Looking sideways
Much of our field of vision is in the horizontal plane, so when a person looks sideways, they are either looking away from what is in front of them or looking towards something that has taken their interest.
A quick glance sideways can just be checking the source of a distraction to assess for threat or interest. It can also be done to show irritation ('I didn't appreciate that comment!').
Looking to the left can indicate a person recalling a sound. Looking to the right can indicate that they are imagining the sound. As with visual and other movements, this can be reversed and may need checking against known truth and fabrication.