A device or component that reduces sound. Depending on context, it can refer to a car's muffler, a piano damper pedal, or a gun silencer (suppressor).
車の消音器が壊れて、走ると排気音が大きくなった。
The car's muffler broke, and the exhaust noise became loud when driving.
ピアノの消音器を踏むと、音が柔らかくなる。
Pressing the piano's damper pedal softens the sound.
多くの国で銃の消音器は規制の対象になっている。
In many countries, gun silencers are subject to regulation.