I did some tests with mod_vmd this afternoon, but I'm only finding about 33% of the voice mail beeps and did have 1 false-positive in my test of 7 voice mail machines. I've recorded the audio of the session in .wav files that were both successful and not, as a comparison. I can upload the .wav files if they would be useful.

mod_vmd works great for voicemails of Skype Users, and kall8.com, but has issues dealing with mobile phone carriers.

sprint - not successful

tmobile - not successful

verizon - not successful

panasonic home answering machine system - not successful

kall8 - SUCCESS

skype - SUCCESS

I'm wondering if you can recommend a simple fix, like changing some of the constants like MAX_FREQ, or MIN_TIME at the top of the mod_vmd.c source file, or if better success requires more complex analysis.  Do you have any recommendations on how this might be done? Listening to the .wav's its apparent the beeps are not as loud for the mobile phone carriers as they are with skype and kall8. Any guidance would be greatly appreciated.