The car muffler is a part used to reduce the noise generated by the engine of the motor vehicle. Since the length difference between the two pipes is equal to half the wavelength of the sound wave emitted by the car, the interference of the two trains of sound waves when they are superimposed cancels each other out. Attenuate the sound intensity, so that the sound is reduced, so as to have the effect of silencing.
Technological process is an important indicator basis to measure whether an enterprise is advanced, whether it has market competitiveness, and whether it can keep ahead of competitors. With the development of my country’s automobile muffler market, the application and research and development of core production technology related to it will definitely become the focus of attention of enterprises in the industry.
Resistive mufflers mainly use porous sound-absorbing materials to reduce noise. The sound-absorbing material is fixed on the inner wall of the airflow channel or arranged in the pipeline in a certain way to form a resistive muffler. When the sound wave enters the resistive muffler, a part of the sound energy is rubbed in the pores of the porous material and converted into heat energy and dissipated, so that the sound wave passing through the muffler is weakened. A resistive muffler is like a purely resistive electrical circuit, and the sound-absorbing material is similar to a resistor. Therefore, people call this muffler a resistive muffler. Resistive mufflers have good muffling effects for medium and high frequencies, but poor muffling effects for low frequencies.
The resistant muffler is composed of tubes and chambers with abrupt interface, as if it is an acoustic filter, similar to an electrical filter, each chamber with tubes is a mesh of the filter, and the air quality in the tubes is equivalent to Electrical inductance and resistance, called sound quality and sound resistance. The volume of air in the chamber is equivalent to an electrical capacitance, which is called sound compliance. Similar to an electrical filter, each tubed cell has its own natural frequency. When sound waves containing various frequency components enter the first short pipe, only sound waves of certain frequencies near the natural frequency of the first mesh can reach the second short pipe through the mesh, while other frequencies Sound waves cannot pass through the mesh. It can only be reflected back and forth in the small room, so we call this structure with filtering function for sound waves as acoustic filter. Select the appropriate tube and chamber to combine. The noise of certain frequency components can be filtered out, so as to achieve the purpose of noise reduction. Resistive mufflers are suitable for eliminating medium and low frequency noise.
The resistive structure and the resistive structure are combined in a certain way to form an impedance composite muffler.
The micro-perforated plate muffler is generally made of pure metal sheet with a thickness of less than 1mm, and the sheet is perforated with a drill bit with a hole diameter of less than 1mm, and the perforation rate is 1% to 3%. By choosing different perforation rates and cavity depths with different plate thicknesses, the spectral performance of the muffler can be controlled to obtain a good muffler effect within the required frequency range.
The structure of the small hole muffler is a straight pipe with closed ends, and many small holes are drilled in the pipe wall. The principle of the small hole muffler is based on the frequency spectrum of the jet noise. If the total area of the nozzle is kept unchanged and replaced by many small nozzles, when the airflow passes through the small hole, the frequency spectrum of the jet noise will shift to high frequency or ultra-high frequency. High frequency can significantly reduce the audible sound components in the frequency spectrum, thereby reducing interference and harm to people.
The basic principle of the active muffler is to use electronic equipment to generate a sound wave with the same size and opposite phase as the original sound field in the original sound field, so that it can cancel the original sound field within a certain range. This kind of muffler is a set of instruments, mainly composed of a microphone, an amplifier, a phase shift device, a power amplifier and a loudspeaker.