JP2012103556A - Sound absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorber being a thin type compared with a conventional sound absorbing material formed of a porous material, capable of absorbing sound in an arbitrary frequency band, and capable of absorbing wide-range sound from a low frequency band to a high frequency band.SOLUTION: A sound absorber 1 has a configuration formed by stacking four layers, a membrane vibration layer 2, a skeleton layer 3, a porous layer 4, and a sound insulation layer 5 in this order. The membrane vibration layer 2 is provided with pores 6, and the skeleton layer is provided with cavity parts 7. As for the pores 6 of the membrane vibration layer, the cross-sectional area in a direction perpendicular to the stacking direction is smaller than the cross-sectional area in the direction perpendicular to the stacking direction with respect to the cavity parts 7, and the pores 6 and the cavity parts 7 form a structure equivalent to Helmholtz resonator.

Description

  The present invention relates to a sound absorber.

  Conventionally, as a sound absorber, what was formed, for example using glass wool is known. Such a glass wool sound absorber is said to be excellent in the characteristic of absorbing sound in a relatively high frequency range.

  Conventionally, a sound absorber using a mechanism called a Helmholtz resonator has also been proposed (see, for example, Patent Document 1). In the technique described in Patent Document 1, a Helmholtz resonator is constituted by a paper material.

Japanese Patent Laid-Open No. 9-228506

  However, the glass wool sound absorber has a problem that it is difficult to absorb sound in a relatively low frequency range. In addition, in the case of a glass wool sound absorber, there is a problem that it is difficult to dispose the glass wool layer in a narrow space because the glass wool layer has to be correspondingly thick in order to exhibit the desired sound absorbing performance.

  Further, as in the technique described in Patent Document 1, when the sound absorber is made of a paper material, it is difficult to configure a sound absorber excellent in sound absorption characteristics, and obtaining a sufficiently satisfactory sound absorption effect It was difficult.

Furthermore, in the glass wool sound absorber and Helmholtz resonator type sound absorber as described above, it was not possible to prevent the sound that could not be absorbed by the sound absorber from passing through the sound absorber.
The present invention has been made in order to solve the above-mentioned problems, and its purpose is to make it thinner than conventional sound absorbers and to produce sound in a wide sound range from a low frequency range to a high frequency range. An object of the present invention is to provide a sound absorber that can absorb sound and prevent sound transmission.

Hereinafter, the configuration employed in the present invention will be described.
In order to achieve the above-mentioned object, the sound absorber according to claim 1 is formed of a first resin composition having a specific gravity of 2 to 5 and having vibration damping properties, and has a thickness of 0.05 to 1 mm. The thin film body is formed of a film vibration layer that vibrates when receiving sound and a second resin composition having a JIS A hardness of 60 or less and having vibration damping properties, and supports the film vibration layer. A skeleton layer that becomes a skeleton, a porous layer that is formed of a third resin composition and is a porous body having open cells, and a fourth resin composition that has a specific gravity of 2 to 10 A sound insulating layer that blocks sound transmission by reflecting the sound when receiving sound, and in the order of the membrane vibration layer, the skeleton layer, the porous layer, and the sound insulating layer. A laminated structure formed by laminating, wherein the skeleton layer includes a space penetrating the skeleton layer in the lamination direction of the laminated structure. The cavity is formed in a state where one end of the both ends in the stacking direction is closed by the membrane vibration layer, and the other end is closed by the porous layer. The layer is formed with pores that penetrate the membrane vibration layer in the stacking direction and communicate with the cavity.

  In this sound absorber, the specific gravity of the first resin composition is 2 to 5. If the specific gravity is 2 or less, the sound absorption frequency increases, and the effect of absorbing low-frequency sound tends to decrease. On the other hand, when the specific gravity is 5 or less, the rigidity becomes high and membrane vibration hardly occurs (although low-frequency sound is absorbed appropriately, the absorption tends to decrease).

  The thickness of the first resin composition is 0.05 to 1 mm. When the thickness is 0.05 mm or less, when sound is received, the rigidity is insufficient, the elasticity is excessively weakened, the return is reduced, and there is a tendency that membrane vibration is hardly caused. On the other hand, if the thickness of the first resin composition is 1 mm or more, the rigidity becomes too high, and in this case also, there is a tendency that membrane vibration is difficult to occur.

  The specific gravity of the fourth resin composition is 2-10. If the specific gravity is 2 or less, it tends to be difficult to reflect sound. On the other hand, if the specific gravity is 10 or more, moldability tends to be lowered and production tends to be difficult.

In the sound absorber configured as described above, when sound hits the membrane vibration layer, the membrane vibration layer causes membrane vibration, so that sound in a low frequency range is absorbed.
In addition, the pores of the membrane vibration layer have a cross-sectional area perpendicular to the stacking direction that is smaller than a cross-sectional area perpendicular to the stacking direction relative to the cavity, and these pores and cavities are Helmholtz. A structure corresponding to a resonator is formed. Since such pores and cavities are provided, when sound enters the pores, the air in the cavities functions as an elastic body, and the air in the through-hole vibrates vigorously in the resonance frequency range. Absorbed.

  Furthermore, since the skeleton layer is a soft body formed of a material having a hardness of 60 or less in JIS A hardness, when the air in the cavity is compressed by sound pressure, the pressure received from the compressed air The skeleton layer is expanded and contracted, and the energy of sound is lost here.

Therefore, as compared with a skeleton layer formed of a material having no stretchability, the efficiency of converting sound energy into heat is improved by being expanded and contracted, so that the sound absorbing effect is enhanced.
In addition, the sound that cannot be absorbed by the membrane vibration layer, the skeleton layer, and the porous layer is reflected by the sound insulation layer and is incident on the porous layer again, so that the reflected sound is also absorbed by the porous layer and the like.

  Therefore, according to the sound absorber having the above-described mechanism, for example, a thin film can be formed as compared with a porous material such as glass wool, and furthermore, a sound in a wide sound range from a low frequency range to a high frequency range can be obtained. Can be absorbed. Moreover, since the sound insulation layer as described above is provided, the effect of preventing sound transmission can be improved as compared with a sound absorbing material not provided with the same sound insulation layer.

  In the sound absorber as described above, the specific dimensions and the like of the pores formed in the membrane vibration layer are arbitrary as long as the desired effects can be obtained. It is preferable that a through hole of about 2 mm is formed.

Moreover, as a cavity part, if the dimension of a lamination direction is about 1-5 mm and the cross section perpendicular | vertical to a lamination direction is circular, for example, a thing with a diameter of about 5-30 mm is preferable.
In addition, the porous layer preferably has a dimension in the stacking direction of about 1 mm or more. Also, the material of the porous layer is not particularly limited, but in order to lose sound energy by receiving sound and vibrating, a material having a low hardness is preferable. For example, the hardness is JIS A hardness. It is preferable to be formed of a foam material having a very low hardness such as 10 or less. Specific examples of such a low-hardness foamed material include, for example, a polyol-based fluororubber foam. Furthermore, from the viewpoint of losing sound energy, the porous layer preferably has vibration characteristics with a loss coefficient of 0.6 or more.

The sound absorber according to claim 2 is characterized in that in the sound absorber according to claim 1, the sound absorber has heat resistance usable in an environment up to an upper limit temperature of 130 degrees.
With such a sound absorber, unlike a sound absorber made of a resin composition having low heat resistance such as urethane rubber, the sound absorber deteriorates due to heat even in a high temperature environment up to an upper limit temperature of 130 degrees. The desired sound absorption effect can be maintained without causing problems. Therefore, the sound absorber can be arranged even in places where it was difficult to arrange with conventional products having low heat resistance, for example, in the vicinity of automobile motors or compressors.

The sound absorber according to claim 3 is characterized in that, in the sound absorber according to claim 1 and claim 2, the dimension of the laminated structure in the stacking direction is 10 mm or less.
According to the sound absorber configured as described above, since the thickness is 10 mm or less, a space necessary for installing the sound absorber in the device can be reduced, and a small machine can be used. Can also be installed easily.

  The sound absorber according to claim 4 is the sound absorber according to any one of claims 1 to 3, wherein the first resin composition includes a polyol-based fluororubber as a matrix in the matrix. It is a composition in which one or two kinds selected from calcium carbonate, talc, barium sulfate and SUS powder are blended.

  According to the sound absorber configured as described above, as the first resin composition, a polyol-based fluororubber filled with one or two kinds selected from calcium carbonate, talc, barium sulfate and SUS powder. Since such a resin composition is used, it becomes a vibration-damping material having a specific gravity of 2 or more, and a membrane vibration layer having a desired performance can be formed.

  Furthermore, the sound absorber according to claim 5 is the sound absorber according to any one of claims 1 to 4, wherein the fourth resin composition is formed of barium sulfate in a resin material serving as a matrix. It is a composition in which one or two selected from tungsten and SUS powders are blended.

  According to the sound absorber configured as described above, as the fourth resin composition, a resin material used as a matrix filled with one or two kinds selected from barium sulfate, tungsten, and SUS powder is used. Therefore, if it is such a resin composition, it will become a material with a vibration suppression property with a specific gravity of 2 or more, and the sound-insulation layer provided with the expected performance can be formed.

(A) is a top view which shows an example of a sound-absorbing body, (b) is an AA sectional view. (A) is explanatory drawing which shows the structure of a vibration apparatus, (b) is a graph which shows an example of a resonance curve. It is a graph which shows the vibration transfer function of each sample. It is explanatory drawing which shows the sound-absorbing body installed in the wall surface of the box surrounding a vibration and noise source. (A) is explanatory drawing which shows the example which affixed the sound absorption body directly to the plane part of a noise / vibration source, (b) is the description which shows the example which affixed the sound absorption body directly to the curved surface part of a noise / vibration source FIG. (A) is explanatory drawing which shows the example in which the cross-sectional shape of a cavity part is a rectangle, (b) is explanatory drawing which shows the example in which the cross-sectional shape of a cavity part is a hexagon.

Next, an embodiment of the present invention will be described with an example.
[Structure of sound absorber]
The sound absorber 1 shown in FIGS. 1A and 1B has a structure in which four layers of a membrane vibration layer 2, a skeleton layer 3, a porous layer 4, and a sound insulation layer 5 are laminated in this order. The thickness (dimension in the stacking direction) of the sound absorber 1 is 10 mm.

  The membrane vibration layer 2 is a thin film body having a thickness of 0.25 mm. This membrane vibration layer 2 is formed of a vibration-damping resin composition. In this embodiment, a resin composition (specific gravity is 2) filled with calcium carbonate using a polyol-based fluororubber as a matrix. ).

  Similarly to the membrane vibration layer 2, the skeleton layer 3 is also formed of a resin composition having vibration damping properties. However, the skeleton layer 3 is formed of a soft resin composition more than the membrane vibration layer 2, and in this embodiment, the skeleton layer 3 is formed of a polyol-based fluororubber, and the hardness thereof is 46 as a JIS A hardness. It has become.

  The porous layer 4 is formed of a porous material having open cells. In this embodiment, the porous layer 4 is formed of a polyol-based fluororubber foam having a JIS A hardness of 10 and having a skeleton layer of 3 or more. It is extremely soft.

  The sound insulation layer 5 is formed of a material having a large specific gravity and excellent sound insulation. In this embodiment, the sound insulation layer 5 is formed of a resin composition (specific gravity is 4) formed by filling a barium sulfate with a polyol-based fluororubber as a matrix. Yes.

  As shown in FIG. 1B, the membrane vibration layer 2 has pores 6 penetrating the membrane vibration layer 2 in the thickness direction (stacking direction), and the skeleton layer 3 has a thickness of the skeleton layer 3. A cavity 7 that penetrates in the vertical direction (stacking direction) is formed.

  The pore 6 has a circular shape with a diameter of 1 mm in the cross section perpendicular to the stacking direction, the cavity 7 has a circular shape with a cross section of 20 mm in diameter, and a stacking dimension of 3 mm. The pores 6 and the cavity 7 form a structure corresponding to a Helmholtz resonator.

[Performance evaluation]
Next, in order to evaluate the performance of the sound absorber 1, first, the vibration characteristics of the laminated body including the membrane vibration layer 2, the skeleton layer 3, and the porous layer 4 were measured (Example 1). For comparison, the vibration characteristics of the felt (Comparative Example 1) and the vibration characteristics of the neoprene sponge (Comparative Example 2) were measured by the same method. The evaluation items were the three items of maximum vibration transmissibility, loss coefficient, and zero cross.

  The measurement method of vibration characteristics (maximum vibration transmissibility, loss coefficient, zero cross) is as follows. First, four test pieces having a thickness of 3 mm, a length of 5 mm, and a width of 5 mm were cut out from the sample. Next, a vibration device 8 as shown in FIG. The vibration device 8 is a device that generates vibration of a predetermined frequency to vibrate the vibration table 9. Moreover, the load board 10 and the attachment board 12 (The total weight of the load board 10 and the attachment board 12 is 400g) were prepared.

  Four test pieces 11 are placed on the vibration table 9, and a mounting plate 12 and a load plate 10 are further placed in this order from above, and the test piece 11 is sandwiched between the vibration table 9 and the mounting plate 12. Fixed with. Four test pieces 11 were arranged at each of the four corners of the vibration table 9 so as to support the mounting plate 12 at four points.

  Next, the vibration exciter 8 was operated at an acceleration of 0.4 G to vibrate the vibration exciter 9. At this time, the frequency of vibration was changed from 10 Hz to 1000 Hz under a sweep condition of 1 oct / min (458 sec).

  And the vibration of the load board 10 arrange | positioned at the upper part of each test piece 11 was detected with the acceleration pick-up 13, and the resonance curve was produced as shown in FIG.2 (b). This vibration test was conducted under the condition of a temperature of 24 degrees.

(Evaluation item 1) Maximum vibration transmission rate When the acceleration at which the vibration device 8 vibrates the test piece 11 is a ₀ and the acceleration of the test piece 11 detected by the acceleration pickup 13 is a, the vibration transmission rate τ is , Τ = a / a ₀ (see FIG. 3).

  A frequency response function in which the vibration transmissibility τ is converted into a magnification (logarithm) using the following formula, the magnification is plotted on the vertical axis, and the frequency is plotted on the horizontal axis, is a frequency characteristic with respect to the vibration acceleration of the test piece 11 (FIG. 2 (b)).

Magnification [dB] = 20 log ₁₀ τ
(Evaluation Item 2) Loss Coefficient Next, the loss coefficient tan δ decreased by 3 dB from the resonance frequency f0 (Hz) indicating the peak value (resonance magnification) of the resonance curve in FIG. Based on the indicated frequencies f1 and f2 (f1 <f0 <f2), the loss coefficient tan δ = (f2−f1) / f0 was calculated.

(Evaluation Item 3) Zero Cross The zero cross point is a frequency at which the resonance curve shows 0 dB, and there is an effect of suppressing vibration transmission (anti-vibration effect) at a frequency higher than this frequency (see FIG. 2B).

  Table 1 shows the resonance frequency, maximum vibration transmissibility, loss factor, and zero cross of each sample.

  As is clear from FIGS. 2B, 3, and Table 1, the loss factor tan δ in Example 1 is larger than those in Comparative Example 1 and Comparative Example 2. Therefore, it can be seen that Example 1 is a sound absorber superior in vibration damping properties compared to the case where felt or neoprene sponge is used. In addition to the laminate shown in Example 1, the sound absorber 1 is further laminated with a sound insulation layer, so that it can be expected that a higher vibration damping effect is exhibited, and further, the sound insulation effect is improved. It can be expected.

[effect]
For example, as shown in FIG. 4, the sound absorber 1 configured as described above has the membrane vibration layer 2 facing the noise / vibration source side so that sound is incident from the pores 6 of the membrane vibration layer 2. Thus, the sound insulation layer 5 is installed in contact with the wall surface of the box surrounding the noise / vibration source.

In such an installation state, when the sound coming from the noise / vibration source hits the membrane vibration layer 2, the membrane vibration layer 2 vibrates, and the low frequency sound is absorbed by the sound absorption effect by this membrane vibration.
Further, since the pore 6 of the membrane vibration layer 2 and the cavity 7 of the skeleton layer 3 form a structure corresponding to a Helmholtz resonator, when sound in the resonance frequency region is incident from the pore 6, the cavity 7 acts as an elastic body, and vibrations of air are generated around the vicinity of the pores 6 so that sound is absorbed by friction loss.

  Furthermore, since the skeleton layer 3 is formed of a low-hardness material, the skeleton layer 3 including the cavity 7 can be easily expanded and contracted. Therefore, when the air in the cavity 7 is compressed by the sound pressure, the skeleton layer 3 is expanded and contracted by the pressure, so that the efficiency of converting sound energy into heat is improved, and the sound absorption effect is enhanced. Furthermore, since the volume of the cavity 7 increases or decreases due to deformation, the frequency range to which the resonator corresponds is widened.

Further, the sound in the high frequency band that could not be absorbed by the membrane vibration layer 2 and the skeleton layer 3 is absorbed when passing through the open cells of the porous layer 4.
In addition, the sound that cannot be absorbed by the membrane vibration layer 2, the skeleton layer 3, and the porous layer 4 is reflected by the sound insulation layer 5. Since the sound insulating layer 5 has a high specific gravity due to the blending of barium sulfate, the sound hitting the sound insulating layer 5 is reflected and reenters the porous layer 4 and is absorbed.

  Therefore, according to the sound absorber 1 having the above mechanism, it is possible to absorb sound in a wide sound range from a low frequency range to a high frequency range. Therefore, such a sound absorber 1 exhibits excellent sound absorbing performance even if it is made thinner than a glass wool sound absorber or a Helmholtz resonator type sound absorber made of a relatively hard material. As a result, the space required for installing the sound absorber 1 in the device can be reduced, and it can be easily installed in a small machine. Furthermore, since the sound insulation layer 5 is provided, the effect of preventing sound transmission can be improved as compared with a sound absorbing material that does not have the same sound insulation layer 5.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to said specific one Embodiment, In addition, it can implement with a various form.

  For example, in the above-described embodiment, it is installed on the wall surface of the box surrounding the noise / vibration source, but the installation location may be directly attached to the noise / vibration source. As shown in FIG. 5A, the vibration / noise source 14 has a flat surface portion 14 and the noise / vibration source 15 has a curved surface portion 15 as shown in FIG. 5B. The shape of the sound absorber can be freely changed along the direction, and the membrane vibration layer 2 side can be attached to a noise / vibration source.

  Therefore, in such a case, unlike the case where it is installed on the wall of the box surrounding the noise / vibration source, the vibration generated from the noise / vibration source can be directly absorbed, so that self-vibration is reduced. Thus, it is possible to reduce solid propagation sound.

  Furthermore, although the cavity 7 has a circular cross-sectional shape, the cavity 7 may have a cross-sectional shape other than a circle. For example, the cavity 7 has a quadrangular cavity 16 as shown in FIG. Alternatively, it may be a hollow portion 17 having a hexagonal cross section as shown in FIG.

  However, in the cavity portion 7, sound is applied to the skeleton layer 3 that forms the inner wall of the cavity portion 7, and the skeleton layer 3 is expanded and contracted to enhance the sound absorption effect. Therefore, the inner wall of the cavity portion 7 is easily stretched and deformed. Is preferable.

  In the above embodiment, an example is shown in which the sound insulation layer 5 side is in contact with the wall surface of the box surrounding the noise / vibration source toward the noise / vibration source side toward the membrane vibration layer 2 side. It was confirmed that the same sound absorption effect could be obtained even if the sound insulation layer 5 side was directed to the noise / vibration source side and the membrane vibration layer 2 side was in contact with the wall surface of the box surrounding the noise / vibration source. . Therefore, if necessary, there is no problem even if the sound absorber 1 is installed with its front and back reversed.

  DESCRIPTION OF SYMBOLS 1 ... Sound absorption body, 2 ... Membrane vibration layer, 3 ... Skeletal layer, 4 ... Porous layer, 5 ... Sound insulation layer, 6 ... Fine hole, 7 ... Hollow part, 8 ... Excitation apparatus, 9 ... Excitation table, 10 ... Load plate, 11 ... Test piece, 12 ... Mounting plate, 13 ... Accelerometer, 14 ... Vibration / noise source has a flat surface portion, 15 ... Noise / vibration source has a curved surface portion, 16 ... Cross-sectional shape Quadrilateral hollow portion, 17 ... hollow portion having a hexagonal cross-sectional shape.

Claims (5)

A thin film body having a specific gravity of 2 to 5 and a vibration-damping first resin composition, and a thickness of 0.05 to 1 mm, and a membrane vibration layer that vibrates when receiving sound, ,
A skeleton layer formed of a second resin composition having a JIS A hardness of 60 or less and having vibration damping properties, and a skeleton layer that supports the membrane vibration layer;
A porous layer formed of a third resin composition, which is a porous body having open cells, and a fourth resin composition having a specific gravity of 2 to 10, and receives sound. And a sound insulation layer that blocks sound transmission by reflecting the sound when the film vibration layer, the skeleton layer, the porous layer, and the sound insulation layer are laminated in this order. There,
The skeleton layer is a space penetrating the skeleton layer in the stacking direction of the stacked structure, and one end of the stacking direction is closed by the membrane vibration layer, and the other end is the porous layer. A cavity that is closed by the stratum corneum is formed,
The sound absorbing body, wherein the membrane vibration layer is formed with pores that penetrate the membrane vibration layer in the stacking direction and communicate with the cavity. The sound absorber according to claim 1, wherein the laminated structure has heat resistance that can be used in an environment up to an upper limit temperature of 130 degrees. The sound absorber according to claim 1 or 2, wherein a dimension in a stacking direction of the stacked structure is 10 mm or less. The first resin composition is a composition in which one or two kinds selected from calcium carbonate, talc, barium sulfate and SUS powder are blended in the matrix using a polyol-based fluororubber as a matrix. The sound-absorbing body according to any one of claims 1 to 3, wherein the sound-absorbing body is characterized. The fourth resin composition is a composition in which one or two kinds selected from barium sulfate, tungsten, and SUS powder are blended in a resin material serving as a matrix. The sound absorber according to claim 4.