muffler vs acoustic device

muffler and acoustic device both are nouns.

Word	Noun	Adjective	Verb	Adverb
muffler	Yes	No	No	No
acoustic device	Yes	No	No	No

As nouns, acoustic device is a hypernym of muffler; that is, acoustic device is a word with a broader meaning than muffler:

muffler: a tubular acoustic device inserted in the exhaust system that is designed to reduce noise
acoustic device: a device for amplifying or transmitting sound

muffler (noun)	acoustic device (noun)
a scarf worn around the neck	a device for amplifying or transmitting sound
a tubular acoustic device inserted in the exhaust system that is designed to reduce noise
a device that decreases the amplitude of electronic, mechanical, acoustical, or aerodynamic oscillations