The sound of a machine designed to produce mechanical energy. Combustion engines burn a fuel to create heat, which then creates a force. Electric motors convert electrical energy into mechanical motion. Other classes of engines include pneumatic motors and clockwork motors.
The sound of a simple instrument usually consisting of metal cast in the shape of a hollow cup, whose sides form a resonator which vibrates in a single tone upon being struck by a "clapper" suspended within, or by a separate mallet or hammer.