Endless Whisper is a Chrome extension that plays an inaudible tone to keep the sound card awake.
I made this in order to fix an obscure bug that occurs when my Chromebook is connected to an external monitor with analog audio out. When I visit a website with audio, I hear a loud pop as the sound turns on, followed by another pop several seconds after the audio stops.
With this extension running in the background, Wham! problem solved. Technically, the whisper is not completely endless, as it disables itself when the system is locked or idle for 10 minutes.
https://chrome.google.com/webstore/detail/endless-whisper/kelacednepiemffffghpohmbkcohcimp