jack_delay is a small command line JACK app you can use to measure the
latency of your sound card. It uses a phase measurements on a set of
tones to measure the delay from the output to the input. Accuracy is
about 1/1000 of a sample.
Definitely read the docs in /usr/doc/jack_delay-$VERSION/README to
understand how to use this.
This requires: jack-audio-connection-kit
Maintained by: B. Watson
(the SlackBuild does not include the source)