Klarinet Archive - Posting 000587.txt from 1997/03

From: Luuk van Buul <vanbuul@-----.COM>
Subj: Re: Acoustic effects
Date: Tue, 18 Mar 1997 02:36:55 -0500

>
> Gary Young wrote:
>
> >>... The fan imparted
> >>a strange slow vibrato-like effect to the clarinet sound. (I don't
> >>understand the acoustics of this.) At first I was irritated, but then I
> >>realized this was the sort of thing Cage would have loved, and really got
> >>into the sound.
> >
>
> If you pivot around quickly while playing (preferably a note with lots of
> fingers down like low E or B above middle C) you can get the same effect.
> Walking quickly will also produce this effect. I believe it is because the
> different overtones in the clarinet sound are being doppler shifted (each
> overtone shifted differently according to its frequency) and they go out of
> tune with each other. Effectively the tones that make up the clarinet sound
> "split up". I love this effect.
>
> Jerry Korten
> NYC
>
When a 'steady' sound is produced in a room, points where large or small
amplitudes build up are more or less randomly distributed in space. The exact
locations of these points are dependent on the frequencies present in the sound
spectrum and the lay-out of the room including furniture, people etc.
In his book 'Fundamentals of Musical Acoustics' A.H.Benade explains that this
pattern shifts unpredictably when moving anything around in the room bigger than
about 30cm. It is not important whether this moving around is done by the
sound source itself, other people in the room or a wind fan (if big enough).

So the described effect is most likely due to changing acoustical 'eigenstates'
of the room you're playing in.

Luuk van Buul
--
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L.J.M. van Buul vanbuul@-----.com
Philips Research Waalre Philips Optoelectronics
Prof.Holstlaan 4
5656 AA Eindhoven Tel. +31 40 2744649
The Netherlands Fax. +31 40 2744335
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