... a world-class motor sport destination and leading business, education, leisure and entertainment venue with a brand that is synonymous with excellence and innovation SILVERSTONE CIRCUIT MASTERPLAN APPENDIX H NOISE & VIBRATION
REPORT AS5900.110808.NMR1 SILVERSTONE MASTERPLAN 2011 SILVERSTONE MASTERPLAN NOISE MODELLING REPORT TECHNICAL REPORT Noise Emissions Modelling Prepared: 8th August 2011 Silverstone Circuit Towcester Northamptonshire NN12 8TN
CONTENTS 1. Introduction 1 2. Noise Modelling Methodolgy 1 2.1 Meteorological Conditions 2 2.2 Assessment Locations 3 2.3 Calculation Assumptions and Input Data 3 3. Further Studies 6
1. INTRODUCTION Noise emissions associated with both on and off-circuit activity have been assessed as part of the environmental impact assessment submitted in support of the Silverstone Masterplan outline planning application. This report provides additional detail on the noise modelling procedures and techniques employed in developing the noise impact assessment elements of the Environmental Statement. 2. NOISE MODELLING METHODOLGY To calculate noise emissions levels over a wide area surrounding the Silverstone Circuits, noise propagation has been calculated using ISO9613 [1] algorithms implemented by integration with topographical GIS data and measured vehicle noise emissions levels using a recognised computer modelling package [2] to industry accepted standards. This allows meteorological, air absorption, ground absorption and topographical effects to be considered in detail, enabling far field predictions of noise emissions to the environment to be modelled with known precision. In summary terms, the ISO9613 method applies the following equation to predict the equivalent continuous downwind octave-band sound pressure level L ft (DW) at each receiver location (or point on the mapping grid), calculated between 63Hz and 8kHz: L ft (DW) = L w + D c (A div + A atm + A gr + A bar + A misc ) Where Lw and Dc are the sound power level and directivity of the source respectively, and the A terms represent geometrical divergence, atmospheric absorption, ground attenuation, barrier and miscellaneous [3] other effects respectively. For each receptor calculation, levels from each contributing source (including image sources due to reflections) are summed logarithmically per source and across the eight standard octave bands following the application of the standard A-weighting to relate to human hearing response. 1 ISO 9613 Acoustics - Attenuation of sound during propagation outdoors - Part 1: Calculation of the absorption of sound by the atmosphere and Part 2: General method of calculation. 2 Datakustic software, CadnaA 3 A misc comprises the contribution associated with propagation through foliage, industrial areas and built up regions. Silverstone Masterplan Noise Modeling Report Page 1 of 6
where: n is the number of contributions i (sources and paths); j is an index indicating the eight standard octave bands from 63Hz to 8kHz Af denotes the standard A-weighting defined in IEC 651 The long term averaging procedure described in ISO9613 p2, clause 8 to account for averaging out the effects of variable prevailing weather conditions over time has not been implemented as the intention of the modelling exercise is to provide like for like direct comparisons of typical snapshots. Meteorological effects are discussed in detail below. 2.1 Meteorological Conditions To standarise the comparative snapshot noise maps, all calculations have been undertaken assuming standard downwind propagation in all directions. Temperature and humidity were set to 10 C and 70% respectively. As the key comparison in this case is the difference between two different scenarios, rather than of absolute levels, this single met case has been assessed. The model can, however, if required for future reference, be interrogated to provide a prediction in any defined meteorological condition. An illustration has also been provided to illustrate to range of variation caused by varying the wind speed and direction only, and to set other comparisons against this context. These comparisons of circuit and traffic noise emissions are shown in figures 2,3 & 4 of the noise chapter in the ES, reproduced below for reference. Figure 2 (neutral) Figure 3 (northerly) Figure 4 (s-westerly) Silverstone Masterplan Noise Modeling Report Page 2 of 6
2.2 Assessment Locations Specific assessment locations have been discussed with the local authority consultees, and at their request also relate to specific locations relevant to discussions in the community liaison forum. Moreover, the use of noise mapping across a large area surrounding the site enables the impact at any and all receptors within this range to be considered. Extending the propagation model further, for example to account for receptors in Towcester, would be well beyond the range of the ISO9613 propagation method s validity. In fact at table 5 in ISO 9613-2:1996, estimated accuracy figures are only given to a maximum source to receiver separation (d) of 1000m (at ±3dB L AT (DW)) 2.3 Calculation Assumptions and Input Data Detailed topographical data for the Silverstone Estate was supplied by the planning team, and is the common base on which the outline application drawings were prepared. Offsite topographical data has been obtained from digitising Ordnance Survey mapping data and validated by site observations and photography. The majority of the landform around the Silverstone circuit site is agricultural, wooded or grassland. The default ground absorption characteristic in the noise emissions model, therefore, is set to a ground absorption factor of 1.0, with significant paved and tarmac areas defined individually as zero. The traffic flow data below, supplied by the transport consultant has been input into the model for the relevant assessment scenarios. CadnaA implements the calculation methods described in CRTN [4], which are based on a combination of standard propagation theory and empirically derived formulae and tables. The precision of this method is accepted to be greatest when dealing with relatively fast, free flowing major roads supporting reasonable (>4000 vehicles per 18-hour day) flow rates. Of the roads modelled, therefore, the precision of the source levels predicted from the A43 and Brackley Road is the greatest, with the low flow prediction tables (1000-4000 vehicles per day) used for most of the Dadford Road scenarios. The validity of these source levels has been confirmed by validation against existing site survey data. 4 Calculation Of Road Traffic Noise (CRTN): 1988 [DoT Welsh Office. HMSO] Silverstone Masterplan Noise Modeling Report Page 3 of 6
The noise map predictions cannot be expected to hold for the unusual traffic conditions which prevail during major events (ie the F1 British Grand Prix), during which road priorities are changed and queuing traffic is widespread. These conditions are dealt with under specific agreements with the local authority and highways agency. Location Current 2021 No development 2031 No development 2021 Intermediate 2031 All Built (High Flows) adford Road Northbound Silverstone Southern entrance - A43 adford Road Southbound Silverstone Southern entrance - A43 2756 / 7% 3621 / 7% 3810 / 7% 5934 / 7% 12528 / 7% 3045 / 7% 3926 / 7% 4123 / 7% 6562 / 7% 14066 / 7% Dadford Road South of Silverstone Southern Entrance 2054 / 6% 2833 / 7% 2971 / 7% 3365 / 7% 5238 / 7% New site entrance overbridge from A43 - - - - 11899 / 6% rackley Road Off Slip (A43), count at two way section of link Brackley Road Between Dadford Rd and Central Silverstone 2733 / 6% 3217 / 6% 3651 / 6% 3903 / 6% 3651 / 6% 4199 / 6% 4997 / 6% 5666 / 6% 6207 / 6% 7462 / 6% A43 Northbound - within the A43 / Dadford Road Jn 11505 / 11% 13415 / 11% 15481 / 11% 13415 / 11% 19519 / 11% A43 Southbound - within the A43 / Dadford Road Jn 11685 / 11% 13610 / 11% 15680 / 11% 13610 / 11% 19219 / 11% Dadford Road South of Brackley Rd Junction 3887 / 7% 4589 / 7% 5264 / 7% 6600 / 7% 7025 / 7% Measured source data conducted directly by ASA staff has been used as the primary basis for the noise model calculations, using the following vehicles to provide for the generic circuit emissions levels shown in the models for corporate supercars, off-road experience, race and customer karting, club racing and customer track use respectively. Source Levels rpm Lp/w dist 63 125 250 500 1000 2000 4000 8000 db(a) Ferrari 360 Generic Supercar 4000 Lp 1m 64 91 77 84 87 83 75 68 90 Nissan Navara 4x4 2500 Lp 1m 81 78 75 74 70 68 64 57 76 2 stroke Kart Competition Kart? Lp 10m 64 72 87 83 85 89 85 83 93 4 stroke Kart Customer Kart? Lp 10m 81 79 82 77 75 78 73 74 83 Cosworth test Club race car 14500 Lw n/a 93 103 103 126 117 122 118 115 127 adjusted test data Customer race car -7dB Lw n/a 86 96 96 119 110 115 111 108 120 Additional adjustments made to take account of other noise survey work which has made available as follows: 20 th June 2007 survey measurements by Hyder consulting in preparation of Silverstone Development Brief. 11-16 th August 2010 near circuit survey measurements (Hyder Consulting) and simultaneous pit lane noise logs Silverstone circuit monitoring data for 2011 MotoGP event. Silverstone Masterplan Noise Modeling Report Page 4 of 6
Acoustic Consultancy Services survey data via MSA for corporate karts and competition racing 2-stroke karts. The noise source characteristics used for the circuit use comparisons is that of an equivalent line source relating to a stream of noise sources around the circuit, averaged over time. This is the method used from road traffic predictions, and has been found to work reasonably well to describe the pattern of noise propagation from motor-racing circuits in the medium and far field (if referenced back to real measurement data to equate to a notional equivalent line source power level). In the near field, however, the technique is less accurate, as closer to the source the individual vehicles are more distinct, as moving point sources. For the determination of likely near field noise exposure levels at the closer plots to the circuit (ie in figure 13.19 of the ES Noise chapter as per the extract below) individual vehicle source locations have been modelled and summed to provide the worst case combination of maximum noise levels around the circuit, but with more realistic local propagation characteristics. This also provides a more precise basis for subsequent, more detailed modelling of noise exposure of individual buildings during the detailed design and implementation phases involved in building out the masterplan. The noise propagation model outputs can be used directly as inputs to an external building fabric calculation which will be required to establish design specific performance specifications for the facade, glazed elements and ventilation systems as required in order to maintain suitable internal noise levels. Silverstone Masterplan Noise Modeling Report Page 5 of 6
3. FURTHER STUDIES The noise propagation models described in this report and presented in the Environmental Statement represent an appropriate level of detail and precision for this outline application, which deals with relatively high level concepts of overall impact and differences between different cases and scenarios. In the reality of day to day changes in circuit activity, vehicle types and numbers and the interaction of these noise sources with the environment, there is much more to study than can be realistically or usefully undertaken as part of this exercise. For example, recent work has shown lower levels of noise emissions from Moto GP motorcycle racing (with all other factors equal) on right-handed corners than left-handed corners. This is thought to be due to the majority of the field running exhaust systems mounted either centrally or on the right hand side of the bike, which are screened to a greater extent by the vehicle as it leans to the right in right hand corners. Similarly, it is known that the highest noise levels experienced in the village of Whittlebury occur when race cars or bikes turn through and exit Copse corner under power. This is the closest part of the circuit, and critically it is also one of the few occasions during a lap when the vehicles exhausts turns directly towards the village. Mitigation in the form of solid building structures on the outside of the Copse corner would therefore be very helpful, but the precise location extent and form required would involve a study of the specific noise source directivity characteristics of different vehicle exhaust systems, coupled with driving techniques under different conditions. This level of detailed analysis is beyond the scope of the current exercise, but should be considered in further refining the detail of the individual built form elements and optimising the noise control afforded to the circuit during the build out phases of the masterplan developments. E H Clarke ALAN SAUNDERS ASSOCIATES Silverstone Masterplan Noise Modeling Report Page 6 of 6