Sound absorbing materials are mainly divided into microporous and fibrous types. They are not essentially different. The sound absorbing principle is to leave an accessible passage for the sound (the passage of numerous tiny holes that are connected together, or by countless fibers). The crosses are mixed together to form a small number of small gaps, but the sound will not come out once it enters. Because the passage is too messy and too long, the sound is drilled inside and drilled to the left and right, which is gradually consumed in the process. Energy plays a role in sound absorption.
All the things with a long, delicate passage that can be used for sound absorption, such as cotton, various fiber gangs, cotton, sponges, and carpets; but things like ordinary foam, egg boxes, and wood boards have no sound absorption. .
In addition, the needle-like surface (like a "planar" formed by bundling many needles into a bundle) is the best sound-absorbing material in the theory. The acoustic laboratory is all designed in such a way that after the sound reaches the "needle"-like surface, It constantly reflects inward and never reflects outward. This surface can completely absorb sound (and light) like a black hole. This is the “sound squeak†used in the muffler room. However, this method is expensive, and the general recording studio and the HIFI listening room do not need such a thorough sound absorption, so the materials are used in the front.
Need to remind everyone that the sounds of different frequencies are absorbed differently. High-frequency sounds have a short wavelength and are easily absorbed, while low-frequency sounds have long wavelengths that can easily penetrate obstacles. For low-frequency sound, it is not only difficult to sound, but also difficult to absorb. It doesn't crash like a high-frequency sound in a messy, small passage, but it's easy to go around. However, as long as you thicken the sound absorbing material to a certain extent, you can absorb the low frequency above 130Hz. More acoustic knowledge is available on the China Home Theater Network ().
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