Introduction to the types of muffler in car
Do you know what types of muffler in car are? The resistive muffler mainly uses porous sound-absorbing materials to reduce noise. The sound-absorbing material is fixed on the inner wall of the air flow 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 and energy consumption is dissipated, so that the sound wave passing through the muffler is weakened. The resistive muffler is like an electrical pure resistance circuit, and the sound-absorbing material is similar to a resistor. Therefore, people call this muffler a resistive muffler. The resistive muffler has good muffling effect on middle and high frequency, but poor muffling effect on low frequency.
The resistant muffler is a combination of a pipe and a chamber with a sudden change interface. It looks like an acoustic filter, which is similar to an electrical filter. Each small chamber with a pipe is a mesh of the filter, and the air quality in the pipe is equivalent to Electrical inductance and resistance are called acoustic quality and acoustic resistance. The volume of air in the chamber is equivalent to the electrical capacitance, which is called acoustic compliance.
The micro-perforated plate muffler is generally made of a pure metal sheet with a thickness of less than 1mm, and a drill bit with a hole diameter of less than 1mm is used to perforate the sheet, and the perforation rate is 1% to 3%. Choosing different cavity depths with different perforation rates and plate thicknesses can control the spectral performance of the muffler to achieve a good muffler effect in the required frequency range.
The structure of the small hole muffler is a straight pipe with a closed end, and many small holes are drilled in the wall of the pipe. The principle of the small hole muffler is based on the frequency spectrum of the jet noise. If the total area of the nozzle remains unchanged and many small nozzles are used instead, when the airflow passes through the small hole, the frequency spectrum of the jet noise will shift to high frequency or ultra-high frequency. The high frequency significantly reduces the audible 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 equal in magnitude and opposite to the original sound pressure in the original sound field, so that it can cancel out the original sound field within a certain range. This kind of muffler is a set of equipment, mainly composed of microphone, amplifier, phase shift device, power amplifier and loudspeaker.
