Mark, what you're talking about is called a sound level meter.  As an
audiologist, I've worked on this problem for years.  You can get a very
expensive ine that can be attached to a serial device but what you have to
remember is that if the meter makes any sound it destroys the very measures that
you are trying to make.  This is even true using headphones if you are trying to
measure low spl levels.

Tom


Tom Brennan  KD5VIJ, CCC-A/SLP
web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html