Source: voip-tech.blogspot.com

SoliCall is a small free application that integrate itself with your favourite VoIP software and, while we’re speaking, by some particular audio filters, it reduce or eliminate unwanted background noises that could be sensed by the microphone or by another audio input used for making VoIP calls.
This software is very easy to configure, you just need to specify the audio source used for VoIP calls, SoliCall will filter the audio and "purify it" from possible background noises, rustles, etc.
The main setting to execute in your VoIP software, Skype, MSN Messenger, and others softwares that allow the vocal communication, will be to specify in the audio setting option window the device "SoliCall Audio Device", like as you have another audio card installed into your computer.
Free download available at this link.