Re: A tuning fork sound effect....

["W. Barlow Newbolt" <wnewbolt@liberty.uc.wlu.edu>]

On Thu, 1 May 1997, von Philp wrote:

> A student of mine was messing around with my tuning forks and noticed the
> following interesting effect:
>
> > From a distance of about 5 cm from the ear, a tuning fork is slowly moved
> past the ear in a horizontal plane perpendicular to the ear canal.  When
> this is done, the sound appears to alternate loud and soft intensity every
> few centimeters the tuning fork is moved.
>
> First question:	Have any of you ever noticed this effect?  (If you haven't
> tried this, do so at your first opportunity!)
>
> Second question:  Why does the sound get louder and softer?  My first guess
> is constructive and destructive interference (as in a resonance tube). 
> However, I want to be sure that it is not simply caused by a more direct
> alignment of the sound down the ear canal.
>
> Any thoughts?
>
> -- Ralph von Philp
>
> P.S.	If this is a new effect, I shall call it the Newman effect, after the
> student (P. Tyler Newman) that first pointed it out to me.
This sounds like interference.  After all, you have two tines on the fork 
and each one may be considered a source of the acoustic wave.  So..we 
have interference. 

W. Barlow Newbolt              540-463-8881  (telephone)
108 Parmly Hall                540-463-8884  (fax)
Washington and Lee University  newbolt.w@fs.science.wlu.edu	
Lexington, Virginia 24450      wnewbolt@liberty.uc.wlu.edu

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