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, so that it can obtain a good muffler effect in 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 shifter, a power amplifier and a loudspeaker .