To record a simple WAV sample from the microphone and save it to a file called `hello.wav’, install sox and type:
$ rec hello.wav
this command begins an 8,000 Hz, monaural 8-bit WAV recording to the file `hello.wav’, and keeps recording until you interrupt it with C-c.
While the default is to make a low-fidelity recording — 8,000 Hz, monaural 8-bit samples — you can specify that a high-fidelity recording be made.
(But remember that high-fidelity recordings take up much more disk space.)
To make a stereo recording, use the `-c’ option to specify the number of channels, giving 2 as the argument. To make a 16-bit recording, give `w’ (“wide”) as the argument to the `-s’ (“sample size”) option.
Set the recording sample rate by giving the samples per second to use as an argument to the `-r’ option. For CD-quality audio at 44,100Hz, use `-r 44100′.
Finally, to record a file in a particular format, either give the name of the format as an argument to the `-f’ option, or use the traditional file name extension for that format in the output file name (see Sound File Formats).
To make a high-fidelity recording from the microphone and save it to a WAV-format file called `goodbye.wav’, type:
$ rec -s w -c 2 -r 44100 goodbye.wav
(From DSL cookbook)