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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、電阻消聲器

1、 Resistance Muffler

電阻式消聲器利用吸聲材料的吸聲功能來消除噪聲。其結構是將吸聲材料固定在有空氣流動的管道內壁上，或以一定的方式布置在管道或殼體內，形成一個阻性消聲器。吸聲材料能部分吸收入射到其上的聲能。聲能被吸收的原因是吸聲材料的多孔性和疏松性。當聲波進入孔隙時，孔隙中的空氣和物質由于摩擦和粘滯阻力產生微小振動。相當一部分聲能被轉換成熱能并被吸收。

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.管式消聲器

1. Tubular muffler

管式消聲器是簡單的消聲器。它只在管壁內緣粘貼一層吸聲材料，所以又稱“管襯”。其特點是制造方便，阻力小，但只適用于小風管，直徑一般不超過400mm。管式消聲器僅對中高頻吸聲有一定的消聲效果。低頻率下性能差。

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.板和格式消聲器

2. Plate and format muffler

管式消聲器低頻性能差，易通過中、高速率噪聲。此外，當管道截面面積較大時，會影響高頻噪聲的消聲效果。這是因為高頻聲波(短波長)在管道中以窄束傳播。

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.

管面積大時,聲波之間的聯系和管壁上的吸聲材料降低,這樣沉默的高頻聲音降低,因此,空氣管的很大部分,部分可分為幾個網格,芯片和格式消音器。片狀消聲器應用廣泛，結構簡單。格式消聲器的有效截面積不得小于風管的截面積，因此體積較大，每個格網的尺寸應控制在200mm×200mm左右。板式消聲器的板間間距一般在100~200mm范圍內。當板間距加大時，消聲量相應減小。

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.