"SoX is a power-packed command-line tool for various types of
audio processing. It's very useful as an audio format converter,
and it can be used for resampling audio files, converting between
endianness, audio encoding and modifying other attributes of common
audio file formats.
"Its main power, however, is its effect plugins. It can apply
various effects to audio in the same way a digital audio
workstation does. You can add echoes, filter frequencies, reduce or
increase volume, remove noise and do various other advanced digital
signal processing on sound samples..."