In the ordinary life, because of the noise, noise, noise and other kinds of noise together, the car is not quiet in the car, there is a irritable noise. However, there are also some friends who have questioned the effect of the sound insulation after upgrading the car, and think that the effect of the noise after the automobile upgrading is very little or even no effect. It also increases the weight loss and fuel consumption of the vehicle, which is mainly caused by the improper brand and quality of the sound insulation products chosen by the car friends. How should a car sound insulation be done? The whole body of cars is a noise source. Where does the noise come from? We should find out different sources of noise on the vehicle so as to cure the noise. Experts say there are four sources of automobile noise: engine noise, tyre noise, air noise and body structure noise. 1. engine noise. In addition to the mechanical sound emitted by the body, it also includes the noise of the intake system, that is, the high speed gas enters the cylinder through the air filter, the intake pipe and the valve. In the flow process, a very strong aerodynamic noise will be produced. The engine noise is mainly transmitted to the cockpit by the retaining wall and the front chassis of the cab. 2. tire noise. The general tire noise consists of three parts: one is the air flow of the tread clearance and the air noise around the tire; the two is the vibration noise caused by the vibration of the matrix and the pattern part, and the three is the pavement noise caused by the uneven pavement. 3. air noise. One is the noise of the air, which is caused by the pressure change around the body around the body; two is the wind leakage, or the sound of suction, the noise produced by the interaction between the cab and the body crevice and the air flow around the body; the three is the other noise, including the cavity resonating, etc. 4. noise of body structure. It is mainly influenced by two factors, one is the vibration transfer mode of the body structure, and the two is the noise caused by the vibration of the metal components in the body. Sound insulation is generally suitable for cars equipped with lower, more comfortable or lower end cars. If the high-end car, the original sound insulation has been quite good, and then spend money to do soundproof instead of superfluous. The driver of the noise reduction surgery feels that the engine sounds too loud at high speed, and the sound outside the car can be heard clearly. When the speed was higher than 80km, the sound of the tire was particularly obvious. According to the owner's response, the driver found that the noise source of the car came from four main aspects after road test and vehicle detection. The first is the noise of the engine itself. Due to the cost problem in vehicle design, some parts do not use the best material, such as the car hood does not use sound absorption material, the firewall does not attach the sound material to cause the sound of the engine through the dashboard and chassis into the car. Secondly, the door noise conduction and body sealing is insufficient. The four door of a car is the nearest structure from the car. The door is composed of sheet metal parts and door decorations. The master pointed out that the new car under the market price of less than 300 thousand, most of the door parts do not do sound insulation, so it can feel a clear metal sound at the closing of the door. Third, tire noise, leaf plate and chassis conduct noise. The noise produced by the tire is first directly related to the material of the tire, but the main reason is the car body. When the tire makes noise, the sound will be introduced into the car through the leaf plate and the chassis. Fourth, the transmission of metal parts is an important way for the noise transmission of this vehicle. Generally speaking, some parts of low-end cars and high-end cars are directly formed by metal without any sound reduction measures. Special attention must be paid to the construction of sound insulation.