Maestro's tuning fork
From Tardis Wiki, the free Doctor Who reference
Maestro's Tuning Fork is a tool used by Maestro in The Devil's Chord.
Maestro's tuning fork was used by Maestro in The Devil's Chord to locate the Doctor and Ruby Sunday when the Doctor used his sonic to cancel out all sounds. See the Manual of style and Layout guide if you have questions.
Uses
Maestro uses their tuning fork when The Doctor emits a sonic sound using his sonic screwdriver to find him. They find him by putting the resonating tuning fork in a nearby puddle, drowning out and cancelling the sonic noise, making the Doctor and Ruby findable
