# Patent

## Title
Soundproof room

## Abstract

The soundproof room (41a) has an interior space (43a) defined by soundproof walls (44a, 45a, 46a, 47a). The soundproof room (41a) includes a sound absorber (11a) whose sound absorbing face absorbs sound in the room and is exposed in the room. The sound absorber (11a) has a varying depth dimension from a front face (19a), serving as the sound absorbing face, toward the depth direction. The sound absorber (11a) is formed by stacking a plurality of layer members from the front face (19a), serving as the sound absorbing face, in the depth direction.

## Background
TECHNICAL FIELD
This invention relates to soundproof rooms (hereinafter, they may be sometimes simply referred to as “room”), and particularly relates to a soundproof room with a sound absorbing structure that absorbs sound generated in the soundproof room.
BACKGROUND ART
Conventionally, some sound rooms and audio rooms, which are used for instrument playing, movie appreciation, and other sound-related events, are equipped with a soundproof structure that prevents sound generated inside the room from leaking outside the room, as well as a sound absorbing structure that eliminates standing waves remaining in corners of the room in order to improve acoustics that instrument players and listeners perceive in the room and that absorbs sounds in some audio frequency ranges generated in the room and reflected off on walls of the room in order to enhance the reverberation of the sound in the room. Conventionally used sound absorbing structures in rooms include sound absorbing panels and sound absorbing materials.
Technologies relating to absorption of sound generated in a room are disclosed in Japanese Unexamined Utility Model Application Publication No. 1987(SHO62)-42607 (Patent Literature 1) and Japanese Unexamined Patent Application Publication No. 2007-286387 (Patent Literature 2). According to the sound room disclosed in Patent Literature 1, bass absorbers having a approximately triangular cross section are installed along almost the entire length of joints between walls and the ceiling of a room, two surfaces of each bass absorber fitting along a wall and the ceiling, respectively, and one surface facing obliquely downward to the inside of the room. Patent Literature 1 intends to effectively absorb low-pitched sounds with these bass absorbers. Patent Literature 2 discloses a sound improving member for improving sound in a structure. The sound improving member is installed at the boundary between structure surfaces that compose the structure in two directions or three directions, and includes a positioning section in contact with the structure surfaces and a tilted face that is inclined relative to the structure surfaces in two directions or three directions while the positioning section is in contact with the structure surfaces to effect positioning. The tilted face of the sound improving member reflects or absorbs sound to improve the sound inside the structure.
CITATION LIST
Patent Literature
PTL1: Japanese Unexamined Utility Model Application Publication No. 1987(Sho62)-42607
PTL2: Japanese Unexamined Patent Application Publication No. 2007-286387
SUMMARY OF INVENTION
Technical Problem
However, even the bass absorber disclosed in Patent Literature 1 and the sound improving member disclosed in Patent Literature 2 cannot properly absorb sound in a room, and consequently the people playing instruments sometimes feel annoyed with the sound. This is because Patent Literature 1 absorbs only low-pitched sound, but does not absorb high-pitched sound. In addition, the simple structure of Patent Literature 2 in which the sound improving member has only the tilted face may be sometimes insufficient to absorb sound. In both cases, even if people play instruments in a room, the sound from the instruments does not properly reach the people's ears, and therefore it can be said that both are unsatisfactory sound absorbing structures.
This invention has an object to provide a soundproof room capable of more properly absorbing sound in the room.
Solution to Problem
The soundproof room according to an embodiment of the invention has an interior space defined by soundproof walls. The soundproof room includes a sound absorber whose sound absorbing face absorbs sound in the room and is exposed in the room. The sound absorber has a varying depth dimension as viewed from the sound absorbing face toward a depth direction. The sound absorber is formed by stacking a plurality of layer members from the sound absorbing face in the depth direction.
According to the soundproof room, the sound absorber included in the soundproof room has a varying depth dimension from the sound absorbing face, which absorbs sound, toward a depth direction. When sound enters through the sound absorbing face exposed in the room, the relatively thick part can efficiently absorb sounds with long wavelengths in a low audio frequency range, while both the relatively thick part and the relatively thin part can efficiently absorb sounds with short wavelengths in a high audio frequency range. In short, the sound absorber can efficiently absorb sounds in a broad audio frequency range from high to low. Since this sound absorber is formed by stacking a plurality of layer members from the sound absorbing face in the depth direction, even if layer members arranged on the sound absorbing face side cannot completely absorb sounds and allow the sounds to pass therethrough, the other layer members arranged further than the sound absorbing face in the depth direction can absorb the sounds permeated. Thus, this sound absorber can absorb sound in the room more properly.
In addition, the sound absorber may be configured to include a first segment whose depth dimension from the sound absorbing face is 23 cm or greater, and a second segment whose depth dimension from the sound absorbing face is less than 23 cm. According to the configuration, the first segment can reliably absorb sounds in a low audio frequency range, while both the first and second segments can reliably absorb sounds in a high audio frequency range. Thus, this sound absorber can absorb sound in the room still more properly.
Furthermore, the sound absorber may be configured to include a maximum depth region whose depth dimension from the sound absorbing face is the greatest, and a depth increasing region whose depth dimension increases while approaching to the maximum depth dimension from the sound absorbing face, the depth increasing region being adjacent to the maximum depth region. According to this configuration, the sound absorber can efficiently and continuously absorb sounds across the low audio frequency range to the high audio frequency range.
The sound absorber may be configured to be a approximately triangular prism in shape. According to this configuration, effective use of the interior space of the room installed with the sound absorber can be achieved.
In addition, a first layer member disposed at the sound absorbing face may be configured to have a density higher than that of a second layer member disposed further than the sound absorbing face in the depth direction. According to this configuration, the first layer member having a high density can reflect sound appropriately. Therefore, more comfortable reverberation can be achieved.
Furthermore, each of the layer members may be made of a nonwoven fabric. The nonwoven fabric enables proper sound absorption and sound reflection.
Advantageous Effects of Invention
According to the soundproof room, the sound absorber included in the soundproof room has a varying depth dimension from the sound absorbing face, which absorbs sound, toward a depth direction. When sound enters through the sound absorbing face exposed in the room, the relatively thick part can efficiently absorb sounds with long wavelengths in a low audio frequency range, while both the relatively thick part and the relatively thin part can efficiently absorb sounds with short wavelengths in a high audio frequency range. In short, the sound absorber can efficiently absorb sounds in a broad audio frequency range from high to low. Since this sound absorber is formed by stacking a plurality of layer members from the sound absorbing face in the depth direction, even if layer members arranged on the sound absorbing face side cannot completely absorb sounds and allow the sounds to pass therethrough, the other layer members arranged further than the sound absorbing face in the depth direction can absorb the sounds permeated. Thus, this sound absorber can absorb sound in the room more properly.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a perspective view showing the appearance of a sound absorber to be installed in a soundproof room according to an embodiment of the present invention.
FIG. 2 illustrates the sound absorber in FIG. 1, as viewed in a direction of Arrow II in FIG. 1.
FIG. 3 illustrates the sound absorber in FIG. 1, as viewed in a direction of Arrow III in FIGS. 1 to 2.
FIG. 4 illustrates the sound absorber in FIG. 1, as viewed in an opposite direction to Arrow III in FIGS. 1 to 2.
FIG. 5 illustrates the sound absorber in FIG. 1, as viewed in a direction of Arrow V in FIG. 2.
FIG. 6 illustrates the sound absorber in FIG. 1, as viewed in a direction of Arrow II in FIG. 1.
FIG. 7 is a perspective exploded view showing the sound absorber disintegrated into a plurality of layer members.
FIG. 8 is a schematic cross-sectional view showing one of the layer members making up the sound absorber.
FIG. 9 is a cross-sectional view showing a part of a semifinished product in a manufacturing process of an example method for manufacturing the sound absorber.
FIG. 10 is a schematic perspective view showing a part of a soundproof room according to the embodiment of the invention.
FIG. 11 is a schematic cross-sectional view of the soundproof room according to the embodiment of the invention, as viewed from the ceiling side.
FIG. 12 is a cross-sectional view of the soundproof room taken along Line XII-XII in FIG. 11.
FIG. 13 is an enlarged view of an area where the sound absorber is installed in the soundproof room.
FIG. 14 is an enlarged view of the area where the sound absorber is removed in the soundproof room.
FIG. 15 is a graph showing the relationship between the reverberation and sound pitch in the soundproof room.
FIG. 16 is an enlarged view of the area, indicated by XVI in FIG. 11, where the sound absorber is installed in the soundproof room according to the embodiment of the invention.
FIG. 17 is a cross-sectional view of a soundproof room according to another embodiment of the invention.
FIG. 18 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 19 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 20 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 21 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 22 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 23 is a schematic perspective view of a soundproof room according to yet another embodiment of the invention.
FIG. 24 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 25 is a cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 26 is a schematic cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 27 is a schematic cross-sectional view of a soundproof room according to yet another embodiment of the invention.
FIG. 28 is a schematic perspective view of a soundproof room according to yet another embodiment of the invention.
FIG. 29 is a schematic perspective view of a soundproof room according to yet another embodiment of the invention.
FIG. 30 is a schematic perspective view of a soundproof room according to yet another embodiment of the invention.



DESCRIPTION OF EMBODIMENT
With reference to the drawings, embodiments of the present invention will be described below. FIG. 1 is a perspective view showing the appearance of a sound absorber 11a to be installed in a soundproof room according to an embodiment of the present invention. FIG. 2 shows the sound absorber 11a in FIG. 1 as viewed in the direction of Arrow II in FIG. 1, that is, FIG. 2 is a so-called top view of the sound absorber 11a viewed from above. In order to provide a clear understanding, layer members, which will be described later, are not illustrated in FIG. 2. FIG. 3 illustrates the sound absorber 11a in FIG. 1, as viewed in a direction of Arrow III in FIGS. 1 to 2. FIG. 3 corresponds to a front view of the sound absorber 11a, as viewed from the side of a sound absorbing face, or a front surface, which will be described later. FIG. 4 illustrates the sound absorber 11a in FIG. 1, as viewed in an opposite direction to Arrow III in FIGS. 1 to 2. FIG. 4 corresponds to a back view of the sound absorber 11a, as viewed from the side of a back surface, which will be described later. FIG. 5 illustrates the sound absorber 11a in FIG. 1, as viewed in a direction of Arrow V in FIG. 2. In order to provide a clear understanding, the illustration of layer members, which will be described later, is partially omitted in FIGS. 3 to 5, and FIGS. 6, 7, and 9, which will be described later. Arrow III in FIGS. 1 to 2 and other drawings indicates the depth direction of the sound absorber 11a. 
Referring to FIGS. 1 to 5, the sound absorber 11a to be installed in the soundproof room according to this embodiment of the invention is approximately in the shape of a triangle prism, or exactly a pentagonal prism. The outer shape of the sound absorber 11a is composed of a top face 12a located at one end of the pentagonal prism sound absorber 11a in the longitudinal direction, a bottom face 13a located at the other end in the longitudinal direction, a first side face 14a, a second side face 15a, a third side face 16a, a fourth side face 17a, and a fifth side face 18a, which are side surfaces of the sound absorber 11a and extend along the longitudinal direction. The second side face 15a and third side face 16a are adjacent to each other. The fourth side face 17a is provided between the first side face 14a and the second side face 15a. The fifth side face 18a is provided between the first side face 14a and the third side face 16a. The top face 12a and bottom face 13a are in the shape of a pentagon, while the first side face 14a, second side face 15a, third side face 16a, fourth side face 17a, and fifth side face 18a are all in the shape of a rectangle. Among the first side face 14a, second side face 15a, third side face 16a, fourth side face 17a, and fifth side face 18a, the first side face 14a has the largest area. The second side face 15a and third side face 16a are designed to have an equal area that is the second largest. The fourth side face 17a and fifth side face 18a are also designed to be equal in area. If FIG. 5 shows the second side face 15a viewed in the direction of Arrow V in FIG. 2, the second side face 15a is symmetrically identical to the third side face 16a viewed in the direction of Arrow B1 in FIG. 2.
When the sound absorber 11a is installed in the soundproof room, which will be described later, the rectangular first side face 14a is referred to as a front face 19a that is exposed in the room, while the rectangular second side face 15a and third side face 16a are referred to as a back face 20a that is covered by walls composing the room. Specifically, the first side face 14a corresponds to the front face 19a, which is exposed in the room, of the sound absorber 11a, while the second side face 15a and third side face 16a correspond to the back face 20a, which is covered by walls composing the soundproof room, more concretely, soundproof walls, of the sound absorber 11a. The sound absorber 11a is installed at a given position in the room with the bottom face 13a located vertically on the lower side. That is, the vertical direction corresponds to the downward direction indicated by Arrows II in FIGS. 1, 3 to 5.
The sound absorber 11a is a approximately triangular prism having an isosceles right triangle section. Except for a corner 21a, which is the right angle corner of the isosceles right triangle, the other two corners, a corner 22a and corner 23a, more specifically, a corner 22a between the first side face 14a and second side face 15a and a corner 23a between the first side face 14a and third side face 16a are both chamfered as if they are straightly cut off by a predetermined thickness in the longitudinal direction. This removal of the corners 23a, 24a shapes the fourth side face 17a and fifth side face 18a. The corner 22a and corner 23a are indicated by dotted lines in FIG. 2. That is, the sound absorber 11a is approximately a triangle in cross section when it is cut along a plane including a line extending from the front face 19a to the back face 20a. 
Referring to the top face 12a for the purpose of description, the shape of the top face 12a, that is, an isosceles right triangle is presented by a first line 24a defining the first side face 14a, a second line 25a defining the second side face 15a, and a third line 26a defining the third side face 16a. The second line 25a and third line 26a form an angle A1 of 90 degrees. The first line 24a and second line 25a form an angle A2 of 45 degrees. The first line 24a and third line 26a form an angle A3 of 45 degrees. A fourth line 27a defining the fourth side face 17a and a fifth line 28a defining the fifth side face 18a are provided so as to straightly extend along the direction of Arrow III, which is an upward direction on the sheet of FIG. 2. Therefore, the sound absorber 11a has a varying depth dimension from the front face 19a to the back face 20a. In other words, the sound absorber has a varying thickness as viewed from the sound absorbing surface toward the depth direction. In this case, since the second side face 15a and the third side face 16a are inclined surfaces extending with respect to the first side face 14a, the thickness of the sound absorber 11a continuously varies within a range from the front face 19a to back face 20a. 
Length L1 from one end 29a to the other end 29b of the first line 24a is selectively set to, for example, 46 cm (centimeters). Length L2 from one end 29c to the other end 29d of the second line 25a and length L3 from one end 29e to the other end 29d of the third line 26a are both selectively set to, for example, 35 cm. Length L4 from one end 29a to the other end 29c of the fourth line 27a and length L5 from one end 29b to the other end 29e of the fifth line 28a are both selectively set to, for example, 2 cm. Length L6 of the perpendicular bisector extending from the corner 21a between the second line 25a and third line 26a to the first line 24a is selectively set to, for example, 25 cm. The sound absorber 11a set as above includes a first segment 31a with a length in the thickness direction from the front face 19a to the back face 20a of 23 cm or longer, and second segments 31b, 31c with a length in the thickness direction from the front face 19a to the back face 20a of less than 23 cm. In other words, the sound absorber 11a includes a first segment 31a with a depth dimension from the sound absorbing face of 23 cm or greater, and second segments 31b, 31c, each with a depth dimension from the sound absorbing face of less than 23 cm. The second segment 31b is located near the second side face 15a, while the second segment 31c is located near the third side face 16a. The position of 23 cm from the first side face 14a in the thickness direction is indicated by a dot 32a on the second side face 15a side and a dot 32b on the third side face 16a side. Lengths L7 of normal lines drawn from the first line 24a to the dot 32a and from the first line 24a to the dot 32b are 23 cm, respectively.
By the way, the sound absorber 11a includes a maximum depth region whose depth dimension is the greatest and depth increasing regions whose depth dimension increases while approaching the maximum depth dimension from the sound absorbing face, the depth increasing regions being adjacent to the maximum depth region. Specifically, the maximum depth region having the maximum depth dimension corresponds to the region where the corner 21a between the second line 25a and third line 26a is located. The depth increasing regions, which are adjacent to the maximum depth region and increase their depth dimensions while approaching the maximum depth dimension from the sound absorbing face, correspond to regions 30a, 30b containing the second side face 15a and third side face 16a, respectively.
Length L8 in the longitudinal direction, that is, in the height direction, from the top face 12a to bottom face 13a is selectively set to, for example, 240 cm. The length L1 may be sometimes regarded as a length in a lateral direction, or a shorter side direction, that is a width direction. In addition, the longitudinal direction equivalent to the height direction may be sometimes referred to as a vertical direction.
The sound absorber 11a is formed by stacking a plurality of layer members 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, 33i, and 33j. FIG. 6 illustrates the sound absorber 11a in FIG. 1, as viewed from above, more specifically, in a direction of Arrow II in FIG. 1. The view of FIG. 6 corresponds to that of FIG. 2, and shows the layer members 33a to 33j which are merely part of the layer members. FIG. 7 is a perspective exploded view showing the sound absorber 11a disintegrated into the layer members 33a to 33j. FIG. 8 is a schematic cross-sectional view showing the layer member 33a which is one of the layer members making up the sound absorber 11a. 
Referring to FIGS. 1 to 8, the sound absorber 11a is a so-called layered structure 34a formed by stacking the plurality of layer members 33a to 33j. A description will be made about the configuration of the layer member 33a that is located closest to the front face 19a, or the sound absorbing face, and composes the first side face. The layer member 33a is made of a nonwoven fabric. More specifically, the layer member 33a is made of polyester-based fibers 35a, and more concretely, is a layered member made by intricately intertwining a plurality of PET (Polyethylene terephthalate) fibers with a predetermined length. Other materials selected for the layer member 33a are, for example, glass wool, rock wool, etc.
Length L1 from a lateral end face 36a to a lateral end face 36b of the layer member 33a is equivalent to the lateral length L1 of the first side face 14a. The end face 36a forms a part of the fourth side face 17a, and the end face 36b forms a part of the fifth side face 18a. The thickness of the layer member 33a or, more specifically, the length, which is indicated by L9 in FIG. 8, between a face 37a located upward with respect to the direction of the thickness of the layer member 33a and the other face 37b located downward with respect to the thickness direction, is approximately a few mm (millimeters). The face 37a forms a part of the top face 12a, and the face 37b forms a part of the bottom face 13a. The other layer members 33b to 33j are composed of the same materials as the layer member 33a, but have different densities, or different weight per unit volume from the layer member 33a. Specifically, the layer member 33a located closest to the front face 19a is configured to have a density higher than the densities of the other layer members 33b to 33j. By placing the layer member 33a with the highest density at the closest position to the front face 19a, a certain degree of sound is reflected at the first side face 14a, that is the front face 19a. Reflection of the certain degree of sound is effective to provide reverberation in the room. The sound absorber 11a, which is a layered structure 34a, is formed by stacking such layer members 33a to 33j in the thickness direction, or the depth direction.
To stack the layer members 33a to 33j, each of the layer members 33a to 33j is joined to the adjacent one of the layer members 33a to 33j so as to intertwine their fibers with each other at a certain degree. Consequently, the sound absorber 11a formed by stacking the layer members 33a to 33j is treated as a piece of layered structure 34a, and even if the sound absorber 11a is lifted up, the sound absorber 11a will not disintegrate into individual layer members 33a to 33j. It is not necessary to make the borders between the layer members 33a to 33j clear enough to be perceived by eyes or other types of visual check. For example, the layered structure 34a may be configured so that high-density parts and low-density parts appear alternately. It is of course possible to interpose an adhesive member or a holding member between the opposed surfaces of the adjacent layer members 33a to 33j. It is also possible to apply pressure to the stacked layer members 33a to 33j in the direction along which the layer members 33a to 33j are stacked in order to somewhat intertwine the fibers on the surfaces of the respective layer members 33a to 33j, thereby forming the layered structure 34a. 
Among the layer members 33a to 33j, some layer members having the same size are disposed near the first side face 14a. More specifically, in this embodiment, four layer members 33a to 33d with the same length L8 in the longitudinal direction and the same length L1 in the shorter side direction are stacked on the side of the first side face 14a. From the midpoint of the layered structure 34a in the stack direction, the layer members 33e to 33j with the same length L8 in the longitudinal direction, but different lengths L1 in the shorter side direction, are stacked so that the layered structure 34a gradually becomes shorter in the shorter side direction. In short, the layer members 33a to 33j are stacked so as to form the shape shown in FIGS. 2 and 6 when viewed from the top face 12a or bottom face 13a. In this embodiment, the edges of the layer members 33e to 33j are beveled. In addition, the layer member 33j, which is located furthest from the front face 19a, is shaped into a triangular prism. The sound absorber 11a is configured so that its thickness in the stack direction indicated by Arrow III in FIG. 6 continuously varies, and more specifically, the thickness of the sound absorber 11a is the greatest at the lateral center in the left-to-right direction on the sheet of FIG. 6, and the length L1 in the shorter side direction extending toward the end faces 36a, 36b in the left-to-right direction continuously becomes shorter. In short, the second side face 15a and third side face 16a are configured to be inclined straightly with respect to the first side face 14a. In this embodiment, each end face of the layer members 33e to 33j defines the back face 20a of the sound absorber 11a. 
The following is a brief description about an example method for manufacturing the above-described sound absorber 11a. FIG. 9 is a cross-sectional view partially showing a semifinished product 38a in a manufacturing process of the method for manufacturing the sound absorber 11a. Referring to FIG. 9, firstly, a plurality of layer members 39a, 39b, 39c of the same lengthwise and widthwise dimensions are stacked on top of each other. Then, the semifinished product 38a is cut into the shape of a finished product, that is, the sound absorber 11a. The dotted lines in FIG. 9 indicate sections 40a to be cut at this stage. The sound absorber 11a can be manufactured in this manner. This method can manufacture the sound absorber 11a more efficiently.
For a case where the sound absorber 11a is installed in a soundproof room, which will be described later, the sound absorber 11a can be configured to include a detachable mechanism enabling attachment and detachment of the sound absorber 11a to/from the soundproof room. Available detachment mechanisms include, for example, a stopper, a fastener, and so on that can hold the sound absorber 11a on walls in the soundproof room. Alternatively, the undermentioned soundproof room can be configured to include a mounting member. Furthermore, the sound absorber 11a can be equipped with a transport means, such as casters, at the lower side of the bottom face 13a. The transport means facilitate movement of the sound absorber 11a when the sound absorber 11a is installed in or removed from the soundproof room.
A description will be made about a soundproof room according to the embodiment of the present invention. FIG. 10 is a schematic perspective view showing a part of a soundproof room 41a according to the embodiment of the invention. FIG. 11 is a schematic cross-sectional view of the soundproof room 41a according to the embodiment of the invention, as viewed from a ceiling 48a, which will be described later. FIG. 12 is a cross-sectional view of the soundproof room 41a taken along XII-XII in FIG. 11. FIGS. 13 and 14 are both enlarged views of an area where the sound absorber 11a is installed in the soundproof room 41a, but FIG. 14 shows the area without the sound absorber 11a. In the interest of clarity, FIGS. 13 and 14 omit a part of the sound absorber 11a and undermentioned mounting member, more concretely, an upper part in the height direction of the sound absorber 11a. Also, hatching is omitted in some drawings.
Referring to FIGS. 10 to 14, the soundproof room 41a according to the embodiment of the present invention allows the playing of musical instruments (not shown) or other performances to be held in an interior space 43a thereof and is equipped with a soundproof structure. This means that the soundproof room 41a to be described below is constructed with soundproof walls. The soundproof room 41a is provided with a sound absorber 11a configured as shown in FIG. 1. The soundproof room 41a is composed of four walls 44a, 45a, 46a, 47a, a ceiling 48a, and a floor 49a. The walls 44a, 45a, 46a, 47a, ceiling 48a, and floor 49a have flat wall surfaces 50a, 51a, 52a, 53a, a flat ceiling surface 54a, and a flat floor surface 55a, respectively, on the side of the interior space 43a of the soundproof room 41a. The wall surfaces 50a and 51a are provided so as to oppose to the wall surfaces 52a and 53a, respectively. The ceiling surface 54a is provided so as to oppose to the floor surface 55a in the vertical direction. The soundproof room 41a is in the shape of approximately a so-called rectangular parallelepiped. Specifically, the walls 44a, 45a, 46a, 47a of the soundproof room 41a compose four corner portions 56a, 57a, 58a, 59a, and the corner portions 56a, 57a, 58a, 59a formed with the wall surfaces 50a, 51a, 52a, 53a have an angle of 90 degrees as viewed from the ceiling 48a. The soundproof room 41a is designed large enough to hold various types of playing of musical instruments, such as a drum, piano, tuba, and cello, in the interior space 43a thereof. Though it is not illustrated, the soundproof room 41a is also provided with necessary lighting equipment and a door or some kinds of access means through which people, musical instruments, etc. enter and exit the room.
Mounting members 60a, 61a that are used to mount the sound absorber 11a are provided on adjacent wall surfaces 50a and 51a. The location of the mounting members 60a, 61a is in the vicinity of a corner portion 56a, which is a corner of the soundproof room 41a formed with the wall surfaces 50a and 51a. Both the mounting members 60a, 61a are triangular prisms with the cross section of an isosceles right triangle if they are cut through by a plane perpendicular to the longitudinal direction. The mounting member 60a is attached to a wall surface 50a with its side face 62a, which defines the longer side of the isosceles right triangle, abutting against the wall surface 50a. Similarly, the mounting member 61a is attached to a wall surface 51a with its side face 63a, which defines the longer side of the isosceles right triangle, abutting against the wall surface 51a. When the mounting members 60a, 61a are respectively provided on the wall surfaces 50a, 51a, their side faces 64a, 65a, each defining a shorter side of the isosceles right triangle, are opposed to each other. Length L10 between the side face 64a and side face 65a is nearly equal to, or, just to be on the safe side, somewhat longer than the length L1, which is the lateral length of the first side face 14a of the sound absorber 11a. 
The sound absorber 11a is fit into the mounting members 60a, 61a for installation. Specifically, the sound absorber 11a is installed at the corner portion 56a formed with the wall 44a and the wall 45a of the soundproof room 41a. The sound absorber 11a installed there is removable from the soundproof room 41a. The first side face 14a of the sound absorber 11a serves as the front face 19a, that is exposed in the soundproof room 41a. In addition, the second side face 15a, which composes a part of the back face 20a of the sound absorber 11a, faces the wall surface 50a, while the third side face 16a, which composes the other part of the back face 20a of the sound absorber 11a, faces the wall surface 51a. In short, the back face 20a of the sound absorber 11a is covered with the walls 44a, 45a, more concretely, with the wall surfaces 50a, 51a. The second side face 15a and third side face 16a are configured so as make contact with the wall surface 50a and wall surface 51a, respectively, or so as to allow very little clearance to be left between the second side face 15a and wall surface 50a, and between the third side face 16a and the wall surface 51a. In this case, the fourth side face 17a is also covered with the wall surface 50a. In other words, the fourth side face 17a is configured so as to make contact with the wall surface 50a, or so as to allow very little clearance to be left between the fourth side face 17a and the wall surface 50a. In addition, the fifth side face 18a is also covered with the wall surface 51a. In other words, the fifth side face 18a is configured so as to make contact with the wall surface 51a, or so as to allow very little clearance to be left between the fifth side face 18a and the wall surface 51a. The top face 12a is opposed to the ceiling surface 54a, and the bottom face 13a is opposed to the floor surface 55a. Specifically, the top face 12a and bottom face 13a are configured so as to make contact with the ceiling surface 54a and floor surface 55a, respectively, or so as to allow very little clearance to be left between the top face 12a and ceiling surface 54a, and between the floor surface 55a and bottom face 13a. 
According to the soundproof room 41a, the sound absorber 11a included in the soundproof room 41a has a varying thickness as viewed from the front face 19a, which serves as a sound absorbing face that absorbs sound, toward the depth direction. When sound enters through the sound absorbing face exposed in the soundproof room 41a, the relatively thicker part can efficiently absorb sounds with long wavelengths in a low audio frequency range, while both the relatively thick part and the relatively thin part can efficiently absorb sounds with short wavelengths in a high audio frequency range. In short, the sound absorber 11a can efficiently absorb sounds in a broad audio frequency range from high to low. Since the sound absorber 11a is formed by stacking the layer members 33a to 33j from the sound absorbing face in the depth direction, even if the layer members arranged on the sound absorbing face side cannot completely absorb sounds and allow the sounds to pass therethrough, the other layer members arranged further than the sound absorbing face in the depth direction can absorb the sounds permeated. Therefore, this soundproof room 41a can absorb sound in the room more properly.
The following is a detailed description about the sound absorption. FIG. 15 is a graph showing the relationship between reverberant sound, that is, reverberation and pitch of sound in the soundproof room 41a. In FIG. 15, the vertical axis represents the degree of the reverberant sound, while the horizontal axis represents the pitch of sound. Along the vertical axis, the sound is reverberated more, or the reverberant sound is prolonged toward the upper end of the vertical axis, while the sound is reverberated less, or the reverberant sound is shortened toward the lower end of the vertical axis. On the other hand, along the horizontal axis, the pitch becomes higher, or the audio frequency range becomes higher toward the right end of the horizontal axis, while the pitch becomes lower, or the audio frequency range becomes lower toward the left end of the horizontal axis. In FIG. 15, the solid line 66a indicates a measurement result of the soundproof room 41a according to the embodiment of the invention, the dot-and-dash line 66b indicates a measurement result of a conventional sound absorbing material, and for reference purposes, the dashed double-dotted line 66c indicates a measurement result when no sound absorbing material was used, that is, sound absorption was not carried out. The conventional sound absorbing material herein is a flat plate-like sound absorbing material, such as an acoustical panel, with a constant thickness, or approximately 10 mm. The graph in FIG. 15 indicates the relationship in a relative manner to provide a clear understanding, and therefore, a description will be made with the horizontal axis that is roughly classified into a low audio frequency range 67a, a middle audio frequency range 67b, and a high audio frequency range 67c. For example, the low audio frequency range 67a denotes an octave band with a center frequency of 125 Hz, while the high audio frequency range 67c denotes an octave band with a center frequency of 500 Hz. The middle audio frequency range 67b denotes an octave band between the low audio frequency range 67a and high audio frequency range 67c. 
With reference to FIG. 15, in the case where no sound absorbing material is used as indicated by the dashed double-dotted line 66c in FIG. 15, the sound is of course not absorbed, and therefore is reverberated for a long time across all ranges from the low audio frequency range 67a to the high audio frequency range 67c. Such reverberation is not preferable at all. In the case where a conventional sound absorbing material is used as indicated by the dot-and-dash line 66b in FIG. 15, the sound is absorbed evenly in comparison with the case without any sound absorbing material, and therefore the reverberation time can be somewhat shortened toward the high audio frequency range 67c. However, the conventional sound absorbing material drastically absorbs only the sound in a certain frequency range in the range 67d, encircled by a dotted line in FIG. 15. Actually, the reverberation time of the sound in the certain frequency range is short, but the sound in ranges somewhat higher or lower than the range is not absorbed well and its reverberation time is long. In addition, the conventional sound absorbing material excessively absorbs sound in an ascending manner from the middle audio frequency range 67b to the high audio frequency range 67c, and consequently, the reverberation time of the sound in the high audio frequency range 67c is shortened. This reverberation makes the sound in the high audio frequency range 67c typically husky, while prolonging the sound in the low audio frequency range 67a noticeably, and consequently an unbalanced reverberation is not anywhere near what the people playing music desire.
On the other hand, in the case of the soundproof room 41a according to the embodiment of the invention, the sound absorber 11a absorbs sound in the low audio frequency range 67a at a gradually increasing absorption rate with an increase in pitch, thereby shortening the reverberation time. The absorption rate of the sound absorber 11a exhibits nearly constant values from the middle audio frequency range 67b to the high audio frequency range 67c, and is maintained when the reverberation time of the sound becomes short to a certain degree. The sound absorber 11a provides this reverberation effect. Such reverberation exhibits good balance and is desirable, for example, for people who play music in the soundproof room 41a. 
These results possibly come from the following reasons. FIG. 16 illustrates an area where the sound absorber 11a is placed in the soundproof room 41a according to the embodiment of the invention on an enlarged scale, and also is an enlarged view of the area encircled by XVI in FIG. 11. The sound absorber 11a in FIG. 16 is equivalent to that in FIG. 2. Referring to FIG. 16, the sound absorber 11a installed in the soundproof room 41a according to the embodiment of the invention has a varying thickness as viewed from the sound absorbing face toward the depth direction. In this description, the sound absorber 11a is roughly divided, based on the difference in thickness, into a first segment 31a with a length in the thickness direction from the front face 19a to the back face 20a of 23 cm or longer, and second segments 31b, 31c each with a length in the thickness direction from the front face 19a to the back face 20a of less than 23 cm. The first segment 31a absorbs sound in the low audio frequency range 67a. In a case of a sound with a frequency of 125 Hz, which is a typical frequency of the extremely low-pitched sounds of pianos, for example, the wavelength of the sound is approximately 2.72 m. Since it is considered that a sound absorbing material having a thickness of one twelfth of the frequency of a sound can absorb the sound, 2720 cm/12=approximately 23 cm. Thus, if the length of the first segment 31a in the thickness direction is set to be 23 cm or longer, the sound absorber 11a can reliably absorb the sound of frequency 125 Hz. In case of dimension errors during manufacture of the sound absorber 11a, a length of 25 cm is ensured for length L6, which is the length of the first segment 31a in the thickness direction. In addition to the first segment 31a, the second segments 31b, 31c each with a length less than 23 cm can absorb sounds in the high audio frequency range 67c whose wavelengths are shorter than 23 cm, for example, a sound with a frequency of 500 Hz. Accordingly, the first segment 31a, which is regarded as a sound absorbing area for sounds in the low audio frequency range 67a, is configured to be relatively small, while the first segment 31a and second segments 31b, 31c, which are regarded as a sound absorbing area for sounds in the high audio frequency range 67c, are configured to be relatively large. The absorption rate for the sounds in the low audio frequency range 67a, more specifically in an octave band with a center frequency of 125 Hz is set to 0.5 or higher, while the absorption rate for the sounds in the high audio frequency range 67c, more specifically in an octave band with a center frequency of 500 Hz is set to 0.8 to 1.0. Setting the absorption rate for the sounds in the octave band with a center frequency of 125 Hz to a value lower than 0.5, for example 0.4 or 0.3, may impair the comfortable bass sounds for players and listeners. On the other hand, if the absorption rate for the sounds in the octave band with a center frequency of 500 Hz is set to a value less than 0.8, for example 0.7 or 0.6, sounds in a high audio frequency range are not absorbed sufficiently and reverberates too much, which may cause offensive sound for the players and listeners. However, the sound absorber 11a becomes continuously thinner, more specifically, the sound absorber 11a includes a maximum depth region whose depth dimension from the sound absorbing face to the corner 21a is the greatest, and depth increasing regions 30a, 30b that are located adjacent to the maximum depth region and have a depth dimension increasing while approaching the maximum depth dimension from the sound absorbing face, thereby efficiently and continuously absorbing sounds across the low to high audio frequency ranges smoothly. Thus, the sound absorber 11a can also efficiently absorb sounds in the middle audio frequency range 67b between the low audio frequency range 67a and high audio frequency range 67c. 
With the above-describe configuration, the soundproof room 41a according to the embodiment of the invention can achieve more proper sound absorption in the room. In short, setting the absorption rate of the sound absorber 11a for sounds in an octave band with a center frequency of 125 Hz to 0.5 or higher, and setting the absorption rate of the sound absorber 11a for sounds in an octave band with a center frequency of 500 Hz to from 0.8 to 1.0 can provide more appropriate reverberation.
Although the sound absorber 11a in this embodiment is approximately triangular in cross section, the present invention is not limited thereto, and, for example, the sound absorber 11a may have the following cross section.
FIG. 17 is a cross-sectional view of a soundproof room 41b according to another embodiment of the present invention. FIG. 17 shows an equivalent area to the area XVI in FIG. 11. In the embodiment shown in FIG. 17, like components are denoted by like numerals as of FIG. 11 and the other drawings and therefore the description thereof will not be reiterated. This is applied to the following drawings.
Referring to FIG. 17, the soundproof room 41b of this embodiment of the invention includes a sound absorber 11b. The structure of walls and other components making up the soundproof room 41b is the same as that shown in FIG. 10 and some other drawings. Specifically, the soundproof room 41b is composed of walls 44a, 45a, 46a, 47a, a ceiling 48a, and a floor 49a. The sound absorber 11b includes a top face, a bottom face, a front face 19b composed of a first side face 14b, and a back face 20b composed of a second side face 15b and a third side face 16b. The second side face 15b and third side face 16b are flat, but the first side face 14b has a curved surface. In this embodiment, the first side face 14b is shaped like an arc in cross section as shown in FIG. 17. More specifically, the first side face 14b is in the shape of a concave arc toward the inside of the sound absorber 11b. Even such a shaped sound absorber 11b can have a varying length in the thickness direction and thereby can more properly absorb sound. Alternatively, the first side face 14b can be shaped into a convex arc toward the outside of the sound absorber 11b. Furthermore, the first side face 14b can be composed of a plurality of curves.
Yet another embodiment shown below is also acceptable. FIG. 18 is a cross-sectional view of a soundproof room 41c according to the embodiment of the present invention. Referring to FIG. 18, the soundproof room 41c of this embodiment of the invention includes a sound absorber 11c. The structure of walls and other components making up the soundproof room 41c is the same as that shown in FIG. 10 or other drawings. The sound absorber 11c includes a top face, a bottom face, a front face 19c composed of a first side face 14c, and a back face 20c. The first side face 14c is flat, but the back face 20c has a curved surface. In other words, the back face 20c is shaped into an arc in cross section as shown in FIG. 18. Specifically, the back face 20c is in the shape of a convex arc toward the outside of the sound absorber 11b. The sound absorber 11c in this shape can more properly absorb sound in the room. This shape creates a clearance 68c between the back face 20c and wall surfaces 50a, 51a, and the back face 20c is not exposed in the soundproof room 41a, but is surrounded by the walls 44a, 45a. Therefore, the presence of the clearance 68c does not particularly affect the reverberation. Alternatively, the back face 20c can be shaped into a convex arc toward the inside of the sound absorber 11b. Furthermore, the back face 20c can be composed of a plurality of curves.
The sound absorber can be also configured as indicated below. FIG. 19 is a cross-sectional view of a soundproof room 41d according to yet another embodiment of the present invention. Referring to FIG. 19, the soundproof room 41d of this embodiment of the invention includes a sound absorber 11d. The structure of walls and other components making up the soundproof room 41d is the same as that shown in FIG. 10 and some other drawings. The sound absorber 11d includes a top face, a bottom face, a front face 19d composed of a first side face 14d, and a back face 20d composed of a second side face 15d, a third side face 16d, and a fourth side face 17d. The first side face 14d, second side face 15d, third side face 16d are all flat. The fourth side face 17d is also flat and is in parallel with the first side face 14d in cross section shown in FIG. 19. This shape creates a triangular clearance 68d between the wall surfaces 50a, 51a and the fourth side face 17d as viewed from the ceiling 48a. This configuration is also acceptable. Because the back face 20d is also surrounded by the walls 44a and 45a as with the case of the above embodiment, the clearance 68d does not particularly affect the reverberation. The fourth side face 17d of course can be shaped into an arc, and also does not need to be in parallel with the first side face 14d. Alternatively, the fourth side face 17d can be composed of a plurality of inclined flat surfaces.
Although the sound absorber 11a in the above-described embodiment is installed at the corner portion 56a of the soundproof room 41a, the present invention is not limited thereto, and therefore the sound absorber 11a can be installed at other parts of the soundproof room 41a, for example, in the vicinity of the corner portion 56a. This is also applied to the other sound absorbers in the other embodiments.
FIG. 20 is a cross-sectional view of a soundproof room 41e according to yet another embodiment of the present invention. FIG. 20 shows an area in the vicinity of the area XVI shown in FIG. 11. Referring to FIG. 20, the soundproof room 41e of this embodiment of the invention includes a sound absorber 11a having the configuration shown in FIG. 1 and some other drawings. A wall 45e, which is one of the components making up the soundproof room 41e, includes a recessed portion 70e that is recessed from a flat wall surface 51e toward the outside of the soundproof room 41e. The recessed portion 70e is composed of two wall surfaces 71e, 72e. Each of the wall surfaces 71e, 72e is formed so as to extend straight at an angle with respect to the wall surface 51e. The recessed portion 70e formed with the wall surfaces 71e, 72e has a shape into which the sound absorber 11a fits. Specifically, the wall surface 71e is shaped so as to fit with the second side face 15a, while the wall surface 72e is shaped so as to fit with the third side face 16a. The amount by which the recessed portion 70e is recessed with respect to the wall surface 51e is equivalent to the thickness of the sound absorber 11a. 
In this embodiment, the second side face 15a is abutted against the wall surface 71e and the third side face 16a is abutted against the wall surface 72e to house the sound absorber 11a in the recessed portion 70e. The soundproof room 41e can be configured in this manner to have the sound absorber 11a installed therein. According to the configuration, the sound absorber 11a does not stick out from the wall surface 51e in the soundproof room 41e. The elimination of the sticking part of the sound absorber 11a from the soundproof room 41e allows effective use of free space in the soundproof room 41e. 
The sound absorber and soundproof room can be also configured as indicated below. FIG. 21 is a cross-sectional view of a soundproof room 41f according to yet another embodiment of the present invention. FIG. 21 shows an equivalent area to the area XVI in FIG. 11. Referring to FIG. 21, the soundproof room 41f of this embodiment of the invention includes a sound absorber 11a having the configuration shown in FIG. 1 and some other drawings and a sound absorber 11f having the same configuration as that of the sound absorber 11a. In short, the soundproof room 41f includes two sound absorbers 11a and 11f. A wall 45f, which is one of the components making up the soundproof room 41f, includes a first recessed portion 70f that is recessed from a flat wall surface 50f toward the outside of the soundproof room 41f. The first recessed portion 70f is composed of two wall surfaces 71f, 72f. Each of the wall surfaces 71e, 72e is formed so as to extend straight at an angle with respect to the wall surface 50f. The first recessed portion 70f formed with the wall surfaces 71f, 72f has a shape into which the first sound absorber 11a fits. A wall 45f, which is one of the components making up the soundproof room 41f, includes a second recessed portion 73f that is recessed from a flat wall surface 51f toward the outside of the soundproof room 41f. The second recessed portion 73f is composed of two wall surfaces 74f, 75f. Each of the wall surfaces 74f, 75f is formed so as to extend straight at an angle with respect to the wall surface 51f. The second recessed portion 73f formed with the wall surfaces 74f, 75f has a shape into which the second sound absorber 11f fits. The wall surface 72f of the first recessed portion 70f and the wall surface 74f of the second recessed portion 73f are flatly contiguous with each other in the area of the corner portion 56a. 
In this embodiment, the second side face 15a is abutted against the wall surface 71f and the third side face 16a is abutted against the wall surface 72f to house the first sound absorber 11a in the first recessed portion 70f. In addition, the second side face 15f is abutted against the wall surface 74f and the third side face 16f is abutted against the wall surface 75f to house the second sound absorber 11f in the second recessed portion 73f. The soundproof room 41f is configured in this manner to have the first sound absorber 11a and second sound absorber 11f installed therein. According to the configuration, the two sound absorbers, that is, the first sound absorber 11a and second sound absorber 11f do not stick out from the wall surfaces 50f and 51f, respectively, of the soundproof room 41f. The elimination of the two sticking parts of the sound absorbers 11a, 11f from the soundproof room 41f allows effective use of free space in the soundproof room 41f. 
The sound absorber and soundproof room can be also configured as indicated below. FIG. 22 is a cross-sectional view of a soundproof room 41g according to yet another embodiment of the present invention. Referring to FIG. 22, the soundproof room 41g of this embodiment of the invention includes a sound absorber 11a having the configuration shown in FIG. 1 and some other drawings, and a sound absorber 11g having the same configuration as that of the sound absorber 11a. A wall 45g, which is one of the components making up the soundproof room 41g, includes a projecting portion 76g that projects from a flat wall surface 51g toward the inside of the soundproof room 41g. This projecting portion 76g is composed of three wall surfaces 77g, 78g, 79g. The wall surface 78g extends straight in parallel with the wall surface 51g. The wall surface 77g and wall surface 79g extend straight in the direction perpendicular to the wall surface 51g toward the inside of the soundproof room 41g. When viewed in cross section, the projecting portion 76g has simply a rectangular shape projecting with respect to the wall surface 51g. The amount by which the projecting portion 76g projects from the wall surface 51g corresponds to either of the length of the third side face 16a of the first sound absorber 11a and the length of the second side face 15g of the second sound absorber 11g. The wall surfaces 77g, 79g are shaped so as to fit with the third side face 16a of the first sound absorber 11a and the second side face 15g of the second sound absorber 11g, respectively.
In this embodiment, the second side face 15a is abutted against the wall surface 51g and the third side face 16a is abutted against the wall surface 77g to install the first sound absorber 11a. In addition, the second side face 15g is abutted against the wall surface 79g and the third side face 16a is abutted against the wall surface 51g to install the second sound absorber 11g. The soundproof room 41g is configured in this manner to have the two sound absorbers 11a, 11g installed therein. According to the configuration, in the soundproof room 41g having the projecting portion 76g projecting inwardly and two sound absorbers 11a, 11g, the two sound absorbers 11a, 11g can be placed in the soundproof room 41g by taking advantage of corners formed with the projecting portion 76g and the wall 45g, thereby allowing effective use of free space in the soundproof room 41g. 
The sound absorber and soundproof room can be also configured as indicated below. FIG. 23 is a schematic perspective view of a soundproof room 41h according to yet another embodiment of the present invention. FIG. 23 shows an area corresponding to the area in FIG. 10. Referring to FIG. 23, the soundproof room 41h of this embodiment of the invention includes three sound absorbers 80h, 81h, 82h. These three sound absorbers 80h to 82h have the same fundamental functionality as that of the sound absorber 11a shown in FIG. 1 and some other drawings, but are different in dimension. Specifically, the length of the sound absorbers 80h to 82h in the height direction is set to be somewhat short in comparison with the sound absorber 11a in FIG. 1. In this embodiment, the first sound absorber 80h is installed in a corner portion 56a between the wall surfaces 50a, 51a of the adjacent walls, which make up the soundproof room 41h. The installed first sound absorber 80h extends vertically along its length, or in the direction from the ceiling surface 54a to the floor surface 55a. In addition, the second sound absorber 81h is installed in a corner portion 83h between the wall surface 51a of a wall and the ceiling surface 54a of the ceiling, the wall and ceiling making up the soundproof room 41h. The installed second sound absorber 81h extends horizontally along its length. Furthermore, the third sound absorber 82h is installed in a corner portion 84h between the wall surface 51a of the wall and the floor surface 55a of the floor, the wall and floor making up the soundproof room 41h. The installed third sound absorber 82h extends horizontally along its length. The sound absorbers 80h, 81h, 82h can be configured in this manner.
The soundproof room according to the present invention can include an exposed area adjusting mechanism that adjusts the exposed area of the surface of the sound absorber exposed in the room.
FIG. 24 is a cross-sectional view of a soundproof room 41i according to yet another embodiment of the present invention. Referring to FIG. 24, the soundproof room 41i of this embodiment of the invention includes a sound absorber 11a having the configuration shown in FIG. 1 and some other drawings. The sound absorber 11a is installed with its front face 19a exposed in the soundproof room 41i. 
Attached on a wall surface 50a of the soundproof room 41i is a mounting member 60a that is used to hold a door 85i to adjust the exposed area of the front face 19a of the sound absorber 11a. The door 85i includes a flat plate member 86i and a support member 87i that rotatably supports the plate member 86i within a predetermined angle range. The shape and area of the plate member 86i are set to be large enough to cover the front face 19a of the sound absorber 11a when the door 85i is in a so-called closed state. Specifically, the plate member 86i has a predetermined thickness and is slightly larger than the first side face 14a as viewed from the front face 19a. FIG. 24 indicates the door 85i in a closed state, while FIG. 25 indicates the door 85i in an open state. As appreciated from the drawings, the door 85i can be opened and closed by turning the plate member 86i about the support member 87i, serving as a rotational center axis, in the direction indicated by Arrow B2 in FIG. 24 and the reverse direction.
The door 85i configured as above enables adjustment of the exposed area of the front face 19a, which serves as a sound absorbing face of the sound absorber 11a in the soundproof room 41i. Thus, the degree at which the sound absorber 11a absorbs sound can be changed, and accordingly the reverberation time in the soundproof room 41i can be adjusted. Therefore, the soundproof room 41i can readily provide more appropriate reverberation, for example, to people who play music in the soundproof room 41i. This door 85i can be separated into a plurality of door segments in the height direction of the front face 19a to use the door segments as doors 85i. This configuration allows a door 85i located at a height to be opened and a door 85i located at another height to be closed. Of course, the reverberation can be adjusted by adjusting the open/close angle of the plate members 86i. 
The sound absorber and soundproof room can be also configured as indicated below. FIG. 26 is a schematic cross-sectional view showing a soundproof room according to yet another embodiment of the present invention. FIG. 26 shows the soundproof room viewed from the ceiling, and corresponds to the view of FIG. 11. Referring to FIG. 26, a soundproof room 41j of this embodiment of the invention includes two sound absorbers 11a, 11j both having the configuration shown in FIG. 1 and some other drawings. The soundproof room 41j is composed of four walls 44a, 45a, 46a, 47a, a ceiling, and a floor, as with the case of FIG. 11. The walls 44a, 45a, 46a, 47a, ceiling, and floor have flat wall surfaces 50a, 51a, 52a, 53a, a flat ceiling surface, and a flat floor surface, respectively, on the side of the interior space.
As with the case shown in FIG. 11, the first sound absorber 11a is installed in a corner portion 56a between the wall 44a and wall 45a. The second sound absorber 11j is installed in a corner portion 58a between the wall 46a and wall 47a. This second sound absorber 11j is also placed with a first side face 14j, serving as a front face 19j, exposed in the soundproof room 41j and with a second side face 15j and a third side face 16j, serving as a back face, covered with the wall 46a and wall 47a, respectively. In this embodiment, the first sound absorber 11a is placed so-called diagonally opposite to the second sound absorber 11j. In addition, the soundproof room 41j includes a door 85i that adjusts the exposed area of the front face 19a of the first sound absorber 11a and a door 85j that adjusts the exposed area of the front face 19j of the second sound absorber 11j. The soundproof room 41j configured as above is acceptable. According to the configuration, the soundproof room 41j equipped with the two sound absorbers 11a, 11j can provide more favorable reverberation by changing the opening/closing state of the doors 85i, 85j. In FIG. 26, the door 85i of the first sound absorber 11a is open, while the door 85j of the second sound absorber 11j is closed.
The sound absorber and soundproof room can be also configured as indicated below. FIG. 27 is a schematic cross-sectional view of a soundproof room according to yet another embodiment of the present invention. FIG. 27 shows the soundproof room viewed from the ceiling, and corresponds to the views of FIGS. 11 and 26. Referring to FIG. 27, a soundproof room 41k of this embodiment of the invention includes four sound absorbers 11a, 11j, 11k, 88k having the configuration shown in FIG. 1 and some other drawings. As with the case shown in FIGS. 11 and 26, the soundproof room 41k is composed of four walls 44a, 45a, 46a, 47a, a ceiling, and a floor. The walls 44a, 45a, 46a, 47a, ceiling, and floor have flat wall surfaces 50a, 51a, 52a, 53a, a flat ceiling surface, and a flat floor surface, respectively, on the side of the interior space.
As with the case shown in FIG. 11, the first sound absorber 11a is installed in a corner portion 56a between the wall 44a and wall 45a. As with the case shown in FIG. 26, the second sound absorber 11j is installed in a corner portion 58a between the wall 46a and wall 47a. The third sound absorber 11k is installed in a corner portion 57a between the wall 45a and wall 46a. The fourth sound absorber 88k is installed in a corner portion 59a between the wall 44a and wall 47a. In this embodiment, the first sound absorber 11a, second sound absorber 11j, third sound absorber 11k, and fourth sound absorber 88k are placed simply in four corners of the rectangular soundproof room 41k as viewed from the ceiling.
Also, the soundproof room 41k includes a door 85i that adjusts the exposed area of the front face 19a of the first sound absorber 11a, a door 85j that adjusts the exposed area of the front face 19j of the second sound absorber 11j, a door 85k that adjusts the exposed area of the front face 19k of the third sound absorber 11k, and a door 90k that adjusts the exposed area of the front face 89k of the fourth sound absorber 88k. The soundproof room 41k can be configured as above. According to the configuration, the soundproof room 41k equipped with the four sound absorbers 11a, 11j, 11k, 88k can provide more favorable reverberation by changing the opening/closing state of the doors 85i, 85j, 85k, 90k. 
The sound absorber and soundproof room can be also configured as indicated below. FIG. 28 is a schematic perspective view of a soundproof room 41m according to yet another embodiment of the present invention. FIG. 28 shows an area corresponding to the area in FIG. 10. Referring to FIG. 28, the soundproof room 41m of this embodiment of the invention includes a sound absorber 11a having the configuration shown in FIG. 1 and some other drawings. The sound absorber 11a is installed with its front face 19a, serving as a sound absorbing face, exposed in the soundproof room 41m. 
Attached on wall surfaces 50a, 51a of the soundproof room 41m are mounting members 60a, 61a, respectively, to which a door 91m is attached to adjust the exposed area of the front face 19a of the sound absorber 11a. The door 91m is like a shutter including a plurality of flat plate members 92m, 93m. Specifically, the plate members 92m, 93m that are movable in the vertical direction, as indicated by Arrow B3 in FIG. 28 or the reverse direction, are attached to the mounting members 60a, 61a. Moving the plate members 92m, 93m vertically can adjust the exposed area of the front face 19a of the sound absorber 11a in the soundproof room 41m. 
The sound absorber and soundproof room can be also configured as indicated below. FIG. 29 is a schematic perspective view of a soundproof room 41n according to yet another embodiment of the present invention. FIG. 29 shows an area corresponding to the area in FIG. 10. Referring to FIG. 29, the soundproof room 41n of this embodiment of the invention includes a sound absorber 11a having the configuration shown in FIG. 1 and some other drawings. The sound absorber 11a is installed with its front face 19a exposed in the soundproof room 41n. 
Attached on wall surfaces 50a, 51a of the soundproof room 41n are mounting members 60a, 61a, respectively, to which a screen member 94n is attached to adjust the exposed area of the front face 19a of the sound absorber 11a. The screen member 94n is attached to the mounting members 60a, 61a. The screen member 94n is, for example, a rolled-up cloth-like member, and is extensible in the longitudinal direction of the sound absorber 11a, or in the vertical direction, as indicated by Arrow B4 in FIG. 29, or the reverse direction. The screen member 94n can adjust the exposed area of the front face 19a, serving as a sound absorbing face, freely from the full open position to the full closed position. Specifically, the screen member 94n has a lower end. The screen member 94n can be pulled down and held at any position by stopping pulling the lower end to cover a part of the front face 19a, thereby adjusting the exposed area of the front face 19a. FIG. 30 shows the screen member 94n with the lower end stopped at a desired position.
Though it is not illustrated, the aforementioned exposed area adjusting mechanism can be implemented in different ways. For example, a rotational shaft is provided to a sound absorber 11a in FIG. 2, so as to extend on the corner 21a in the longitudinal direction, and this rotational shaft is attached to, for example, a corner portion 56a of the room 41a shown in FIG. 11. Turning the sound absorber 11a about the rotational shaft serving as the center of rotation makes it possible to expose some part of the front face 19a in the room 41a to adjust the exposed area, or to hide the front face 19a. To implement this, it is desirable to form a storage by recessing a part of a wall 44a to house the sound absorber 11a. Of course, the rotational shaft can be provided anywhere in the room 41a. Furthermore, the rotational shaft does not need to always extend in the longitudinal direction.
Alternatively, the sound absorber 11a can be configured in such a way as to be pulled out from a wall 44a like a drawer and to be housed in the wall 44a. According to the configuration, the sound absorber 11a is pulled out from a wall surface 50a of the wall 44a by a certain extent to expose the front face 19a in a room 41a so that the necessary exposed area required for a necessary degree of reverberation can be ensured. In this case and the aforementioned case of the rotational shaft, it may be preferable to provide a member functioning as a handle, a grip, etc. somewhere on the front face 19a or back face 20a. 
In the above-described embodiments, the layer members are made of a nonwoven fabric; however, the present invention is not limited thereto, and the layer members may be made of a woven fabric or may be made of a paper-like material, for example.
Although the mounting members, doors attached to the mounting members, and screen member attached to the mounting members are attached to the soundproof room in the above-described embodiments, the sound absorber itself can be equipped with those. In other words, the sound absorber that absorbs sound in a room can be equipped with the exposed area adjusting mechanism for adjusting the exposed area of the sound absorbing face exposed in the room.
Although the embodiments of the present invention have been described with reference to the figures, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the above illustrated embodiments within the same scope as, or an equivalent scope to, the present invention.
INDUSTRIAL APPLICABILITY
The soundproof room according to the invention is effectively used to meet demands for more proper sound absorption.
REFERENCE SIGNS LIST
11a, 11b, 11c, 11d, 11f, 11g, 11j, 11k, 80h, 81h, 82h, 88k: sound absorber, 12a: top face, 13a: bottom face, 14a, 14b, 14c, 14d, 14g, 14j, 15a, 15b, 15d, 15g, 15j, 16a, 16b, 16d, 16g, 16j, 17a, 17d, 18a, 62a, 63a, 64a, 65a: side face, 19a, 19b, 19c, 19d, 19j, 19k, 89k: front face, 20a, 20b, 20c, 20d: back face, 21a, 22a, 23a: corner, 24a, 25a, 26a, 27a, 28a, 66a, 66b, 66c: line, 29a, 29b, 29c, 29d, 29e: end, 30a, 30b, 67a, 67b, 67c, 67d: region, 31a, 31b, 31c: segment, 32a, 32b: dot, 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, 33i, 33j, 39a, 39b, 39c: layer member, 34a: layered structure, 35a: fibers, 36a, 36b: end face, 37a, 37b: face, 38a: semifinished product, 40a: section, 41a, 41b, 41c, 41d, 41e, 41f, 41g, 41h, 41i, 41j, 41k, 41m, 41n: soundproof room, 43a: interior space, 44a, 44f, 45a, 45e, 45f, 45g, 46a, 47a: wall, 48a: ceiling, 49a: floor, 50a, 50f, 51a, 51e, 51f, 51g, 52a, 53a, 71e, 71f, 72e, 72f, 74f, 75f, 77g, 78g, 79g: wall surface, 54a: ceiling surface, 55a: floor surface, 56a, 57a, 58a, 59a, 83h, 84h: corner portion, 60a, 61a: mounting member, 68c, 68d: clearance, 70e, 70f, 73f: recessed portion, 76g: projecting portion, 85i, 85j, 85k, 90k, 91m: door, 86i, 92m, 93m: plate member, 87i: support member, 94n: screen member.

## Claims

1. A soundproof room, comprising:
walls defining an interior space; and
a sound absorber, the sound absorber being substantially triangular in cross-section, and having a first side face, a second side face adjacent the first side face, a third side face adjacent to the first side face and adjacent to the second side face, a top face, and a bottom face opposite the top face, wherein the sound absorber comprises:
a first layer member having a sound absorbing surface and a rear surface opposite the sound absorbing surface, wherein the sound absorbing surface faces the interior space, and the first side face comprises the sound absorbing surface; and
a plurality of second layer members stacked on the rear surface of the first layer member in a depth direction away from the interior space,

wherein
the first layer member and the second layer members of the plurality of second layer members each have a corresponding thickness such that the sound absorber is configured to have a gradually increasing rate of sound absorption in a first frequency range having a center frequency of about 125 Hz, and a substantially constant rate of sound absorption over a second frequency range having a center frequency of about 500 Hz,
each second layer member of the plurality of second layer members has a corresponding surface area,
a first surface area of one second layer member of the plurality of second layer members is greater than a second surface area of a different second layer member of the plurality of second layer members, and
the second layer member having the first surface area is closer to the first layer member than the second layer member having the second surface area,
the first layer member has a first density,
the second layer members of the plurality of second layer members have a second density,
the first density is greater than the second density, and
each of the first layer member and each second layer member of the plurality of second layer members comprise a same material.

2. The soundproof room according to claim 1, wherein the sound absorber comprises:
a first segment having a first thickness extending from the sound absorbing surface in the depth direction, the first thickness being at least 23 cm; and
a second segment having a second thickness extending from the sound absorbing surface in the depth direction, the second thickness being less than 23 cm.

3. The soundproof room according to claim 1, wherein the sound absorber comprises:
a maximum depth region having a first thickness extending from the sound absorbing surface in the depth direction, the first thickness being a greatest thickness in the depth direction; and
a depth increasing region having a varying thickness that increases while approaching the maximum depth region, the varying thickness extending from the sound absorbing surface in the depth direction,
wherein the depth increasing region is adjacent to the maximum depth region.

4. The soundproof room according to claim 1, wherein the first layer member and each second layer member of the plurality of second layer members comprise an unwoven fabric.

5. The soundproof room of claim 1, wherein the surface area of the second layer members of the plurality of second layer members decreases as a distance away from the first layer member increases in the depth direction.

6. The soundproof room of claim 5, wherein the surface area of each second layer member of the plurality of second layer members is different.

7. The soundproof room of claim 1, wherein the surface area of each second layer member of the plurality of second layer members is different.

8. The soundproof room of claim 1, wherein the sound absorption is based on an amount of time a sound output to the interior space is reverberated.

9. A soundproof room, comprising:
walls defining an interior space; and
a sound absorber, the sound absorber being substantially triangular in cross-section, and having a first side face, a second side face adjacent the first side face, a third side face adjacent to the first side face and adjacent to the second side face, a top face, and a bottom face opposite the top face, wherein the sound absorber comprises:
a first layer member having a sound absorbing surface and a rear surface opposite the sound absorbing surface, wherein the sound absorbing surface faces the interior space, the first side face comprises the sound absorbing surface, and the first layer member has a first density; and
one or more second layer members stacked on the rear surface of the first layer member in a depth direction away from the interior space, wherein the one or more second layer members have a second density less than the first density, and each of the one or more second layer members comprises a same material as the first layer member,

wherein the first layer member and the one or more second layer members each have a corresponding thickness such that the sound absorber is configured to have a variable rate of sound absorption in a first frequency range having a center frequency of about 125 Hz.

10. The soundproof room of claim 9, wherein the sound absorber is further configured have a substantially constant rate of sound absorption in a second frequency range having a center frequency of about 500 Hz.

11. The soundproof room of claim 10, wherein the sound absorber is further configured have a substantially constant rate of sound absorption in a third frequency range between the first frequency range and the second frequency range.

12. The soundproof room of claim 11, wherein the variable rate of sound absorption in the first frequency range gradually increases over the first frequency range to a sound absorption value associated with the third frequency range.

13. The soundproof room of claim 9, wherein each of the first layer member and the one or more second layer members comprises an unwoven material having corresponding fibers, and the fibers of the first layer member are intertwined with the fibers of one of the second layer members.

14. The soundproof room of claim 13, wherein the fibers of two of more second layer members are intertwined.

15. The soundproof room of claim 9, wherein the first layer member and the one or more second layer members comprise a woven material.

16. A soundproof room, comprising:
walls defining an interior space; and
a sound absorber, the sound absorber being substantially triangular in cross-section, and having a first side face, a second side face adjacent the first side face, a third side face adjacent to the first side face and adjacent to the second side face, a top face, and a bottom face opposite the top face, wherein the sound absorber comprises:
a first layer member having a sound absorbing surface and a rear surface opposite the sound absorbing surface, wherein the sound absorbing surface faces the interior space, the first side face comprises the sound absorbing surface, and the first layer member has a first density; and
one or more second layer members stacked on the rear surface of the first layer member in a depth direction away from the interior space, wherein the one or more second layer members have a second density less than the first density, and each of the one or more second layer members comprises a same material as the first layer member,

wherein the first layer member and the one or more second layer members each have a corresponding thickness such that the sound absorber is configured to have a gradually increasing rate of sound absorption in a first frequency range having a first center frequency and a substantially constant rate of sound absorption over a second frequency range having a second center frequency greater than the first center frequency.

17. The soundproof room of claim 16, wherein the gradually increasing rate of sound absorption is parabolic.

18. The soundproof room of claim 16, wherein the first center frequency is 125 Hz and the second center frequency is 500 Hz.

19. The soundproof room of claim 16, wherein the sound absorption value is based on an amount of time a sound is reverberated in the interior space after being output.

20. The soundproof room of claim 16, wherein the first layer member and the one or more second layer members comprise a woven material.