Sure-Fire Tips for Encoding High-Quality, Low-Bandwidth Audio, Part 2

Filter Types and Additional Resources

All audio editors have a handful of filters in common. What follows are some of the most common filters and an explanation of what they do.

Highpass/Lowpass: Apply highpass or lowpass filtering to get rid of certain frequencies. A highpass filter will pass all high frequencies above a predetermined setting and cut off the rest. A lowpass filter will pass all low frequencies below a predetermined setting and cut off the rest.
Notch Hum: Notch filtering is useful for taking out a frequency range, such as a 60Hz hum associated with electrical line interference.
Compressor: A compressor is useful for averaging out audio levels so quiet passages can be heard and louder segments can be reduced in volume.
Noise Gate: A noise gate is useful for suppressing noise during pauses in speech or music.
Parametric Equalization: A parametric equalizer is useful for changing the parameters of sound. It gives the user control over changes in frequency, gain and Q (the width of the band the equalizer is working on).
Chorus: Chorus algorithms can be useful for creating multiple versions of a voice track so it sounds like more than one person is talking or singing at one time.
Flanger: To create a flange effect, two copies of one signal are made. One is delayed slightly in time and, when you put the two together again, some frequencies cancel and some frequencies reinforce and you get the swishing sound associated with flanging.
Multitap delay: This effect is commonly used to simulate the natural acoustics in a room. By delaying a clap sound at various intervals, for example, you can simulate a natural setting whereby the clap is heard bouncing off each of the walls in a room.
Reverb: A reverb filter takes a sound, holds it in the gate for a (user specified) beat, and releases it.