An Anechoic Chamber for SPCR

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FIELD RESEARCH

Sunday Oct 5, 2008 between 8 and 9:30, I stationed myself with laptop and SLM on the south-facing sundeck and heard some 30 jet planes. Almost all of them were departures. My guess is that a plane is loudest when taking off because all the engines are going full blast while the plane is accelerating and climbing. In contrast, when landing, the engines are at much lower power and decelerating; only when the brakes are jammed on at touchdown does the noise actually increase, and by this time, it's not audible from SPCR.

I could not see every plane, especially the landings. Each departing plane was audible for a minimum of about two minutes; most of the visible larger commercial planes headed east or SE could be heard for around five minutes. The recorded minimum SPL of these planes was about 50 dBA; the maximum was 75 dBA. When no planes were audible (a rare pause), the ambient dropped to about 40~45 dBA. This was a Sunday when there are usually somewhat fewer flights. YVR's web site lists real-time info on passenger flight arrivals and departures. In the 24 hours following 9AM Oct 5, 332 departures and 304 arrivals were listed.


Commercial jet liner seen south of SPCR sundeck about one minute after takeoff.


Same jet, two minutes after takeoff. It stayed audible almost five minutes in total.

There was also a strange occurrence of a NAV Canada Bombardier CRJ200 twin-jet plane repeatedly flying loops over Vancouver. It flew almost directly overhead about a dozen times at probably no higher than 3,000' altitude. This has been noted in the past; it appears to happen about twice a year.


Unbelievably annoying NAV Canada jet that flew a dozen passes at lower altitude over SPCR in about one hour.
(Cropped photo captured with Nikon D80 at 135mm - 7.5x zoom.)

Lest you jump to the conclusion that SPCR's neighborhood must be incredibly noisy, I hasten to assure you that it is not. The average resident (not cursed with an inconsiderate noisy neighbor) would tell you that it is quiet and peaceful, even though planes and cars are audible from time to time. The lab is also on on the ground floor, which is considerably more insulated than the upstairs south-facing deck.

It's the takeoff noise of larger jets that is most audible; these must average about 20 an hour. Trying to measure and records sounds under 30 dBA@1m — and often under 20 dBA — makes airplane noise difficult for SPCR. It's the main problem that drove me to find the solution in a soundproof room... but that's much easier to say than it was to build.



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