noun
operating sound; running noise
Refers to the sound produced by a machine, device, or system while it is running or functioning.
新しい冷蔵庫は作動音がとても静かだ。
The new refrigerator's operating sound is very quiet.
エアコンの作動音が気になって眠れない。
The running noise of the air conditioner bothers me and I can't sleep.
Compound of 作動 (operation, functioning) and 音 (sound).