My little desk-computer has a pretty dirty audio path. I can turn up the audio to hear the chirps of the power regulators over the speakers; when the CPU is leaning on the PSU. Even just keystrokes in my editor cause a flurry of chirps as the clock-rate is increased and the systems races to idle within a few milliseconds.

When a process stalls I would already know whether it's IO or computation. Depending on the chirping I may reach for either ping or top to investigate further. Sometimes I leave these chirps on for hours. It's nonintrusive feedback to me about background tasks and when they clear.

I actually worry that my next machine will not have this flaw. And now I'm thinking of a syscall-chirp generator to get an even better feel for the pulse of the machine :-)