Dell XPS, experienced on both 15.10 and 16.04. When system sounds play, there is often “crackling” noise around the sound. Video and music playback are okay.
Sound played over USB does not have this problem.
This is due to power management turning on and off the sound card as needed, and not being quite fast enough.
Not sure of the fix for 15.10, but for 16.04:
# Enable audio power saving for Intel HDA, AC97 devices (timeout in secs). # A value of 0 disables, >=1 enables power save. SOUND_POWER_SAVE_ON_AC=0 SOUND_POWER_SAVE_ON_BAT=0 # Disable controller too (HDA only): Y/N SOUND_POWER_SAVE_CONTROLLER=Y
POWER_SAVE values to 0, as in the example above.
$ sudo tlp start
Now your sound works as it should!