$sound diffraction around a barrier$

$sound diffraction around a barrier$

Yes, that’s actually 99% of the science behind the highway sound barrier.

$sound diffraction around a barrier$

This works through reducing the amount of sound energy able to pass over the wall via diffraction. Every additional meter above the line of sight reduces the sound by an additional 1.5 decibels. Diffusion diagram by Marcelo Reis~commonswiki, (CC-BY-SA 3.0)Īccording to metrics by the Department of Transportation, in order to achieve a 5 decibel reduction of noise, a barrier must be built at the line of sight (and hearing) of the average individual. Care must be taken to make sure that the reradiation of sound from diffusion doesn’t produce an increase in the amount of sound able to pass over the wall via diffraction. This is why newer-generation sound walls feature brick-like texturing, corduroy concrete, or other embossed patterns. If a wall is effectively textured, it can also diffuse sound, causing it to scatter in a variety of directions, which can further aid in the reduction of noise. Diffraction diagram by the Federal Highway Administration Since no wall is infinitely tall, a certain percentage of sound passes over the top of the wall (the fancy acoustical term for this is diffraction), effectively hopping the fence into suburbia. The taller the wall, the more surface area it will have to effectively do all three of these things. Sound reacts to solid walls in three ways: it is reflected (bounces off the surface) absorbed and/or transmitted (passes through the barrier to the other side.) Noise barrier diagram by the Federal Highway Administration Sound wall along Highway 695 outside Cantonsville, MD image by the author It is a wall: a hard surface made of wood, concrete, brick, or other reflective, strong and durable material. In fact, it is one of the simplest solutions in the entire field of acoustics. The concept of the sound barrier and how it works is remarkably simple. But how do these walls work, and what led to their development? Sound Wall in California by Michael Patrick (CC-BY-SA 2.0)Ī 2010 survey by the Federal Highway Administration counted 2,748 linear miles of noise barriers built along highways in the U.S. The image of the endless walls lining the sides of the interstate continues to fascinate me even today, as a young adult and a graduate student in acoustics. In the car, we zoomed past miles of acoustic barriers my childish mind registered as some kind of giant band-aids. When I was a little girl, my parents took us to Washington, DC to pay a lengthy visit to the Smithsonian, some historical monuments, and other sites.

$sound diffraction around a barrier$

Sound diffraction around a barrier