JP4998234B2 - Acoustic diffuser - Google Patents

Description

  The present invention relates to an acoustic diffuser that scatters (diffuses) sound waves, and is configured to be able to scatter sound waves in a relatively wide band including a low frequency range with a relatively thin configuration.

  The acoustic diffuser is installed on the wall or ceiling of a hall or listening room and scatters sound waves in the room, and is used to adjust the sound in the room. Conventional acoustic diffusers include those described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2 below. The acoustic diffuser described in Patent Document 1 is a member in which members formed in a triangular cross section, a semicircular cross section, a circular arc shape, or the like are installed on a wall surface or a ceiling. The acoustic diffuser described in Patent Document 2 is configured such that two acoustic panels each having a convexly curved surface are arranged next to each other, and the mutual angle between both acoustic panels is variable. The acoustic diffuser described in Non-Patent Document 1 is a member in which a member having a cylindrical surface, a sawtooth surface, a spherical surface, or the like is installed on a wall surface. The acoustic diffuser described in Non-Patent Document 2 is a so-called “Schröder diffuser”, in which a number of grooves of various depths partitioned by a rigid material are arranged along the wall or ceiling. is there.

Japanese Patent No. 3580718 JP 2006-30995 A "Architectural Acoustic Engineering Handbook", Gihodo, 1968, p196 “Indoor acoustics”, Ichigaya Publishing Co., Ltd., Kuttorf Heinrich, 2003, pp 54-57

  The convex-shaped acoustic diffuser described in Patent Document 1 and Non-Patent Document 1 needs to have a large overall size according to the wavelength of the scattering target, and needs to be thick enough to scatter the low frequency range. It was. Similarly, the movable acoustic panel of the acoustic diffuser described in Patent Document 2 needs to have a sufficient thickness to scatter the low frequency range. The Schröder diffuser described in Non-Patent Document 2 also requires a sufficient thickness because the groove depth needs to be increased in order to scatter the low sound range. As described above, the conventional acoustic diffuser needs to have a sufficient thickness to scatter the low sound range, and is not suitable for a relatively small room such as a home acoustic room.

  The present invention is intended to solve the problems in the prior art and to provide an acoustic diffuser that can scatter a relatively wideband sound wave including a low frequency range with a relatively thin configuration.

  The acoustic diffuser of the present invention has a plurality of spaces arranged in a plane and partitioned from each other by a partition wall. Each of the spaces is closed at the back by a rear wall and the front forms an opening. The portions are respectively closed by the film-like sound absorbing material, and the arrangement height of the film-like sound absorbing material from the rear wall between the adjacent spaces in at least one direction and the layer of the air layer behind the film-like sound absorbing material The thickness is different.

  As is well known, the sound absorption coefficient characteristic of the film-shaped sound absorbing material has a relatively sharp peak at the resonance frequency (natural frequency), and the maximum sound absorption coefficient is also large. At frequencies other than the peak, the sound absorption rate decreases rapidly. This peak resonance frequency can be controlled relatively easily by changing the thickness of the air layer behind the film-like sound absorbing material and the sheet thickness of the film-like sound absorbing material, and has a desired sound absorption peak frequency (resonance frequency). A film-like sound absorbing material can be designed. A film-like sound absorbing material having a sound absorption peak frequency in a low sound range of about 200 Hz can also be configured to be thin.

  According to the acoustic diffuser of the present invention, since the layer thickness of the air layer behind the film-like sound absorbing material is made different between adjacent spaces, the sound absorption peak frequency is shifted between the two film-like sound absorbing materials. Due to the deviation of the sound absorption peak frequency, a discontinuous surface of acoustic impedance is formed. When a sound wave is incident on a portion where the acoustic impedance is discontinuous, a diffracted wave is generated, and the diffracted wave influences each other to scatter acoustic energy in a direction other than specular reflection. In this way, a scattering effect is obtained in the vicinity of both sound absorption peak frequencies. In particular, the sound absorption characteristics of the film-shaped sound absorbing material have a relatively sharp peak at the resonance frequency as described above, and the sound absorption coefficient decreases rapidly at frequencies other than the peak, so that discontinuity of acoustic impedance is easily realized and sufficient scattering effect is obtained. There is a feature that it is easy to obtain (in comparison, the scattering effect is difficult to obtain because the peak is broad and low in the case of a plate-like sound absorbing material). As described above, since the film-like sound absorbing material having the sound absorption peak frequency in the low sound range of about 200 Hz can be configured to be thin, the acoustic diffuser of the present invention can scatter sound waves in the low sound range with a relatively thin structure.

  Further, according to the present invention, since the arrangement height of the film-like sound absorbing material from the rear wall is made different between adjacent spaces, the surface shape due to the arrangement of the film-like sound absorbing material is uneven. Due to the unevenness of the surface shape, the sound wave is scattered in a higher sound range than due to the discontinuity of the acoustic impedance. Therefore, according to the present invention, it is possible to scatter a relatively wideband sound wave including a low sound range with a relatively thin configuration.

The acoustic diffuser of the present invention has the normal incident sound absorption coefficient characteristics of the two film-like sound absorbing materials in the adjacent spaces , the first primary resonance frequency of the first film-like sound absorbing material having the lower primary resonance frequency, and the primary The sound absorption coefficient of the first film-like sound absorbing material between the second film-like sound absorbing material having the higher resonance frequency and the second primary resonance frequency is higher than the peak value at the first primary resonance frequency. first in frequency you decrease the value of either 10-20% sound absorption coefficient in the primary resonant frequency, the absorption sound rate of the first film-like sound absorbing material in decreasing course toward the second and absorption sound rate of the second film-like sound absorbing material in a process for decreasing toward the low frequency side is set so as to match the peak value of the primary resonance frequency of. According to this, it is possible to obtain a scattering effect due to impedance discontinuity between both primary resonance frequencies.

  In this invention, the said rear wall can be comprised with the plate-shaped member fixed to the back part of the said partition wall, for example. In this case, the plate-like member and the partition wall can be formed of an integrally molded product of the same material or an assembly of separate parts. The rear wall may be a wall surface of a chamber to which the acoustic diffuser is attached.

  The acoustic diffuser of the present invention is set so that the arrangement height of the film-like sound absorbing material from the rear wall is higher as it is located at the center of the arrangement of the film-like sound absorbing material, and lower as it goes to the periphery. The surface shape due to the arrangement of the film-like sound absorbing material may be generally mountain-shaped. According to this, a relatively high sound range can be scattered by the surface shape of the mountain.

  In the acoustic diffuser according to the present invention, for example, the partition wall is formed in a grid shape in which a vertical partition wall and a horizontal partition wall are arranged at uniform intervals, and the space is formed in a rectangular shape having the same size. Can be.

  The acoustic diffuser of the present invention can vary the sheet thickness of the film-like sound absorbing material between the adjacent spaces. According to this, the difference in the thickness of the air layer behind the film-like sound absorbing material and the difference in the sheet thickness of the film-like sound absorbing material are combined to form a discontinuous surface of acoustic impedance between the adjacent film-like sound absorbing materials. Can be scattered.

  In the acoustic diffuser of the present invention, a stepped portion having various arrangement positions in the space depth direction between adjacent spaces is formed integrally with or separately from the peripheral edge of the inner peripheral surface of each space. Each film-like sound absorbing material is housed in each space, a peripheral portion is supported on the stepped portion, and a ring shape is formed for each space from above (including a ring shape in which a part is cut out). ), And the film-like sound absorbing material is fixed by sandwiching the peripheral portion of the film-like sound absorbing material between the stepped portion and the suppressing member.

Embodiment 1
Embodiments of the present invention will be described below. FIG. 1 shows an embodiment of an acoustic diffuser according to the present invention. (A) is a front view, (b) is AA arrow sectional drawing of (a). The acoustic diffuser 10 includes a panel body 15 having a partition wall 14 (rigid wall) protruding from the front surface of a flat plate-like member 12 having a predetermined plate thickness. The plate-like member 12 and the partition wall 14 are made of an integrally molded product made of metal such as aluminum or plastic. Alternatively, after the plate-like member 12 and the partition wall 14 are configured separately, the panel body 15 can be configured by bonding with a bonding material such as an adhesive or a screw. The partition wall 14 is formed in a cross beam shape in which vertical partition walls and horizontal partition walls are arranged at uniform intervals. As a result, a plurality of (16 in this example) spaces 16 having the same shape and the same dimensions, which are partitioned by the partition wall 14, are arranged and formed on the front side of the plate-like member 12. Each space 16 is closed at the back by a rear wall (rigid wall) formed by the plate-like member 12, and the front part forms an opening 16a. The openings 16a are respectively closed with a film-like (sheet-like) sound absorbing material 18. The film-like sound absorbing material 18 in each space 16 is composed of, for example, an organic sheet (vinyl chloride film, canvas, rubber sheet, etc.) having the same material and the same sheet thickness, and is formed into a predetermined shape, for example, by molding (die cutting) using a press or the like. ing. The arrangement height h (= layer thickness of the back air layer) of the film-like sound absorbing material 18 from the rear wall surface 12a (the surface of the plate-like member 12) differs between the spaces 16 adjacent to each other in each direction. The surface of the panel body 15 is covered with an acoustically permeable cloth 20 such as a saran net for decoration as necessary. At the four corners of the plate-like member 12 of the panel body 15, holes 22 for inserting screws for fixing the acoustic diffuser 10 to the wall surface of the chamber are formed.

  The dimensions of the acoustic diffuser 10 in FIG. 1 can be designed to be thin, for example, about 40 to 80 cm in length and width, and about 1 to 5 cm in thickness. The thickness of the partition wall 14 is preferably thin so that the scattering effect due to the discontinuity of the acoustic impedance is efficiently generated between the adjacent film-like sound absorbing materials 18 and 18. Therefore, when the four film-like sound absorbing materials 18 are arranged vertically and horizontally as shown in FIG. 1, assuming that the length (or width) of the entire acoustic diffuser 10 is 40 cm, each film-like sound absorbing material 18 is arranged. If the vertical (or horizontal) dimension of the acoustic diffuser 10 is 80 cm, the vertical (or horizontal) dimension of each film-shaped sound absorbing material 18 is 20 cm or less. Become. When the entire thickness of the acoustic diffuser 10 is 1 cm, the arrangement height h of the film-like sound absorbing material 18 from the rear wall surface 12a is h <(1 cm—the thickness of the plate-like member 12), and the acoustic diffuser When the thickness of the whole 10 is 5 cm, the arrangement height h of the film-like sound absorbing material 18 from the rear wall surface 12a is h <(5 cm−plate thickness of the plate-like member 12). The sheet thickness of the film-like sound absorbing material 18 can be set to about 0.5 to 2 mm, for example.

  FIG. 2 shows an example of the installation structure of the film sound absorbing material 18 in each space 16. (A) is a top view, (b) is BB arrow sectional drawing of (a). Steps 24 are respectively formed at the peripheral edge of the inner peripheral surface of each space 16 (side surface of the partition wall 14). The height h of the step portion 24 from the rear wall surface 12a is different between the adjacent spaces 16 and 16. The peripheral edge portion of the film-shaped sound absorbing material 18 is supported on the step portion 24. An annular holding member 26 (a part in the circumferential direction may be cut out) is fitted into the space 16 from above. As a result, the film-like sound absorbing material 18 is sandwiched between the step portion 24 and the holding member 26 and is fixed and held in a state where it floats from the rear wall surface 12 a in the space 16.

  The operation of the acoustic diffuser 10 having the above configuration will be described. FIG. 3 shows an example of the normal incident sound absorption coefficient characteristic of one film-like sound absorbing material 18 of the acoustic diffuser 10. F1 is a primary resonance frequency, and F2 is a secondary resonance frequency. The normal incident sound absorption coefficient characteristic of the film-shaped sound absorbing material 18 has a relatively sharp peak at the resonance frequency, and the maximum sound absorption coefficient is also large (particularly at the primary resonance frequency). At frequencies other than the peak, the sound absorption rate decreases rapidly. The resonance frequency that becomes the peak can be controlled relatively easily by changing the thickness of the air layer behind the film-like sound absorbing material 18 or the sheet thickness of the film-like sound absorbing material 18. That is, by increasing the thickness of the air layer behind the film-shaped sound absorbing material 18 or increasing the sheet thickness of the film-shaped sound absorbing material 18, the resonance frequency is lowered, and the layer thickness of the air layer behind the film-shaped sound absorbing material 18 is decreased. Alternatively, the resonance frequency is increased by reducing the sheet thickness of the film-like sound absorbing material 18.

  In this embodiment, by making the layer thickness of the back air layer different between the adjacent film-like sound absorbing materials 18, 18, the resonance frequencies are mutually shifted between the adjacent film-like sound absorbing materials 18, 18. A peak is generated. FIG. 4 shows an example of normal incident sound absorption coefficient characteristics A, B, and C of three film-like sound absorbing materials 18-1, 18-2, and 18-3 adjacent to the acoustic diffuser 10. F1-1, F1-2, and F1-3 are the primary resonance frequencies of the respective film-like sound absorbing materials 18-1, 18-2, and 18-3, and F2-1, F2-2, and F2-3 are the secondary resonance frequencies. Indicates. The primary resonance frequencies F1-1, F1-2, and F1-3 are F1-1 <F1-2 <F1-3. Assuming that the frequency bands F1-1 to F1-3 are set as bands for which the scattering effect due to the discontinuity of the acoustic impedance is expected, the vertical and horizontal dimensions of each film-like sound absorbing material 18 are the lowest frequency F1 for which the scattering effect is expected. Is set to be sufficiently shorter than the wavelength corresponding to 1, and crosses the characteristic B at a frequency at which the sound absorption coefficient of the characteristic A decreases to about 10 to 20% of the sound absorption coefficient α1 at the primary resonance frequency F1-1. Each of the film-like sound absorbing materials 18-1 and 18-2 depends on the layer thickness of the back air layer so that the sound absorption coefficient crosses the characteristic C at a frequency at which the sound absorption coefficient decreases to about 10 to 20% of the sound absorption coefficient α2 at the primary resonance frequency F1-2. , 18-3 (the other sound absorbing materials 18 adjacent to each other are sequentially set in this manner). Thereby, the acoustic impedance becomes discontinuous between the adjacent film-like sound absorbing materials 18-1, 18-2, 18-3, and the scattering effect due to the discontinuity of the acoustic impedance is obtained in the frequency bands F1-1 to F1-3. . Specifically, assuming that the frequency band F1-1 to F1-3 is a band where the scattering effect due to the discontinuity of acoustic impedance is expected and the band is 200 to 400 Hz, for example, F1-1 = 200 Hz, F1-2 = 300 Hz, F1-3 = 400 Hz can be set. Although the scattering effect is smaller than the acoustic impedance discontinuity due to the primary resonance frequencies F1-1, F1-2, and F1-3, the acoustic impedance is also discontinuous in the frequency bands F2-1 to F2-3 due to the secondary resonance frequency. A scattering effect is obtained.

  Further, since the film-like sound absorbing material 18 has different surface heights between adjacent ones, the surface of the acoustic diffuser 10 as a whole is uneven. Due to the unevenness of the surface shape, a sound wave scattering effect can be obtained in a high sound range (for example, 500 Hz or more) as compared with the discontinuity of acoustic impedance. As described above, the scattering effect can be obtained in a relatively wide band including a low sound range with a relatively thin configuration. Further, as described above, the vertical and horizontal dimensions of each film-shaped sound absorbing material 18 can be set sufficiently shorter than the wavelength corresponding to the lowest frequency at which the scattering effect is expected, so that each film-shaped sound absorbing material 18 has a small area. The area of the entire acoustic diffuser 10 can be reduced.

  Examples of installation of the acoustic diffuser 10 in a room (a room such as an audio room in a general home, a room in an office, etc.) are shown in FIGS. FIG. 5 shows the acoustic diffuser 10 fixed to the wall surface 30 of the chamber 28 with screws 32. FIG. 6 shows the acoustic diffuser 10 suspended by a wire 36 from the ceiling 34 of the chamber 28. FIG. 7 shows the acoustic diffuser 10 mounted on a leg 38 with casters and disposed in the chamber 28.

The acoustic characteristic improvement effect by the acoustic diffuser 10 will be described. As shown in FIG. 8, speakers 42 and 44 are arranged in the chamber 40 at a distance r from the rear wall 46. An acoustic diffuser is not disposed in the vicinity of one speaker 42. In the vicinity of the other speaker 44, the acoustic diffuser 10 according to the present invention is disposed on the rear wall surface 46 and the side wall surface 48, respectively. FIG. 9A shows frequency characteristics measured in the room 40 when sound is emitted from the speaker 42 (the speaker 44 is silent). The direct sound emitted from the speaker 42 interferes with the reflected sound reflected by the rear wall 46,
r / λ = (2n + 1) / 4 (λ: wavelength of sound, n = 0, 1, 2,...)
A dip due to interference occurs at the frequency. Next, FIG. 9B shows frequency characteristics when sound is emitted from the speaker 44 (the speaker 42 is silent). Part of the sound emitted from the speaker 44 and reflected by the wall surfaces 46 and 48 is scattered and absorbed by the acoustic diffuser 10, so that there is less interference with the direct sound and the dip is mitigated. Therefore, the sound quality is improved.

<< Embodiment 2 >>
Another embodiment of the acoustic diffuser according to the present invention is shown in FIG. This is a film-like sound absorbing material disposed so as to form a generally chevron shape for the entire acoustic diffuser. (A) is a front view, (b) is a cross-sectional view taken along CC and DD in (a), and (c) is an equivalent surface shape of the entire acoustic diffuser. The acoustic diffuser 50 is different from the acoustic diffuser 10 of the first embodiment (FIG. 1) only in the number of the film-shaped sound absorbing materials arranged and the surface shape of the entire sound diffuser due to the arrangement of the film-shaped sound absorbing materials. The other configurations are the same. The same code | symbol is used for the part which is common with the acoustic diffuser 10 of FIG. A total of 25 film-like sound absorbing materials 18 are arranged in the acoustic diffuser 50 in the vertical and horizontal directions. The arrangement height h of the film-like sound absorbing material 18 from the rear wall surface 12a is the highest in the center in both the vertical and horizontal directions, and gradually decreases toward the peripheral edge. As a result, the surface shape of the acoustic diffuser 50 as a whole is formed in an approximately chevron shape (in this example, a quadrangular pyramid) with the center portion apex as shown in the equivalent surface shape of (c).

  According to the above configuration, the layer thickness of the back air layer is different between the adjacent film-like sound absorbing materials 18 and 18 in the radial direction centered on the center film-like sound absorbing material 18 (the adjacent film-like shape in the circumferential direction). The sound-absorbing materials 18 and 18 have the same back-thickness air layer thickness), thereby obtaining a relatively low-frequency scattering effect due to acoustic impedance discontinuity, and at the same time a relatively high-frequency range due to the surface shape of the mountain. Scattering effect can be obtained. The frequency of the sound wave scattered by the surface shape of the chevron is about 540 Hz or more when one side of the base of the chevron is 40 cm, and is about 270 Hz or more when the base is 80 cm. As described above, the scattering effect can be obtained in a relatively wide band including a low sound range with a relatively thin configuration.

<< Embodiment 3 >>
FIG. 11 shows still another embodiment of the acoustic diffuser according to the present invention. (A) is a front view, (b) is EE arrow sectional drawing of (a). In this case, the rear wall that closes the back portion of the film-like sound absorbing material arrangement space is constituted by the wall surface of the chamber. The acoustic diffuser 60 is different from the acoustic diffuser 10 of the first embodiment (FIG. 1) only in that it does not include the plate member 12 (FIG. 1), and the other configurations are the same. The same code | symbol is used for the part which is common with the acoustic diffuser 10 of FIG. Each space 16 of the acoustic diffuser 60 is open at both the back and the front. Each space 16 is provided with a film-like sound absorbing material 18 at an appropriate height position. The acoustic diffuser 60 is attached to a wall surface 62 (rigid wall) of the chamber with four corners fixed with screws 64. Thereby, the back portion of each space 16 is closed with the wall surface 62 of the chamber as the rear wall. According to this, compared with the acoustic diffuser 10 of Embodiment 1, it can comprise at a light weight with few materials, since there is no plate-shaped member 12. FIG. The operation of the acoustic diffuser 60 is the same as that of the acoustic diffuser 10 of the first embodiment.

  In the above embodiment, each film-like sound absorbing material is composed of sheets of the same material and the same thickness. Instead, each film-like sound absorbing material is composed of sheets of the same material with different thicknesses or sheets of different materials. You can also Moreover, in the said embodiment, although each film-form sound-absorbing material was made into the same shape and the same dimension, it is not restricted to this, It can also be set as a different shape and a different dimension.

It is the front view and sectional drawing which show Embodiment 1 of the acoustic diffuser by this invention. It is the top view and sectional drawing which show an example of the installation structure of the film-form sound absorption material 18 in each space 16 of FIG. It is a figure which shows an example of the normal incidence sound absorption coefficient characteristic of one film-form sound-absorbing material 18 of the acoustic diffuser 10 of FIG. It is a figure which shows an example of the normal incidence sound absorption coefficient characteristic of the three film-like sound-absorbing materials 18 which the acoustic diffuser 10 of FIG. 1 adjoins. It is a perspective view which shows the example of installation with respect to the chamber | room of the acoustic diffuser 10 of FIG. It is a perspective view which shows the other example of installation with respect to the chamber | room of the acoustic diffuser 10 of FIG. It is a perspective view which shows another example of installation with respect to the chamber | room of the acoustic diffuser 10 of FIG. It is a top view which shows arrangement | positioning of the speaker and acoustic diffuser in a room for measuring the characteristic of FIG. It is a figure which shows each frequency characteristic with and without an acoustic diffuser in the vicinity of a speaker in arrangement | positioning of FIG. It is the front view which shows Embodiment 2 of the acoustic diffuser by this invention, sectional drawing, and a perspective view which shows the equivalent surface shape of the whole acoustic diffuser. It is the front view and sectional drawing which show Embodiment 3 of the acoustic diffuser by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,50,60 ... Acoustic diffuser, 12 ... Plate-shaped member (rear wall), 14 ... Partition wall, 16 ... Space, 16a ... Opening, 18 ... Membrane sound-absorbing material, 24 ... Step part, 26 ... Suppression member 62 ... The wall surface (rear wall) of the room.

Claims (5)

A plurality of spaces arranged in a plane and partitioned from each other by partition walls;
Each of the spaces is closed at the back by the rear wall and the front forms an opening,
Each of the openings is closed with a film-like sound absorbing material,
For at least one direction, the arrangement height of the film-like sound absorbing material from the rear wall and the layer thickness of the air layer behind the film-like sound absorbing material differ between the adjacent spaces ,
The normal incident sound absorption coefficient characteristics of both film-like sound absorbing materials in the adjacent spaces are as follows:
A primary resonance frequency (hereinafter referred to as “first primary resonance frequency”) having a lower primary resonance frequency (hereinafter referred to as “first film-like sound absorption material”) and a membrane having a higher primary resonance frequency. Sound absorption coefficient of the first film-like sound absorbing material between the first resonance frequency (hereinafter referred to as “second primary resonance frequency”) and the first sound-absorbing material (hereinafter referred to as “second film-like sound absorbing material”) is first. A frequency that decreases to a value of 10 to 20% of the sound absorption coefficient at the first primary resonance frequency in the process of decreasing from the peak value at the primary resonance frequency toward the high frequency side,
A sound absorption coefficient of the first film-shaped sound absorbing material;
An acoustic diffuser that is set so that the sound absorption coefficient of the second film-like sound absorbing material in the process of decreasing from the peak value at the second primary resonance frequency toward the low frequency side coincides . Acoustic diffuser of the rear wall according to claim 1 Symbol placement consists of a plate-like member fixed to the back of the partition wall. Acoustic diffuser of the rear wall according to claim 1 Symbol placement consists of the wall surface of chamber the acoustic diffuser is mounted. An arrangement height of the film-like sound absorbing material from the rear wall is set such that the height of the film-like sound-absorbing material located in the center of the arrangement of the film-like sound-absorbing material is higher as it goes to the peripheral edge, The acoustic diffuser according to any one of claims 1 to 3 , wherein the surface shape of the ring substantially forms a mountain shape. The sheet thickness of the film sound absorbing material is made different between the adjacent spaces, and the acoustic impedance due to the difference in the layer thickness of the air layer behind the film sound absorbing material and the sheet thickness of the film sound absorbing material acoustic diffuser as claimed in relatively any one of claims 1 4 for diffusing the low range by discontinuity.

Images