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.

一、电阻消声器

1、 Resistance Muffler

电阻式消声器利用吸声材料的吸声功能来消除噪声。其结构是将吸声材料固定在有空气流动的管道内壁上，或以一定的方式布置在管道或壳体内，形成一个阻性消声器。吸声材料能部分吸收入射到其上的声能。声能被吸收的原因是吸声材料的多孔性和疏松性。当声波进入孔隙时，孔隙中的空气和物质由于摩擦和粘滞阻力产生微小振动。相当一部分声能被转换成热能并被吸收。

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.管式消声器

1. Tubular muffler

管式消声器是简单的消声器。它只在管壁内缘粘贴一层吸声材料，所以又称“管衬”。其特点是制造方便，阻力小，但只适用于小风管，直径一般不超过400mm。管式消声器仅对中高频吸声有一定的消声效果。低频率下性能差。

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.板和格式消声器

2. Plate and format muffler

管式消声器低频性能差，易通过中、高速率噪声。此外，当管道截面面积较大时，会影响高频噪声的消声效果。这是因为高频声波(短波长)在管道中以窄束传播。

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.

管面积大时,声波之间的联系和管壁上的吸声材料降低,这样沉默的高频声音降低,因此,空气管的很大部分,部分可分为几个网格,芯片和格式消音器。片状消声器应用广泛，结构简单。格式消声器的有效截面积不得小于风管的截面积，因此体积较大，每个格网的尺寸应控制在200mm×200mm左右。板式消声器的板间间距一般在100~200mm范围内。当板间距加大时，消声量相应减小。

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.