ABSTRACT
A graphic analogy can help one to understand why random noise never really goes away. Constant random noise, such as the hiss from recording at a bad level, would be equivalent to the dirty gray pattern. This noise is too random to remove with an equalizer or filter, since such a filter would also affect the dialog. But noise-reduction software, properly tuned, can tell the difference between a desirable object and its background. It lowers the volume when dialog stops. The graphic equivalent to this would be partially erasing the noise surrounding the recorder. Most current pop music is too broadband for noise reduction software to do an effective job. Other forms of complex music that have some dynamics and spectral movement may benefit from noise reduction, depending on the recording. The actual amount of masking varies with the frequency, volume, and overall timbre of both sounds, but it's always there to some degree.
