One of the artifacts in Artie's bag, this tuning fork is capable of restoring a person's hearing, as long as its user covers their eyes, taps the tuning fork, and then places the fork behind their head.
Tuning Fork

Artie using the Tuning Fork

The person having their eyes closed when it is used is apparently a safety measure.

Artie used it to restore Pete and Myka's hearing after they were rendered deaf by the Goblet of Severan.