muffler

Short definition from Wiktionary

Noun

1. 1
   Something or someone that muffles: A part of the exhaust pipe of a car that dampens the noise the engine produces.
2. 2
   Something or someone that muffles: An accessory for a firearm that lessens the noise at the muzzle.
3. 3
   Something or someone that muffles: A type of scarf.
4. 4
   Something or someone that muffles: A gas mask.