JPH05281978A - Sound absorbing device - Google Patents

Abstract

PURPOSE:To obtain the sound absorption characteristic in a frequency wider than the sound absorption characteristic of powder alone by laminating >=2 kinds of the powders varying in sound absorption peak frequencies via an air layer in a thickness direction. CONSTITUTION:Two kinds of the powders 1a, 1b are laminated in the thickness direction into a thin box body 4 opened on one side via the air layer 3 formed between two sheets of acoustically transparent sheets 2a by holding these sheets at the boundary thereof. The opening of the box body 4 is closed by the acoustically transparent sheet 2b to form a panel. The layer of 15mm thickness of the silica powder la having, for example, 35mum average grain size and 0.078g/cm<3> bulk density is formed on the front surface. Two sheets of non-woven fabrics 2a having 20mum thickness are extended and the air layer 3 having 5mm thickness is formed therebetween. The layer of 15mm thickness of the silica powder 1b having 150mum average grain size and 0.27g/cm<3> bulk density is formed on the deep side thereof. As a result, the sound absorption characteristic in the wide frequency range is obtd. by the synergistic effect of the two powder layers varying in the sound absorption characteristic and the air layer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing device used for acoustic processing in a listening room, a musical instrument practice room and the like.

[0002]

2. Description of the Related Art One of the problems in a small space such as a listening room or an instrument practice room is the occurrence of a booming phenomenon in which a sound of a specific frequency is emphasized and sounds like a "bonbon."

This is a phenomenon in which a resonance state of the sound occurs in the room due to the relationship between the wavelength of the sound generated from the stereo device and the musical instrument and the size of the room.

That is, in the listening room, the musical instrument practice room, etc., the low range is generated within the wavelength range of sounds (1.7 [cm] to 17 [m]) in the audible range of 20 to 20 kHz. This occurs because the wavelength of sound (500 [Hz] or less) becomes approximately the same as the length of one side of the room, and when the indoor space is large, such as in a concert hall, the frequency falls below the audible range. Therefore, it does not cause a problem, but in a small space such as a listening room or a musical instrument practice room, it appears in the low frequency range and becomes unpopular with problems such as "the sound is muffled" and "the sound is not clean".

In order to eliminate this booming phenomenon, it is sufficient to absorb the sound in the low range. For that purpose, the sound absorbing material is arranged on the wall surface or ceiling surface in the room.

Conventionally, as a sound absorbing material in the low sound range, a powder as disclosed in Japanese Patent Application No. 2-223529 is known.

[0007]

In the above-mentioned prior art, the frequency characteristics of the normal incidence sound absorption coefficient (hereinafter abbreviated as "sound absorption characteristics") measured using an acoustic tube are shown by dotted lines in FIGS. 2 and 3. It will be Yamagata's. The sound absorbing mechanism is to absorb sound energy by longitudinal vibration of the powder layer. FIG. 4 shows the longitudinal vibration in one cycle T seconds of the laminated powder layers 5.

Glass wool, which is commonly used as a sound absorbing material, has a high sound absorption coefficient in the low sound range (see FIG. 5).
However, it is not yet sufficient from the viewpoint of whether or not it has a frequency band with a large sound absorption coefficient.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sound absorbing device using powder having broader sound absorbing characteristics than using only powder. Is.

[0010]

According to the present invention, two or more kinds of powders 1 having a sound absorption peak in the frequency characteristic of sound absorption coefficient and having different frequencies of the sound absorption peak are provided with an air layer 3 in the thickness direction. The sound absorbing device is characterized in that the sound absorbing device is laminated.

[0011]

[Operation] The sound absorbing device of the present invention has a sound absorbing characteristic in a wide frequency range by a synergistic effect of a plurality of powder layers having different sound absorbing characteristics and an air layer.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 relates to a first embodiment of the present invention, in which two kinds of powders (1
a, 2b) as a boundary between two acoustically transparent sheets 2a
The sheets are sandwiched and laminated in the thickness direction with an air layer 3 formed therebetween, and the opening side thereof is closed by an acoustically transparent sheet 2b. The width is generally 300 to 900 [mm], and the height is 1800 to 2
This is a sound absorbing device having a 400 [mm] panel.

In order to form the box body 4, wood, gypsum board, calcareous board, wood wool cement board, wood chip cement board, etc. are usually used as the acoustically transparent sheets 2a, 2b.
A tote having a transmissivity of 0.8 or more in a frequency band of 20 to 4 kHz is used, and a breathable woven fabric such as saran cloth or glass cloth or having a thickness of about 0.
A thin film having a thickness of 05 [mm] or less, for example, a polyethylene sheet,
It is common to use vinyl film or the like.

The powder layers to be laminated are not limited to two layers. FIG. 2 shows a case where the sound absorption characteristics when two types of silica powder are laminated via an air layer are compared with a conventional one. The dotted line shows an average particle size of 35 [μm] and a bulk density of 0.
078 [g / cm ³ ], 35 [mm] thick, consisting of only one layer of silica powder, the solid line shows that silica is laminated 15 [mm] thick on the surface side, and a 20 [μm] thick nonwoven fabric (acoustic) Transparent sheet) and stretch 5 sheets between them
An air layer of [mm] was taken, and the powder layer on the inner side was formed of silica powder having an average particle size of 150 [μm], a bulk density of 0.27 [g / cm ³ ] and a thickness of 15 [mm]. It can be seen that the latter has a wider range of sound absorption characteristics. FIG. 3 shows sound absorption characteristics in the case opposite to FIG. That is, the dotted line shows the average particle size of 150 [μm] and the bulk density of 0.2.
7 [g / cm ³ ], a thickness of 35 [mm] consists of only one layer of silica powder, and the solid line shows the silica on the surface side 1
5 [mm] thick layers are laminated, and two non-woven fabrics (acoustic transparent sheets) having a thickness of 20 [μm] are stretched, and 5 [mm] between them.
, And the powder on the back side has an average particle size of 35 [μm
], The bulk density is 0.078 [g / cm ³ ], and the thickness is 15 [
[mm] silica, it is clear that the latter is broader in this case as well.

The powders 1a and 1b thus laminated are shown in FIG.
Thin box 4 and acoustically transparent sheets 2a, 2b
If a panel is formed with and, a sound absorbing device having sound absorbing characteristics shown by solid lines in FIGS. 2 and 3 can be obtained.

The powder used in the present invention is not limited to silica and may be any powder as long as it absorbs sound by longitudinal vibration of the powder layer, and usually has a particle size of about 0.1 to 1000 μm and a bulk. It has a density of about 1.0 g / cm ³ , and examples thereof include gold mica powder, silica powder, ultrafine acrylic powder, talc powder, and calcium silicate powder. For example, gold mica powder having an average particle size of 40 μm and a bulk density of 0.37 g / cm ³ , an average particle size of 1.7 to 7.5 μm and a bulk density of 0.06.
~ 0.14 g / cm ³ wet silica powder, average particle size 23 ~
28 μm, spherical silica powder having a bulk density of 0.84 to 0.92 g / cm ³ , average particle size of 1 to 2 μm, bulk density of 0.30 g
/ Cm ³ acrylic ultrafine powder, average particle size 1.5-3.2μ
Examples thereof include talc powder having m 2, a bulk density of 0.25 g / cm ³ , and calcium silicate powder having an average particle size of 20 to 30 μm and a bulk density of 0.08 g / cm ³ . The thickness of the packed layer of powder is usually in the range of 1 to 100 mm.

[0018]

According to the sound absorbing device of the present invention, two or more kinds of powders having a sound absorbing peak in the frequency characteristic of sound absorbing coefficient and having different sound absorbing peak frequencies are laminated through an air layer in the thickness direction. Therefore, sound absorption characteristics in a wider frequency range than the sound absorption characteristics of the powder alone can be obtained.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention.

FIG. 2 is a diagram showing frequency characteristics of the sound absorption coefficient of the same.

FIG. 3 is a diagram showing a frequency characteristic of a sound absorption coefficient of a conventional example.

FIG. 4 is a diagram showing a sound absorption principle of powder.

FIG. 5 is a diagram showing sound absorption characteristics of glass wool.

[Explanation of symbols]

 1a powder 1b powder 2a acoustically transparent sheet 2b acoustically transparent sheet 3 air layer 4 box

Claims (1)

[Claims] 1. A characteristic that two or more kinds of powders 1 having a sound absorption peak in a frequency characteristic of sound absorption coefficient and having different frequencies of the sound absorption peak are laminated through an air layer 3 in a thickness direction. Sound absorber.