Filtering

A filter is a device for eliminating selected frequencies from the soundspectrum, and in some cases to emphasize the level of other frequencies.

Lowpass filter: Removes frequencies above its cutoff frequency

Highpass filter: Removes frequencies below its cutoff frequency

Bandpass filter: Only allows frequencies to pass through above and below a specified range

Notch filter: Allows frequencies to pass between specified ranges ( = Band-Reject filter )