Noise control measures from acoustic principles
Sound absorption
Noise in the limited space of a car consists of both direct sound level meter and reflected noise. Sound absorption is the use of special passive materials to change the direction of sound waves in order to absorb their energy. Reasonable arrangement of sound-absorbing materials can effectively reduce the amount of sound energy reflection, to achieve the purpose of sound absorption and noise reduction. Commonly used sound-absorbing materials due to environmental protection, waterproofing, fire prevention, lightweight and other conditions, can be used for automotive sound-absorbing materials are relatively rare, calm sound insulation sound-absorbing cotton is the R & D staff in the research and analysis of the noise characteristics of a number of car models on the basis of the characteristics of the noise of automotive noise creatively developed profiled sound-absorbing groove design, in the traditional a unit of the soundproofing area is integrated into a sound-absorbing area of more than 2 times each sound-absorbing groove The width, depth, slope and curvature of each sound-absorbing slot are simulated and determined by mathematical algorithms for the characteristics of car noise. Due to the gradual transition nature of the sound-absorbing layer, the acoustic impedance of the material and the acoustic impedance of the air can be better matched, so that a wider band of sound waves can be efficiently absorbed.
Vibration damping
The shell of the car is generally made of sheet metal, the vehicle driving process, the vibration of the source of the vibration transmitted to the car body, in the form of elastic wave propagation in the car body, these sheet vibration will produce noise, while causing the vibration of the other parts of the car body, these parts and the radiation of noise to the outside, the propagation of the pathway to install the elastic materials or components, isolation or attenuation of vibration propagation, it can be achieved vibration damping The purpose of noise reduction can be achieved. Available damping measures are mainly vibration isolation and damping, calm car damping protection rubber is based on the principle of damping research and development. In addition, calm sound-absorbing cotton in the pasting process using manual brushing way, special adhesive in the curing will have good elasticity and flexibility, the formation of a layer of damping damping, can withstand the impact and vibration of the car body.
Sealing
A large number of tests have shown that: the control of the overall noise inside the car is closely related to the sealing performance of the car body. Good sealing can effectively reduce the overall noise of the vehicle, especially for high-speed driving in the process of wind noise has a very good inhibition effect. Vehicle travelling in the process of generating turbulence is to cause the root cause of wind noise - vehicle driving at high speed in the process of a certain part of the body there will be periodic airflow separation, vortex dragged out from the sides of the body, moving in the direction of the airflow, thus generating noise. The way to prevent this noise is to avoid airflow separation as much as possible and to disrupt the periodic wake flow with appropriate methods. General sealing is only the use of sealing to improve the noise outside, calm professional seals in the noise blocking at the same time, will avoid airflow separation and the periodic tail flow to achieve disruption, fundamentally reduce wind noise.
