Principles and methods of automobile sound insulation

To be precise, what we do is noise reduction, because no matter what we do, we cannot isolate the sound, but we can reduce the noise as much as possible, mainly through the combination of three methods: shock absorption, sound insulation, and sound absorption.
The materials are mainly 1. Butyl rubber shock-absorbing board; 2. High-density EVA foam with adhesive backing (5cm thick); 3. Sound-absorbing cotton (with and without adhesive backing; 4. High-density polyester fiberboard.

sound insulation mat
1) The principle of butyl rubber shock absorber: first do a small experiment, tap the cup with a chopstick continuously, the cup makes a crisp sound, and then press the side of the cup with a finger, the sound becomes low and lasts for a long time shorten. From the above, we can draw two reasons: 1) Using something elastic to stick to the surface of the object can change the amplitude and absorb energy to reduce the sounding time and sound intensity; 2) It only needs to be done on one side of the surface of an object. Paste, can play the effect of shock absorption. Therefore, in many experience sharing, it is wrong to emphasize that the visible positions are all covered. One is a waste of materials and time, and the other is that after the paste is full, it is equivalent to thickening the iron plate, and the iron plate becomes a whole. The effect of the shock is gone, causing the bass to fill the entire car, and many people have the urge to abandon the car.
2) High-density EVA foam is mainly used for sound insulation, and it is glued to the inner lining of the wheel. This material has a certain hardness and flexibility, which can meet the requirements of pasting and be resistant to stones. The inner lining surface of luxury cars is furry, which can absorb tire noise and scatter it in different directions, reducing the noise intensity. EVA foam has a certain elasticity. When the tire noise is transmitted to the surface, it will cause a certain deformation to it, reducing the noise intensity. For the corresponding principle, please refer to the spring shock absorber, which uses the spring to absorb energy, and we use the deformation of the rubber itself. absorb energy.
3) The sound-absorbing cotton mainly uses the internal sparse fibers to rub against the incoming noise and convert it into heat energy to reduce the noise. Is the sound outside when you cover the quilt? Note that the sound-absorbing cotton with adhesive backing is used in the wheel lining, not in the car to avoid pollution.
4) High-density polyester fiberboard, the material is relatively hard, it is mainly laid under the foot pad to further absorb the low-frequency noise entering from the chassis.

Post time: Jun-01-2022