An Anechoic Chamber for SPCR

Reference|Recommended | The Silent Front
Viewing page 2 of 11 pages. Previous 1 2 3 4 5 6 7 8 9 10 11 Next

CAUSES OF INCREASED AMBIENT NOISE FOR SPCR

The city of Vancouver has grown, and the traffic of cars and aircraft within audible distance of the SPCR lab has increased significantly. In the past, external noise was light enough that we did not have to wait long to get the few minutes of low noise needed to listen or take measurements for a product. Now, both cars and planes intrude frequently, and there are many days, especially in summer, when it's too frustrating to measure or record any product acoustics at all.

As in many cities, there are quiet pockets in Vancouver. This neighborhood, near the geographical center of Vancouver a bit south of Queen Elizabeth park, was pretty quiet and sleepy ten years ago. Now there are more drivers negotiating their automobiles through the neighborhood, sometimes in an effort to bypass heavier traffic on major routes. It's blocked from downtown noise by a ridge roughly 100~125m elevation that runs east-west across the center of the city, with a peak at Queen Elizabeth Park (33rd Avenue), elevation 170m (550') above sea level. The downtown peninsular 5km to the north is probably just 20' to 100' above sea level (similar to Manhattan), and Richmond, across Fraser River 2km to the south is flat river delta land just barely above sea level. As you go north beyond the ridge, noise from downtown (mostly vehicular traffic noise) increases steadily. South of the ridge, at about 90m elevation, this house is insulated from downtown noise, but more exposed to the air traffic to and from the Vancouver International Airport (YVR) some 6km to the southwest.


Pilot's view of Vancouver from 7300m up, looking towards the west. Most of it is greenish, due to the large number of trees in the city. This contrasts against the browner/grayish patches downtown and vicinity, which is more conventionally urban — asphalt, brick and concrete. (Click on the photo for a larger 1024px wide image to appear in a new window or tab.)

While street traffic is annoying, the house is far enough away from the closest major thoroughfare, Main St, to be modest except during rush hours in the morning and late afternoon. The random local traffic is more intrusive but usually short-lived. We can still get SPL readings of just 18 dBA in our labs in the middle of the day, at least for brief stretches.

900 FLIGHTS A DAY

The noise of air traffic is more insidious. YVR on Lulu Island at the western end of Richmond is Canada's aviation gateway to Asia and the Pacific, and it's just 6km away from SPCR. A commercial jet plane taking off is audible from inside the lab almost as soon as it is airborne, if it is heading in an easterly or southerly direction. The planes coming from or going to eastern Canada or the US tend to fly east-west over Richmond, close to the Fraser River. They get closer to SPCR before they move farther away, and there are no hills or mountains to block the noise for a hundred km to the south. There's a straight line-of-sight (and sound) between these planes and this house. The commercial flights that go north tend not to be as audible because they're moving in a westerly direction as well, away from this house as soon as they are airborne. There are three main runways for large jet planes. Two run east-west while one runs NW-SE; it's no surprise that the planes most approach and take off in the E-W path that keeps them in line-of-sight to this house.


Courtesy of YVR

There are numerous smaller (mostly propeller) planes, seaplanes and helicopters at much lower altitudes. These are not all landing at YVR; many land in pads in downtown Vancouver or onto the water at Burrard Inlet north of downtown. Many small planes appear to travel in a north / south direction, often over the immediate neighborhood, sometimes directly overhead. Some are running scheduled flights in standard routes; others are running tourist flights. The noise of these aircraft is of shorter duration, but just as intrusive as the big jets, as they fly at lower altitude.

Over the past year, there appears to have been a change in the air routes over the city for small planes. They were far less frequent in the past. The change could be a natural outgrowth of expanding traffic or business, but I cannot help suspect partisan group action by residents of the posher west side neighborhoods. The natural route between the airport and the Vancouver harbor north of downtown is directly over the west side. It's not inconceivable that influential residents of the west side neighborhoods lobbied municipal and airport authorities to redirect traffic away from their neighborhoods.


The number and frequency of smaller planes over SPCR is difficult to ascertain, but they contribute to the noise as well.
(Copyright photo courtesy of conlawprof)

YVR states that the annual number of aircraft movements has increased only marginally over the last 15 years, from 290,297 in 1992 to 328,563 in 2007. However, the number of passengers passing through VYR during the same period has risen from 9.9 million to 17.5 million. Similarly, cargo movement has increased from 144,000 tons to 226,200 tons. This suggests that the increase in aircraft movements is due mostly to large commercial jets, which of course, cause the greatest noise. The average number of aircraft movements works out to be 900 daily. A study of daily flight schedules at YVR shows there are only a handful of flights between midnight and 6AM, so the vast majority of the 900 flights are in the 18 hours from 6AM to midnight. It works out to be about 50 flights per hour, on average.



Previous 1 2 3 4 5 6 7 8 9 10 11 Next

The Silent Front - Article Index
Help support this site, buy from one of our affiliate retailers!
Search: