Diffraction Calculator

This is a very "crude" calculator that measures the level of a source over a distance* as well as the diffraction per frequency. Please note that this calculator aims to illustrate some basic concepts on airborne sound/noise propagation and it should not be used in any other way.

*metric only, for now, sorry guys

Here's how to use it:

• The distance from the wall slider is controlling how far the source is going to be from the sound barrier.

• The wall height is the barrier height

• The frequency is the frequency of the sound that is emitted from the source. That helps with the calculation of diffraction

• The source level at 1m from the source. This helps calculate the level attenuation over a distance.

• Moving the mouse over the drawing area, you can move the "ruler" and see the resulting level at that distance.

• The blue arrow represents the line of sight of the sound as it goes over the wall/barrier

• The red arrow represents the deflection of the sound for the specified frequency due to diffraction

• For very low frequencies and combinations of barrier height/distance the model "breaks" (which is expected as the sound just passing through instead of passing over).

Important: This model should not be used for serious work as it is oversimplified. More specifically, it makes a series of assumptions such as: 

1. The source is a point source.
   With environmental noise, most noise sources are rarely anything close to "point sources"

2. The source is in the free field.
   Since there has to be the ground, this is not a free field. The attenuation in reality should still follow the inverse square law, but theoretically, I would expect a +3dB boost.

3. Doesn't take into account the surrounding
   Buildings, trees, and other large surfaces reflect sound, thus the actual levels might be different from those provided here

4. Diffraction
   It is assumed that the wall is a line raising at a specific height over the ground. In practice, the material and the geometry of the edge of the wall can play a significant role in the diffraction. However, this is out of the scope of this model as it aims to illustrate the basic principles and not an accurate estimation.

Enjoy!