Sound Interference and Beats

Sound interference creates beats when two or more close frequencies combine. In music, this shows up as a changing loudness that rises and falls. The pattern comes from superposition, the adding together of waves. Constructive interference makes the sound stronger, while destructive interference makes it weaker.

When two sound waves of equal amplitude and slightly different frequencies interfere with each other, the displacement equation for the resultant wave at a particular position can be determined. Its intensity rises and falls alternately with time.

The total length of the time axis represents one second. When the two waves are in phase, th...