Gong

A gong is made from a large flat metal disc shape when hit it produces a sound that is loud and a distinct. It is sometimes used for musical instruments and a signalling device in the Western world but in Tibet sound of gong summons monks into the prayer hall.

The Benefits of Gong Baths, Sound Baths, & Sound Healing
Reduced stress.
Relief from anxiety.
Better sleep (this is one of the most cited benefits!)
Released emotional blockages.
Better mood.
Improved focus.
Mental clarity.
Creative insights.