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Camberwell Library21 March 20134/ Representative Noise Levels4. Representative Noise Levels4.1 Noise levels from another nearby site have been used for the assessment of the facade andventilation requirements. A noise survey is planned for the proposed site but this has not yetconcluded. This report will be updated with the relevant survey results when they becomeavailable.4.2 A noise survey on Grove Lane was conducted on Friday 23 rd November 2012. Thismeasurement, recorded over a 30-minute period between 16:03 and 16:33, was taken underfree-field conditions (at least 3.5m away from any reflective surface with the exception of theground) with the microphone positioned at a height of approximately 1.5m and approximately5m from the road kerb. In addition, a longer term survey was also undertaken on site which wascarried out for a period of 24h.4.3 The main noise source identified while conducting the short-term noise survey was some trafficrunning along Grove Lane and the aircraft flyovers. In order to gain a representative L A01,30minmeasurement for the internal noise levels the short term measurement was used since it wasverified that the L A01 , 30min was caused by aircrafts rather than other intermittent sources.4.4 The weather during the course of the survey was partly cloudy, dry and without wind gusts. Thetemperature was approximately 8°C. All road surfaces in the surrounding area were dry.4.5 The noise monitoring equipment used during the course of the short-term survey comprised ofone Larson Davis 824 Class 1 sound level meter (serial number: 1725). On site calibrationchecks were performed on the meter before and after the survey using the same Larson DavisCAL200 Acoustic Calibrator as described above. The calibration checks were found to be withinthe permitted tolerances of BS EN 61672-1: 2003. This meter had a valid calibration certificateat the time the noise survey was carried out.4.6 The following parameters were measured during the course of the survey: L Aeq , L Amax , L A1 , L A90and 1/1 octave band frequency data.4.7 The results of the survey have been summarised in Table 3 below.Date L Aeq, T L A1, 30min L A90, T23-24/11/2012 58- 62 70 44 – 49Table 3: Summary of the noise measurements taken on Grove Lane4.8 It should once again be stressed that the above can only provide an indication of the levels ofnoise we can expect on the proposed site. This will need to be verified by measurements on theproposed site, failing which any recommendations made on the basis of the above data arelikely to be sub-optimal.5
Camberwell Library21 March 20135/ External Building Fabric & NoiseIntrusion5. External Building Fabric & Noise Intrusion5.1 External Fabric5.1.1 It is assumed that the external building fabric will be a cavity masonry construction or anequivalent massive construction. In addition, the roof has also been assumed to be of a similarmake up such as a concrete slab.5.1.2 On this basis, the external fabric will result in a substantial reduction of any noise breaking intothe rooms. As such, the elements that will require greater attention are the glazing andventilation elements of the façade build-up. These are discussed below.5.2 Ventilation Strategy5.2.1 Based on clarifications obtained from Mansell Ltd., the ventilation is to be provided by naturalmeans. Typically, louvres located below the glazing and louvres/rooflights located at roof levelwill provide the necessary airflow.5.2.2 Our assessment of the new building’s acoustic ventilation and façade requirements is based onthe noise survey data reported herein. As noted previously, this data, while consideredrepresentative is subject to verification by actual measurement. Failing this, the discussion ofnoise levels below is likely to be inaccurate.5.2.3 In order to calculate the expected noise levels inside the proposed library with a strategy ofnatural ventilation via open windows, noise levels from the surrogate survey (L Aeq,30min ) areindicative of the general ambient levels, and short term levels (L A01,30min ) indicative of the aircraftflyovers.5.2.4 When assessing the acoustic viability of a natural ventilation strategy, it is typically assumedthat a partially open window provides a 13 dB level difference between external and internalnoise levels.5.2.5 Based on the above reduction, the resultant noise levels within the Library is expected to be asset out below:LocationInternal Noise Levels L Aeq,30min(dB)Internal Noise Levels L A1,30min (dB)Library 45 - 49 57Table T4: Calculated internal noise levels with natural ventilation5.2.6 As can be noted, the reported internal noise levels are up to 9dB higher that the recommendeddesign criteria, although the aircraft flyover noise is expected to be only 2dB above therecommended levels for such a noise source.6
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