What sound phenomenon would a piano tuner listen for in tuning the piano strings?
Beats! Beats are when two frequencies are similar, but not exact. If so, the listener can hear a definite increase and decrease in amplitude as the two frequencies interact constructively, then destructively. When the piano wire is adjusted such that the tones produce no beats, they are in tune. It’s kind of like hearing a “WaaaAAAaaaAAAaaaAAA” sort of noise. The spacing between the AAA’s and the aaa’s corresponds to the difference in frequencies.
