As people pay more and more attention to the indoor environment, sound-absorbing materials, as an important means to improve the indoor acoustic environment, have been widely used in various buildings, vehicles, and machinery. So, what is the sound-absorbing principle of sound-absorbing materials?
The sound-absorbing principle of sound-absorbing materials can be attributed to two types: air impedance type and pore impedance type. These two principles will be described in detail below.
First, air impedance type sound-absorbing material
Air impedance type sound-absorbing materials use the reflection and transmission of sound waves by the gas layer on the surface of the material to achieve sound absorption. Specifically, when sound waves strike the surface of a sound-absorbing material, they interact with the gas layer on the surface of the material. That is, part of the sound wave is reflected, and the other part of the sound wave passes through the gas layer and enters the interior of the sound-absorbing material, and then continuously reflects, attenuates, and scatters inside the material, and finally converts into heat energy and is absorbed.
In this process, the impedance of the gas layer is a key factor in determining the reflection and transmission of sound waves. The greater the difference between the impedance of the gas layer and the impedance of the air, the stronger the ability of sound waves to pass through the surface of the material, thereby achieving better sound absorption. Therefore, air impedance sound-absorbing materials usually use some special treatment methods on the surface of the material, such as adding porous materials, reducing surface hardness, increasing surface roughness, etc., to increase the impedance of the gas layer, thereby improving the sound-absorbing effect.
Second, pore impedance type sound-absorbing materials
Pore impedance type sound-absorbing material is the use of the pore structure inside the material on the sound wave reflection, scattering and absorption to achieve sound absorption. The basic principle of pore impedance sound-absorbing materials is that sound waves incident on the inside of the material will interact with the air molecules inside the material, resulting in pressure changes and movement, thus generating reflection, scattering and absorption.
Unlike air-impedance sound-absorbing materials, the sound-absorbing effect of pore-impedance sound-absorbing materials is related to the pore structure of the material. Specifically, when the pore diameter is larger than the sound wavelength, the sound wave can enter the pore, resonance and absorption; and when the pore diameter is smaller than the sound wavelength, the sound wave can not enter the interior of the pore, but only in the pore around the reflection and scattering.
Therefore, pore impedance sound-absorbing materials usually adopt some special pore structure design to realize the best sound absorption effect. For example, some pore-impedance sound-absorbing materials are made of multi-layer fiber materials, and the pore structure of each layer of fiber is different, to achieve the absorption of sound waves of different frequencies. Other pore-impedance sound-absorbing materials are made of foam or honeycomb structures, which utilize pores and gaps of different sizes to achieve the sound-absorbing effect.
It should be noted that the sound-absorbing effect of air-impedance and pore-impedance sound-absorbing materials is affected by several factors, such as the thickness of the material, density, porosity, surface treatment methods and so on. Therefore, when designing and selecting sound-absorbing materials, it is necessary to consider the specific application scenarios and requirements, and select the most suitable sound-absorbing materials.
Summary
The sound-absorbing principle of sound-absorbing materials can be summarized into two types: air-impedance type and pore-impedance type. Air impedance type sound-absorbing material is to use the gas layer on the surface of the material to reflect and transmit sound waves to realize sound absorption, while pore impedance type sound-absorbing material is to use the internal pore structure of the material to reflect, scatter and absorb sound waves to realize sound absorption. In practical application, it is necessary to choose the most suitable sound-absorbing material according to the specific application scenario and requirements, and at the same time, pay attention to the impact of the material’s thickness, density, porosity, surface treatment and other factors on the sound-absorbing effect.
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