[RTTY] checking the soundcard??

[Doug Faunt N6TQS +1-510-655-8604]

The audio output from my laptop has an audible artifact of some sort
in the left channel.  I can't really describe it to the servicing
people, and they won't repair it unless I can tell them what's wrong.

Is there any sort of soundcard program that I could run, with the
output patched into the mic input (no line input) that would do a
loopback test of the sound system?  If I can show a distinct
difference between the two output channels, it would make life simpler.
I actually worry that it might affect the transmitted audio.

Or alternatively, a pair of programs so that I could check one
computer against another?

73, doug