A muffler assembly, comprising a muffler unit, wherein the muffler unit comprises: a side plate, wherein the side plate comprises an upper side plate and a lower side plate which are oppositely arranged; and a partition plate, wherein the partition plate comprises a first partition plate, a second partition plate and a third partition plate, the first partition plate and the third partition plate are connected to the lower side plate, the second partition plate is connected to the upper side plate and arranged between the first partition plate and the third partition plate; wherein a first muffler channel is formed by enclosure of the first partition plate and the second partition plate, a second muffler channel is formed by enclosure of the first partition plate, the third partition plate and the lower side plate, and a third muffler channel is formed by enclosure of the second partition plate and the third partition plate, wherein the first muffler channel, the second muffler channel and the third muffler channel are sequentially in communication, and a cross-sectional area of the first muffler channel and a cross-sectional area of the third muffler channel are both less than a cross-sectional area of the second muffler channel, wherein at least one of the first partition plate, the second partition plate and the third partition plate is provided with a sound insulation plate, the sound insulation plate is arranged in the first muffler channel and/or the third muffler channel, wherein a surface of the second partition plate facing the first partition plate is provided with the sound insulation plate, and a surface of the third partition plate facing the second partition plate is provided with the sound insulation plate, characterized in that the sound insulation plate is rotatably connected to the second partition plate and the third partition plate, and the sound insulation plate is fixed with the second partition plate and the third partition plate in a position-limitation manner when rotating to a certain angle. a side plate, wherein the side plate comprises an upper side plate and a lower side plate which are oppositely arranged; and a partition plate, wherein the partition plate comprises a first partition plate, a second partition plate and a third partition plate, the first partition plate and the third partition plate are connected to the lower side plate, the second partition plate is connected to the upper side plate and arranged between the first partition plate and the third partition plate; wherein a first muffler channel is formed by enclosure of the first partition plate and the second partition plate, a second muffler channel is formed by enclosure of the first partition plate, the third partition plate and the lower side plate, and a third muffler channel is formed by enclosure of the second partition plate and the third partition plate, wherein the first muffler channel, the second muffler channel and the third muffler channel are sequentially in communication, and a cross-sectional area of the first muffler channel and a cross-sectional area of the third muffler channel are both less than a cross-sectional area of the second muffler channel, wherein at least one of the first partition plate, the second partition plate and the third partition plate is provided with a sound insulation plate, the sound insulation plate is arranged in the first muffler channel and/or the third muffler channel, wherein a surface of the second partition plate facing the first partition plate is provided with the sound insulation plate, and a surface of the third partition plate facing the second partition plate is provided with the sound insulation plate, characterized in that the sound insulation plate is rotatably connected to the second partition plate and the third partition plate, and the sound insulation plate is fixed with the second partition plate and the third partition plate in a position-limitation manner when rotating to a certain angle.