A diffuser is a component fitted over the exhaust outlet to break up the exhaled gas into bubbles small enough not to be seen above the surface the water, and make less noise (see acoustic signature). They are used in combat diving, to avoid detection by surface observers or by underwater hydrophones, Underwater mine disposal operations conducted by clearance divers, to make less noise, to reduce the risk of detonating acoustic mines, and in marine biology, to avoid disruption of fish behavior.