White noise occurs if the registry setting values for Automatic Gain Control (AGC) are set incorrectly.
These are usually the bad values:
AGCsamplesize is 4e20 hex (20000 decimal) and should be 1f40 hex (8000 decimal).
AGCgainthreshold is 28 hex (40 decimal) and should be 5 hex (5 decimal).
This problem can be eliminated by changing the registry settings to the correct values, as described in the Automatic Gain Control Registry Keys table. This is found in the Automatic Gain Control section of Audio Quality.
Cisco Unity needs to be rebooted to get the registry changes to work.