| [Visitor (116.162.*.*)]answers [Chinese ] | Time :2023-02-18 |  muffler
overview
There are many types of silencers, but in terms of their muffling mechanism, they can be divided into six main types, namely resistive silencers, resistant silencers, impedance composite silencers, micro-perforated plate silencers, small hole silencers and active silencers.
Resistive silencer
It mainly uses porous sound-absorbing materials to reduce noise. Fixing the sound-absorbing material on the inner wall of the airflow channel or arranging it in the duct in a certain way constitutes a resistive silencer. When the sound wave enters the resistive silencer, part of the sound energy rubs in the pores of the porous material and is converted into heat energy dissipation, so that the sound wave passing through the silencer is weakened. Resistive silencers are like electrically pure resistance circuits, and sound-absorbing materials are similar to resistors. Therefore, people call this silencer a resistive silencer. The resistive silencer has a good effect on medium and high frequency muffling and poor effect on low frequency muffling. (Mainly used in generator unit silencer)
Resistant silencer
It is a combination of tubes and chambers of the mutation interface, as if it is an acoustic filter, similar to an electrical filter, each small chamber with a tube is a mesh of the filter, and the air quality in the tube 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 called sonic. Similar to electrical filters, each tubular chamber has its own natural frequency. When sound waves containing various frequency components enter the first stub, only certain frequencies near the natural frequency of the first mesh can pass through the mesh to the second stub, while sound waves of other frequencies cannot pass through the mesh.It can only be reflected back and forth in a small chamber, so we call this structure that filters sound waves an acoustic filter. Select the appropriate tubes and chambers for combination. It can filter out the noise of certain frequency components to achieve the purpose of sound reduction. Resistant silencers are suitable for eliminating low and medium frequency noise...
Impedance composite silencer
It is composed of a combination of resistive structure and resistant structure in a certain way.
Micro-perforated plate silencer
Generally, it is made of pure metal sheet with a thickness of less than 1mm, and a drill with a hole diameter of less than 1mm is perforated on the thin plate, and the perforation rate is 1% to 3%. Choosing different perforation rates and different cavity depths with different plate thicknesses can control the spectral performance of the silencer and achieve good sound suppression in the required frequency range.
Small hole silencer
The structure is a straight pipe with closed ends and many small holes drilled into the wall of the tube. The principle of small hole silencer is based on the spectrum of jet noise, if the total area of the nozzle is kept unchanged and replaced by many small nozzles, when the air flow through the small hole, the spectrum of jet noise will move to high frequency or ultra-high frequency, so that the audible sound component in the spectrum is significantly reduced, thereby reducing interference and harm to people.
Active silencer
The basic principle is that in the original sound field, electronic equipment is used to generate a sound wave equal to the original sound pressure and opposite to the phase, so that it cancels out the original sound field within a certain range. This silencer is a set of instrument devices, mainly composed of microphones, amplifiers, phase shift devices, power amplifiers and speakers. |
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