Intake noise includes the pulsating sound of the air taken in and the resonance sounds.
A pulsating sound has a relatively high frequency. It is determined by the air volume, shape of the air cleaner, and the diameter and length of the intake hose.
A resonance sound has a relatively low frequency. It is generated when the frequency of the intake noise and resonance frequency of the intake system coincide at a particular engine rpm.
Also, fluctuation of the intake air pressure sometimes emits radiated sounds from the outside surface of intake system component. Vibration in the intake system is also transmitted to the interior.
When the frequency of the intake noise coincides with the resonance frequency in the cabin or in the intake system, noise increases causing booming noise and engine noise. An intake resonator is commonly used to alter the resonance frequency in the intake system and thus reduce the booming noise and engine noise.
Air cleaner case
Rubber mounts are used in mounting the air cleaner housing to the body, which prevents the transmitting of intake noises to the vehicle body.
Exhaust System Vibration and Sounds
Exhaust noise includes the sound of the gas discharged from the muffler, and radiated sounds from the outside of the exhaust pipe and muffler.
The discharged sound can be reduced by the silencing characteristics of the muffler. But if the muffler capacity is not large enough, the engine power output will be affected. Radiated sound is caused by the vibration of the component walls due to the fluctuation of the exhaust pressure, which causes vibration in the ambient air.
Sometimes vibration in the exhaust system is also transmitted to the vehicle body and generates a transmitted sound.
Vehicle side solutions