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First, the generation of noise in the car:
The noise in the vehicle is mainly caused by the noise (engine noise) of mechanical components such as the engine, the friction noise (road noise) between the tire and the ground, the collision and friction noise (wind noise) caused by the car breaking through the air curtain, and the external environment. The sound (such as the sound of a large container truck whistling past.), internal noise caused by the vibration of cockpit interior panels, and other components.
The noise inside the car is mainly low-frequency noise (250hz -- 500hz). Its penetrating power is very strong and it is also a difficult part of acoustic noise technology. The way the company finds the most effective way to deal with internal noise is through experiments. The sound-absorbing board is loaded with a sound-absorbing groove to buffer and absorb the noise energy so as to achieve the best sound-absorbing and noise-reducing effect.
Surveys show that motor vehicle noise accounts for 85.5% of urban traffic noise. The spread of vehicle noise is closely related to the number of roads and the size of traffic measurement. In cities with narrow passageways and high-rise buildings on both sides, noise is reflected back and forth, making it even more noisy. The same source of noise is more open on the streets, which sounds 5-10 dB more. In motor vehicles, the noise of heavy vehicles such as trucks and buses is 89-92 decibels, while the noise of light vehicles such as cars and jeep is about 82-85 decibels. There is also a large relationship between the speed of the car and the size of the noise. The faster the vehicle speed, the greater the noise, the speed increase by 1 time, and the increase of noise by 6-10 dB.
Second, the source of noise:
★ Chassis: a. The car floor sound insulation material is not good, easy to transmit road noise to the cockpit. Many mid- and low-end car chassis are equipped with only a few shock-absorbing rubber sheets and a small amount of sound-absorbing blankets. b. Suspension system is poorly assembled, loose, or parts aging failure, can not effectively reduce the vibration. c. The vehicle sheet metal process and the use of sheet metal thickness are not enough.
★ Tires: a. The friction sound between the tire and the ground during driving is transferred from the wheel arch to the cockpit. b. Vibration noise due to uneven road surface is transferred to the cockpit.
★ Posts: a. Due to poor assembly or resonance with the car body. b. The cracks in the post cause wind noise at high speeds. c. The interior cavity of the post causes resonance with the body.
★ Engine: a. The noise and vibration of the engine running into the cockpit by the firewall. b. Under the instrument panel, the wall noise from the cockpit is introduced by the firewall.
★ Roof: The top sheet metal is too thin, causing resonance with the body.
★Assembly: Various noises caused by poor assembly or design, such as common screw loosening and damping rubber mat aging.