8th October 2021
How Do Acoustic Walls Work?

As technology progressed after the industrial revolution, we introduced ourselves to a new threat that was entirely unheard of until that stage in time: noise pollution. Between cars, trains, and the general clattering of machines, the small cities that were prominent in that time soon became unbearably loud. To escape the noise, people began taking advantage of the new modes of transport to move out into the suburbs, but by doing so, they took the noise with them, creating highways and longer railways that started generating noise pollution that you simply couldn't escape. Consequently, engineers created the first acoustic walls to reduce the effect of noise pollution, and today, we're going to break down exactly how they achieve that.

Don't Overcomplicate The Science
If you didn't know any better, you might be tempted to assume that these walls operate by cancelling out the soundwaves through some complicated, harmonic science. Unfortunately, you'd be wrong. Instead, the science really is as simple as it sounds: if you put a solid object between the highway and everyone else, the highway will probably seem quieter. There is no advanced curvature, no advanced science. Just a thick block of a durable, reflective material, such as brick, wood, or concrete.

The Gritty Details
When sound interacts with a solid wall, three things tend to happen. First, a portion of that sound is reflected, bouncing off harmlessly in the direction it came. Another portion of that sound is absorbed by the wall, and it is heard on neither side. The remaining portion of the sound, which might be the majority or barely anything at all depending on the material of the wall, will be left to be transmitted through to the other side.

Of course, that's only the sound that actually strikes the wall. Some of the energy that forms the sound wave will instead travel upwards, 'diffracting' itself over the wall. When you're trying to work out how much noise is going to end up on the other side of the wall, then, you need to think about what's being transmitted, and what's being diffracted.

Beautiful Silence
Finally, then, how complicated is it to calculate how effective these walls really are? Well, it's actually exceedingly simple. As a general rule of thumb, when a wall is built to the line of sight of the observer, there will be a 5-decibel reduction in noise. For every meter above that you build, there will be a further 1.5 decibel reduction. Of course, if you'd like to go above and beyond, you can also texture the wall to increase diffusion and decrease diffraction, but this general rule is generally accurate enough to not need to worry about that. Considering how useful and simple these walls are, if you'd like to install one yourself, you'll need the number one acoustic wall contractor available, Abi Civil. To speak with our team of civil contractors in NSW about what we can do for you, call us on 1300 402 510.