GKrellMSS displays a VU meter showing left and right channel audio
levels and also has a chart that shows combined left and right
audio channels as an oscilloscope trace.

There are two buttons to the left of the VU Meter which select an
oscope horizontal sweep speed ranging from 100 microseconds (usec)
per division to 50 miliseconds (msec) per division. There are 5
horizontal divisions, so a trace sweep time can range from 500 usec
(1/2000 sec) to 250 msec (1/4 sec). The oscope trace is triggered
by a positive zero crossing audio signal to give nice stable
displays.

There is also a sensitivity level adjustment for the VU Meter and
oscope chart. Use the mouse wheel to adjust, or left click and drag
the sensitivity krell.

Author: Bill Wilson <bill@gkrellm.net>
WWW: http://web.wt.net/~billw/gkrellmss/gkrellmss.html