Feb 2001 update:
  There is a new module on cpan that does lots of stuff with voice modems
  using perl.   Currently looks like unix only, but there was mention
  of a windows effort also:

     http://search.cpan.org/search?mode=module&query=ivrs

  Here is a unix program that can be used to create raw voice modem files:

     http://home.sprynet.com/~cbagwell/sox.html

-------------
Got this from Brian Klier

MNBryGuy: AT#SPK=<mute>,<spkr>,<mic> 

The #SPK command can be used to control the microphone state (mute or on),
 adjust the speaker volume, and microphone gain. The #SPK parameters are are valid only
 after the modem has entered the Voice Online (VCON) mode while in the #VLS=6 setting 
(after a VCON during originate or answer). The modem will respond "ERROR" otherwise. 

Parameters: 

<mute> Mute Parameter Number 

0 microphone mute 

1 microphone on (default) 

2 Room Monitor mode (mic on max AGC, speaker off) 

<spkr> Speaker Output Attentuation 

Range: 0 to15 (speaker attenuation in 2 dB steps) 

0 0 dB attneuation 

. 

5 10 dB attenuation (default) 

. 

15 30 dB attentuation 

16 Speaker mute 

<mic> Microphone Gain Parameter 

Range: 0 to 3 

0 0 dB 

1 6 dB gain (default) 

2 9.5 dB gain 

3 12 dB gain 

