The principle of ventilation pipe muffler is resistance sound absorption and noise reduction, with better effect than medium and high frequency broadband characteristics. The principle and good effect of drug-resistant noise reduction are low, medium frequency and pulsation characteristics, micro perforated muffler and impedance composite muffler. Muffler is a device that uses the principles of sound absorption, reflection and interference to reduce the airflow noise in ventilation and air conditioning system. According to different silencing principles, it can be divided into resistance type, resistance type, resonance type and compound type.
1、 Resistance Muffler
Resistance Muffler uses the sound absorption function of sound-absorbing materials to eliminate noise. The structure is that the sound-absorbing material is fixed on the inner wall of the pipe with air flow, or arranged in the pipe or shell in a certain way to form a resistive muffler. The sound absorbing material can partially absorb the sound energy incident on it. The reason why sound energy is absorbed is the porosity and porosity of sound-absorbing materials. When sound waves enter the pores, the air and materials in the pores produce small vibration due to friction and viscous resistance. A considerable part of sound energy is converted into heat energy and absorbed.
1. Tubular muffler
Tubular muffler is a simple muffler. It only pastes a layer of sound-absorbing material on the inner edge of the pipe wall, so it is also called "pipe lining". It is characterized by convenient manufacture and low resistance, but it is only suitable for small air ducts, and the diameter is generally no more than 400mm. The tubular muffler only has a certain silencing effect on medium and high frequency sound absorption. Poor performance at low frequencies.
2. Plate and format muffler
The tubular muffler has poor low-frequency performance and is easy to pass through medium and high-speed noise. In addition, when the cross-sectional area of the pipeline is large, the silencing effect of high-frequency noise will be affected. This is because high-frequency sound waves (short wavelengths) travel in narrow beams in pipes.
When the pipe area is large, the connection between sound waves and the sound-absorbing material on the pipe wall is reduced, so that the silent high-frequency sound is reduced. Therefore, a large part of the air pipe can be divided into several grids, chips and format silencers. Sheet muffler is widely used and has simple structure. The effective cross-sectional area of the format muffler shall not be less than the cross-sectional area of the air duct, so the volume is large, and the size of each grid shall be controlled within 200mm × About 200mm. The spacing between plates of plate muffler is generally within the range of 100 ~ 200mm. When the plate spacing increases, the silencing amount decreases accordingly.