JP4782193B2 - Method, apparatus, and system for changing reverberation time in space - Google Patents

Description

  The present invention relates to a method of changing the reverberation time of space, and more particularly to a method of changing the reverberation time of space in a low frequency range. The invention further relates to a sound absorbing device and a system of such a device used for said change of the reverberation time of the space. The invention further relates to a space comprising such a device and / or system, whereby the reverberation time of the space can be changed.

  It is well known in the art that one of the acoustic parameters that affect the perceived sound quality in a listening room, such as a concert hall or auditorium, is the reverberation time of the space. However, the optimal reverberation time depends on various music and speech, so the recommended reverberation time in the space where classical music is played is in the range of 1.5 to 2.0 seconds, but rhythmic music The reverberation time recommended in the space where is played is in the range of 0.8 seconds to 1.0 seconds. In order to achieve the best speech intelligibility that can be achieved, auditoriums may benefit from even shorter reverberation times. Furthermore, the reverberation time should ideally be approximately the same over the appropriate frequency range of the program component. However, in general, reverberation time tends to decrease with frequency, for example, more air absorption in the air at higher frequencies, and more sound absorption at spatial boundaries at higher frequencies. , As well as the presence of people in the space. Therefore, low-frequency reverberation often tends to be too much compared to high-frequency reverberation, which is unacceptably “low-pitched” sound is played back in space and music is perceived. Details may be lost, and speech intelligibility may worsen. FIG. 1 shows the measured reverberation time, which varies depending on the frequency of the seven different rooms that may be used for live performance or playback of music. The figure shows an average reverberation time T30 of about 1 second above 500 Hz, but the average at low frequencies increases to about 1.5 seconds at 63 Hz. Moreover, it can be seen from FIG. 1 that the reverberation time varies greatly from space to space.

  In view of the above, it is often necessary to have a means of changing the reverberation time of a given space in a desired manner, and it is particularly beneficial to selectively reduce the reverberation time at low frequencies.

  Devices for changing the reverberation time of a listening room are known in the art. Some of them are primarily useful at high frequencies, and the reverberation time simply provides a thin layer of sound-absorbing material (eg a thin layer of mineral wool covered by a protective screen) at selected boundaries of the space May be reduced. Although many practical implementations have been successfully applied for many years, selectively reducing the reverberation time at low frequencies is somewhat more difficult to implement. Three different embodiments should be mentioned that reduce the reverberation time at low frequencies (and work to some extent at higher frequencies).

  1. A panel that is sufficiently thick of sound-absorbing (porous) material should have a low frequency (as well as a higher frequency) if the panel thickness is sufficient compared to the wavelength of sound at the lowest frequency at which the reverberation time must be effectively reduced. ). Examples of materials that can be applied to such panels are glass fiber, mineral wool, and sintered metal. Such panels may be attached directly to the boundary or may be spaced from the boundary, thereby improving performance at low frequencies. The panel may also be suspended from the ceiling, thereby allowing access to the panel from both sides. Apart from the required thickness, which can exceed 1 meter, where absorption of significantly lower frequencies of acoustic energy is required, such panels do not selectively absorb sound at low frequencies, but rather, given a Depending on the frequency, which is approximately constant above the lower critical frequency (especially determined by the thickness of the panel and the acoustic properties of the particular material used) and decreases below this lower critical frequency The low frequency of the reverberation time cannot be selectively reduced, as shown, and thus often required.

  2. Low frequency sound absorption can be achieved, for example, by applying a so-called panel absorber or membrane absorber consisting essentially of a rigid frame adapted to be attached to a wall or other boundary of space, for example a given resonant frequency. It can be realized within a limited bandwidth of one octave around. A thin flexible panel, for example plywood, is provided on the frame and at a given distance from the wall or boundary, which is driven to vibrate by a sound field in space. The mass and stiffness of the panel and the compliance of the air volume defined by the frame, the panel, and the rear boundary of the panel determine the resonant frequency of the absorber, and the internal loss determines the Q value of the resonator and hence its bandwidth. Is decided. Sound attenuating materials such as mineral wool may be introduced into cavities in the frame to increase absorption and change the Q value of the absorber. Since the compliance of the air in the cavity depends on the amount of air in the absorber, the resonant frequency may be changed by changing the depth of the resonator and maintaining the peripheral dimensions of the frame. Thus, the deeper absorber provides a lower resonant frequency. A more precise description of these mechanisms is given in the summary of the invention.

  3. Low frequency sound absorption can also be achieved using so-called Helmholtz resonators, consisting essentially of one or more passages or tubes of a given length and cross-sectional area, one or more of them. A path represents an acoustic mass, one longitudinal end of one or more paths is coupled to a sound field in space, and the other end represents an acoustic compliance that is essentially proportional to the volume of the cavity. Coupled to a volume cavity. The specific combination of mass and compliance determines the resonant frequency of the Helmholtz resonator, and the internal loss determines the Q value or effective bandwidth of the Helmholtz resonator. At and near the resonant frequency, the input impedance of the resonator is very low, and therefore the resonator selectively absorbs sound energy from the surrounding sound field in the frequency range near the resonant frequency. As with the panel absorber, a damping material such as mineral wool may be introduced into the Helmholtz resonator to change its Q factor. In practice, Helmholtz resonators are often of some form similar to the panel absorbers described above, and thin flexible panels are made into thicker rigid panels with a pattern of passages through the panels. Replaced. However, Helmholtz resonators with a single passage or tube and cavity have also been used to change the reverberation time and / or suppress unwanted low frequency spatial modes.

(Background theory about membrane absorber)
Membrane absorbers typically consist of a lightweight plate in front of a closed cavity. In many cases, the cavity is filled with a porous material, which provides damping of the system. When deriving the theoretical characteristic equation of the membrane absorber, it is assumed that the wall and the back surface of the cavity are rigid, and that the bending stiffness of the plate is negligible compared to the stiffness of the air column in the cavity Is done. The system consists of a unit area mass m of the plate, a cavity depth d, and a loss due to the flow resistance of the porous material, an internal loss in the plate, and a loss in the joint along the edge of the plate. Characterized by loss r _i , ρ is the density of air or other gas in the cavity, and c is the speed of sound.

  The acoustic impedance of the system can be expressed as:

The resonant frequency of the system is found when Im {Z} = 0.

This shows that the resonant frequency at which absorption should be maximal is inversely proportional to the square root of both the membrane mass and the cavity depth. According to this theory, to obtain maximum absorption at about 63 Hz when the cavity depth is 0.2 m, the membrane must have a mass of about 5 kg / m ² . However, pressurizing the cavity increases the stiffness of the system and may allow for the application of lighter materials.

The impedance of the absorber can be adjusted to maximize absorption at the resonant frequency and the usable bandwidth of the absorber (half-value width B _r ). If the impedance is too high in comparison with the radiation resistance r _s of the film, the sound field incident is reflected away from the film, not absorbed. If the impedance is too low, the internal loss is too small and the sound energy absorbed is not sufficient. The impedance ratio between the internal loss and the external radiation resistance can be expressed as the following equation.

Therefore, the maximum absorption coefficient and the absorption bandwidth can be described as follows:

  In the above, it has been assumed that the absorber is of approximately the same depth d throughout the device. In many of the embodiments of the invention described in the detailed description of the invention, this is not the case, and the depth d varies in a characteristic predetermined manner across the surface of the absorber. In such an embodiment, it is also possible to determine at least an approximation of the resonance frequency, absorption coefficient, and absorption bandwidth by applying the above formula and inserting the average value of the device depth d. There is something wrong. Alternatively, the above equation may be reformulated with respect to the actual air or gas volume and the corresponding compliance known in the acoustics field.

(Measurement of reverberation and absorption coefficient)
The absorption coefficient of the specimen can be calculated from the measured reverberation time of the empty reverberation room and the reverberation room in which the specimen is present as:

式中、Ｖは残響室の体積、Ｓ_Ｓは試験片の面積、

は試験片が存在するチャンバ内の残響時間、Ｔ_６０は空のチャンバの残響時間である。

Where V is the volume of the reverberation chamber, S _S is the area of the specimen,

The reverberation time in the chamber where the specimen exists, T ₆₀ is the reverberation time of the empty chamber.

  The above-described prior art absorber may achieve a very high absorption coefficient at and around the resonance frequency, and even if an absorption coefficient of about 0.9 is satisfactorily realized using such an absorber. Good. However, such prior art absorbers have a number of disadvantages, some of which are described below.

  The sound absorption characteristics of the above-described prior art absorber cannot be easily changed after the absorber is constructed. Specifically, large changes in the absorption coefficient α and / or resonant frequency cannot be achieved by small modifications of a given absorber. Also, the absorption coefficient is systematically in a simple manner, for example a change involving a shift between a very high absorption coefficient and a very low absorption coefficient, ie essentially an on / off function of the absorber. It can not be changed.

  The absorber described above is a rather bulky structure that, once installed in a given space, becomes difficult or even impossible to remove from it. They are considered fixed installations within a particular space and are not considered installations that can be easily removed from a given space, transported to another space and used there. Even if it can be removed and transported to another space, such absorbers are bulky, and thus a large cost is incurred by transport.

  Even if a sound absorber of the type described above is transported to another space and does not need to be applied there, in some situations, a given number of absorbers are applied in the space, In some situations, it may be desirable to apply a smaller number of absorbers, or even no absorbers may be required at all, for example depending on the type of music performance planned in the space. In these cases, storage of a number of somewhat bulky absorbers can also be a problem.

  In the context of the above, one object of the present invention is to provide an apparatus, system, and method for selectively changing the reverberation time of space at low frequencies (but not limited to).

  A further object of the invention is that the effect on the reverberation time can be easily changed, for example by changing the absorption coefficient α and / or the resonance frequency (s) or the effective bandwidth of the device or system, An apparatus, system, and method are provided. Specifically, as described above, it is desirable to switch the intrinsic on / off function of the absorber, i.e., between a very high absorption coefficient and a very low absorption coefficient within a certain frequency range.

  It is a further object of the present invention to provide an apparatus and system that facilitates transportation and storage of the apparatus and system.

  These and other objects and advantages are located in a sound field in the air and absorb sound energy that absorbs acoustic energy from the sound field within a predetermined frequency range, particularly within a low frequency range (but not limited to). In accordance with the invention realized by an apparatus, the apparatus comprises an at least partially flexible body including one or more cavities, wherein at least a portion of the outer surface of the body is in contact with the sound field. And the body is expandable by supplying gas to the at least one cavity and foldable by removing gas therefrom, so that the absorption coefficient α and resonance frequency of the body Can be varied, and therefore determine the frequency range where maximum absorption occurs.

  In principle, the desired change in the reverberation time of a given space is to use a single device as described above, for example depending on the size of the space, the size of the absorber, and the various acoustic properties of the device. In many instances, a number of such devices are advantageously used to form the system to cover a sufficiently large predetermined area of space. Many configurations of such systems are possible, some examples of which are described in the detailed description of the invention.

  Basically, a system for reducing the reverberation time of space includes a plurality of sound absorbing devices of the above-mentioned basic configuration according to the present invention, and the system supplies gas to each main body from a supply source and removes it therefrom. It further includes a conduit that can. Each of the bodies may comprise valve means for separately controlling the supply of gas to and removal of gas from each of the bodies, or alternatively, all the bodies of the system or within the system The main body group may be provided with a common valve means.

  Specifically, the valve means can be remotely controlled and the system can comprise a centralized controller that separately controls the static pressure within each body, and thus the compliance or dimensions of each body. Instead of using the static pressure in the body as a controlled variable, the tension of the body material can be monitored, for example, by a piezoelectric element, or the dimensions and shape of the body can be monitored by other means.

  The system can further comprise means for measuring the reverberation time of the space in which the system is installed, thereby facilitating proper configuration of the system. Of course, such means can be provided in connection with only a single device according to the invention. In addition, the system comprises data storage means for storing the measured reverberation time of the device or system and the corresponding parameter settings for later analysis and retrieval, whereby the device or system parameter selection (overall device Empirical improvement of the typical absorption area, required expansion, optimal material properties, etc. can be facilitated.

  Alternatively, instead of actually inflating and deflating the body of the device according to the invention by supplying air or other suitable gas to the body and withdrawing it, the body is self-expandable according to the invention. Self-expandable means may be provided in the form of (alternatives briefly described in the detailed description of the invention).

式中、αは吸収係数、Ｖは空間の体積、ｃは音速である。従って、本発明による装置又はシステムを適用する前の、空間の残響時間の特定の値、空間の所望の残響時間、及び特定の周波数域において装置によって実現可能な吸収係数αを前提として、吸収体の必要な総表面積、従って吸収体の必要数を計算することが可能である。 The present invention further includes the step of introducing one or more main bodies according to any one of claims 1 to 7 into a space, and a required total area S _S of the one or more main bodies is determined by the following equation: The present invention relates to a method for reducing a reverberation time of a space at least in a low frequency range from a given reverberation time (T ₆₀ ) to a desired reverberation time (T _60.S ).

In the equation, α is an absorption coefficient, V is the volume of space, and c is the speed of sound. Therefore, the absorber is premised on a specific value of the reverberation time of the space, the desired reverberation time of the space, and the absorption coefficient α realizable by the device in a specific frequency range before applying the device or system according to the invention It is possible to calculate the total surface area required and thus the required number of absorbers.

  In accordance with certain embodiments of the present invention, the apparatus, system, and method specifically include from about 63 Hz to about when the maximum absorption coefficient is at least 0.7 and the available bandwidth is at least one octave. It is designed to change the reverberation time in the 125 Hz frequency range, that is, in the frequency range where many spaces exhibit unacceptably high reverberation time as described at the beginning in connection with FIG.

  As a supplement to the inflatable / collapseable body described above, it is emphasized that the device according to the invention can further comprise an absorption device effective at higher frequencies. Such a coupling device is described in the detailed description of the invention, and the high frequency absorber is provided as a thin sheet of suitable fabric with a sufficiently high flow resistance, for example, to be effective as a sound absorber at higher frequencies. can do.

  The invention will be more fully understood from the following detailed description of various embodiments, taken in conjunction with the drawings, in which:

Referring now to FIG. 2, the device according to the invention now comprises a sufficiently rigid frame structure 1 comprising an edge 1 "surrounding a central part 1 'and thus forming an open box-like or tray-like support structure. A schematic view of the first embodiment is shown: On the opposite side of the central part 1 ′, a thin flexible membrane 2 floats supported by an edge 1 ″. The frame structure and membrane form an internal cavity 4, which can be inflated / deflated using air or another suitable gas via a conduit and valve device indicated by reference numeral 10. The cavity 4 is optionally provided with an edge 1 at an appropriate distance from the center 1 ′, for example in the form of a panel 3 of porous material provided in the center 1 ′ or of a fabric having an appropriate flow resistance. A certain amount of acoustic damping material can be provided in the form of a sheet suspended between. In the expanded state, the acoustic energy of the incident sound field, schematically illustrated by S in FIG. Are absorbed by the device by internal friction within the flexible membrane 2 and, if a sound-absorbing material is introduced into the cavity 4, in part by friction and thus heat is generated in this material. Maximum absorption occurs at the resonant frequency of the membrane, and the resonant frequency is determined by the compliance of the membrane and air cavities, as well as the mass, or the membrane as described in the invention disclosure. To present a membrane results in an internal friction involved in the absorption of the incident sound field of acoustic energy, thus converting the vibration energy into heat, must be made of a suitable material. The mass of the film (m per ^2), therefore the resonance frequency of the apparatus, showing an example of a material suitable for film of various devices by receiving. the present invention the influence of the selection of film materials shown below.

  FIG. 3 shows the actual measurement of the absorption coefficient (α), which varies with the frequency of the device according to the invention comprising the above-described absorption panel 3 of the kind shown in FIG. In the expanded state, an absorption coefficient of about 0.8, ie about 80% of the sound energy incident on the membrane, is absorbed by the device, reaching a frequency of 63 Hz, and in the frequency range of about 1 octave around this frequency, A high absorption coefficient is realized. Due to the presence of the absorbent material 3 in the cavity 4 of the device, in a contracted (“vacuum”) state, the compliance of the film not on the surface of the absorbent material 3 is reduced (ie, the rigidity is increased). Even at higher frequencies, a relatively high absorption coefficient of about 0.6 is still achieved.

  Therefore, depending on the state of the device, very high absorption of acoustic energy can be achieved at and near two different frequencies, i.e. depending on the state of the device, the reverberation of the space in which the device is installed. The time can be changed at two different frequencies. If the absorption panel 3 was not provided in the cavity 4, significant absorption was still achieved at and near the frequency of 63 Hz, but essentially no absorption was achieved in the contracted state, thus reducing the reverberation time. Did not become an on / off device to change.

  The apparatus shown in FIG. 3 includes the substantially rigid frame structure described above, which can be made of, for example, plywood or molded plastic material, but in many applications, at least in most cases, the present invention. It is beneficial to avoid rigid structures in the devices according to, thereby facilitating transport and storage of those devices. This is especially important for mobile applications where multiple such devices are moved from one location to another and temporarily set up to form a system that spans a large area of space. . In such applications, it is desirable if the device according to the invention is actually fully folded and if a relatively heavy support structure can be further avoided. The embodiments of the device according to the invention shown in FIGS. 4, 5, 6 and 7 are all of this foldable type.

  Accordingly, FIGS. 4a, 4b and 4c show various types of schematic views of a second embodiment of the device according to the invention in a “mattress” configuration. As shown in FIG. 4a, the apparatus includes upper and lower (not shown) generally flat surfaces 5 bounded by edges 7 ', 7 ", thus forming an internal cavity in the mattress. May have a rectangular shape of a conventional mattress. Both the flat portion 5 and the edges 7 ', 7 "are made of a suitable flexible material, so that the mattress is fitted with a suitable valve By supplying pressurized air or other gas through an inlet 10 with means, it can be in an expanded state as shown in FIG. 4a. In order to maintain the inflated mattress in its proper, generally rectangular shape, a cross connection 6 is provided in the interior between two opposed flat surfaces 5 as is well known. It should be understood that other shapes of mattress other than the rectangular shape shown in FIG. 4a are also possible without departing from the invention.

  4b and 4c show two cross-sectional views of two different types in the mattress embodiment of the present invention. Thus, the type shown in FIG. 4b includes a flexible surface 5 on one opposite side of the mattress and comprises a cross connection 6 and a flexible edge 7 ″. Suspended from the ceiling or the other support structure, and thus can provide access to the incident sound field on either the opposed, generally flat surfaces of the device, as opposed to the device shown in FIG. In addition, the device shown in FIG. 4 c includes only one flexible surface 5, but the opposite flat sides of the “mattress” structure consist of a substantially rigid panel 44. This panel, as indicated by reference numeral 45, extends beyond the edge 7 ", thus providing a flange-like edge that facilitates mounting the device to eg a ceiling or wall.

FIG. 5 includes an inflatable frame structure 8 ′, 8 ″ for floating at least one flexible membrane 9, although one of these is a substantially rigid panel, as in the previous embodiment. FIG. 6 shows a schematic view of a third embodiment of a foldable type device according to the invention, which may be present. The frame structure is provided by the hollow annular structures 8 ′ and 8 ″ shown in FIG. In order to realize a relatively hard frame structure, it may be inflated with air at a pressure p ₁ exceeding the atmospheric pressure via the inlet and the valve member 11. One or two flexible membranes 9 float above this frame structure, thereby forming a cavity 12 between the membranes. The cavity 12 can be varied (expanded / deflated) by controlling the pressure p ₂ of air or other gas in the cavity, which also comprises an inlet and valve means 10. Also, in this embodiment, it should be understood that the flexible membrane (or one membrane and a substantially rigid panel) 13, including inflatable edges 15 ', 15 ", without departing from the invention, Other shapes besides the illustrated cylindrical shape may be envisaged, as illustrated in the embodiment shown in FIG. 6, which forms an inflatable rectangular frame structure on which 14 can float. In this embodiment, there are also separate inlet and valve members 16, 17 to control the pressure in the individual cavities.

  FIG. 7 shows a schematic diagram of an embodiment of the device according to the invention of an “ice pack” structure somewhat similar to the mattress structure shown in FIGS. 4a, 4b and 4c. The apparatus includes a body of mattress-like structure, generally indicated by reference numeral 18 and divided into a plurality of parts 20, 20 ', which parts may be of the same shape and dimensions, Is not essential, and each part is bounded by a beam structure 19. The individual portions that each form the internal cavity 21 may be in fluid communication with each other, or a given portion may be in fluid communication with certain other adjacent portions, thereby providing a given At the inlet and valve member, air or other gas used to expand the device can be supplied and flow to the rest of the part. However, it is also possible to provide a partition 22 between adjacent portions, whereby the device can be divided into a number of compartments, for example in matrix columns and rows as shown in FIG. Accordingly, each of these compartments includes a separate inlet and valve member 10 for inflating / deflating a portion of the particular compartment.

  Referring now to FIG. 8, a sixth embodiment of the device according to the present invention is shown. Specifically, FIG. 8a shows a schematic exploded perspective view of this embodiment, floating between opposed, generally straight, longitudinal edges 29 of a separated cylindrical configuration with slits 35. FIG. Opposite membranes 25 and 26, through which the membranes 25, 26 are introduced into the edges and later attached to the edges (and to each other) in an airtight manner, thereby between the ends 27 facing the membranes An internal cavity can be formed and the edge is also secured to the membrane and the edge in an airtight manner. Edge 27 can be made of a single sheet of suitable flexible material, but increases the hardness (moment of inertia) around the associated plane, thereby preventing the cylindrical configuration in the expanded state of the device. Therefore, it is also possible to form the edge portion 27 as an inflatable body. One or more intermediate shape retaining members 28 may be provided at appropriate locations within the internal cavity to achieve the desired shape of the device in the expanded and deflated states. The shape retaining member 28 includes a suitable passage 36 that allows air or other gas to pass between the various compartments formed within the device by introducing the member 28. The longitudinal edge 29 can accommodate a correspondingly shaped longitudinally extending rod 32 (ie substantially cylindrical in the case of FIG. 8), which is accessible through a recess 31 in the edge. The purpose of floating the device or connecting a given device to an adjacent device, as shown in FIG. 8c, so that a system of devices can be constructed; Through a tube or other pipeline 34 (provided with suitable valve means) when provided with an internal passage in communication with the device cavity through the side branch 33 along the longitudinal length of May serve two purposes: from the supply of air or other gas to the internal cavity of the device. In FIG. 8b, a plan view and a cross-sectional view along line II-II are shown, thus showing the configuration of the biconvex lens shape of the embodiment shown in FIG. However, it should be understood that other cross-sectional shapes may be selected without departing from the present invention. Finally, FIG. 8c shows a part of the system of the device according to this embodiment of the invention, where individual columns of the device are suspended from eg a ceiling or other support structure, each device being connected to the edge described above. It is connected to an adjacent device by a connecting member 37 that is formed to releasably engage with the rod 32 through a recess 31 in the bottom. Air or other suitable gas may be passed between adjacent rows of devices via tubes or pipelines 34 in the outermost row of devices as shown in FIG. 8c, and via short tubes or pipelines 38. , Supplied to the device from an external source. It should be understood that other patterns of fluid interconnections between the various devices are possible without departing from the system of devices according to the present invention.

  Although not specifically shown or described in detail, air or gas supply lines to individual devices according to the invention or to various groups of devices according to the invention may be air or gas from or to the device. It should be understood that valve means can be provided to control the flow of other gases. Thus, for example, it is possible to provide that individual device with its separate valve means, whereby the expansion of each individual device can be controlled separately. The valve may be a manual but remotely controllable valve, for example, it may be controlled by a centralized control system as mentioned below.

  Referring now to FIG. 9, there is shown a schematic perspective view of a seventh embodiment of the device according to the present invention, the device being mounted on a space boundary 40 and comprising a low frequency absorbing member 42 and a high frequency absorbing member 46. With both, the reverberation time of the space is changed not only at low frequencies but also at higher frequencies. Although the device according to this embodiment is shown and described as being mounted on the boundary, it may alternatively be designed to float freely from the ceiling, for example, in which case a high frequency absorber (such as a fabric) ) 46 may be provided on either side of the central low frequency absorber 42.

  Returning to FIG. 9a, a low frequency absorber 42 according to the present invention, eg, a “mattress” or “ice pack” design device described above in connection with FIGS. 4a, 4b, and 7, respectively, and a high frequency absorber. A seventh embodiment of the device according to the invention is shown, including 46, for example a suitable fabric. In the deflated state, the low frequency absorber 42 is wound around a drum 43, which is mounted for rotation about a longitudinal axis thereof within a support / suspending structure or bracket 41 and a belt 44. Or driven by motor 45 through other equivalent means. The motor may be remotely controlled, for example from a centralized control system, so that other functions of the device or system of devices may also be controlled and monitored. Similarly, the high frequency absorber 46 is, in this embodiment, wound around a drum 47 and guided over a suitable roller 48 to an unwinding position substantially parallel to the low frequency absorber. As shown in FIG. 9a, the motor drives both absorbers 42 and 46, but it is also possible to provide a separate drive for each of these devices, thereby leaving the other device in an inactive state. In this way, one of the devices can be brought to its activated unwinding position. If desired, the absorber may be operated manually.

  Lower rails 49 and 50 are provided at the lower end of the absorbers 42 and 46, respectively, and the lower rail 50 of the high frequency absorber mainly provides the necessary weight for the lower end of the device. Thus, it helps to extend downward in a substantially flat form parallel to the low frequency absorber. The low frequency absorber 42 is generally much heavier than the high frequency absorber 46 and the lower rail 49 of the low frequency absorber 42 is primarily a fixed fixture for the lower support 51 attached to the wall 46. Can be used to provide an inlet and valve member 52 through which air or other gas is supplied to and withdrawn from the device 42. The lower support 51 may comprise means for establishing a fluid connection between the inlet and valve member 52 and the source, but the device 42 may be supplied with air or gas by other means. . A valve may also be provided on the lower support 51 instead of the inlet 52 to the device 42. Figures 9b, 9c, and 9d show three different states of this embodiment of the invention: (b) essentially inactive, (c) the high frequency absorber is in action, The low frequency absorber is inactive, indicating that it has not yet expanded, and (d) both devices are in operation.

  9a to 9d show an apparatus including both the low-frequency absorption part 42 and the high-frequency absorption part 46, but when the correction of the high-frequency reverberation time is unnecessary, the support / suspending structure 41 is a low-frequency absorption apparatus It is emphasized that it may be formed to include only 42. The structure 41 may be formed so as to include the high frequency absorption device 46 on either side (front surface and rear surface) of the low frequency device 42.

  In any of the embodiments shown in FIGS. 4-9, the inflatable low frequency absorber may include one or more internal cavities in which no acoustic damping material is provided in the cavities. In these cases, the absorption effect is mainly due to the internal friction of the film itself. However, it is also possible to provide an acoustic damping material in the cavity, for example a panel of porous material such as mineral wool or a thin sheet such as a fabric having a sufficiently high acoustic flow resistance. be able to.

  If the various absorbers according to the invention are of sufficient surface area to achieve the desired effect on the reverberation time of the space, they can be used separately, but the absorbers according to the invention It is also possible to assemble a larger modular system and thereby achieve the desired surface area required to achieve the required effect on the reverberation time of the space. Such a system can include, for example, a matrix structure of absorber devices of a given number of rows and columns, each device being required to achieve the required resonant frequency and the absorption coefficient as described above. Connected in a selected manner by a pipeline that supplies air / gas to expand the absorber to a certain extent and supplies air / gas to the inflatable frame portion described in connection with some of the embodiments. .

  Each individual absorbent device may be provided with its own valve means as described above, or the valve means may be provided in a particular group of devices. The valve means may for example be remotely controllable (infrared, Bluetooth, etc.) from a central control console and the expansion / contraction of the device may be controlled from the console. The system also includes a sensor that measures the pressure of the device, thereby allowing the control console to monitor that the system is functioning correctly. Furthermore, the system may comprise means for measuring the reverberation time of the space, for example before and after expanding the absorber. It is also possible to use the absorber system according to the invention to tune the device to different resonant frequencies, for example to achieve a wider effective frequency range in order to change the reverberation time of the space.

  Normally, the absorber can be tuned to a resonant frequency of 63 Hz or 125 Hz, but this is simply regarded as a general resonant frequency.

  In a practical embodiment, the system can include, for example, 100 absorbers according to the present invention and can be controlled from a dedicated control console. Alternatively, control and monitoring can be performed from a portable personal computer with appropriate software supplied with the system. This software makes it possible to measure the reverberation time as described above and is necessary to achieve the optimal reverberation time based on the physical dimensions of the input space and the expected number of audiences. Includes an algorithm that can calculate the total number of active absorbers. Past data (eg, reverberation times before and after other spaces in which the system was used) can also be stored in appropriate data storage means for later analysis and retrieval.

  As mentioned in the disclosure of the invention, alternative embodiments of the device of the present invention are also within the scope of the present invention, including means for self-expanding (or self-expanding) the air- or gas-filled body of the device. . This embodiment is somewhat similar to a self-expanding mattress used, for example, in camping, and includes an external air or gas permeable enclosure with, for example, a sponge rubber structure inside the device. Such expansion can be facilitated when expansion to the appropriate depth / dimension is not prevented. Thus, this embodiment of the absorption device can form part of the device described above as the seventh embodiment, for example, but can also be used in many other contexts.

Furthermore, the inflatable / If the pressure p ₂ of air or gas of the expandable body in the cavity is equal to ambient atmospheric pressure, the valve means of the supply line relative to the body, the device according to the invention, assembly, and during operation of the system Note that it may be left open.

  Referring to FIG. 10a, the actual design of the support / suspension structure 41 of the seventh embodiment of the present invention described above is shown. This structure is formed as a housing 55 that houses the rollers of the low-frequency and high-frequency absorbers, so that these devices or one of them may be partially or fully contained within the housing. According to the example. By providing a housing, it may serve as a general protection means when the device is not in use, as well as a fire protection means. Thus, the assembly or system may comprise a means for detecting fire / smoke, which activates the drive mechanism of the assembly, thereby pulling one or both of the absorbers 42, 46 back into the housing. Specifically, as shown in FIGS. 10a and 10b, the housing may comprise an upper portion 55 pivotally connected to the body of the housing 54, so that the upper portion 55 is It automatically rotates until the housing is closed as shown on the left side of FIG. 10b. Of course, the housing may also be closed by the upper portion 55 as a general protective measure of the absorber housed in the housing.

  Referring to FIG. 11, finally, as an illustration, a computer simulation of a system of a sound absorbing assembly according to the present invention floated along one boundary of a hall to change the reverberation time of a concert hall is shown.

An inflatable / expandable and foldable / compressible body according to the present invention must be able to absorb acoustic energy from the surrounding sound field. As described above in the background art, this capability relates to the impedance ratio between the internal loss of the flexible material of the absorber and the external radiation resistance of the absorber. In the case of the embodiment shown in FIG. 2 and the resulting absorption coefficient shown in FIG. 3, a 2 mm thick Ryanyl®, a PVC material having a density of 2.96 kg / m ² was applied. Yes. However, other materials, for example suitable polymer materials mixed with sand or other particulate materials, may be used in the absorber according to the invention, thereby increasing the wall thickness of the absorber, It should be understood that the weight / density of the material is increased.

It is a figure which shows the actual measurement value of the reverberation time T30 in seven different space which can be used for the reproduction | regeneration of a live music performance and sound. 1 is a schematic view of a first embodiment of a device according to the invention comprising a substantially rigid frame structure covered by a thin flexible membrane. FIG. FIG. 3 shows the absorption coefficient (α) depending on the frequency of the device according to the invention of the type shown in FIG. Figure 2 is a schematic view of a second embodiment of the device according to the invention in a "mattress" configuration. Figure 2 is a schematic view of a second embodiment of the device according to the invention in a "mattress" configuration. Figure 2 is a schematic view of a second embodiment of the device according to the invention in a "mattress" configuration. Fig. 6 is a schematic view of a third embodiment of the device according to the invention comprising an inflatable frame structure for floating at least one flexible membrane. Fig. 6 is a schematic view of a fourth embodiment of the device according to the invention, which is an alternative to that shown in Fig. 5; FIG. 6 is a schematic view of a fifth embodiment of the device according to the invention with an “ice pack” structure. FIG. 7 is a schematic exploded perspective view of a sixth embodiment of the device according to the invention. FIG. 8b is a plan view and a cross-sectional view of the embodiment shown in FIG. 8a. 1 is a schematic perspective view of a system of an apparatus according to the present invention assembled to form a system for changing the reverberation time of space. FIG. FIG. 9 is a schematic perspective view of a seventh embodiment of the device according to the invention with both a low frequency and a high frequency absorbing member mounted on the boundary of the space. FIG. 9b is a schematic perspective view of the embodiment of the invention shown in FIG. 9a in a different state. FIG. 9b is a schematic perspective view of the embodiment of the invention shown in FIG. 9a in a different state. FIG. 9b is a schematic perspective view of the embodiment of the invention shown in FIG. 9a in a different state. It is a schematic perspective view of the actual specific example of the 7th Example of this invention. It is a schematic perspective view of the actual specific example of the 7th Example of this invention. It is a schematic perspective view of the actual specific example of the 7th Example of this invention. FIG. 2 shows a computer simulation of the installation of the system according to the invention in a concert hall.

Claims (31)

A sound absorbing device that is arranged in a sound field in the air and absorbs acoustic energy from air in the sound field at least within a predetermined low frequency range,
And one or more cavities (4,12,13) to including body, each cavity, have a outer surface that absorbs acoustical energy from the air of the sound field in contact with the air in the sound field in the movable And each cavity has a variable volume due to movement between an expanded or expanded state and a compressed or folded state due to fluctuations in internal gas pressure in air in the sound field of the outer surface at least in use. whereby, Ru can alter the absorption coefficient (alpha) and / or resonance frequency of the body, and the body,
Means for changing the internal gas pressure of the one or more cavities to change the absorption coefficient (α) and / or resonance frequency of the body .   The sound absorbing device according to claim 1, wherein the low frequency region has an upper limit frequency of about 200 Hz.   The sound absorbing device according to claim 1, wherein the low frequency range is 50 Hz to 125 Hz. In the sound absorbing device of claim 1, the material of said body, at least the low frequency range are selected such that there is substantial impedance match between the air of the main body and the front Kion field Sound absorbing device. Sound-absorbing device according to claim 1, wherein the internal gas pressure, the have been changed through the valves provided in the conduit between the at least one cavity with a source of said gas, is pre-Symbol Valve A sound absorbing device comprising means for remotely controlling the valve. 2. A sound absorbing device according to claim 1 , wherein said main body is further provided with attachment means (32, 37) for engaging with corresponding attachment means provided on one or more sound absorption devices. .   The sound absorbing device according to claim 1, wherein at least one of the at least one cavity (4, 12, 13) is provided with a sound absorbing material (3) in the cavity. The sound absorbing device according to claim 1, wherein the at least one cavity is provided with an internal self-expanding or self-expanding means. 2. The sound absorbing device of claim 1, wherein the body is an inflatable and foldable frame structure or extension to provide the body with at least one of sufficient hardness , desired shape and desired depth. Sound absorbing device surrounded by a possible and compressible frame structure (8, 15 ', 15 "). A sound absorbing assembly disposed in the sound field in the air, and at least one sound-absorbing device for absorbing acoustic energy from the sound field at low frequency ranges in which at least a predetermined,
Wherein at least one roller means which can be wound a sound-absorbing unit (43), said roller means (43) Bei a structure and a driving means for rotating the Eteori,
The sound absorbing device is
A body including one or more cavities (4, 12, 13) having an outer surface, at least a portion of which is in contact with the air of the sound field, in an expanded or expanded state due to variations in internal gas pressure; A body that is movable between a compressed or folded state;
Means for changing the internal gas pressure of the one or more cavities to change the absorption coefficient (α) and / or resonance frequency of the body . In the sound absorbing assembly according to claim 10, at least one of said high-frequency absorbing means supported by the high-frequency absorption means Ru can be wound (46) the second row La on the structure Zotai (41) ( 46). 12. The sound absorbing assembly according to claim 11 , wherein the structure is formed as a housing that houses low frequency and high frequency absorbers when the assembly is in an inoperative state. 11. The sound absorbing assembly according to claim 10 , further comprising means for automatically winding the low frequency absorber (42).   12. The sound absorbing assembly according to claim 11, wherein the high frequency absorbing device (46) is a piece of material having a flow resistance sufficient to provide high frequency sound absorption. The sound from the sound field in the air there is provided a method of variably absorbed,
In the step of introducing a series of partially elastic body into the air of the sound field, wherein the body, the resonant frequency, thus determining the effective frequency range that substantially absorb acoustic energy from the sound field an acoustic mass and acoustic compliance, and the acoustic resistance which is selected for the acoustic energy of air in the sound field and a indicates to the outer surface, introducing a body,
Attaching each body in the air of the sound field such that the outer surface contacts the air of the sound field and absorbs acoustic energy from the sound field;
In order to change the absorption coefficient (α) and / or the resonance frequency of the main body in a process of providing a closed volume with gas pressure to each main body, each main body has an internal gas pressure at least by movement of the outer surface. Providing a closed volume that is changeable between an expanded or expanded state and a compressed or folded state due to fluctuations in:
Changing the gas pressure in each closed volume of the body in the air of the sound field, whereby, and a step of changing the absorption coefficient (alpha) and / or resonance frequency of the body, methods. 16. The method of claim 15, wherein the acoustic resistance of the outer surface in contact with the sound field of the one or more bodies is a substantial impedance between the outer surface and the sound field air. The method further comprising the step of selecting that a match exists. 16. The method according to claim 15, wherein the resonance frequency f ₀ , acoustic resistance ratio μ , maximum absorption coefficient α _max , and absorption bandwidth Br are

Given by the method. Even without least a method of reducing to a reverberation time between sky that put in the low frequency range given reverberation time (T ₆₀₎ from a desired reverberation time (T _60.S),
A step of introducing into the space a sound absorbing device that absorbs acoustic energy from a sound field at least in a predetermined low frequency range, wherein the sound absorbing device has a main body including one or more cavities; An outer surface at least a part of which is in contact with the air in the sound field, and has an outer surface movable between an expanded or expanded state and a compressed or folded state due to fluctuations in the internal gas pressure of the cavity. Introducing the sound absorbing device into the space;
Changing the internal gas pressure of the one or more cavities to change the absorption coefficient (α) and / or resonant frequency of the body;
Hoisting the sound absorbing device onto a structure with rollers by a drive mechanism when fluctuations in gas pressure are no longer desired . The method according to claim 18, wherein the required total surface area S _S of the previous SL present of the backing device, the following equation

Where α is the absorption coefficient of the sound absorber, V is the volume of the space, and c is the speed of sound. The method according to claim 18, wherein the reduction of reverberation time, Ri primarily to put in a low frequency range is determined by the resonance frequency and absorption bandwidth, the resonance frequency f _0, the acoustic resistance ratio mu, maximum The absorption coefficient α _max and the absorption bandwidth Br are given by

Given by the method. A system for reducing the reverberation time of space , comprising a plurality of sound absorbing assemblies, a structure including a roller and a driving mechanism for rotating the roller, and a conduit.
Each sound absorbing assembly has at least one sound absorbing device disposed in a sound field in air and absorbing acoustic energy from said sound field in at least a predetermined low frequency range;
The sound absorbing device is a main body including one or more cavities, and has an outer surface at least a part of which is in contact with air of the sound field, and is expanded or expanded due to fluctuations in internal gas pressure and compressed or compressed. A body movable between the folded states, and means for changing the internal gas pressure of the one or more cavities to change the absorption coefficient (α) and / or the resonance frequency of the body. And
The at least one sound absorbing device is wound around the roller of the structure,
A system wherein gas pressure is supplied to and removed from the sound source from a gas source through the conduit . The system of claim 21, before Kia assembly, valve means for controlling the gas pressure before Kia in assembly is provided, the system. The system of claim 22, wherein the valve means is capable remote control, the system further comprises a central control device for controlling the gas pressure before Kia assembly system. The system of claim 21 , wherein the system further comprises means for measuring a reverberation time of a space in which the system is installed. The system of claim 21, further comprising a data storage means for storing the parameters of response reverberation time及beauty pairs are measurement before Kia assembly system. A sound absorbing system that is disposed in a sound field of space and absorbs acoustic energy from the air of the space within at least a predetermined low frequency range, the sound absorbing system comprising:
A series of sound absorbers having first and second side surfaces, the first and second side surfaces having at least one of the first and second side surfaces in contact with air in the space; And means for attaching the series of sound absorbing devices,
Each of the series of sound absorbing devices has a body including one or more cavities;
The main body is a first and second opposing surface, and one of the first and second side surfaces in which one of the first and second opposing surfaces is in contact with the air in the space. Including first and second opposing surfaces that absorb acoustic energy from the air in the space,
Each cavity has a volume that is variable in use by movement between an expanded or expanded state and a compressed or folded state due to fluctuations in internal gas pressure in air in the space of at least the one opposing surface. And
A sound absorbing system comprising means for changing the internal gas pressure of the one or more cavities of the series of sound absorbing devices to change the absorption coefficient (α) and / or resonance frequency of the body . 27. A sound absorbing system according to claim 26, wherein the low frequency region has an upper limit frequency of about 200 Hz. The sound absorption system according to claim 26, wherein the low frequency range is 50 Hz to 125 Hz. 27. The sound absorbing system of claim 26, wherein the material of the body is selected such that there is a substantial impedance match between the body and air in the sound field, at least in the low frequency range. Sound absorption system. 27. The sound absorbing system according to claim 26, wherein at least one of the at least one cavity is provided with a sound absorbing material in the cavity. 27. A sound absorbing system according to claim 26, wherein the pressure means changes at least two gas pressures in the cavity separately from each other.

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