The basic principle and structure of the muffler!

Muffler means that for airflow pipes that have noise propagation at the same time, noise reduction devices such as pipes and elbows with sound-absorbing lining or pipes with sudden changes in cross-sectional area and other discontinuous acoustic impedance can be used to attenuate or reflect the noise in the pipe. Go back.

Speaking of sound, it is necessary to explain the mechanism of its production: we need to make a simple introduction to sound.

The three elements of sound are: sound source, transmission and reception. Propagation relies on media, such as air, water, and steel pipes; sound sources are objects that excite the vibration of the medium. For example, exhaust sound waves are produced by the exhaust gas from the engine and the exhaust gas vibrates in the exhaust pipe; and the human ear is a kind of Receiving device.

The vibration of the medium produces sparse and dense regions of molecules, which are often referred to as sound waves (similar to water waves). The adjacent molecular dense area (or sparse area, you can put your hand on the outlet section of the muffler and you will feel that the pressure is intermittently increasing and decreasing, the large is the dense area, the small is the sparse area) The length of the distance determines the frequency of the sound wave, The longer the distance, the lower the sound frequency (bass), the shorter the distance, the higher the sound frequency (treble). In GT analysis, the exhaust noise frequency is generally not more than 1000Hz (the accuracy of GT with noise frequency exceeding 1000Hz will be reduced), of which the part below 100Hz can be considered as bass, the 100 to 300Hz can be considered as midrange, and the frequency above 300Hz belongs to treble, which is different from the normal music division of low, medium and treble. The size of the sound is expressed in decibels. The sound of normal speech is about 60~70 decibels, and the sound of F1 racing cars can reach 100~110 decibels.