An air cleaner for an internal combustion engine is arranged to reduce intake noise. The air cleaner includes an air cleaner element for cleaning an intake air, and an elastic member for reducing intake noise by utilizing an inside space of the air cleaner. An inside space of the elastic member is in communication with the inside space of the air cleaner through a communication passage. Preferably, a surrounding space formed between the elastic member and a case portion for receiving the elastic member is opened to the outside.

Intake sound reduction device for internal combustion engine includes an elastic member formed into substantially cylindrical shape and having an open base end, a top end sealed by an end surface wall and a bellows circumferential wall; a base plate retaining base end of elastic member; and a communication pipe whose one end is connected to base plate so that a volume chamber formed inside elastic member communicates with an intake passage of the engine. Intake sound reduction device has first resonance system formed by expansion and contraction in axial direction of elastic member and second resonance system formed by film-vibration of end surface wall. When either one of resonance frequencies of the first and second resonance systems is primary resonance frequency and the other is secondary resonance frequency, the primary resonance frequency is set to 30200 Hz and the secondary resonance frequency is set to 50300 Hz.

An air cleaner for an internal combustion engine is arranged to reduce intake noise. The air cleaner includes an air cleaner element for cleaning an intake air, and an elastic member for reducing intake noise by utilizing an inside space of the air cleaner. An inside space of the elastic member is in communication with the inside space of the air cleaner through a communication passage. Preferably, a surrounding space formed between the elastic member and a case portion for receiving the elastic member is opened to the outside.

Intake sound reduction device for internal combustion engine includes an elastic member formed into substantially cylindrical shape and having an open base end, a top end sealed by an end surface wall and a bellows circumferential wall; a base plate retaining base end of elastic member; and a communication pipe whose one end is connected to base plate so that a volume chamber formed inside elastic member communicates with an intake passage of the engine. Intake sound reduction device has first resonance system formed by expansion and contraction in axial direction of elastic member and second resonance system formed by film-vibration of end surface wall. When either one of resonance frequencies of the first and second resonance systems is primary resonance frequency and the other is secondary resonance frequency, the primary resonance frequency is set to 30200 Hz and the secondary resonance frequency is set to 50300 Hz.