What are some alternatives?
When comparing Noise Blocker and Audacity, you can also consider the following products
Krisp - Mute the background noise during your calls
Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.
NoiseGator - A simple noise gate app intended for use with VOIPs like Skype.
LMMS - Make music with a free, cross-platform tool
SoliCall Pro - Removes noise & echo from any VoIP call. Can also be used for call recording.
Ardour - Record, edit, and mix on Linux, Mac OS X, and Windows.