Have you verified that you don't simply have a faulty aduio connection somewhere on the output side of the soundcard?
You are right. It's sort of a faulty speaker system and the power to the speaker systems was being ON/OFF cycled.
I have primary machine that is powered by a UPS and the speaker system is also powered by the UPS. If the machine goes on SLEEP mode, the power to the speaker system is automatically turned off. The problem audio was from my sub machine and was fed to this speaker system. Thus, if the primary machine goes to sleep, the speaker output was shut off. Then, if I press keyboard or mouse for the primary machine, the speaker out came alive.
Thank you very much for your suggestion.