Can't record audio without also playing it

The new recording options are very cool. Setting display_screen to False, and record_screen_dir, it's possible to record the video without watching it.

The same does not seem to be possible with sound though. If you don't set sound to True, 'record_sound_filename' doesn't save the sound. It'd be good if that'd be possible. (Not sure if this is a bug or an enhancement. It's inconsistent with the behaviour of video)