[pianotech] False Beats and Changing Beat Rates

Albert Picknell pnrfqsnrk at yahoo.ca
Thu Feb 3 18:27:00 MST 2011


Hi List

Okay, so I'm tuning a single treble string that has a false beat, let's say E6 (the other two strings of that note are muted off).  I play the E6 with C4 a major 17th below, and listen to the beat.  The beat starts off very rapid, but gradually slows down as the notes decay.  Is anyone aware of any explanation that has been given for this phenomenon?  I assume the phenomenon has something to do with the presence of false beats, because I only hear it when false beats are present.

I can think of several possible explanations:

#1. The false-beating string is actually dropping in pitch as the tone decays.

#2. The strings of the lower note (in this case C4) are actually rising in pitch as the tone decays, whereas the upper string with the false beat does not rise in pitch.  I doubt this is the correct answer, because the slowing of the beat rate occurs during a portion of the tonal envelope during which an ETD does not show the lower note rising in pitch.

#3. The slower beat rate heard after a period of decay (when the false beat seems to have faded somewhat) is the true beat rate.  During the earlier phase of the tonal envelope, when the false beats are more prevalent, some interference pattern is happening that causes the beat rate to sound faster than it really is.

#4. I can't think of a #4.

Cheers,
Bert




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