CN102693718A - Variable aperture cell-semiopen foam sound absorption structure - Google Patents

Abstract

The invention discloses a variable aperture cell-semiopen foam sound absorption structure. The aperture of the structure is increasingly changed along the incident direction of a sound wave, and the change is an abrupt increase change along the incident direction of the sound wave or a linearly increasing change along the incident direction of the sound wave. When the sound wave is propagated from an open pore to a main pore, a size is abruptly expanded by ten times to dozens of times, so that the kinetic energy of the sound wave is attenuated under the abrupt change of the size, quickly externally applies work, and is converted into heat energy for dissipation; the aperture is increased, so that the expansion function of the abruptly changing cell-semiopen foam structure is far more powerful than that of a homogeneous cell-semiopen material; and in addition, on a part with an increased aperture, a contact area between air and a pore wall is enlarged, so that the adhesion function of the air is enhanced, and a sound absorption coefficient is increased. Compared with that of the homogeneous cell-semiopen foam sound absorption structure, the intermediate/low-frequency sound absorption performance of the variable aperture cell-semiopen foam sound absorption structure is improved by 10 to 20 percent.

Description

Semi-open-cell foam sound-absorbing structure with variable pore size

technical field

The invention relates to a semi-open-cell foam sound-absorbing structure, in particular to a semi-open-cell foam sound-absorbing structure with variable pore size.

Background technique

With the development of society, the noise problem is becoming more and more serious. Noise directly affects the quality of life of human beings, and even has an impact that cannot be underestimated on human psychology, physiology and many other aspects. Therefore, noise is a serious pollution that must be controlled. At present, it has become a very economical, reasonable and effective means to control noise through the principle of sound absorption in construction and various engineering fields.

Sound absorption refers to the phenomenon that the sound energy is converted into heat energy and dissipated when the sound is incident on a certain interface and passes through the medium. The sound absorption capacity of a material is characterized by the sound absorption coefficient, which is the ratio of the absorbed sound energy to the total incident sound energy. The larger the sound absorption coefficient, the stronger the sound absorption capacity of the material. Open-cell foam materials are widely used as sound-absorbing materials because of their large sound absorption coefficient, small specific gravity, and remarkable adaptability to harsh working conditions. According to Huygens' principle, the vibration of the sound source causes the particle vibration of the medium, and the vibration propagates in the form of disturbance. Open-cell foam materials have many tiny gaps and continuous air cells, so they have some air permeability. When the sound wave is incident on the open-cell foam material, the disturbance of the sound wave causes the air in the gap and the bubble to move violently, resulting in strong friction between the air and the cell wall. Due to the frictional resistance and air viscous force, a considerable part of the sound energy is converted into heat energy, and the generated heat energy is quickly dissipated by the heat exchange between the air and the hole wall, so that the sound wave energy is significantly attenuated.

Semi-open-cell foam is a special kind of open-cell foam. The principle of sound absorption is the same as that of open-cell foam. Optimization of sound absorption performance. Semi-open cell foam is prepared by infiltration method. During preparation, the molten metal solution is poured into a container filled with water-soluble particles of a certain size. After the liquid is solidified, the particles are dissolved in water and taken out to obtain a semi-open cell foam. This structure is easy to prepare and has good sound absorption performance, so it is a material with good application prospects. Semi-open-cell foams can be characterized by three independent physical parameters, including pore size D, connectivity ratio δ = d/D, and porosity Ω. Same as open-cell foam, semi-open-cell foam has good high-frequency sound absorption performance and poor low-frequency sound absorption performance.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the object of the present invention is to provide a semi-open-cell foam sound-absorbing structure with variable pore size, which can improve the sound-absorbing performance of the foam material at low frequencies.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A semi-open-cell foam sound-absorbing structure with variable pore size, the pore size of the semi-open-cell foam sound-absorbing structure increases and changes along the sound wave incident direction.

The pore size of the semi-open foam sound-absorbing structure changes abruptly along the incident direction of the sound wave.

The pore size of the semi-open foam sound-absorbing structure changes linearly and incrementally along the sound wave incident direction.

Compared with the homogeneous semi-open-cell foam sound-absorbing structure, the semi-open-cell foam sound-absorbing structure of the present invention has a 10% to 20% increase in the sound-absorbing performance of the medium and low frequencies. According to an important sound-absorbing structure of the semi-open-cell foam Mechanism: When the sound wave propagates from the connected pores to the main pores, due to the sudden expansion of the volume ten to dozens of times, the sound wave energy is attenuated due to the sudden change in volume, and the sound energy quickly acts externally and is converted into heat energy and dissipated. Due to the enlarged pore size, the expansion effect of semi-open-cell foam structures with variable pore size is much larger than that of homogeneous semi-open-cell materials. In addition, for the portion with increased pore diameter, due to the increase of the contact area between the air and the pore wall, the air viscous effect is strengthened and the sound absorption coefficient increases.

Description of drawings

Figure 1 is a schematic diagram of the sudden increase in the pore size of the present invention.

Fig. 2 is a graph showing the linear and continuous increase of the pore size of the present invention, wherein: Fig. 2 (a) is a schematic diagram of the structure of the linear and continuous increase of the pore size; Fig. 2 (b) is a coordinate diagram of the linear and continuous increase of the pore size.

Figure 3 is a comparison of the sound absorption performance of semi-open-cell foam with sudden change in pore size and homogeneous semi-open-cell foam.

Figure 4 is a comparison of the sound absorption properties of semi-open-cell foam with linearly increasing pore size and homogeneous semi-open-cell foam.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, it is a schematic diagram of the sudden increase in the preferred pore size of the present invention, assuming that the pore size of the homogeneous semi-open cell foam along the sound incident direction is D, the pore size of the first half is changed to D ₁ , and the pore size of the second half is changed to is D ₂ , and D ₁ <D ₂ ,

As shown in Figure 2, it is a schematic diagram of the preferred linear increase of the porosity of the present invention. Let the homogeneous semi-open-cell foam pore diameter be D, and change the porosity to D ₁ , D ₂ , D ₃ layer by layer along the sound wave incident direction. , D ₄ , increasing linearly, $\mathrm{D.}=\frac{{\mathrm{D.}}_1+{\mathrm{D.}}_2+{\mathrm{D.}}_3+{\mathrm{D.}}_4}{4}.$

Example 1

Suppose there is a homogeneous semi-open cell foam with a thickness of 10mm along the sound wave incident direction, a connectivity rate of 0.25, a pore diameter of 1.24mm, and a porosity of 66.8%. Change the aperture of the front 5mm to 1mm, and the aperture of the rear 5mm to 1.48mm. The semi-open-cell foam with a sudden change in pore size is the same in mass and volume as the homogeneous semi-open-cell foam, but the sound absorption performance at medium and low frequencies is improved by 10% to 20%. Comparison of sound absorption properties of homogeneous semi-open-cell foams.

Example 2

Suppose there is a homogeneous semi-open-cell foam with a thickness of 10mm along the sound incident direction, a pore diameter of 1.24mm, a connectivity rate of 0.25, and a porosity of 66.8%. The connectivity was varied linearly from 0.79 mm to 1.69 mm along the incident direction. The linearly increasing pore size semi-open cell foam has the same mass and volume as the homogeneous semi-open cell foam, but the mid-low frequency sound absorption performance has been improved by 10% to 20%, as shown in Figure 4, which is the linearly increasing pore size semi-open cell of this embodiment Comparison of sound absorption properties of foam and homogeneous semi-open cell foam.

Claims (3)

1. A semi-open-cell foam sound-absorbing structure with variable pore size, characterized in that: the pore size of the semi-open-cell foam sound-absorbing structure increases along the sound wave incident direction. 2. The semi-open-cell foam sound-absorbing structure with variable pore size according to claim 1, characterized in that: the pore size of the semi-open-cell foam sound-absorbing structure changes abruptly along the sound wave incident direction. 3. The semi-open-cell foam sound-absorbing structure with variable pore size according to claim 1, characterized in that: the pore size of the semi-open-cell foam sound-absorbing structure linearly increases along the sound wave incident direction.

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