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　　1. Ventilation duct resistance muffler: It absorbs sound energy and reduces noise by absorbing sound data inside the box. It is commonly used to eliminate high and intermediate frequency noise. However, it is not suitable for high temperature, high humidity and high speed because of the structure.

　　2、抗式消聲器：是經過改動截面來消聲的。我們常用的消聲靜壓箱都是這個原理。普通降低中、低頻噪音，對風系統沒有詳細的請求。

　　2. Reactor muffler: It is muffled by changing cross section. This is the principle of our commonly used silencing static pressure box. Normally, there is no detailed request for wind system to reduce medium and low frequency noise. 

　　3、阻抗復合式：當然是分離二者的構造原理。能夠消弭低中高頻噪音。但是對風系統的請求同阻式消聲器關于普通的民用空調通風系統，我個人以為選用阻抗復合消聲器為好。阻性消聲用具有良好的中高頻消聲性能。按氣流通道幾何外形不同，可分為直管式、片式、折板式、迷宮式、蜂窩式、聲流式、障板式、彎頭式等。

　　3. Impedance Compound: Of course, it is the construction principle of separating the two. It can eliminate low, medium and high frequency noise. But for the requirement of the air system, I personally think it is better to choose the impedance compound muffler for the ordinary civil air conditioning and ventilation system. Resistive silencer has good performance of medium and high frequency noise elimination. According to the geometrical shape of airflow passage, it can be divided into straight tube type, sheet type, folded plate type, labyrinth type, honeycomb type, acoustic flow type, baffle type, elbow type, etc.

　　抗性消聲器適用于消弭中低頻噪聲或窄帶噪聲。按其作用原理不同，可分為擴張式、共振腔式和干預式等多種型式。阻抗復合式消聲器，有共振腔、擴張室、穿孔屏等聲學濾波器件，綜合了阻性消聲器良好的中高頻消聲特性和阻抗性消聲器較好的低頻消聲特性，因而其消聲頻帶寬，它是常用的規范消聲器系列之一。

　　Resistant mufflers are suitable for eliminating medium and low frequency noise or narrowband noise. According to its different principles, it can be divided into expansion type, resonant cavity type and intervention type. Impedance compound muffler has resonant cavity, expansion chamber, perforated screen and other acoustic filters. It combines the good middle and high frequency muffler characteristics and the good low frequency muffler characteristics of impedance muffler. Therefore, its muffling frequency bandwidth is one of the most commonly used standard muffler series.

　　適合風速為6～8米/秒，高可到達8～12米，可單獨運用，也可串聯運用。消聲效果：低頻10～15dB/m，中頻15～25dB/m，高頻25～30dB/m，均勻阻力系數為0.4。依據《空氣調理》，消聲彎頭、消聲靜壓箱均屬于消聲器的一種。消聲器是一種既能允許氣流經過，又能有效地阻止或削弱聲能向外傳播的安裝。

　　Suitable for wind speed of 6-8 m/s, up to 8-12 m, can be used alone or in series. Acoustic attenuation effect: low frequency 10-15 dB/m, medium frequency 15-25 dB/m, high frequency 25-30 dB/m, uniform resistance coefficient 0.4. According to Air Conditioning, muffler elbow and muffler static pressure box belong to one kind of muffler. Muffler is a kind of installation which can not only allow air to pass through, but also effectively prevent or weaken the sound energy to spread outward.