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Diffraction Affects Blocking Noise

by Ron Kurtus (20 June 2017)

A common way to block noise from reaching your house is to add a wall in your back yard. Unfortunately, the diffraction property of sound waves still allows some noise to go around the wall or fence. You can increase the height of the wall or try to diffuse the diffraction.

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Effort to block noise

If your house is near a busy freeway, or there is some other source of noise reaching your home, you might want to find a way to block out that noise. A common way to do that is to build a tall fence or wall in an attempt to block out the sound and noise.

A solid wall or fence can reflect some sound waves and absorb other waves, such that very little noise gets through the wall.

Diffraction property at edge

The problem is that some noise still seems to reach your back yard, due to the diffraction property of sound.

When sound waves reach the edge of an obstacle, that edge causes waves to curve as if the edge was a source of the sound. This is a form of diffraction of the sound waves.

Edge diffracts the noise

Edge diffracts the noise

Possible solutions

Since the diffraction is caused at the edge of the wall, placing objects or material above that edge can help to diffuse the diffraction. One example is placing shrubs that go above the top of the wall. In this way, the wall stops much of the noise, while the shrub diffuses the other part of the noise.

You can also build a higher wall, but that may not be practical.


You can add a wall in your back yard to try to block noise from reaching your house. This is only a partial solution, since the diffraction property of sound waves still allows some noise to go around the wall or fence. You can increase the height of the wall or try to diffuse the diffraction to reduce the noise.

Be wise

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