Understanding the purpose of noise gate software starts with understanding the concept of a noise gate in the first place. You can think of it as the opposite of a compressor - where a compressor cancels out the audio signal above a certain "threshold" level, a noise gate cancels the signal out if it's below a predetermined level. When used together, they can confine the sound to a sort of "range tunnel." On its own, noise gate software has a variety of uses, such as reducing the static and noise from intermittent audio sources in the mix. The level of attenuation is adjustable, and many noise gates will also allow you to change their attack and release settings to soften the effect when they open and close.
The hissing of cassette tapes and the rumbling of vinyl records are just two examples of unwanted sounds that noise gates can eliminate, which makes them valuable tools for digitizing music from older analog recordings. Noise gates can also be used in tandem with band-pass filters to skim background noise out of music and voice recordings. And of course, anything noise gate hardware can do, noise gate software can do digitally. If you use a SONAR X2 Producer system, then the Cakewalk PC4K S-Type Expander / Gate Module is a good suggestion to start with; since it also includes an expander, it's essentially two tools in one. For other applications that support open plug-in architectures, try the Wave Arts MR Gate Software Download on for size.
Any one of the noise gate software options in this section could be the right choice for you, and since the decision can come down to personal preference, it's up to you to determine which one that will be. The good news is that you shouldn't have trouble doing so - just narrow down the field based on platform support and features, and soon enough you'll have figured out the best noise gate to suit the unique needs of your digital workspace.