psycho-acousti-what?

[Ed Sutton]

Hi Mark-
    Perhaps what you're hearing is related to the phenomenon called
"difference tones."  If two flutes or recorders play an interval of two
adjacent notes of the overtone series, you may also hear the fundamental
pitch of the series "out of nowhere."  It is probably a beat caused by the
interference of the two pitches, beating so rapidly that we hear it as a
tone.
    Once you hear it with flutes, it is hard not to hear it. It sounds like
a tone that is everywhere: in the air, in the ear, in your head, yet comes
from nowhere.  It can feel like a buzz in the ears.
    Sometimes you can hear difference tones on pianos, but it is generally
very faint.  Once in a while I have heard an especially clear difference
tone on a piano, don't know why.
    When I think of the percussive sound you are describing, and that it can
be pretty painful tuning unisons on such a piano (use earplugs!!!!), I
wonder if what you are hearing is an  percussive difference tone.
    Perhaps if you change the third to something a little more pure, the
sensation will change...this might be a diagnostic for difference tones.
You might also look for a damper problem at the difference tone pitch. I had
a piano where playing B4 and D#5 simultaneously would cause B2 to sound at
the fundamental.  Is this work, play or madness?
    Just guessing....
        Ed Sutton

----------
>From: Mark Cramer <cramer@BrandonU.CA>
>To: caut@ptg.org
>Subject: psycho-acousti-what?
>Date: Tue, Feb 13, 2001, 2:51 PM
>

> A year ago, a client told me she had several notes on her (Baldwin) console
> that physically hurt her ear when she played them.
>
> I tried the notes, which were the first few above the tenor/treble break,
> and noted they were a bit harsh, but thought (to myself) maybe she was
> exagerating a bit.
>
> I tried them as major thirds, which she had been playing, and nothing. Then
> I turned my head a bit in her direction, played them again, and "Ouch!" It
> was as though someone was pressing their finger between my upper jaw-bone
> and ear!
> Definitely painful!
>
> I remember trying every bit of "voicing voodoo" I know, to no avail. Indeed,
> I had forgotten about this til yesterday. A music teacher with a Baldwin (no
> I'm not picking on brands) 52" vertical, who never seemed pleased with the
> treble, said the magic words; "it hurts!"
>
> It's exactly the same phenomenon! At first listen, these hammers "sound"
> soft at the crown, but hard, very hard in the shoulders. The sound is a big
> muffled boom, but with little sustain.
>
> I went at C5 on the big upright with a single needle to probe the shoulder,
> certain I would fined hardener,.. but nothing. The shoulder felt is soft,
> much easeir to needle than a Renner, Yamaha, etc., even at the crown. I
> needled all over the place, and could not change the sensation of the tone
> one little bit!
>
> What is the problem?
>
> If you have experienced this, you will know exactly what I'm talking about,
> and I would sure love to hear from you. Yes, especially if you've been able
> to solve it.
>
> On my next visit, I'm taking a variety of hammers to test, but I'm not so
> sure hammers are the problem!?
>
> thanks, as always
>
> Mark Cramer,
> Brandon University
>