Two speakers next to each other oscillate in phase,one at 404 Hz and the other at 400 Hz.If you stand in front of them,you will hear a sound of frequency 402 Hz that fluctuates between loud and soft with a frequency of 4 Hz.

Question

Quizplus · Accepted Answer

This phenomenon is known as beats, which occurs when two sounds of slightly different frequencies are played together. The frequency of the beat is equal to the difference between the two frequencies, which in this case is 4 Hz. This creates the perception of a fluctuating loudness of the sound, but the average frequency heard is the average of the two original frequencies, which is 402 Hz.

Two Speakers Next to Each Other Oscillate in Phase,one at 404