Why is that when the hammer hits only one string on the piano, there is an oscillation and not a solid note throughout. I hear it like a wave of sound, not an absolute pitch. It doesn’t happen on other keys but very noticeable on the D# and E one octave about middle C. Piano tuner calls this phenomenon having “beats” on a single note? He can’t figure out the reason. It happens on some of the keys, even though all strings and parts are new after being entirely rebuilt last year.
Beats are a phenomenon that occurs when two sounds of frequencies that are a little different(out of tune) but not too different are played at the same time. This occurs due to the interference of the waves. Pianos usually have three strings per note and one of these strings being out of tune could cause this effect.