Re: Help: using mics as earphones

["Daniel J. Levitin" <levitin@xxxxxxxxxxxx>]

Daniel -

It is possible to use a microphone as a loudspeaker and vice - versa.  As
transducers, each of them is involved in the transformation of one kind of
energy to another.  The microphone's diaphragm responds to pressure in the
air by moving in and out and the in and out motion is converted to a
continuous analog voltage.  When the voltage is applied to a speaker, it
turns the electrical energy into a pattern of in and out motions that cause
vibrations in the air roughly analogous to those that caused the microphone
to vibrate in the first place.

The problem you might experience is that microphone diaphragms are very
sensitive (by necessity) and if you try to drive one "in reverse" it will
work, but only with very small input voltages -- if you try to make it too
loud you'll blow it up.  Microphones and loudspeakers are optimized in
their design (including factors such as damping) to do what they were
intended to do.  There are some commercial "dual purpose" devices that are
microphone and loudspeaker built in one, and Radio Shack used to sell
something like this.  If what you're looking for is a really tiny speaker,
though, I suggest you look at some of the products that were designed for
that purpose, such as those sold by Etymotic Research.

Dan Levitin


==============================================
Daniel J. Levitin, M.Sc., Ph.D.               Phone: (650) 842-6236
Interval Research Corp.                      FAX:     (650) 354-0872
1801C Page Mill Road                          email: levitin@interval.com
Palo Alto, CA  94304

Lecturer, Departments of Music, Psychology and Computer Science
Visiting Scholar, Center for Computer Research in Music and Acoustics
Stanford University, Stanford, CA  94305

Please note: After July 8 my email address will be levitin@ccrma.stanford.edu

Home Page: http://www-ccrma.stanford.edu/~levitin
================================================