A deadening device is a tool used to reduce the intensity of sound or vibration. A 'muter' (5 letters) is a type of deadening device that is used to reduce the volume of sound, while a 'DAMPER' (6 letters) is a type of deadening device that is used to reduce the intensity of vibration. Both types of deadening devices are used in a variety of applications, such as soundproofing rooms, dampening the vibrations of musical instruments, and reducing noise pollution.