Automobile muffler can be divided into three types: resistance muffler, resistive muffler and impedance composite muffler according to the principle and structure of noise reduction.
1. Resistant muffler The muffler is a kind of various muffling units such as expansion chambers and resonance chambers, which are formed by pipes, partitions and other components. When sound waves are reflected and interfered during propagation, the sound energy is reduced to achieve the purpose of noise reduction. The muffler of the resistant muffler has a limited frequency band. Generally, the muffling effect is good for the low and middle frequency bands, the high frequency muffling effect is poor, and the truck uses a resistant muffler.
2. Resistive muffler E is a muffler that is filled with sound absorbing material around the pipe through which the internal exhaust gas passes to absorb the sound energy to achieve the purpose of muffling. It has good sound-absorbing effect on medium and high frequency, and is rarely used as a car exhaust muffler. It is usually combined with a resistant muffler. -
3. Impedance composite muffler is a muffler composed of a combination of a resistant muffling unit and a sound absorbing material, which has the common features of a resistant and resistive muffler. It has a good sound-absorbing effect on low, medium and high frequency noise.
Reduce engine exhaust noise and allow high temperature exhaust to be safely and efficiently discharged. As part of the exhaust pipe, the muffler should ensure that the exhaust is unobstructed, the resistance is small and the strength is sufficient. The muffler should withstand high temperature exhaust from 500 °C to 700 °C to ensure that it does not damage or eliminate the noise reduction effect within the specified driving range of the car.
Car noise mainly comes from automobile exhaust noise. If no muffler is added, the noise can reach more than 100 decibels at a certain speed. Followed by engine noise and tire noise, the engine noise can reach more than 90 decibels when the car is running normally, and the tire noise can reach 95 decibels when the vehicle speed is above 90 km/h. Therefore, adding a muffler to the exhaust system can reduce the exhaust noise of the car by 20-30 decibels. On the engine side, replacing the diesel engine with a gasoline engine can reduce engine noise by 6-8 dB.