Audio quality of recorded messages is very poor and has a high frequency sound in the background.

Go into Settings -> General and check 'Apply Audio High Pass Filter', then
experiment with different values to see what gives the best result.

If you use a CURL telephony card, the input volume may be set too high
By default it is set to 8.
Click start -> All programs -> Easy Tapi -> Line detector
Then click Settings -> Volume Settings and select the channel you are recording from.
Change the Input volume from 8 down to a lower level. 0 works Good.
This will reduce the background noise and stop the high frequency.

Volver a IVM, Contestador telefónico