Interference of Sound – Beat

We have now struck two tuning forks that vibrate at minimally different frequencies. What we hear are so-called beats. In other words, we perceive fluctuations in the volume of the resulting sound wave along the time axis.

What has happened due to the sound waves of the two tuning forks interfering? Initially, the first and the second sound wave had different frequencies, but their amplitudes and phases were equal. When we combine the two spinning wheels, it becomes apparent that the different rotation frequencies of the wheels result in an increasing phase difference over time. This causes the periodic volume fluctuations, or beats.

That’s exactly the effect we have observed at Omega’s doorbell: when tones with very similar frequencies are superimposed, the result is a beat. It is clearly audible as a variation in volume of the echoing sound.