Appendix G Noise and Vibration Assessment

Transcription

1 Appendix G Noise and Vibration Assessment Annex G1: Noise Perception and Terminology Annex G2: Baseline Noise Monitoring Annex G3: Construction Information Annex G4: Operational Information

2 Annex G1: Noise Perception and Terminology

3 Appendix G Noise and Vibration Annex G1: Noise Perception and Terminology G.1.1. G.1.2. Between the quietest audible sound and the loudest tolerable sound there is a million to one ratio in sound pressure (measured in pascals, Pa). Because of this wide range a noise level scale based on logarithms is used in noise measurement called the decibel (db) scale. Audibility of sound covers a range of approximately 0 to 140 db. The human ear system does not respond uniformly to sound across the detectable frequency range and consequently instrumentation used to measure noise is weighted to represent the performance of the ear. This is known as the 'A weighting' and annotated as db (A) or LpA db. Table 1 below lists the sound pressure level in db (A) for common situations. Table 1: Sound Pressure Levels for a Range of Situations Typical Noise Levels Example 0 Threshold of hearing 30 Rural area at night, still air 40 Public library Refrigerator humming at 2m 50 Quiet office, no machinery Boiling kettle at 0.5m 60 Normal conversation 70 Telephone ringing at 2m Vacuum cleaner at 3m 80 General factory noise level 100 Pneumatic drill at 5m 120 Discotheque - 1m in front of loudspeaker 140 Threshold of pain G.1.3. G.1.4. The noise level at a measurement point is rarely steady, even in rural areas, and varies over a range dependent upon the effects of local noise sources. Close to a busy road, the noise level may vary over a range of 5, whereas in a suburban area this may increase up to 40 and more due to the multitude of noise sources in such areas (cars, dogs, aircraft etc.) and their variable operation. Furthermore, the range of night time noise levels will often be smaller and the levels significantly reduced compared to daytime levels. Background Noise Levels A parameter that is widely accepted as reflecting human perception of the ambient noise is the background noise level, L 90, this is usually A weighted and can be displayed as L 90 or L A90 (db). This is the noise level exceeded for 90 % of the measurement period and generally reflects the noise level in the lulls between individual noise events. Over a one hour period, the L A90 will be the noise level exceeded for 54 minutes. April 2014 Page 1

4 Ambient or Activity Noise Levels G.1.5. G.1.6. G.1.7. G.1.8. G.1.9. G The equivalent continuous A-weighted sound pressure level, L Aeq (or L eq ) is the single number that represents the total sound energy measured over that period. L Aeq is the sound level of a notionally steady sound having the same energy as a fluctuating sound over a specified measurement period. It is commonly used to express the energy level from individual sources that vary in level over their operational cycle. L max levels The L Amax,slow and L Amax,fast measurement parameters are the maximum instantaneous sound pressure level attained during the measurement period (30 seconds, 5 minutes etc.), measured on the slow or fast response setting of the sound level meter. This is sometimes expressed as L Amax db or L max. Even though sounds appear fairly steady to the human ear they are seldom if ever steady in level. To accommodate this factor, sound level meters (SLMs) are generally provided with at least two meter responses or exponential averaging circuits. Fast meter response has a time constant of 1/8th of a second (125ms) and approximates the integration time of human hearing. The slow time response (time constant = 1 second) is intended to obtain an approximate average value of rapidly fluctuating levels from simple meter readings. Noise Changes Human subjects are generally only capable of noticing changes in noise levels of no less than 3. It is generally accepted that a change of 10 in an overall, steady noise level is perceived to the human ear as a doubling (or halving) of the noise level. (These findings do not necessarily apply to transient or non-steady noise sources such as changes in noise due to changes in road traffic flow, or intermittent noise sources). Sound Power Sound power is the rate per unit time at which airborne sound energy is radiated by a source. It is expressed it watts (W). Sound power level or acoustic power level is a logarithmic measure of the sound power in comparison to the reference level of 1 pw (picowatt). The sound power level is given the letter "Lw" or SWL. It is not the same thing as sound pressure (Lp). Any Lp value is dependent of the distance from the noise source and the environment in which it was measured. Lw values are preferred for noise prediction purposed as their value is independent of distance or environment. There are recognised formulas for converting Lw to Lp. A-weighted sound power levels are usually denoted LwA (db) or sometimes Lw (dba) or SWL (dba). Sound Reduction Index The sound insulation properties of a material are described by the term sound reduction index (R) i.e. it is a measure of the reduction in the amount of sound transmitted through a material. The higher the sound reduction index the greater the attenuation provided by the material. The value of R depends on a range of factors, in particular the mass of the material, the nature of the material, and the frequency of the sound. The R values for April 2014 Page 2

5 individual octave bands can be combined into an overall single figure, the weighted sound reduction index Rw. Internal Noise Levels G G G G In an enclosed space such as an individual room, or a building, the noise from a source can not propagate in the same way as outdoors because the propagation of the sound is obstructed by the boundaries (walls, ceiling and floor) of the building. These surfaces together with the contents of the building reflect a proportion of the sound back inside the building or room, the amount depending on the absorption coefficient of the various surfaces. Therefore the overall noise level at a position within the building is a combination of the sound received directly from the source (the direct sound field) and the sound received from reflections from the internal surfaces (the reverberant sound field). The more absorptive the surfaces in a building the less sound is reflected and the lower the contribution of the reverberant sound field to the overall noise level. Frequency Spectrum Frequency is the rate at which the air particles vibrate. The more rapid the vibrations, the higher the frequency and perceived pitch. Frequency is measured in Hertz (Hz). A young person with average hearing can generally detect sounds in the range 20 Hz to 20,000 Hz (20 khz). Figure 9A.1 below illustrates the range of frequencies, for example, the lowest note on a full scale piano, A, has a fundamental at 28 Hz, and the highest, G, a fundamental at 4186 Hz (there will be higher order harmonics). Human speech is predominantly in the range 250 Hz Hz. The musical term octave is the interval between the first and eighth note in a scale and represents a doubling of frequency. A series of octave and one-third octave bands have been derived, as shown on Figure 1 and these are commonly used in noise measurements where it is necessary to describe not only the level of the source noise but also the frequency content. The frequency content of a noise source can be useful for identifying acoustic features such as a whine, hiss or screech. April 2014 Page 3

6 Figure 1: Octave and 1/3 octave frequency bands April 2014 Page 4

7 Annex G2: Baseline Noise Monitoring

8 Annex G2: Baseline Noise Monitoring G.2.1. Baseline Noise Monitoring Baseline noise monitoring was undertaken during the period 18th September to 25th September and 9th October to 16th October G.2.2. The monitoring data for each long-term noise monitoring location are given in Tables 2 and 3. Table 2: Long-term Noise Monitoring: Barnacre Date Day Daytime Noise Level 7am to 11pm Night-time Noise Level 11pm to 7am 18/09/2013 Wed /09/2013 Thurs /09/2013 Fri /09/2013 Sat /09/2013 Sun /09/2013 Mon /09/2013 Tue /09/2013 Wed Weekday Weekend Table 3: Long-term Noise Monitoring: Orchard Cottage Date Day Daytime Noise Level 7am to 11pm Night-time Noise Level 11pm to 7am 09/10/2013 Wed /10/2013 Thurs /10/2013 Fri /10/2013 Sat /10/2013 Sun /10/2013 Mon /10/2013 Tue /10/2013 Wed April 2014 Page 5

9 Date Day Daytime Noise Level 7am to 11pm Night-time Noise Level 11pm to 7am Weekday Weekend Short-term attended monitoring Table 4: Short-term Noise Monitoring: ST1 - Marsh Common Lane Date Day Daytime Noise Level Night-time Noise Level 7am to 11pm 11pm to 7am 18/09/2013 Wed /09/2013 Wed Table 5: Short-term Noise Monitoring: ST2 - Severnwood Gardens Date Day Daytime Noise Level Night-time Noise Level 7am to 11pm 11pm to 7am 18/09/2013 Wed /09/2013 Wed Table 6: Short-term Noise Monitoring: ST3 - Severn Road Date Day Daytime Noise Level 7am to 11pm Night-time Noise Level 11pm to 7am 18/09/2013 Wed April 2014 Page 6

10 Annex G3: Construction Information

11 Annex G3: Construction Information Table 7: List of Assumed Construction Activities and Construction Plant Construction Activity Plant Sound Power Level Lw No. of plant Overall Lw On-time (% of hour) Reference Site clearance Earthworks CFA Piling Excavations and foundations Slab construction Chainsaw BS 5228 Table D.2 no 14 Dozer Dumper BS 5228 Table C.2 average no.s BS 5228 Table C.2 average no.s Scraper BS 5228 Table D.9 no 14 Loading lorries BS 5228 Table C.2 average no.s Excavator BS 5228 Table C.2 no 2 Dumper BS 5228 Table C.2 no 32 Dozer BS 5228 Table C.2 no 1 CFA Piling rig Service crane Cement mixer truck Excavator Lorry mounted concrete pump Lorry Cement mixer truck BS 5228 Table C.3 average no.s BS 5228 Table C.3 average no.s BS 5228 Table C.4 average no 32 BS 5228 Table C.2 average no.s BS 5228 Table C.2 average no.s BS 5228 Table D.7 average no.s BS 5228 Table C.4 average no 32 Poker vibrator BS 5228 Table C.4 no. 34 Crawler crane Tower crane Poker vibrator Concrete pump BS 5228 Table C.4 average no.s BS 5228 Table C.4 average no.s BS 5228 Table C.4 average no.s BS 5228 Table C.4 no.28 Steelwork Crane BS 5228 Table C.4 April 2014 Page 7

12 Construction Activity Plant Sound Power Level Lw No. of plant Overall Lw On-time (% of hour) Reference construction average no.s Finishing and fitting Access roads and car parking Hardstanding Generator BS 5228 Table C.4 average no.s Electric drills BS 5228 Table D.6 no.54 Metal cutter BS 5228 Table C.1 no.18 Electric bolter BS 5228 Table D.6 no.54 Lorries/hr BS 5228 Table D.7 average no.s BS 5228 Table C.4 Generator average no.s Welding plant BS 5228 Table C.3 no. 31 Electric drills BS 5228 Table D.6 no. 54 Lorries/hr BS 5228 Table D.7 average no.s Excavator BS 5228 Table C.2 average no.s Dumper BS 5228 Table C.5 no.s 16 Asphalt spreader Road roller BS 5228 Table C.5 average no.s BS 5228 Table C.5 average no.s Excavator BS 5228 Table C.2 average no.s Dumper BS 5228 Table C.5 no.s 16 Cement mixer truck BS 5228 Table C.4 average no 32 Poker vibrator BS 5228 Table C.4 no. 34 April 2014 Page 8

13 Table 8: Construction Road Traffic Data Link Details 2019 Baseline (no construction traffic) Flow % HGV 2019 with construction traffic Flow % HGV % change in road traffic flows 1 A403 - between Kings Road Avenue and Unclassified Road A403 - between B4055 and M A403 - between 'unclassified road' and B M48 - between Junction 1 and the M4 (Junction 21) M5 - between Junction 15/ (M5/M4) and Junction 14 M A4 - between A4162 and A M4 - between Junction 20/ M4/M5 and Junction 19 M4/M A403 junction A403 Severn Road/ Severn Road and Chittening Road A403 outside existing Seabank access 3.6 April 2014 Page 9

14 Annex G4: Operational Information

15 Annex G4: Operational Information G.4.1. Data Sources: All basemapping, Scheme layout and without scheme and with scheme ground heights provided by URS. G.4.2. Modelling assumptions: Buildings heights all 2 storey houses (6m), all 1 storey houses (4.5m). Receptor heights 1.5m ground floor, 4m 1 st floor. Ground absorption wider area 1, industrial areas and hardstanding 0.0, vegetation 0.7, road surfaces 0.0, water bodies 0.0. The ground height of the main development will be 8.5m. A 4m high wall is constructed around three sides of the transformers. Table 9: Source Data Inputs General Assumptions/Information Noise Source Type Sound Pressure Level No. of Plant/ buildings Dimensions (m) Height Source of Noise Data Turbine building HRSG Building Turbine Auxiliary building HRSG Auxiliary building Peaking Plant Internal reverberant Internal reverberant Internal reverberant Internal reverberant Internal reverberant URS data for comparable facility x URS data for comparable facility URS data for comparable facility URS data for comparable facility x 17 9 Assumed same as Turbine Building Noise Source Type Sound Power Level LW No. of Plant/ buildings Dimensions (m) Height Source of Noise Data HRSG Stack Peaking Plant Stack Area URS data for comparable facility Area Assumed same as HRSG stack Hybrid Point Client supplied April 2014 Page 10

16 Noise Source Type Sound Pressure Level No. of Plant/ buildings Dimensions (m) Height Source of Noise Data Cooling Tower (per cell) Gas Turbine Air Inlet Noise Source Point Point Area x 15 (9m above ground) Type noise of Sound Pressure Level No. of Plant/ buildings - - Dimensions (m) Client supplied Height Source of Noise Data Transformer Area 2/3 12 x 3 3 URS data for comparable facility Table 10: Source Data Inputs Internal Reverberant Levels Linear Internal Reverberant Noise Level in Each Frequency Band db Details k 2k 4k 8k Overall Turbine buildings HRSG Buildings Peaking Plant Turbine and HRSG Auxiliary Buildings Workshop Table 11: Source Data Inputs Point Source Levels Linear Sound Power Level in Each Frequency Band db Details k 2k 4k 8k LwA db Stacks (each) Hybrid Cooling Tower (per cell) April 2014 Page 11

17 Table 12: Source Data Inputs Area Source Levels Linear Sound Power Level in Each Frequency Band db Details k 2k 4k 8k LwA db GT Air Inlet façades Transformer large facades and roof Transformer small facades G.4.3. For all buildings the following building constructions were assumed: Table 13: Building Construction Acoustic Properties Details Sound Reduction db in Each Frequency Band Rw db k 2k 4k 8k Corus Single Skin Steel Wall Cladding Kingspan Wall-Lite Hollow Steel Door April 2014 Page 12