Interference of Sound – Sound Intensity

Let us now consider the intensity of the resultant sound wave. We cannot hear sound waves directly; we can only perceive their intensity. What is the main difference between the amplitude of the sound wave and the sound intensity?

Absolute silence cannot be negative. This means in mathematical terms that the sound intensity must be greater than or equal to zero. The sound intensity I is proportional to the square of the amplitude of the sound wave. As a result of squaring, the intensity is always greater than or equal to zero.

The radius of the spinning wheel, or the amplitude, thus corresponds to the root of the sound intensity.

Our brains perceive the rapid fluctuations in pressure and density, that have been generated by the tuning fork and arrive at our ears, not individually, but as a time-averaged pitch. Hence, calculating the sound intensity involves additional temporal averaging.