A silencer, also known as a sound suppressor, suppressor, or sound moderator, is a muzzle device that reduces the acoustic intensity of the muzzle report and muzzle rise when a gun is discharged, by modulating the speed and pressure of the propellant gas from the muzzle and hence suppressing the muzzle blast. weaponsandarms.net

Effectiveness
Suppressors installed on the muzzles of firearms can consistently provide approximately 25 dB of attenuation for 100 percent of the shots fired (see sources). Using a firearm suppressor will reduce the risk of acquiring noise-induced hearing loss, but not eliminate it