By default, audio power saving is turned off by most drivers. It can be enabled by setting the power_save parameter to a time (in seconds) to go in idle.
options snd_hda_intel power_save=1
options snd_ac97_codec power_save=1
Disabling NMI watchdog
The NMI watchdog is a debugging feature to catch hardware hangs and cause a kernel panic. On some systems it can generate a lot of interrupts, causing a noticeable increase in power usage.
kernel.nmi_watchdog = 0
nmi_watchdog as a kernel parameter.