Andrew wrote:

I am hoping that someone could help in finding voice activation switch IC.

I did find one or two very old references to a Motorola MC2830P, but have a
feeling that it is discontinued as I was unable to find any information on
the Motorola site.

I have found a few circuits on the web, but was hoping someone here might
have used something that they would recommend. Something with a low
parts count, and might work with an inexpensive computer microphone or
a headset microphone meant for hands free telephone conversations.

It only needs to be momentary on. Some sort of gain adjustment or
background filtering would be valuable.

any leads?

thanks
andy

Ramsey electronics has a voice operated switch kit:
http://www.ramseyelectronics.com/

It is not a low parts count, but it's relatively cheap and might
be an option for you.