Source:getEffect
Gets the filter settings associated to a specific effect.

This function returns nil if the effect was applied with no filter settings associated to it.
filtersettings = Source:getEffect( name, filtersettings )
name string The name of the effect.
filtersettings ({}) table An optional empty table that will be filled with the filter settings.
filtersettings table The settings for the filter associated to this effect, or nil if the effect is not present in this Source or has no filter associated. The table has the following fields:
filtersettings.volume number The overall volume of the audio.
filtersettings.highgain number Volume of high-frequency audio. Only applies to low-pass and band-pass filters.
filtersettings.lowgain number Volume of low-frequency audio. Only applies to high-pass and band-pass filters.