Sound system is eating away the battery

I added the following to /etc/rc.local

echo 1 | tee /sys/module/snd_hda_intel/parameters/power_save

echo Y | tee /sys/module/snd_hda_intel/parameters/power_save_controller

pkill pulseaudio

pulseaudio --start 

exit 0

And it seems to have done the trick...

Either the sound driver doesn't support power management or it's not enabled. I've no idea what IDT is, but you can enable power management, for example, for an Intel sound device. The older versions of PowerTop used to suggest it, but the newer one has a menu you can navigate with left/right arrow key - Tunables is the entry you want. Try navigating to that entry and see if there is anything related to the sound card that powertop can tune.