How to use a Unix PC as a Vocal Monitor

If you have a computer running on Linux or BSD, a microphone connected to it, and a desire not to spend $50 on a very small amplifier, you can use a one line shell script to listen to yourself sing instead.

Listening to yourself through a vocal monitor gives a better indication of the pitch and timbre of your voice than just listening to yourself, as the sound reaching your ears from your mouth is affected by resonating through your head, like listening to someone talk through a bone wall covered by a wet blanket. A monitor will therefore be a more accurate reproduction of what you sound like to everyone else than "directly" listening to your own voice.

WARNING: Make sure you are using earbuds or extremely well enclosed headphones, NOT speakers, so you won't get feedback from the microphone picking up the output. Feedback squeals can quickly ramp up in volume and cause permanent damage to your hearing.

Once you have made sure that all speakers are disconnected, the following PulseAudio command will send the microphone input to the audio output:

$ pacat -r --latency-msec=50 | pacat -p --latency-msec=50

This command requires PulseAudio, but similar ones are available for Jack/ALSA/OSS e.g. the "alsaloop" command.

When done, press ctrl-C in the terminal to stop it.