FunctionalityExpanders, which are often used with microphones or any source with noise in the background, increase the dynamic range of a signal by lowering the noise floor.
Expanders complement Compressors by increasing (expanding) the dynamic range of the signal. For example, a compressed input dynamic range of 70 dB might pass through an Expander and exit with a new expanded dynamic range of 110 dB. Unlike a Compressor, the Expander reduces gain for signals below the threshold. The ratio still defines output change verses input change. For example, with a ratio of 2:1, for every 10 dB of reduction in input signal, the output is reduced by 20 dB. Operating in this manner, Expanders make the quiet parts quieter. The term downward expander (or downward expansion) evolved to describe this type of application.
The most common use of an Expander is noise reduction. For example, suppose an expander’s threshold level is set just below the quietest vocal level and the ratio control is set for 2:1. In this scenario, when the vocal stops, the signal level drops down to the noise floor. If the noise floor is 10 dB below the threshold, the expander turns the level down an additional 10 dB (due to the 2:1 ratio, a 10 dB decrease becomes a 20 dB decrease), thus resulting in a noise floor improvement of 10 dB.
tip: The Expander is preferred over the Gate in applications requiring a smoother, more transparent response as the noise level decreases and increases.
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