This is known as the "Doppler Effect" or "Doppler Shift".  Look it up in the
encyclopedia or
a fundamental of physics textbook.

Think of when a fire engine drives by, recall how it seems to have a higher
pitch when approaching then a lower pitch after it passes and is going away.

-Dave





"M. Adam Davis" <adavis@UBASICS.COM> on 04/07/2000 07:43:06 AM

Please respond to pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>

To:   PICLIST@MITVMA.MIT.EDU
cc:    (bcc: David E Arnold/SYBASE)
Subject:  Re: Headphones changing pitch automagically [OT]




Well, the act of moving the headphones away from you would cause a drop in
pitch, but it would normallize once the headphones stopped moving away from
you.  The pitch would rise while you bring the headphones towards you, but again
the pitch would normalize when they stopped moving (relative to your head).
The faster you move them, the higher (or lower) the pitch goes.

If the change does not follow this description, then you might be looking at the
inability for the headphones to send higher pitched notes very far, so they
become less-audible the further the headphones are away from you.  This would
make the spectrum of the music sound lower, and you might percieve that the
pitches shifted instead of the top ones disappearing.

Or your psycho.  Perhaps to gov't is beaming info into your head to make you
crazy.  You should try wearing an aluminum helmet (except in thunderstorms!).

-Adam

I respect faith, but doubt is what gives you an education. -- Wilson Mizner

Rich Leggitt wrote:
>
> So I'm building this MP3 player, and I'm listening to the music through
> headphones.
>
> Then I take the headphones off and hold them away so that I can still
> faintly hear the music. And the strangest thing -- there's a very dramatic
> drop in apparent musical pitch. I put the headphones back on, and the
> pitch goes back up. I take them off again and the pitch goes down again.
>
> Now, I don't think the frequency is actually changing (unless perhaps the
> bulb in the refrigerator is also staying on.)
>
> But I'm wondering what's going on? Is this a known phenomenon, i.e. large
> changes in apparent amplitude and/or apparent bandwidth translated by some
> psycho-acoustic process into changes in apparent frequency?
>
> Or perhaps I AM the psycho in 'psycho-acoustic'? :)
>
> -- Rich