Aircraft EGR Noise Measurements 6 Community Noise Monitoring 6 Noise Modelling 6 Noise Monitoring within RAF Brize Norton Structure of this Report 7 2. Technical Basics Introduction Noise Terminology Aircraft Noise Perception, Annoyance and Health Tonal Noise Meteorological Effects Measurements and Modelling Technical Guidance 14 General Guidance 14 MoD Specific Guidance Methodology Introduction Aircraft EGR Noise Measurements 19 Introduction 19 C130 EGR Noise Measurements 20 VC10 EGR Noise Measurements 21 A400M EGR Noise Measurements Community Noise Monitoring Noise Modelling Noise Monitoring within RAF Brize Norton 24

6 ii 4. Investigations Understanding the Issue Aircraft EGR Noise Emissions Operational Mitigation Physical Mitigation Policy Indicators Results Understanding the Issue 31 Noise Exposure during C130 EGR 31 Tonal Characteristics of C130 EGR 34 How does the C130 EGR noise compare to that of the VC10? 36 How does C130 EGR noise compare to the noise produced by other activities at the base? 37 Overall, how do noise levels in communities compare to technical guidance and policy and what were the key findings? 38 Summary of Effects upon Communities Aircraft EGR Noise Emissions Operational Mitigation 43 Changing the Location of the C130 EGR 44 Reorientation of the C130 aircraft for EGR on Bays Use of GPUs instead of APUs 47 Towing of Aircraft to and from the Runway Physical Mitigation 48 EGR Pen at Bay EGR Pen at D30 49 Summary of Results Policy Indicators Conclusions 51 Table 2.1 Typical Noise Levels 10 Table 2.2 Response to Change in Noise Level 10 Table 2.3 PPG24 Noise Exposure Categories for Aircraft Noise 16 Table 5.1 Average Measured Community Noise Levels During C130 Bay 73 South-Facing Engine Ground Run 33 Table 5.2 Average Measured Community Noise Levels During Ground Runs 36 Table 5.3 Average Measured and Modelled Noise Levels in Communities During High power Engine Runs 45 Table 5.4 Average Measured and Modelled Noise Levels in Communities During High Power Engine Runs - North vs. South Facing 46

7 iii Appendix A Table A.1 Weather Conditions 1 st May 2012 Table A.2 Weather Conditions 2 nd May 2012 Table A.3 Weather Conditions 3rd May 2012 Appendix B Table B.1 Table B.2 Table B.3 Table B.4 Table B.5 Table B.6 Table B.7 Appendix C Table C.1 Table C.2 Table C.3 Appendix D Table D.1 Table D.2 Table D.3 Table D.4 Table D.5 Table D.6 Appendix E Table E.1 Table E.2 Table E.3 Table E.4 Table E.5 Summary of 4-engine / High power C130 Engine Running Noise Levels Summary of Engine Running of Other Aircraft Average Measured Community Noise Levels During Ground Runs Summary of Measured Noise Levels at Community Locations during A400M EGR Summary of Measured Community Noise Levels from C130 North-Facing at Bay 72 and C130 South-Facing at Bay 73 Overall Community Noise Levels at Monitoring Locations Average Measured and Modelled Noise Levels in Communities During High Power Engine Runs Overview of C130 Engine Running Measurements, L Aeq at 50m Overview of VC10 Engine Running Measurements, LAeq at 50m Overview of A400 Engine Running Measurements, L Aeq at 50m Measured and Modelled Noise Levels against Wind Characteristics with C130 at High power Modelled Scenarios Noise Level Change and Perception Alternative Bay and Taxiway Locations: Low Power Ground Idle Engine Setting Alternative Bay and Taxiway Locations: Normal Ground Idle Engine Setting Alternative Bay and Taxiway Locations: High power Engine Setting Mess Accommodation Broadband Noise Levels during C130 EGR BS8233 Design Criteria Mess Accommodation Measured Ambient Noise Levels Wing Commanders Accommodation Measured Noise Levels Wing Commanders Accommodation Measured Noise Levels Appendix F Table F.1 C130 APU Measurements (L Zeq ) Table F.2 C130 Low Power Ground Idle (LPGI) Measurements (L Zeq ) Table F.3 C130 Normal Ground Idle (NGI) Measurements (L Zeq ) Table F.4 C130 High Power (Inboards to High power, Outboards to Normal Ground Idle) Measurements (L Zeq ) Table F.5 VC10 APU Measurements (L Zeq ) Table F.6 VC10 Ground Idle Measurements (L Zeq ) Table F.7 VC10 80% High power Measurements (L Zeq ) Table F.8 A400 APU Measurements (L Zeq ) Table F.9 A400 Low Power Ground Idle Measurements (L Zeq ) Table F.10 A400 High Power Measurements (L Zeq ) Table F.11 A400 Max Reverse Measurements (L Zeq ) Table F.12 Community Noise Levels during EGR Table F.13 Community Noise Levels During A400M EGR Table F.14 Community Noise Levels during C130 EGR (North Facing Stand 72) Figure 3.1 Example of Aircraft EGR Noise Emission Measurement Positions 20 Figure 3.2 Noise Monitoring Locations Figure 5.1 Time-Level Trace of C130 EGR on Stand 73 (South Facing) 32 Figure 5.2 Measured Spectral Noise Level during C130 Engine Running at Black Bourton 35 Figure 5.3 Measured Spectral Noise Level during C130 Engine Running at Alvescot 35 Figure 5.4 Measured Spectral Noise Levels During VC10 80% High power Engine Runs 37 Figure 5.5 Example of events include a C130 EGR during a day 41 Figure 5.6 Example of events during a night-time period 41 Figure 5.7 High power Engine Run Directivity Patterns A400M, VC10 and C130 42

8 iv Appendix A Figure A.1 Weather Conditions during Monitoring Figure A.2 Weather Conditions 27 th February 2012 Figure A.3 Weather Conditions 28 th February 2012 Figure A.4 Weather Conditions 4th May 2012 Appendix B Figure B.1 Example Time-Level Trace of a C130 Engine Run on Bay 73 Figure B.2 Example of Several Events Figure B.3 Example Time-Level Trace of a VC10 Engine Run on Taxiway C Figure B.4 C130 Engine Run on Bay 69 Figure B.5 C130 Engine Run on Bay 67 Figure B.6 Measured Spectral Noise Level during C130 EGR at Alvescot Figure B.7 Measured Spectral Noise Level during C130 EGR at Brize Norton Figure B.8 Measured Spectral Noise Level during C130 EGR at Black Bourton Figure B.9 Measured Spectral Noise Level during C130 EGR at Bampton Figure B.10 Time-Level Trace of VC10 EGR on Bay 72 South Facing Figure B.11 Time-Level Trace of C130 EGR on Bay 72 South Facing Figure B.12 Measured Spectral Noise Levels During VC10 80% High power Engine Runs Figure B.13 Measured Spectral Noise Levels During A400M APU Run Figure B.14 Measured Spectral Noise Levels During A400M Low-Speed Ground Idle Engine Run Figure B.15 Measured Spectral Noise Levels During A400M High Power Engine Run Figure B.16 Measured Spectral Noise Levels During A400 Reverse Engine Run Figure B.17 Measured Spectral Noise Levels During C130 High Power Engine Run (North Facing ST72) Figure B.18 Measured Spectral Noise Levels During C130 Maximum Reverse Engine Run (North Facing ST72) Figure B.19 Night-time Time-Level Trace for 13 October 2011 Figure B.20 Night-time Time-Level Trace for 16 October 2011 Appendix C Figure C.1 C130 Measurement Locations Figure C.2 C130 Measured Directivity Patterns Figure C.3 Frequency Content of C130 Whilst Running APU Figure C.4 Frequency Content of C130 during Low Power Ground Idle Figure C.5 Frequency Content of C130 during Normal Ground Idle Figure C.6 Frequency Content of C130 during High power Engine Run Figure C.7 Narrowband Analysis of C130 Noise Emissions Figure C.8 VC10 Measurement Locations Figure C.9 VC10 Measured Directivity Pattern Figure C.10 Frequency Content of VC10 Whilst Running APU Figure C.11 Frequency Content of VC10 During Ground Idle Engine Run Figure C.12 Frequency Content of VC10 During 80% High power Engine Run Figure C.13 APU Directivity Patterns C130 and VC10 Figure C.14 High power Directivity Patterns C130 and VC10 Figure C.15 A400M Measurement Locations Figure C.16 A400M Measured Directivity Pattern Figure C.17 Frequency Content of A400 Whilst Running APU Figure C.18 Frequency Content of A400 During Low Speed Ground Idle Engine Run Figure C.19 Frequency Content of A400 During High power Engine Run Figure C.20 Frequency Content of A400 During Max Reverse Engine Run Figure C.21 APU Directivity Patterns A400M, VC10 and C130 Figure C.22 High Power Engine Run Directivity Patterns A400M, VC10 and C130 Appendix D Plate D.1 C130 Measured Directivity Patterns Figure D.1 Full Power C130 Engine Running at Stand 72 Figure D.2 Modelled EGR Locations Figure D.3 Full Power C130 Engine Running at Stand 57 Figure D.4 Full Power C130 Engine Running Noise Difference Map Stand 57 vs. Stand 72 Figure D.5 Full Power C130 Engine Running Noise Difference Map Stand 78 vs. Stand 72 Figure D.6 Full Power C130 Engine Running on Taxiway F Figure D.7 Full Power C130 Engine Running at Stand 40 Figure D.8 Full Power C130 Engine Running at Stand 53 Figure D.9 Full Power C130 Engine Running Noise Difference Map Stand 40 vs. Stand 72 Figure D.10 Full Power C130 Engine Running Noise Difference Map Stand 53 vs. Stand 72 Figure D.11 C130 Noise Difference Map Stand 72 GPU vs. Stand 72 APU

9 v Figure D.12 Full Power C130 Engine Running Noise Difference Map Stand 72 North vs. Stand 72 South (Baseline) Figure D.13 C130 Noise Differnce Map Stand 30 with EGR Pen vs Stand 30 With EGR Pen Figure D.14 Full Power C130 Engine Running Noise in 4-sided 14m High EGR Pen at Stand 30 Figure D.15 Full Power C130 Engine Running Noise in 4-sided 14m High EGR Pen at Stand 40 Figure D.16 C130 Noise Difference Map Stand 30 with EGR Pen vs Stand 72 Figure D.17 C130 Noise Difference Map Stand 40 with EGR Pen vs Stand 72 (South Facing) Figure D.18 Full Power C130 Engine Running Noise at Stand 72 (South Facing) Figure D.19 Full Power C130 Engine Running Noise at Stand 72 (North Facing) Figure D.20 Full Power C130 Engine Running Noise at Stand 40 Figure D.21 Full Power C130 Engine Running Noise at Stand 40 with EGR Pen Figure D.22 Full Power C130 Engine Running Noise at Stand 30 with EGR Pen Appendix E Figure E.1 Mess Accommodation Noise Levels C130 APU 6 Figure E.2 Mess Accommodation Noise Levels C130 LPGI EGR 7 Figure E.3 Mess Accommodation Noise Levels C130 NGI EGR 8 Figure E.4 Mess Accommodation Noise Levels C130 High Power EGR 9 Figure E.5 Mess Accommodation Noise Levels C130 Maximum Reverse EGR 10 Appendix A Meteorological Conditions during Surveys Appendix B Community Monitoring Appendix C Aircraft EGR Noise Emissions Appendix D Noise Modelling Investigations Appendix E Monitoring within RAF Brize Norton Appendix F Technical Data Tables

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11 1 Glossary of Terms Term Description A400 Acoustic Noise Barrier Air Traffic Control (ATC) Aircraft Holding Aircraft Taxiing Aircraft Towing AMEC Auxiliary Power Unit (APU) Background Noise Level Bays Broadband Noise Levels C130 Daytime Decibels (db) Detuning Facility DIO Downwind Conditions Engine Ground Running (EGR) Airbus A400M Aircraft Four engine turboprop military transport aircraft. Structure designed and built specifically to protect sensitive land uses or reduce noise exposure by reflecting, absorbing and dissipating the passage of noise. ATC is a service provided by ground-based controllers who direct aircraft on the ground and through controlled airspace to primarily avoid aircraft collisions. Aircraft holding is a manoeuvre designed to delay an aircraft already in flight that has arrived at its destination but cannot land yet because of traffic congestion, poor weather or runway unavailability. An aircraft holding pattern is controlled by ATC. Aircraft travelling to and from active runway thresholds under their own power, usually at a setting consummate with the Low Power Ground Idle (LPGI) setting. A method of transporting aircraft around the base. Consists of aircraft being attached to a tow vehicle and being towed to or from an active runway threshold. During a tow the aircraft APU is kept running but the engines are switched off. AMEC Environment and Infrastructure UK Limited. Lead consultant in the preparation of the noise investigations presented in this report The APU is a device within the aircraft that provides energy for functions other than propulsion. These functions may include power to start the main engines, or air conditioning within the cabin whilst passengers are boarding. Usually expressed in the LA90 noise parameter. Is described as the noise existing noise environment in the absence of the noise source under investigation. Expressed in decibels (db). A designated area of apron prepared for parked aircraft, usually to allow passengers or freight to be loaded or unloaded safely. Presented as a single level rather than a number of levels across the constituent frequencies. Usually used to describe the overall noise level. Expressed in decibels (db). C-130 Hercules Aircraft Four propeller engine aircraft, part of the RAF s Air Transport fleet and used primarily to carry troops, passengers or freight. Generally agreed to be between 0700hrs 2300hrs local time The main units used in acoustics. A decibel is a measure of magnitude of sound, changes in sound level and a measured of sound insulation. Decibels are a logarithmic unit. A purpose built structure used for aircraft engine ground running. At RAF Brize Norton there is a VC10 detuning facility. Defence Infrastructure Organisation Conditions experienced when the prevalent wind direction is in the direction of the receptor under investigation Engine Ground Running involves engine checks that involve temporarily advancing the throttles to ensure that engines are capable of producing a number of thrust settings such as those required for taxiing and take-off.

12 2 Term Description Engine Ground Running Pen Extraneous Noise Events Frequency Narrow Band Analysis Ground Noise Ground Power Unit (GPU) Ground Service Equipment (GSE) Inaudible Meteorological Conditions MRO (Maintenance Repair Overhaul) Night-time Noise Directivity Octave Frequency Bands Physical Mitigation Runway Threshold Sound Frequency Sound Level Meter (SLM) Sound Power Level (db) Sound Pressure Level (db) Specific Noise Level Time Level Trace Structures specifically designed to reduce noise levels within surrounding areas from aircraft engine ground running activities. They are usually open at one end to allow aircraft access and typically include a rear blast deflector and acoustically treated sidewalls. Noise events influencing the background noise environment that are not related the specific noise source under investigation. These may include road traffic movements passing the SLM whilst measuring noise from the aircraft. Analysis of noise across its constituent frequencies. Noise from ground-based aircraft activities, such as aircraft taxiing or engine running A power source that can be used by aircraft at stands. Generally have lower noise emissions and can be used as an alternative to aircraft APU. Equipment found at an airport used to service aircraft between flights. The equipment is used for ground power operations, aircraft mobility, and loading operations (passengers / freight). A noise source is either outside the human audibility range or is masked by existing background noise levels The prevailing environmental conditions due to weather. These include wind direction, temperature and humidity. All maintenance operations required in retaining or restoring an aircraft to a state in which it can perform its required function. Generally agreed to be between 2300hrs 0700hrs local time Directivity is a measure of the directional characteristic of a sound source i.e. the measure of the dominance of a noise in one direction over others. A set of internationally agreed frequency bands that are referred to by their centre frequencies. Presenting a noise in its octave bands rather than as a broadband level can give a better understanding of whether there is an tonal aspects to the noise present. Physical structures used to impede, dissipate or reduce the propagation of noise between a source and receiver. An example of physical mitigation is an acoustic barrier. Markings that illustrate the start and end runway. Displaced thresholds marked further along the runway may be used for taxiing, and landing rollout, but not for touch-down. Frequency is a property of sound that most determines pitch and is measured in hertz (Hz). The audible range for the human ear is generally 20Hz to 20kHz. Sounds outside this range are usually inaudible. Instrument for monitoring and recording noise levels The sound power level is a property of a noise source and is independent of the acoustic environment that it is in. It is usually used to describe the amount of noise produced at source. The sound pressure level is a property of a noise source that is dependant on the acoustic environment that it is in. For example a different sound pressure level can be attributed to the same source at different distances from it. The amount of noise at a particular location resulting from the noise source under investigation. Expressed in decibels (db). A figure showing changes in a set parameter over a specified period of time. Time Level Traces have been used to show how noise levels changed at monitoring locations over time.

13 3 Term Description Tonal Noise / Tonality Transient Noise VC10 A noise level which is dominant at a particular frequency or set of frequencies. Noise that consists of relatively short periods of high levels. A descriptor commonly used for aircraft engine ground running activities. Vickers VC10 Aircraft. Jet engine air transport and air-to-air refueling aircraft.

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15 5 1. Introduction 1.1 Background AMEC Environment and Infrastructure UK Limited (AMEC) was commissioned by Defence Infrastructure Organisation (DIO) to undertake a noise assessment of EGR (EGR) activities at RAF Brize Norton in Oxfordshire The assessment was commissioned following noise complaints received by the base from the local community after the arrival of the C130 fleet from RAF Lyneham in the Summer of The RAF and DIO undertook a series of consultation exercises with community groups in order to understand the cause of the noise complaints. This led to the understanding that the majority of the noise complaints originated from C130 ground activities rather than from over-flights. It was understood that an analysis of these complaints showed that they aligned with times when the C130 EGR occurred Historically the base has been associated with the Vickers VC10 jet aircraft, which are due to be withdrawn from service in The base also accommodates other large aircraft such as the C-17 Globemaster and the Lockheed L-1011 TriStar. The VC10 aircraft were originally concentrated on bays to the south of the runway however were then relocated in anticipation of the arrival of the C130s. These VC10 aircraft are now located on bays to the north of the runway with the C130s occupying Bays which are approximately 1km north and north-east of the villages of Black Bourton and Alvescot respectively. Based on information provided by RAF Brize Norton, it is from these villages where the majority of complaints have originated, most notably Black Bourton EGR has historically occurred at the base. Indeed the base has an engine detuning facility for the VC10 aircraft and it is understood that engine testing of VC10 aircraft has occurred to the south of the runway in similar areas to the location of the C130 fleet RAF Brize Norton wish to understand the levels and nature of the noise being generated by C130 EGR activities in the local community and how this may, or may not, differ from noise which has historically been produced by the EGR of other aircraft types notably the VC10. The base also wishes to understand whether any operation procedures or physical measures can be used to minimise noise impacts of EGR activities and whether future changes in the base s aircraft fleet, notably the introduction of the Airbus A400M, will result in similar effects This report documents the technical investigations undertaken by AMEC into EGR noise at RAF Brize Norton between September 2011 and May The report outlines the scope and methodology of these investigations and their findings.

16 6 1.2 Aim The aim of the investigations presented in this report is to provide the RAF and DIO with an understanding of the existing levels and nature of noise being generated by EGR activities upon local communities and sensitive areas of the base. The investigations also aim provide the RAF and DIO with sufficient evidence regarding noise impacts to evaluate options under consideration for mitigating EGR noise. 1.3 Scope of Works The scope of the investigations covered by this report has evolved from AMEC s initial involvement in August The original scope of AMEC s involvement was to provide an understanding of the noise exposure from C130 EGR activities upon local communities. These investigations have evolved to gather evidence on the effectiveness of potential operational and physical mitigation measures, and to seek to understand how developments at the base such as new infrastructure and changes in stationed aircraft may affect the community s exposure to EGR noise in the future The scope of the investigations presented in this report principally cover the following: Aircraft EGR Noise Measurements Measurements of EGR activities from C130, VC10 and A400M aircraft at positions around the aircraft in order to provide comparative noise emission data including directivity patterns and to facilitate the modelling and investigation of mitigation options and noise exposure. Community Noise Monitoring Noise measurements at locations in: Brize Norton; Alvescot; Black Bourton; and Bampton Community noise monitoring has been undertaken and has been used to build up a picture of the general noise environment within these communities and to identify and correlate EGR activities from the base with corresponding noise exposure within them. The community monitoring has been used to understand the impact of various operational changes and mitigation options upon noise exposure in the surrounding communities. Noise Modelling Noise modelling has used aircraft EGR measurements to understand the wider impacts of EGR running activities beyond the locations considered by the community noise monitoring. It has been used to investigate potential changes in noise exposure as a result of a number of operational and physical mitigation measures including:

17 7 Re-orientating or relocating aircraft for EGR EGR Pens; Use of GPUs instead of aircraft APUs; and Towing of aircraft The noise modelling work has included the consideration of average daytime noise levels in order to understand how noise from C130 EGR activities accord with the MoD s current policy on aircraft noise. Noise Monitoring within RAF Brize Norton Noise monitoring has been undertaken within RAF Brize Norton. This monitoring has been undertaken to understand levels of noise exposure at accommodation within the base and how this may change as a result of operational changes to EGR. The measurements have also been used to understand the potential impact of noise levels within crew accommodation. 1.4 Structure of this Report The main body of this report presents the key findings of the investigations undertaken by AMEC at the request of the base and DIO The detailed findings of the investigations undertaken by AMEC, as supplied to DIO and the base are presented in Appendix B to E of this report. Supporting technical data relating to Appendix B to E is supplied in Appendix F.

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19 9 2. Technical Basics 2.1 Introduction The following sections summarise the recommended technical understanding for this report. 2.2 Noise Terminology The ratio between the quietest audible sound and the loudest tolerable sound is a million to one in terms of the change in sound pressure. Due to this wide range, a scale based on logarithms is used in noise level measurement. The scale used is the decibel (db) scale which extends from 0 to 140 decibels (db) corresponding to the intensity of the sound pressure level. A doubling of the noise energy emitted by a particular source equates to an increase of 3 db(a) in the sound pressure level at a particular location The ear has the ability to recognise a particular sound depending on the pitch or frequencies found at the source. Microphones cannot differentiate noise in the same way as the ear; and to counter this weakness the noise measuring instrument applies a correction to correspond more closely to the frequency response of the ear. The correction factor is called A Weighting and the resulting measurements are written as db(a). A Weighting refers to the noise level that represents the human ear s response to sound. The db(a) unit is internationally accepted and has been found to correspond well with people s subjective reaction to noise. Typical db(a) noise levels for familiar noises are given in Table The noise levels given in Table 2.1 are sound pressure levels (Lp) and describe the noise level at a point in space. Noise levels vary over time depending on noise generating activities. The following noise indicators are referenced during the assessment and are described below: L Aeq, T is the equivalent continuous sound level and is the sound level of a steady sound having the same energy as a fluctuating sound over the same period. It is possible to consider this level as the ambient noise encompassing all noise at a given time. L Aeq, T is considered the best general purpose index for environmental noise. The term T represents the duration of the event or reference period; L A90 index represents the noise level exceeded for 90 percent of the measurement period and is used to indicate quieter times during the measurement period. It is usually referred to as the background noise level; L A50 and L A10 refer to the level exceeded for 50% and 10% of the measurement period respectively. L A10 is widely used as a descriptor of traffic noise; L Amax is maximum recorded noise level during the measurement period;

20 10 L Aeq, 8hr is a measure night noise which may apply over any assessment base i.e. a specific date, week or year. L Aeq, 8hr is referenced by much UK noise policy and is defined between hrs; L Aeq, 16hr is a measure daytime noise which may apply over any assessment base i.e. a specific date, week or year. L Aeq, 16hr is referenced by much UK noise policy and is defined between hrs; and SEL (the Sound Exposure Level) (L AE ) is a measure of sound energy, and is the sound pressure level which, if occurring over a period of one second would contain the same amount of energy as the sound event in question. Table 2.1 Typical Noise Levels Appropriate Noise Level Example 0 Limit of hearing 30 Rural area at night, no wind or adverse weather conditions 40 Library 50 Quiet office without noisy machinery, such as typewriters 60 Normal conversation 70 In car noise without radio 80 Household vacuum cleaner 100 Pneumatic drill 140 Threshold of pain When comparing steady state noise levels, it is important to consider human responses and perception. Table 2.2Table 2.2 presents an overview of human perception when comparing two different noise levels. Table 2.2 Response to Change in Noise Level Change in Noise Level Response < 3 Difficult to perceive > 3 Perceptible 10 Up to a doubling of perceived loudness > 10 Over a doubling of perceived loudness

21 Aircraft Noise Noise associated with aircraft from aerodromes is typically split into two categories: i) Air noise (i.e. aircraft on the runway during landing and take-off and in-flight during descent/final approach, climb-out and cruise); and ii) Ground noise (i.e. aircraft running Auxiliary Power Units (APUs) on stand whilst in park mode; Ground Service Equipment (GSE) handling of stationary aircraft, aircraft taxiing to the runway threshold and queuing and holding prior to departure, aircraft start-of-roll for departures, fixed-plant in airport buildings and facilities, and aircraft EGR including any associated Maintenance Repair Overhaul (MRO) operations The differentiation between air and ground noise is made for several reasons. The first of these reasons is that, not surprisingly for most of the time, air noise occurs whilst aircraft are in the air whereas ground noise is associated with aircraft operations on the ground. The second of these reasons is that ground noise events are not as transient as air noise events. For example, an air noise event may last several seconds rising to a peak noise level before falling away, whereas ground noise can last several minutes, if not hours, at more constant levels of noise In the case of EGR noise, this can be characterised by several short burst of high noise levels although noise levels typically increase to their maximum over a longer periods of time (i.e. several minutes) before falling away as the testing concludes EGR is considered ground noise. There are several types of engine ground runs which are usually grouped or specified by either the number of engines being run or the power levels at which the engines are run up to. In many instances, a single engine ground run exercise may consist of a mixture of power settings, the numbers of engines run and the duration of the run and/or the duration at which the engine is run up at different settings. This means that during an engine running exercise, actual noise levels can vary significantly, as can the directivity of the noise from the aircraft and its engines At many civil airports, engines running is prohibited during certain hours of the day or restricted to certain types of engine run because of noise constraints. These airports tend to enforce operational procedures regarding engine running. These procedures include a range of measures intended to minimise the impact of operations upon neighbouring communities. Apart from restrictions upon the hours in which engine running can occur, these measures also include: Limits on the number of engines runs which may be undertaken during a rolling period, such as a month; Restrictions on the areas within the airfield which may be used for engine running; The encouragement of engine runs to be undertaken simultaneously; and Procedures leading to the authorisation for any engine running to avoid any unnecessary engine running activities.

22 Some aerodromes have specially designed engine running facilitates. These facilities often referred to as EGR pens EGR pens are open at one end to allow the aircraft to be installed and removed and typically include a rear blast deflector and acoustically treated sidewalls. They are designed to attenuate noise during the engine run whilst providing a stable aerodynamic profile which does not inhibit proper engine operation and the requirements of the test Other forms of engine testing facilities include engine test cells. However, these facilities often require the engine(s) to be removed from the aircraft in order to conduct the testing. 2.4 Perception, Annoyance and Health Noise is defined by the World Health Organization (WHO) as unwanted sound. There is no difference between sound and noise in terms of how it is generated, transmitted and how the human ear receives it. The difference is in perception which is subjective. Perception varies between people meaning that what is acceptable to one person may not be acceptable to another WHO state that the possible adverse effects that are associated with noise include: Interference with communication; Noise-induced hearing impairment; Sleep disturbance effects; Cardiovascular and psychophysiolocical effects; Mental health effects; Effects on performance; Annoyance; and Effects on social behaviour Most of the research and guidance in relation aircraft noise perception, annoyance and health is associated with air noise. There have been several studies into the effects of air noise upon community annoyance and, for night-time periods, sleep disturbance. This has revealed that in comparison to other forms of transport, air noise is considered as one of the most annoying types of environmental noise and can affect large areas around airports and aerodromes. The research has resulted in criteria for the assessment of those who are annoyed by air noise and at risk of sleep disturbance In the case of ground noise, there are no specific noise and health studies. Instead assessments and consideration of ground noise effects make reference to more general guidance which considers noise level exposure over a representative period of time. In some instances, technical guidance in relation to air noise can be used to assist assessments but should not be relied upon.

23 Tonal Noise A characteristic of noise that can increase its intrusiveness without requiring a change in the overall noise level is the tonality. This additional intrusiveness is considered within some assessments by applying an adjustment to the overall noise level where noise is identified as tonal. In effect, tonal noise is considered to be noisier than an equivalent noise level if it were not tonal. In British Bayard BS4142:1997 the penalty for tonal noise is to rate or increase the overall A-weighted noise level by 5 db(a) Tonality and adjustments due to tonal noise is discussed in British Bayard :1991. The standard states that: In some practical cases, a prominent tonal component may be detected in one-third octave spectra if the level of a one-third octave band exceeds the level of the adjacent bands by 5 db or more, but a narrow-band frequency analysis may be required in order to detect precisely the occurrence of one or more tonal components in a noise signal Tonal noise is widely considered to add to human annoyance response. 2.6 Meteorological Effects The propagation of noise can be greatly influenced by changing meteorological environments, such as average wind speed, direction, air temperatures and humidity. In real terms, noise levels at a receiver upwind of a noise source can be as much as 10-15dB(A) lower than at a receiver downwind of a noise source By recording meteorological conditions during noise surveys it is possible to account for any changes in conditions, which may otherwise result in a range of measured noise levels at a receiver from the same noise source under investigation. It is very possible for noise levels from an identical noise source to be significantly different when measured at distance due to changes in wind direction. 2.7 Measurements and Modelling Noise measurement and noise modelling are tools used to investigate environmental noise. Noise measurement involves the measurement of a specific noise source or the general noise environment using instrumentation Noise modelling entails the calculation of noise using methods that consider the physical propagation of sound in the environment. Noise modelling requires an understanding of the level, tonality and duration of the noise along with information relating to the environment e.g. distances, obstacles, temperature and humidity etc It can often be difficult to compare the results of a measurement against those produced by a model. This can be due to several factors such as the details and assumption incumbent within the model; the meteorological conditions on a particular day during a measurement; and the dominance of a noise source at a measurement position.

24 It should be noted that the results of the noise modelling presented in this technical report consider downwind conditions only. This reflects a worst-case for all locations and assessments contained within the modelling. 2.8 Technical Guidance General Guidance Many ground noise sources can be considered as having some characteristics in common with industrial noise sources. Ground noise assessments therefore often make reference to the guidance advocated within British Bayard BS 4142:1997 Method for rating industrial noise in mixed residential and industrial areas which provides a methodology for determining whether a new or existing noise source is likely to cause noise complaints by comparing the operational noise level with the background level, (i.e. the level that would occur in the absence of the noise source) This approach involves the comparison of ground noise levels, with measured background noise levels (as L A90 ) in the absence of ground noise. It should be noted that response to noise is subjective and the likelihood of complaints regarding ground noise depends on a number of additional factors, as well as the overall noise level. For example, the time during the night when the noise occurs, a change in the noise environment and also attitude to the noise source In almost all cases, ground noise assessments undertaken using the BS4142 methodology upon communities which surround large aerodromes result in a conclusion that complaints are likely. In the case of engine running activities, this conclusion is usually further compounded by the fact that noise from aviation sources can be extremely transient and reach high levels. The BS4142:1997 method is not necessarily suited for these types of transient noise sources Other guidance often referenced in the assessment of ground noise is set out in the World Health Organisation (WHO) publication Guidelines for Community Noise (2000). For outdoor living areas, the guidelines state that noise levels should be below 55dB(A) L Aeq 16hr in order to avoid serious annoyance, and below 50dB(A) L Aeq 16hr in order to avoid moderate annoyance It should be noted that these noise levels relate to an equivalent constant noise level of a 16-hour day and should therefore not be used as a measure of assessment during specific noise events. It also important to add that these guideline values require context in that these guideline levels are lowest threshold values above which research has demonstrated a potential effect. The WHO document also states that approximately 40% of the population of the European Union is exposed to, for example, road traffic noise in excess of the 55 db(a) value, and that half of all European Union residents live in areas that do not ensure acoustical comfort. These guideline values are therefore often viewed as aspirational long term targets and should not be considered as mandatory limits. The WHO guideline values are set at levels below which there is no impact from annoyance or on human health i.e. there would not be any significant health effects for the population at large. The UK Government considers that the guideline values are very low i.e. extremely cautious (Dft 2004 cited in CAA 2006).

25 The 2009 WHO publication Night Noise Guidelines for Europe reviews the health effects of night-time noise exposure, examines exposure-effects relations, and presents guideline values of night noise exposure that are aimed at preventing harmful effects of noise at night based on the findings of numerous research projects. The guidelines presented are thresholds upon which research has indicated the noise increases the risk of health effects. The thresholds include a guideline value of 42 db L night (outside) for self reported sleep disturbance and increased average motility. The guidelines also suggest that complaints may occur at a threshold of 35 db(a) L night (outside) and that cardio-vascular and psychiatric effects could occur at levels of 50 db(a) and 60 db(a) L night (outside) respectively. The guidelines also state that closer examination of impacts of noise should be given examination in the range of db L night and that for noise levels above 55 db L night cardiovascular effects become a major public health concern and are less dependent upon the nature of the noise source For air noise, current Government policy and national planning guidance rely on the 57 db L Aeq 16hr index which is used to signify the approximate onset of significant community annoyance. As with the WHO guidance, this measure is defined as an equivalent constant noise level over a 16-hour daytime and therefore cannot be used to assess specific noise events. It is important to add that the Government defines 63 db L Aeq 16hr as moderate annoyance or a medium level of noise and that 69 db L Aeq 16hr may be considered as a high level of noise. It should be noted that the Government is currently consulting on a change in this guidance and assessment criteria Government noise policy in England is set out in the Noise Policy Statement for England (NPSE) as published in March The NPSE promotes good health and a good quality of life through the management of noise through sustainable development and associated Government policy. The Statement aims to ensure that noise is considered during the development of associated policy and during decision making. Furthermore the Statement aims to ensure that noise is not considered in isolation. The NPSE presents the various existing policy documents, legislation and guidance through which the control of noise can be managed and achieved. It does not however provide any guideline noise levels instead stating that assessment must be based on a series of effect levels In terms of UK planning policy it is requirement of the National Planning Policy Framework (NPPF) to consider noise and vibration effects on residential areas from proposed noise sources. Although the NPPF does not provide details of exact noise limits, the UK planning policy document that it superseded, Planning Policy Guidance Note 24 (PPG24), provided some guidelines on the assessment of noise for residential areas. PPG24 recommended appropriate levels of noise exposure for residential development and expresses this as Noise Exposure Categories (NECs) for different noise sources for day and night-time periods in terms of equivalent constant noise level in terms of L Aeq, 16hr and L Aeq, 8hr respectively. The policy was explicit that the use of NECs is for the purpose of assessing new residential planning applications only and cannot be used to assess proposals that introduce new noise sources into existing residential areas. Nevertheless the NECs do provide some context.

26 16 Table 2.3 PPG24 Noise Exposure Categories for Aircraft Noise Noise Exposure Category (NEC) Daytime LAeq, 16hr, db Night-time LAeq, 8-hour, db Advice to Local Authorities A < 57 < 48 B C Noise need not be considered as a determining factor in granting planning permission, although the noise level at the high end of the category should not be regarded as a desirable level. Noise should be taken into account when determining planning applications and, where appropriate, conditions imposed to ensure an adequate level of protection against noise Planning permission should not normally be granted. Where it is considered that permission should be given, for example because there are no alternative quieter sites available, conditions should be imposed to ensure a commensurate level of protection against noise. D > 72 > 66 Planning permission should normally be refused PPG24 also states that sites where individual noise events regularly exceed 82 db L ASmax several times in any hour during the night should be treated as being in NEC C thus suggesting that some protection against noise is required in this regard In terms of noise from specific noise events, as is the case with engine running, most guidance concentrates on night-time noise and sleep disturbance. This is due to noise from specific events having the potential for an average person to awake from sleep. Most of this guidance is applied for hours between hrs as per the L Amax criterion outlined in PPG BS8233:1999 gives recommended design criteria for internal noise levels for different types of rooms including residential use. The criteria for bedrooms and living rooms, which have been set to avoid sleep disturbance and ensure suitable living/ resting conditions are: Bedrooms Good L Aeq,T 30dB Reasonable L Aeq,T 35dB Living Rooms Good L Aeq,T 30dB Reasonable L Aeq,T 40dB The design criteria in BS8233:1999 are based on guidance contained within the World Health Organisation (WHO) document, Guidelines for Community Noise (1999). In addition to the above, this document recommends that maximum noise levels should not normally exceed 45dB L Amax in bedrooms at night. Although BS8233:1999 does not provide guidance on the application of this criterion however based upon WHO

27 17 guidelines, it is usually expected that the 45 db L Amax criterion should not be exceeded between times during the night The façades of the dwellings provide some degree of attenuation of outdoor noise levels, which will affect the internal noise levels experienced by occupants. The attenuation is at a minimum when windows are open in the façade of the occupied room. The WHO document stipulates that a façade with an open window will provide an attenuation of between 10-15dB(A), therefore an attenuation of 12dB(A) is usually assumed For aircraft noise and sleep disturbance, the CAA recommended assessment based upon the findings of a Department for Transport research project Report of a Field Study of Aircraft Noise and Sleep Disturbance. The study comprised of social surveys, the monitoring of sleep in subjects, sleep diaries and coincidental external noise measurements. The research concluded that for external noise events below 90 db SEL (approximately 80 db L ASmax ), aircraft noise events are most unlikely to cause any increase in measured sleep disturbance from that which would occur during normal sleep. The study found that only when outdoor aircraft noise events were above 90 db SEL that the researchers found differences between sleep arousal rates with and without aircraft noise. For outdoor aircraft noise events between 90 and 100 db SEL the study found that the chance of the average person being wakened by aircraft noise was about 1 in 75. It is important to remember that this research relates to air noise events rather than ground noise events. MoD Specific Guidance MoD environmental policy is covered within Joint Service Publication (JSP) 418 which acknowledges the MoD should conform with the Environmental Protection Act, 1990 (EPA), with notable exemptions for MoD activities that relate to national security. Normal everyday activities at RAF Brize Norton are not covered by this exemption, therefore where there are likely noise issues adequate controls need to be implemented. When considering the impacts of noise from aerodrome activities within MoD environmental policy, controls exist if the noise cannot be permanently reduced below certain threshold levels. If this is the case a Noise Amelioration Scheme Military (NAS(M)) should be considered The controls outlined in MoD environmental policy are similar to those generally considered appropriate for the control of air noise, however in the instance, some understanding of how EGR noise falls within this policy has been requested by the base NAS(M) sets out the following noise thresholds, that if the noise cannot be permanently attenuated below then subsequent actions should be considered: Offer to purchase residential properties exposed to a noise of 72dB L Aeq,16hr or more; Offer to install an acoustic insulation package (the acoustic double glazing system should be at least (10(12)6.4) for residential properties exposed to noise of 66dB L Aeq, 16hr ; and

28 18 63dB L Aeq, 16hr for noise sensitive areas such as schools/colleges, hospitals, care homes;

29 19 3. Methodology 3.1 Introduction This section details the methodology used for areas of scope outlined in Section 1.3 specifically: Community Noise Monitoring; Aircraft EGR noise emission measurements; Noise Modelling; and Measurements within RAF Brize Norton. 3.2 Aircraft EGR Noise Measurements Introduction Aircraft EGR noise measurements have been undertaken to provide a direct comparison of the noise emissions from each aircraft. The EGR noise measurements have been conducted to provide information on the level, directivity and tonal content of each aircraft s noise emissions Noise measurements have been undertaken by AMEC of EGR from C130, VC10 and A400M aircraft at RAF Brize Norton between October 2011 and May The results of the measurements provide an understanding of how noise from the C130 differs from that of the VC10 and whether the noise is likely to be different from the A400M aircraft which is due to arrive at RAF Brize Norton in The power settings used by each aircraft during an EGR differ and are not necessarily comparable however it is possible to classify or group the power settings used during the EGR to reflect what would usually comprise a typical engine test and corresponding activity. For example, the aircraft are tested at power settings that are consummate with take-off, taxi and at idle It should be noted that for safety reasons, aircraft do not always test all engines simultaneously or at high power. Instead engines are tested at the safest possible settings and either in pairs or in isolation Measurements have been undertaken over a range of different and comparable engine runs between the aircraft. These measurements have been undertaken to record noise level in one-third octave bands measurements to indicate whether there was the presence of any potentially intrusive tonal noise characteristics. The measurements were also supplemented with audio recordings to enable a more detailed analysis of the frequency content of the noise emissions For each aircraft and EGR, measurements were taken at positions around the aircraft at distances of approximately 50-75m from the centre of the aircraft. The

30 20 measurements were corrected to a set distance of 50m and analysed in order to derive sound power level information and a directivity pattern for the noise emissions The noise measurements were taken using a Bruel and Kjaar Type 2250 Class 1 integrating Sound Level Meters (SLM). The instrumentation was configured to simultaneously log record noise levels in terms of L eq, L F, L max and L Peak at a sample rate of 100ms in one-third octave frequency bands between 6.3 Hz to 20 KHz in order to identify any tonal or potentially annoying characteristics The measurements were taken in the form of a round robin, with measurements taken at each location for a period of approximately seconds until such time as the L eq noise level for the measurement had stabilised For measurements of noise from the A400M aircraft, due to the limited time-frame, it was necessary for measurements to be undertaken at each of the positions surrounding the aircraft simultaneously with a second AMEC employee measuring at positions on the opposite side of the aircraft. This methodology effectively halved the required time for the survey The noise measurements of each aircraft are discussed in detail in Appendix C and summarised below. Figure 3.1 presents an example of the measurement positions around the aircraft. Figure 3.1 Example of Aircraft EGR Noise Emission Measurement Positions C130 EGR Noise Measurements Noise measurements of a C130 EGR were undertaken during the afternoon of 12th October The measurements were taken with the aircraft south-facing on Bay 73. Measurements were undertaken of the following: APU running;

31 21 Low Speed Ground Idle (LSGI); Normal Ground Idle (NGI); and High Power EGR comprising of inboard engines at high power and outboard engines at NGI AMEC understood that the High Power EGR described above is the highest power ground run undertaken for the C130 at the base due to safety consideration and that a LSGI EGR is consummate with aircraft taxiing. VC10 EGR Noise Measurements Noise measurements of a VC10 EGR were undertaken on 27 February Noise measurements were undertaken with the VC10 aircraft south facing on Bay 72. Observations were also recorded by AMEC employee within the village of Black Bourton during the engine runs. The following engine run scenarios were measured: APU running; Ground Idle; and 80% Thrust The 80% Thrust EGR consisted of the nearest inbound engine on the VC10 aircraft being run at 80% throttle whilst measurements were undertaken on one side of the aircraft, before switching to the opposite inbound engine when measurements moved to the other side of the aircraft AMEC understands that a scenario where more than one VC10 engine is running at a capacity of 80% whilst on the ground is highly unlikely therefore this scenario (i.e single engine running) is considered a worst-case in terms of noise levels. Measurements at the front of the aircraft included both the left and right inbound engines running so that an average sound pressure level could be recorded. A400M EGR Noise Measurements Noise measurements of an Airbus A400M EGR were undertaken on 2 May 2012 with the aircraft north-west facing on Bay 67. The measurements comprised of the following: APU running; Low Speed Ground Idle (LSGI); High Power ; and Maximum Reverse The High Power EGR was undertaken in a similar manner to that of the C130 High Power EGR in that the inboard engines were at high power and outboard engines at lower power setting.

32 Community Noise Monitoring Community noise monitoring has been undertaken for several purposes and has coincided with specific measured activities within the base. For example, community noise monitoring has coincided with Aircraft EGR noise measurements for the C130, VC10 and A400M aircraft to gain and understanding of the resultant noise levels within communities. It has been undertaken to understand how other activities within the base impact upon the community, and provide a general understanding of the environmental noise climate around the base Community noise monitoring has been undertaken on 4 No. occasions between October 2011 and May The monitoring locations were selected by AMEC, with the assistance of RAF Brize Norton, and were undertaken in the villages of: Black Bourton; Alvescot; Brize Norton; and Bampton The four monitoring locations are presented in Figure 3.2 and are described below: Location 1: 6 Grassonmead, Alvescot to the south-west of the base. The sound level meter was attached to a garden shed, at a height that negated façade influences and allowed an unobstructed view towards the base. The monitoring location roughly falls under Runway 26 departures / Runway 08 approach. Location 2: 105 Station Road, Brize Norton to the north-east of the site. The sound level meter was placed in the back garden of the property in a free-field position. The location is approximately 50m north of the runway centreline at the end of Runway 26. The location roughly falls under the Runway 26 approach / Runway 08 departures; Location 3: Aylesbury Mushroom Farms, Black Bourton approximately 400m south of the airfield. The sound level meter was located in the rear garden in a free-field position. Although there are closer residential dwellings to the airfield, this location was selected due to the security of the equipment and was considered to be more representative of the greater population of Black Bourton; and Location 4: Bushy House, Bampton south of the base. The sound level meter was placed in the back garden of the property In the case of the measurements undertaken at Black Bourton and Bampton, for security purposes, the equipment was installed in areas which did not directly overlook the airfield. It is therefore considered that for these locations, measured noise levels may slightly underestimate the exposure at these locations For all rounds of monitoring, noise levels were recorded for a maximum of 1-minute measurement periods and a minimum of 1-second measurement periods.

33 Noise levels were measured in broadband and one-third octave frequency bands in order to provide an understanding of overall noise exposure and to identify any tonal content of the noise The monitoring was undertaken using a combination of unmanned Rion NA-28, NA- 52 and NL-31 Class 1 Sound Level Meters (SLM) housed in environmental protection apparatus Parameters measured by each SLM included L eq, L 90, L 10, L min and L max. Each SLM was calibrated before and after the survey using an appropriate acoustic calibrator with no significant drift in calibration levels observed Where possible the monitoring was conducted in accordance with BS7445-1:2003 Description and measurement of environmental noise. Microphones were positioned at a height of 1.2m above ground level in a free-field position. Battery levels were also checked before and after the measurement to ensure that they remained within acceptable operating parameters Details of the weather conditions encountered during the rounds of monitoring are shown in Appendix A Further details of the community noise monitoring can be found in Appendix B. 3.4 Noise Modelling Noise modelling has been used to provide further understanding of the propagation of C130 EGR noise into the communities surrounding the base and beyond. It has also been used to understand the effectiveness of potential operational and physical mitigation measures and understand how the levels of noise produced by the EGR activities accord with the MoD s current policy on aircraft noise The noise modelling has been undertaken using the LimA noise modelling software suite. The software allows the consideration of a range of factors relating to noise exposure. It models noise exposure using information regarding the location, level and characteristics of the noise within a 3-dimensional model which takes account topography and the layout of the base and surrounding areas. It takes into consideration the attenuation provided by structures such as hangers and residential buildings and has been used to model the effectiveness of specific measures such as EGR pens The noise modelling has used the C130 EGR measurements to model noise propagation from a range of scenarios. The model considers both the directivity of the noise and it tonal and frequency content. Measurements taken within the communities have been used to calibrate the noise model The model uses the methodology as outlined in International Bayard ISO Acoustics Abatement of sound propagation outdoors, Part 2: General method of calculation to the propagation of noise. This standard is internationally recognised and has been used widely in the assessment of noise within the UK. It considers features of noise propagation such as screening, air absorption and ground absorption and allows the consideration of the frequency content of the noise. This is particularly

34 24 important in evaluating whether the noise contains any tones or other annoying characteristics The model has been used to understand the levels of noise during C130 EGR and to understand average daytime levels of noise as a result of the activities in order align with current MoD policy It should be noted that the noise modelling considers downwind propagation and as such, the results produced by the model are considered a worst case. The use of the noise model has been in this context with other considerations such as average wind directions discussed qualitatively Details of the development and calibration of the noise model against the C130 EGR noise measurements are detailed within Appendix D. 3.5 Noise Monitoring within RAF Brize Norton Noise monitoring within RAF Brize Norton has been undertaken to understand typical levels of noise exposure within the base and to understand how noise levels could change Monitoring within the base was undertaken in May 2012 to help understand the impact of changes in the orientation of the aircraft upon noise levels at and within the base s living accommodation To aid understanding of the impact of the C130 EGR, measurements were undertaken both externally and internally. In order provide some understanding of the risk of sleep disturbance during C130 EGR upon crews, measurements within crew accommodation were undertaken considering scenarios where windows were open and closed The monitoring was undertaken over a period of 4 days with noise level recorded for a maximum of 1-minute measurement periods and a minimum of 1-second measurement periods Noise levels were measured in broadband and one-third octave frequency bands in order to provide an understanding of overall noise exposure and to identify any tonal content of the noise The monitoring was undertaken using a combination of unmanned Rion NA-28, NL- 31, B&K 2250 and B&K2260 Class 1 SLMs Parameters measured by each SLM included L eq, L 90, L 10, L min and L max. Each SLM was calibrated before and after the survey using an appropriate acoustic calibrator with no significant drift in calibration levels observed Where possible the outdoor monitoring was conducted in accordance with BS7445-1:2003 Description and measurement of environmental noise. Microphones were positioned at a height of 1.2m above ground level in a free-field position. Battery levels were also checked before and after the measurement to ensure that they remained within acceptable operating parameters.

35 Noise measurement within the accommodation at the base was undertaken at 1m from the windows of the accommodation in an unoccupied room. The SLM was configured to diffuse field settings and positioned at a height of 1.2m Details of the weather conditions encountered during the rounds of monitoring are shown in Appendix A. The resultant noise levels within the surrounding communities from each of the aircraft engine runs are discussed in detailed in Appendix E.

36 26

37 Key: N Monitoring Locations Shilton #! #! CARTERTON # Brize Norton M2 Brize Norton ST57 ST62 DE32 E D30E E TXYE E ST53 E ST68 E E TXYF E # Brize Norton Airfield ST28 E TXYC E TXYG ST39 M17 ST72 E E ST78 E E ST40 E #!! M3 Black Bourton M1 Alvescot # Broadwell Black Bourton Metres Scale: A # Kencot # Alvescot E C130 EGR Noise Assessment Technical Report BAMPTON # M4 Bampton Figure 3.2 Noise Monitoring Locations ! Based upon the Ordnance Survey Map with the permission of the Controller of Her Majesty's Stationery Office. Crown Copyright R22 TROWJ

38 27 4. Investigations This section presents the investigations which have been undertaken by AMEC at the request of DIO and the base Initial work was undertaken by AMEC in October This work aimed to fully understand the cause of the EGR complaints, identify the complexity of the issue and understand what options could be considered to reduce and mitigate noise exposure From this work, further investigations have been undertaken to study the following: How the noise from the C130 EGR compares historically with that of the VC10 and how it may change with the future introduction of the A400M aircraft to the base; and The potential effectiveness and consequences of operational and physical mitigation measures upon noise exposure The further investigations were undertaken between the period December 2011 to May These investigations focussed mainly on providing additional information and understanding and the testing of various options to assist with decision making It should be noted that the investigations requested and undertaken by AMEC concern noise exposure alone. Other considerations, notably the operational impacts of any physical or operational measures, have been considered by the base and are not discussed within this technical report. Likewise, this report does not seek to make any recommendations but instead present objective information to enable DIO and the base to understand the issue and evaluate potential options under consideration. 4.2 Understanding the Issue The first investigations made by AMEC were to understand and provide evidence justifying the nature and level of complaints being received by the base from the surrounding communities. Community noise monitoring was undertaken for a period of a week and coincided with C130 EGR noise measurements Throughout the community monitoring, the base made available detailed records of EGR and runway activities. This information was used to identify and correlate events occurring at the base with noise levels received and measured in the surrounding communities. These events were studied in terms of their duration, noise level and tonal content. This analysis was undertaken in order to align and verify the nature of the complaints raised by the communities This analysis sought to understand what events resulted in different durations and levels of noise exposure. In addition, an understanding of how C130 EGR is different to existing and alternative activities and how this difference may have prompted the responses from the local communities was also considered important and critical in providing context.

39 In order to assist and provide a high level determination of the noise climate around the base, the community noise monitoring has been used to provide a comprehension of the average ambient and background noise climate in the communities. This has taken into account the relevant technical guidance used to make an assessment of noise exposure and to understand how this exposure aligns with current MoD noise policy It should be noted that AMEC are unaware of any noise monitoring undertaken prior to the arrival of the C130 aircraft to the base. This unfortunately makes a direct comparison of the noise climate before and after the arrival of the C130 very difficult however investigations have been made to attempt to provide a better understanding of this. 4.3 Aircraft EGR Noise Emissions An investigation has been undertaken to understand how EGR of the C130 differs from the VC10 and how noise from EGR activities may change in the future with the introduction of the A400M aircraft This investigation has made comparisons of noise emissions from each aircraft during similar EGR power settings. The investigation identifies differences in noise emissions, directivities and tonal content between the aircraft. This investigation has been used to identify how the aircraft's noise emissions during EGR could be used to inform potential operational and physical mitigation measures. 4.4 Operational Mitigation A series of investigations have been made to investigate the effectiveness of operational mitigation measures. These studies include: Changing the location of C130 EGR; Reorientation of the C130 aircraft for EGR; Use of GPUs instead of APUs; and Towing of the aircraft to and from the runway These investigations have used a combination of noise modelling, community noise measurements and measurements within the base to understand the effectiveness and the implications of these measures on noise exposure. 4.5 Physical Mitigation Investigations have been undertaken into options regarding physical mitigation for aircraft EGR. These investigations have principally concerned the construction and operation of a dedicated aircraft EGR pen. These investigations have taken data obtained for an EGR pen, which has been included within the noise model in order to understand the potential benefits of an option of this nature.

40 Policy Indicators Investigations have been undertaken into the impacts of C130 EGR noise in the context of the MoD s environmental policy. A combination of community noise monitoring and noise modelling has been undertaken in order to identify what noise from C130 EGR falls above the action levels set out in this policy for the purchasing of residential dwellings and/or the offer for sound insulation packages It is reiterated that the criterion outlined in MoD environmental policy relates to air noise whereas C130 EGR is considered ground noise.

41 30

42 31 5. Results 5.1 Understanding the Issue This section details the overall results of investigations undertaken into understanding the cause of the complaints due to C130 EGR at the base. This understanding has been developed from the assessment of several aspects, namely: Noise Exposure during C130 EGR; How C130 EGR noise differs to VC10 EGR noise; How C130 EGR noise compares to the noise produced by other activities at the base; and Overall, how do noise levels in communities compare to technical guidance and policy and does this suggest that action should be taken? Detailed results are presented in Appendix B. Noise Exposure during C130 EGR To attain an understanding of noise exposure during the C130 EGR a combination of attended and unattended noise monitoring techniques were used. This approach was opted for to allow observations of the noise to be taken along with the ability to gather more information over a greater number of C130 EGRs as well as provide an understanding of the overall noise climate around the base From discussions with the base and through analysis of the EGR records during the initial monitoring in October 2011, two principle locations for C130 EGR at the base were identified: South of the runway on Bays 70-82; and North of the runway on Bay For the locations identified above the majority of C130 EGR were undertaken on Bays with the aircraft orientated to the south The first attended measurement of a C130 EGR on Bay 73 was undertaken on Wednesday 12 October 2011 at each of the four community locations and at various positions around the aircraft. Figure 5.1 presents a time-level trace of noise levels at each of the 4 No. monitoring locations. Table 5.1 presents the average measured noise levels, in terms of L Aeq, T for each location and EGR power setting.

43 12/10/ :05 32 Figure 5.1 Time-Level Trace of C130 EGR on Stand 73 (South Facing) Brize Norton C130 Max Reverse Inboard, NSGI Outboard C130 Full Power Inboard, NSGI Outboard C130 LSGI C130 NGI C130 APU Sound Pressure Level, db(a) /10/ :02 12/10/ :59 12/10/ :56 12/10/ :53 12/10/ :50 12/10/ :48 12/10/ :45 12/10/ :42 12/10/ :39 12/10/ :36 12/10/ :33 12/10/ :30 12/10/ :27 12/10/ :24 12/10/ :22 12/10/ :19 12/10/ :16 12/10/ :13 12/10/ :10 12/10/ :07 12/10/ :04 12/10/ :01 12/10/ :59 12/10/ :56 12/10/ :53 12/10/ :50 12/10/ :47 12/10/ :44 12/10/ :41 12/10/ :38 Date / Time Alvescot LAeq Brize Norton LAeq Black Bourton LAeq Bampton LAeq client\reports\foi technical report\30976 foi technical final report 12352i1.docx