by David M. Sykes, Vice Chair, The Quiet Coalition
Ever wonder if trees actually help create quiet neighborhoods? Lots of people assume that if they plant a hedge or a row of shrubs that will help control noise. Professional noise control experts usually say, “no that doesn’t work.” But the UK’s BBC reported recently on some research showing that trees—particularly larches and conifers—actually help screen out noise.
The researchers tested 76 samples from 13 different tree species. Co-author Jian Kang, University College London, said that “[b]eside emphasising the effects of vision and shade, urban greening should be considered as well to achieve noise reduction during propagation.”
Here’s the catch–it’s not the trees’ leaves that are performing that service, it’s their bark. In other words, the noise they help control is actually noise traveling horizontally, like road traffic noise. They won’t do much at all for aircraft noise.
Since it’s the trees’ bark that’s performing the service, trees need to be planted pretty closely together to offer much real shielding from noise. Of course, trees also provide other kinds of relief: they screen out visual distractions like passing vehicles, nosy neighbors, etc., and they provide shade from hot sun in the summertime. So if what you really want is to have a quiet, pleasant front or back yard, do two things: put up a solid wall to stop the noise and other intrusions–wooden boards fitted tightly together will do–then put a row of trees or a hedge between you and the fence.
I lived for three and a half decades in Cambridge, Massachusetts, and even though it’s home to two universities, Harvard and MIT, it’s an intense urban environment with
an incredible amount of urban noise. I have had an eight-foot-high board fence on all sides of a relatively small property (houses in Cambridge are spaced pretty closely together).
That wall provided privacy, security, and a measure of solitude, even when we could hear noise on the other side of it.
One subsequently famous architect, Philip Johnson, built himself a simple, private house when he was a grad student in 1940 (he had a lot of money and it was his thesis project). He started by building a 10 foot high wall right at the property line that ran all the way around the property. Into the wall he inserted two tightly fitted, locking, windowless doors one at the front, one at the side. Then inside the fenced enclosure, he divided the whole lot into a flat-roofed indoor area and an open garden separating them with a glass wall that enabled wide open views of the garden from any place inside the house.
Simple, elegant, actually quite remarkable. That’s how you achieve solitude and privacy in an urban area! The house still stands today. In other words, wooden boards work even better than trees if you really want to screen out the noise and bustle of the city! Put in some trees for shade and green space and you’re done!
David Sykes chairs several professional organizations in acoustical science: QCI Healthcare Acoustics Project, ANSI Committee S12-WG44, the Rothschild Foundation Task Force on Acoustics, and the FGI Acoustics Committee. He is lead author of “Sound & Vibration 2.0” (Springer, 2012), a contributor to the NAE’s “Technology for a Quieter America” and the GSA’s “Sound Matters,” and co-founded the Laboratory for Advanced Research in Acoustics at Rensselaer Polytech. A graduate of UC-Berkeley with advanced degrees from Cornell, he is a frequent organizer of professional conferences in the U.S., Europe, Asia and the Middle East.