JT75C - 200 E. 1ST AMERICAN WAY - Laserfiche WebLink

Home Browse Search

ALUC Minutes Page 3 January 15, 2004 Replying to Commissioner Webb, Mr. Mestre confirmed that his various calculations were single- event maximum noise levels, while referring to the locations of the CNEL contours shown in the JW A AELUP. He pointed out the GA noise portion of the JW A CNEL footprint and the types of operations responsible for it. He noted that with 75 dB outside of a closed building, current energy and insulation code requirements provide 25-28 dB of attenuation, so that interior single event levels for noisy airplanes would be around 50 dBA, adding that numerous events at 50 dB would be needed to reach the interior standard of 45 dB CNEL, making it easy to design a building accordingly. Replying to Commissioners Bresnahan and Propst, Mr. Mestre related single event noise levels to CNEL, for various examples of GA aircraft above the site and commercial aircraft to the east, and he described the resulting interior noise in terms of human perception. He added that the AELUP's CNEL contours are based on the 1985 JW A Master Plan, with the actual current measured noise footprint being smaller since quieter aircraft have entered the fleet mix. Replying to Commissioner Harris, Mr. Mestre explained that the EIR for increased JW A operations included a corresponding set of contours, adding that they are still smaller than the 1985 Master Plan's. He noted that, under the Access Plan rules, the airlines could shift to MD 80s and 767s for the approved flight limits and result in similar contours that the ALUC and the County has adopted for planning purposes. Replying to Chairman Bresnahan, Mr. Mestre explained that noise complaint studies do not correlate with actual noise levels, but rather with the ambient levels of different areas around an airport. He added that the loudest 10% of flights account for the complaints, which occur in areas of varying ambient noise, not necessarily in areas of high single event levels, but rather in areas where flights stand out above the background levels. Again replying to the Chairman, Mr. Mestre said that everything is different where helicopter noise is concerned, it being a low-frequency, highly intrusive and little attenuated type of sound. Replying to Commissioner Kranser, Mr. Mestre described Alternative G covered in EIR 573, which proposed extending JW A Runway 19L to the south to support commercial airline flights. Commissioner Kranser noted that Alternative G was a 24 MAP concept, although he is not advocating it, but is merely curious as to its possible effects on the project site. Mr. Mestre recalled that they were bigger contours, although he would have to look it up to see if the 60/65 contours would have reached the site. Replying to Executive Officer Golding, Mr. Mestre described the perception of aircraft noise to people in the foothill areas north of JW A. He explained that the decreased distance to overhead aircraft amounts to an increase of 1 to 1.5 dB, which is not perceptible. He opined that the low ambient levels not the hilly terrain, account for increased annoyance, and he pointed out that experiments can show that the level of background noise is directly related to human perception. He added that the phenomena of fog seeming to increase noise is actually due to the decline of background noise caused by slower surface traffic, hence aircraft seem to sound louder. The Chair thanked Mr. Mestre for his presentation. 75C-166