Patent Grant
9210525
The present invention relates to sound field control apparatuses which change sound field characteristics of a space such as a room. In particular, the present invention relates to a sound field control apparatus and so forth which control a sound field to allow, in the case of television (TV) watching for example, TV audio to be heard only in a specific area and to be reduced in other areas.
Sounds that a person hears include pleasant sounds and unpleasant sounds. Typical examples of the unpleasant sound are factory noises and transportation noises made by cars, airplanes, and the like. On the other hand, examples of the pleasant sound include music. Here, music may be pleasant for a person who is willing to enjoy this music. However, this music is not always pleasant for any other person present nearby. For example, suppose that audio listening and TV watching are enjoyed in a living room of a house. In this case, these sounds are pleasant for those who listen to the sounds near the audio system and the TV. However, for those who enjoy a conversation in the same living room, these sounds may make the conversation hard to hear and thus disturb the conversation. Although those who enjoy the audio listening and TV watching would like to enjoy the sounds at high-volume levels, the volume levels just have to be turned down because the sounds may interrupt the conversation. This leaves much to be desired by those who enjoy these sounds. Here, suppose that elderly man and woman are watching the TV. In general, the elderly have reduced hearing ability and, for this reason, the elderly tend to turn up the volume level considerably high. As a result, the sound from the TV becomes noise that increasingly interrupts the conversation, and this may possibly lead to a family problem.
In order to solve such a problem, the sound may be reproduced (outputted) only in an area for listening to, for example, TV and thus may not be reproduced in other areas. One of the most typical conventional techniques to solve the problem is to use a directional speaker. Classical examples include a geometrically-shaped speaker, such as a horn speaker. With the geometric form, it is relatively easy to obtain directivity at high frequencies. At low frequencies, however, the diameter and depth needs to be long in order to obtain sharp directivity, thereby increasing the size of the speaker. With this being the situation, in recent years, techniques of a parametric speaker (an ultrasonic speaker) and an array speaker may be used. The parametric speaker demodulates an original audio signal in air from ultrasound modulated by an audio signal, using nonlinearity of air with respect to ultrasound. The array speaker obtains directivity by the synthesis of sounds radiated from a plurality of speakers arranged linearly.
However, any of the above directivity control techniques performs control to allow a reproduced sound to propagate in a certain direction (the front direction of the speaker, for example). This means that when a person is present in this direction regardless of whether the person is ahead (in front) of the speaker or behind the speaker, the sound is transferred and thus heard by this person. To be more specific, by strongly controlling the directivity into the front direction of the speaker, it is possible to make it difficult to hear the sound in the right and left directions. However, it is impossible to perform control to allow the sound to be heard only by a person present in front of the speaker in the front direction and not to be heard by a person present behind the speaker in the front direction. In other words, the reaching distance of the sound cannot be controlled. In order to solve this, in a gallery or a museum for example, a directional speaker is fixed to the ceiling to limit the reproduction area to the front of a subject of appreciation, like spotlighting. However, in the case of the environment to watch TV, since the TV screen is located in front of a viewer, the sound needs to be reproduced from the front of the viewer. Otherwise, the image on the screen and the reproduced sound image do not agree with each other, thereby causing extreme discomfort. This can also be said to the case of audio listening. More specifically, it is the most common and pleasant to reproduce the sound image in front of a listener. This is because, since the original sound field of music recorded into a sound source such as a compact disc (CD) is a concert hall or a studio, the original sound field and sound image need to be reproduced to recreate the presence as if the orchestra were actually present at the location.
On account of this, it is desired for the speaker to be placed in front of the listener. The problem described above cannot be appropriately solved by the conventional directivity control technique.
Moreover, in the case of the directivity control technique, a geometrically-shaped speaker such as a horn speaker, a plurality of speakers, or an ultrasound device is used. Thus, a problem arises, for example, that the size of the speaker increases in order to control the sound at low frequencies or that the low-frequency control is difficult. For this reason, the directivity control technique is usually employed for the high-frequency control.
Furthermore, research and development have been conducted on a technique that recreates any sound field by sound field control fully employing signal processing. One of the examples is the boundary sound field control technique employing the Kirchhoff-Helmholtz integral equation. This method controls a sound pressure and sound pressure gradient (sound particle velocity) on the boundary surface in a certain enclosed space to faithfully recreate the original sound field in a different enclosed space having the same form. This method has an advantage in the low-frequency control. However, it is difficult for the method to perform the high-frequency control. Moreover, a problem arises that, for example, since the system scale increases in order to perform the high-frequency control, it is difficult to implement broadband control.
The problems and measures of the directivity control technique and the boundary sound field control technique are disclosed in Patent Literature 1, Patent Literature 2, and Patent Literature 3. Moreover, Patent Literatures 4 and 5 and Non Patent Literatures 1 to 5 also disclose the measures and the like for sound field control.
[PTL 1]
[NPL 1]
However, even the sound field control apparatuses disclosed in Patent Literatures 1 to 5 and Non Patent Literatures 1 to 5 above cannot perform appropriate and sufficient sound field control in the listening area for listening a desired sound and in the nearby area, without any constraint on the arrangement of the configuration.
In view of this, the present invention provides a sound field control apparatus capable of appropriately presenting a desired sound in a listening area and sufficiently reducing the sound in a nearby area without any constraint on an arrangement of a configuration.
The sound field control apparatus in an aspect according to the present invention includes: a listening compensation filter which generates a second output signal by performing signal processing on an input signal from a sound source according to a control characteristic that is previously set, and outputs the second output signal to a second speaker; and a control filter which generates a first output signal by performing signal processing on the second output signal from the listening compensation filter according to a control characteristic that is previously set, and outputs the first output signal to a first speaker, wherein the control characteristic of the control filter is previously set as a first control characteristic that allows a reproduced sound from the second speaker to be reduced at a first control position by a reproduced sound from the first speaker, and the control characteristic of the listening compensation filter is previously set as a second control characteristic that allows a sound having a predetermined target acoustic characteristic to be presented at a second control position by the reproduced sounds from the first and second speakers.
It should be noted that this general and specific aspect may be implemented using a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM. Alternatively, the aspect may be implemented by any combination of systems, methods, integrated circuits, computer programs, and recording media.
The sound field control apparatus according to the present invention can appropriately present a desired sound in a listening area and sufficiently reduce the sound in a nearby area without any constraint on an arrangement of a configuration.
Each of the sound field control apparatuses disclosed in Patent Literatures 1 to 3 above divides a signal from a sound source into at least two frequency bands such as a low frequency band and a high frequency band, and employs the aforementioned boundary sound field control technique for a specific frequency band such as a low frequency band or individually for each frequency band. In addition to this technique, the sound field control apparatus also uses an ultrasonic vibration element. Moreover, spacings between speakers and between sensors in the arrangement are devised. Accordingly, the sound field control apparatus attempts to solve the aforementioned problem that it is difficult to implement the broadband control of the sound field.
Non Patent Literature 1 and Non Patent Literature 2 are published by the inventors of Patent Literature 1, Patent Literature 2, and Patent Literature 3. These Literatures describes that “a conventional method based on the boundary sound field control only controls the characteristics of an area where no sound is desired, and plays no role in what kind of sound is reproduced in an area where the sound is supposed to be reproduced”, regarding the area reproduction employing the boundary sound field control technique. Moreover, Non Patent Literature 2 further describes that “it is suggested that a sound having characteristics different from the characteristics of the original sound is reproduced in the reproduction area”. Furthermore, Non Patent Literature 3 cited as a reference literature in Non Patent Literature 1 and Non Patent Literature 2 describes that the local sound field reproduction system based on the boundary sound field control “can implement sound pressure distribution whereby sound reproduction is confined to the immediate vicinity of the speaker and the sound is sharply reduced in an area at a short distance from the speaker”. It can be understood from this description that, only by an application of the conventional boundary sound field control technique, the original sound source or any sound source cannot be recreated in the reproduction area (such as a living room where the speaker is placed) at any place (for example, an area located at a short distance from the speaker, that is, a viewing position for watching TV such as a sofa that is located at a short distance from the TV instead of being located immediately in front of the TV).
Here, the boundary sound field control technique disclosed in Patent Literatures 1 to 3 corresponds to the conventional technique described in Non Patent Literatures 1 to 3. To be more specific, even the inventions disclosed in Patent Literatures 1 to 3 cannot recreate the original sound source or any sound source at any place in the reproduction area.
In order to solve the problem of the local reproduction system (the sound field control apparatus) based on this conventional boundary sound field control technique, Non Patent Literature 1 describes the method whereby: at least one response control point having a desired characteristic other than 0 is set to define the sound in the reproduction area; and a control weight for a zero control point set on the boundary of the reproduction area and a control weight for the response control point are individually set. This method for performing control by assigning a weight for each control point is disclosed in Patent Literature 4 as well.
Similarly, in order to solve the problem of the local reproduction system based on the conventional boundary sound field control technique, Non Patent Literature 1 and Non Patent Literature 2 describe the method for devising the arrangement of the control speakers. This method is disclosed in Patent Literature 5 as well.
The speakers 1101 to 1104 are applied with the same input signal from a sound source 100 via finite impulse response (FIR) filters 1001 to 1004. By controlling coefficients of the FIR filters 1001 to 1004, the signals applied to the speakers 1101 to 1104 can be individually controlled.
Firstly, impulse responses hij (i=1, 2, 3, 4 and j=1, 2, 3, 4, 5) from the speakers 1101 to 1104 to the microphones 1201 to 1205 are recorded into a response recorder 1400. On the other hand, desired impulse responses aj (j=1, 2, 3, 4, 5) that are desired to be implemented at control points (the positions of the microphones 1201 to 1205) are recorded into a desired-response recorder 1500. Then, outputs from the response recorder 1400 and the desired-response recorder 1500 are inputted into the coefficient determiner 1300. Weight coefficients gj (j=1, 2, 3, 4, 5) of the control points are previously stored in a weight recorder 1600, and these weight coefficients are also inputted into the coefficient determiner 1300. The coefficient determiner 1300 determines filter coefficients wi (i=1, 2, 3, 4) by performing an arithmetic operation indicated by Equation 1 below using the impulse responses hij and aj and the weight coefficients gj, and sets these filter coefficients to the FIR filters 1001 to 1004.
[Math. 1]
W=(GHTGH+δI)−1×GHTGA Equation 1
Here, “b” represents a constant smaller than the maximum eigenvalue of “GHTGH”, and “I” represents a unit matrix. Moreover, “W” represents a transfer function expressing the filter coefficient wi by a frequency domain, and “H” represents a transfer function expressing the impulse response hij by a frequency domain. Furthermore, “A” represents a transfer function expressing the impulse response aj by a frequency domain, and “G” represents a transfer function expressing the weight coefficient gj by a frequency domain.
Here, when a reproduction sound pressure is to be reduced in the hatched area shown in
Next,
[Math. 2]
W=(HTH+δI)−1×HTA Equation 2
Here, “δ” represents a constant smaller than the maximum eigenvalue of “HTH”, and “I” represents a unit matrix. Moreover, “W” represents a transfer function expressing the filter coefficient wi by a frequency domain, and “H” represents a transfer function expressing the impulse response hij by a frequency domain. Furthermore, “A” represents a transfer function expressing the impulse response aj by a frequency domain.
Here, when a reproduction sound pressure is to be reduced in the hatched area shown in
Here, Patent Literature 4 describes, as to the sound field control apparatus 1000, that “since the equation is unusable when M (the number of microphones)>N (the number of speakers), wi (the filter coefficient) whereby the square error is minimum is actually calculated.” Moreover, Patent Literature 4 further describes, “However, this method calculates the filter coefficient whereby the error is minimum” and, unlike the conventional method “that includes an error in principle, by performing an arithmetic operation using a weight coefficient matrix in which an allowable error is set for each control point, the rate of the allowable error can be set for each control point.” To be more specific, in the case of the sound field control apparatus 1000 described above, the results obtained by the microphones 1201 to 1204 corresponding to the weight coefficient g1=g2=g3=g4=1.0 include errors in the first place. In addition to this, the result obtained by the microphone 1205 corresponding to the weight coefficient g5=0.1 includes more errors. On account of this, it is impossible to make the sound quality implemented at the listening position of the microphone 1205 equivalent to the quality of the original sound source having the accuracy desired to be recreated (the characteristic of the microphone 1205 when the sound is reproduced solely by the speaker 1102 in
Here, Non Patent Literature 1 related to Patent Literature 4 describes as follows. “The size of the weight coefficient depends largely on the arrangement and numbers of speakers and control points. When these are changed, performance of the area reproduction also greatly changes. As of now, there are no certain guidelines for determining the arrangement method of the speakers and control points, the numbers of the speakers and control points, and the weight coefficients. It is not easy to determine these.” Moreover, Non Patent Literature 1 further describes that “even when weighted multi-point control is performed, the characteristics are changed depending on the arrangement of the speakers and control points.” To be more specific, Patent Literature 4 filed before the publication of Non Patent Literature 1 cannot describe either with assurance that, even with the introduction of the weight coefficients, the effect whereby the reproduced sound pressure is reduced at the zero control points (the microphones 1201 to 1204) and is not reduced at the response control point (the microphone 1205) can be obtained universally and generally for all frequencies regardless of the arrangement and number of the speakers and control points.
Next, Patent Literature 5 describes the effect achieved by the above-mentioned sound field control apparatus 2000 in the case where the frequency is at 1000 Hz. However, Patent Literature 5 does not describe whether this resulting effect can be generally applied to the cases of other frequencies.
Here, Non Patent Literature 1 and Non Patent Literature 2 related to Patent Literature 5 describe as follows. “The arrangement of the speakers was determined under the following conditions. Firstly, a rectangle or a circle having the response control point at the center was determined.” “Under the condition that the speakers were to be positioned on the edge of this selected rectangle or circle, each of the positions of five speakers was randomly determined.” “In many cases where excellent characteristics were obtained, four speakers were arranged on one vertical edge of the rectangle and one speaker was arranged on the other vertical edge. Moreover, in many cases, out of the spacings among the four speakers arranged on the one edge, the spacing between the middle two speakers was smaller than each of the spacings between these two speakers and the respective outwardly adjacent speakers. On the other hand, no clear tendency was found based on the arrangement of the zero control points.” “As a result of performing the similar simulation at other frequencies, nearly excellent characteristics could also be obtained for frequencies lower than 1 kHz. On this account, it is believed that although the speaker arrangement determined based only on the result of the simulation at 1 kHz was employed, the result of the experiment using a band noise as the sound source was excellent.” To be more specific, on the precondition that this speaker arrangement and the installation condition for the response control point are to be maintained, the effect is obtained for other frequencies different from 1 kHz. Claim 1 in Japanese Patent No. 4359208 cited as Patent Literature 5 includes a matter used to specify the invention that “an arrangement is made to allow a spacing between the sound sources positioned in the middle, out of sound sources arranged on a straight line, to be the smallest and allow a spacing between the sound sources to be larger towards an edge.” From this, it is understood that to maintain the installation condition is essential.
In other words, conversely, it is understood from these descriptions that the invention described in Patent Literature 5 cannot achieve the desired effect unless the speaker arrangement and the installation condition for the response control point are maintained. To be more specific, the arrangement of the speakers 1101 to 1104 of the sound field control apparatus 2000 shown in
In this way, the installation conditions for the speakers and microphones of the sound field control apparatus 2000 are limited. Therefore, a problem arises that the sound field control apparatus 2000 cannot be arbitrary applied to various places and products.
A sound field control apparatus 3000 in
The microphones 3009-1 to 3009-m are arranged at listening positions (in a listening area) where a sound field having a desired characteristic is wished to be recreated. Moreover, the microphones 3010-1 to 3010-m are arranged at positions where a quiet area is wished to be recreated. The microphones 3009-1 to 3009-m and the microphones 3010-1 to 3010-q detect sounds at the respective sound fields, and the control filter 3001 controls sounds to be reproduced from the speakers 3015-1 to 3015-n.
To be more specific, the sound field control apparatus 3000 has a configuration where the listening area and the quiet area are controlled at the same time only by the control filter 3001.
With the basic configuration of the sound field control apparatus 3000, the sound field control apparatus 1000 in
Therefore, in view of the stated problem, the present invention has an object to provide a sound field control apparatus capable of appropriately presenting a desired sound in a listening area and sufficiently reducing the sound in a nearby area without any constraint on an arrangement of a configuration. To be more specific, the present invention has an object to provide a sound field control apparatus which performs control to precisely recreate a desired sound in a listening area for listening the desired sound and to reduce the level of the sound in a nearby area in order not to interrupt, for example, a conversation.
Moreover, the present invention has an object to provide a sound field control apparatus which implements areas for listening different desired sounds at individually different areas in one space.
Furthermore, the present invention has an object to obtain, without limiting a condition for arranging acoustic devices used for control such as speakers and microphones, the effects of the speakers and microphones in the entire frequency band to be controlled, especially when the control speakers are arranged in, for example, the same plane in front of a listener.
In order to solve the stated problem, the sound field control apparatus in an aspect according to the present invention includes: a listening compensation filter which generates a second output signal by performing signal processing on an input signal from a sound source according to a control characteristic that is previously set, and outputs the second output signal to a second speaker; and a control filter which generates a first output signal by performing signal processing on the second output signal from the listening compensation filter according to a control characteristic that is previously set, and outputs the first output signal to a first speaker, wherein the control characteristic of the control filter is previously set as a first control characteristic that allows a reproduced sound from the second speaker to be reduced at a first control position by a reproduced sound from the first speaker, and the control characteristic of the listening compensation filter is previously set as a second control characteristic that allows a sound having a predetermined target acoustic characteristic to be presented at a second control position by the reproduced sounds from the first and second speakers.
With this, the reproduced sound based on the second output signal is outputted from the second speaker. Then, the signal processing is performed on the second output signal by the control filter and, as a result, the reproduced sound is outputted from the first speaker. To be more specific, as the control characteristic of the control filter, the appropriate first control characteristic to reduce the reproduction sound from the second speaker can be set based on the second output signal without consideration of the control characteristic of the listening compensation filter generating the second output signal. Moreover, regardless of the set first control characteristic, the appropriate second control characteristic to present the sound having the predetermined target acoustic characteristic at the second control position can be set as the control characteristic of the listening compensation filter, in accordance with the first control characteristic. As a result, without any constraint on the arrangement of speakers and the like, the desired sound can be appropriately presented in the listening area that is the second control position and the sound is sufficiently reduced in the nearby area that is the first control area.
In other words, since the control filter has the first control characteristic to reduce the reproduced sound from the second speaker at the first control position, the reproduced sound from the second speaker can be always reduced at the first control position regardless of the control characteristic of the listening compensation filter. At the same time, since the listening compensation filter has the second control characteristic to recreate the predetermined target acoustic characteristic at the second control position, the reproduced sounds from the first and second speakers can recreate the predetermined target acoustic characteristic at the second control position. As a result, any sound field characteristics can be implemented at different areas in one space.
Moreover, by performing: generating a target characteristic signal by performing signal processing on the input signal from the sound source according to the predetermined target acoustic characteristic; generating a second detection signal by detecting the reproduced sounds from the first and second speakers using a microphone located at the second control position; and updating the control characteristic of the listening compensation filter according to the input signal, the target characteristic signal, and the second detection signal, the updated control characteristic may be calculated and set as the second control characteristic.
For example, in the updating, a difference between the target characteristic signal and the second detection signal is calculated and the control characteristic of the listening compensation filter is updated using the input signal to reduce the difference.
With this, by the repetition of the above steps, the acoustic characteristic of the sound obtained by synthesizing the reproduced sound from the first speaker and the reproduced sound from the second speaker at the second control position can be sufficiently approximated to the predetermined target acoustic characteristic. More specifically, the second control characteristic can be set to bring about agreement between the acoustic characteristic of the above-mentioned synthesized sound and the predetermined target acoustic characteristic. Thus, the sound having the predetermined target acoustic characteristic can be reliably presented at the second control position.
Furthermore, the first control characteristic of the control filter may be calculated and set before the second control characteristic is set.
With this, the appropriate first and second control characteristics can be set. As a result, the desired sound can be more appropriately presented in the listening area, and this sound can be more sufficiently reduced in the nearby area that is the first control position.
Moreover, by performing: generating a first detection signal by detecting the reproduced sounds from the first and second speakers using a microphone located at the first control position; and updating the control characteristic of the control filter according to the second output signal from the listening compensation filter and the first detection signal, the updated control characteristic may be calculated and set as the first control characteristic.
With this, by the repetition of the above steps to reduce, for example, the acoustic level indicated by the first detection signal, the acoustic level of the sound obtained by synthesizing the reproduced sound from the first speaker and the reproduced sound from the second speaker at the first control position can be sufficiently approximated to 0. To be more specific, the first control characteristic can be set to make the acoustic level equivalent to 0 and, as a result, the reproduced sound from the second speaker can be reliably reduced at the first control position.
Furthermore, the sound field control apparatus may include an n number of the control filters, n being an integer that is at least 2, wherein the listening compensation filter may output the second output signal to an n number of the second speakers, and each of the n control filters may perform signal processing on the second output signal to be outputted to one of the n second speakers that corresponds to the control filter.
With this, the first control characteristic corresponding only to the reproduced sound from the second speaker that is one of the n second speakers can be set as the control characteristic of the control filter. As a result, even when a plurality of the second speakers are present, the appropriate first control characteristic can be set and thus the aforementioned effect can be more reliably obtained.
Moreover, the sound field control apparatus may further include an adder which adds the first output signals outputted from the n control filters and outputs an addition signal, wherein the first speaker may output the reproduced sound according to the addition signal outputted from the adder.
With this, the reproduced sound which corresponds to the first output signals outputted from the n control filters is outputted from the first speaker. Therefore, the first speaker does not need to be used for each of the control filters and the configuration of the whole system including the sound field control apparatus can be simplified.
Furthermore, the sound field control apparatus may include: a first listening compensation filter and a first control filter which are the listening compensation filter and the control filter, respectively; and a second listening compensation filter and a second control filter, wherein the second listening compensation filter may generate a third output signal by performing, according to a control characteristic that is previously set, signal processing on a current acoustic signal to be processed, and output the third output signal to a third speaker, the second control filter may generate a fourth output signal by performing signal processing on the third output signal from the second listening compensation filter according to a control characteristic that is previously set, and output the fourth output signal to the first speaker, the control characteristic of the second control filter may be previously set as a third control characteristic that allows a reproduced sound from the third speaker to be reduced at the second control position by the reproduced sound from the first speaker, and the control characteristic of the second listening compensation filter may be previously set as a fourth control characteristic that allows a sound having a predetermined target acoustic characteristic to be presented at the first control position by the reproduced sounds from the first and third speakers.
With this, at the first control position, the reproduced sound from the second speaker based on the input signal from the sound source can be reduced, and the sound that is based on the acoustic signal and has the predetermined target acoustic characteristic can be presented. At the second control position, the reproduced sound from the third speaker based on the acoustic signal is reduced and the sound that is based on the input signal from the sound source and has the predetermined target acoustic characteristic can be presented. To be more specific, the reproduced sounds to be reduced and the sounds to be presented can be made clearly different between the first control position and the second control position.
Moreover, the second listening compensation filter may perform signal processing on the input signal, as the acoustic signal, which is from the sound source and on which signal processing is performed by the first listening compensation filter.
With this, the first listening compensation filter and the second listening compensation filter perform signal processing according to the respective second and fourth control characteristics on the input signals from the same sound source. Thus, although the sounds are from the same sound source, the acoustic characteristics (the predetermined target acoustic characteristics) of the sounds can be made clearly different between the first control position and the second control position.
Furthermore, the second listening compensation filter may perform signal processing on a signal as the acoustic signal, the signal being different from the input signal which is outputted from the sound source and on which signal processing is performed by the first listening compensation filter.
With this, the first listening compensation filter and the second listening compensation filter perform signal processing according to the respective second and fourth control characteristics on the different signals (the input signal and the acoustic signal). Thus, the sounds to be presented and the acoustic characteristics (the predetermined target acoustic characteristics) of the sounds can be made clearly different between the first control position and the second control position.
Moreover, the third output signal from the second listening compensation filter may be added to the second output signal from the first listening compensation filter by an adder, and a resulting signal is outputted to the second speaker instead of the third speaker.
With this, the second speaker also serves as the third speaker. Thus, the third speaker does not need to be used, and thus the configuration of the whole system including the sound field control apparatus can be simplified.
Furthermore, each of the listening compensation filter and the control filter may include a plurality of taps and perform filtering using previous data included in a current signal to be processed.
With this, filtering such as FIR filtering can be appropriately performed on the signal (the input signal or the acoustic signal) to be processed.
The following is a concrete description of Embodiments, with reference to the drawings.
It should be noted that each of Embodiments described below shows a general or specific example. The numerical values, shapes, materials, structural elements, the arrangement and connection of the structural elements, steps, the processing order of the steps, and so forth described in Embodiments below are only examples, and are not intended to limit the present invention. Thus, among the structural elements in Embodiments below, structural elements not recited in any one of the independent claims indicating top concepts according to the present invention are described as arbitrary structural elements.
A configuration of a sound field control apparatus 101 in Embodiment 1 is described.
The sound field control apparatus 101 in Embodiment 1 includes a listening compensation filter 1, an n number of control filters 5-1 to 5-n, a p number of adders 6-1 to 6-p, a p number of speakers 7-1 to 7-p, and an n number of speakers 8-1 to 8-n. In the present configuration, appropriate (final) coefficients are previously set to the listening compensation filter 1 and the control filters 5-1 to 5-n. Thus, the sound field control apparatus 101 shown in
The sound field control apparatus 101 shown in
To be more specific, a sound field control apparatus in an aspect according to the present invention includes: a listening compensation filter which generates a second output signal by performing signal processing on an input signal from a sound source according to a control characteristic that is previously set, and outputs the second output signal to a second speaker; and a control filter which generates a first output signal by performing signal processing on the second output signal from the listening compensation filter according to a control characteristic that is previously set, and outputs the first output signal to a first speaker. Here, the control characteristic of the control filter is previously set as a first control characteristic that allows a reproduced sound from the second speaker to be reduced at a first control position (a control point) by a reproduced sound from the first speaker. Moreover, the control characteristic of the listening compensation filter is previously set as a second control characteristic that allows a sound having a predetermined target acoustic characteristic to be presented at a second control position (a listening point) by the reproduced sounds from the first and second speakers. It should be noted that the sound source, the listening compensation filter, the control filter, the first speaker, and the second speaker mentioned above correspond, respectively, to the sound source 100, the listening compensation filter 1, any one of the control filters 5-1 to 5-n, at least one of the speakers 7-1 to 7-p, and at least one of the speakers 8-1 to 8-n.
Moreover, like the sound field control apparatus 101 shown in
Next,
In
Here, the control filter 5-1 performs signal processing to reduce the sound reproduced by the speaker 8-1 at a q number of control points 10-1 to 10-q (where q p). To be more specific, the control points correspond to the zero control points described above. Similarly, the control filter 5-n performs signal processing to reduce the sound reproduced by the speaker 8-n at the q control points 10-1 to 10-q. As a result, all the sounds reproduced by the speakers 8-1 to 8-n are reduced at the control points 10-1 to 10-q. It should be noted that control coefficients of the control filters 5-1 to 5-n are previously obtained before the control coefficient of the listening compensation filter 1 is obtained.
As described above, the output signal from the listening compensation filter 1 is reproduced by the speakers 8-1 to 8-1n and also by the speakers 7-1 to 7-p via the control filters 5-1 to 5-n.
At the stage for setting the coefficient of the listening compensation filter 1, the sounds reproduced by the speakers 8-1 to 8-n and the speakers 7-1 to 7-p are detected by the microphones 9-1 to 9-m placed at an m number of listening points (the response control points) (where m≦n). It should be noted that each of the reference signs 9-1 to 9-m refers to a listening point or a microphone placed at the listening point. Each of the detection signals is inputted into the coefficient design unit 2. The input signal from the sound source 100 is inputted into the coefficient design unit 2 and also into the target characteristic unit 3. Here, the target characteristic unit 3 previously stores a desired characteristic (the predetermined target acoustic characteristic) for each of the listening points 9-1 to 9-m. According to this desired characteristic, the target characteristic unit 3 performs signal processing on the input signal from the sound source 100, and outputs the output signal obtained as a result of the signal processing (the target characteristic signal) to the coefficient design unit 2. The coefficient design unit 2 obtains the control coefficient of the listening compensation filter 1 from: the signal from the target characteristic unit 3; the signals from the microphones 9-1 to 9-m; and the input signal from the sound source 100. Then, the listening compensation filter 1 performs signal processing on the input signal from the sound source 100 using this control coefficient, and outputs the output signal obtained as a result of the signal processing to the speakers 8-1 to 8-n and the control filters 5-1 to 5-n. As a result, the sounds are reproduced by the speakers 8-1 to 8-n and the speakers 7-1 to 7-p, meaning that the desired characteristics are recreated at the listening points 9-1 to 9-m.
Here, the system for setting the coefficient of the listening compensation filter 1 may further include a difference extraction unit 4 as in a system 101B shown in
After the target characteristic unit 3 performs the signal processing on the input signal from the sound source 100 according to the desired characteristic, the resulting signal is inputted into the difference extraction unit 4. The signals of the sounds reproduced by the speakers 8-1 to 8-n and the speakers 7-1 to 7-p and detected by the microphones 9-1 to 9-m are also inputted as the detection signals to the difference extraction unit 4.
The difference extraction unit 4 extracts a difference between the output signal from the target characteristic unit 3 and each of the signals from the microphones 9-1 to 9-m. Then, the difference extraction unit 4 outputs the resulting signal as the difference signal to the coefficient design unit 2. On the basis of the input signal from the sound source 100 and the difference signal from the difference extraction unit 4, the coefficient design unit 2 obtains the control coefficient of the listening compensation filter 1 to allow the difference signal from the difference extraction unit 4 to be minimum (ideally, 0). Accordingly, the desired characteristics can be recreated at the listening points 9-1 to 9-m.
Here, the reproduced sounds of the speakers 8-1 to 8-n are reduced at the control points 10-1 to 10-q by the control filters 5-1 to 5-n. On account of this, regardless of the characteristic of the control coefficient of the listening compensation filter 1, the reduction effect is always maintained. Therefore, eventually, the desired characteristics can be recreated at the listening points 9-1 to 9-m and, at the same time, it is quiet at the control points 10-1 to 10-q since the sounds are reduced at these points.
As described above, in a sound field control apparatus in an aspect according to the present invention, the updated control characteristic is calculated and set as the second control characteristic by performing, for example, the following steps. The steps include: generating a target characteristic signal by performing signal processing on the input signal from the sound source according to the predetermined target acoustic characteristic; generating a second detection signal by detecting the reproduced sounds from the first and second speakers using a microphone located at the second control position; and updating the control characteristic of the listening compensation filter according to the input signal, the target characteristic signal, and the second detection signal. For example, in the updating, a difference between the target characteristic signal and the second detection signal is calculated and the control characteristic of the listening compensation filter is updated using the input signal to reduce the difference.
Next,
As described above, the control coefficients of the control filters 5-1 to 5-n (the first control characteristics) of the sound field control apparatus 101 in Embodiment 1 are previously obtained before the control coefficient of the listening compensation filter 1 (the second control characteristic) is obtained. The method for calculating the control coefficients of the control filters 5-1 to 5-n is described as follows. Firstly, like the system 101C shown in
As described above, in a sound field control apparatus in an aspect according to the present invention, the first control characteristic of the control filter is set before the second control characteristic is calculated and set, for example. Moreover, in a sound field control apparatus in an aspect according to the present invention, the updated control characteristic is calculated and set as the first control characteristic by performing, for example, the following steps. The steps include: generating a first detection signal by detecting the reproduced sounds from the first and second speakers using a microphone located at the first control position; and updating the control characteristic of the control filter according to the second output signal from the listening compensation filter and the first detection signal.
It should be noted that the coefficient design units 2 and 20-1 to 20-n shown in
Here, for the sake of simplicity, suppose that a system includes a single speaker 7-1, a single speaker 8-1, a single microphone 9-1, and a single microphone 10-1 as shown in
Firstly, in order to obtain a characteristic of the control filter 5-1 shown in
[Math. 3]
E10=AX+WBX Equation 3
When the detection signal E10 in Equation 3 is minimum, this means that this signal ideally becomes 0. When the solution is found based on this, Equation 4 shown below is obtained.
[Math. 4]
W=−A/B Equation 4
Next, a coefficient z (i) of the listening compensation filter 1 is obtained. Similarly, in
When the output signal E′ in Equation 5 is minimum, this means that this signal ideally becomes 0. When the solution is found based on this, Equation 6 shown below is obtained.
[Math. 6]
Z=BD/(BC−AG) Equation 6
When the coefficients obtained by Equation 4 and Equation 6 as described are applied to
An experiment was actually carried out in order to verify the effectiveness.
As shown in
Furthermore, in order to verify the effect achieved by the sound field control, microphones 11-1 to 11-8 and 12 used for evaluation are placed as shown in
Here, the laboratory 300 is an ordinary room. As shown in
Next, an actual signal processing operation is described.
Firstly, the target acoustic characteristics to be set in the target characteristic unit 3 shown in
[Math. 9]
h1(i+1)=h1(i)+μx(i)e1(i)
h2(i+1)=h2(i)+μx(i)e2(i) Equation 9
In Equation 9, “h1 (i)” represents the coefficient (vector) of the filter 3-1 and “h2 (i)” represents the coefficient (vector) of the filter 3-2. Moreover, “x (i)” represents the measurement input signal (vector) outputted from the sound source 100, and “e1 (i)” represents the difference signal (scalar) of the subtracter 50-1. Furthermore, “e2 (i)” represents the difference signal (scalar) of the subtracter 50-2, and “p” represents a step parameter (scalar) that is an update constant.
Moreover, the target acoustic characteristic can be set freely. The target acoustic characteristic is not limited to the acoustic characteristic obtained when a specific speaker 60 is placed in a listening room or in an anechoic room. The target acoustic characteristic may be: the acoustic characteristic of a speaker built in the TV 301 or in a different video audio apparatus; an ideal flat electrical characteristic with respect to the frequency (simple delay, for example); or a high pass filter (HPF) characteristic in consideration of the low-frequency performance of the speakers 7-1 to 7-50 and 8-1 to 8-8. Depending on the circumstances, the sound field characteristic of a concert hall or a baseball stadium can be set as the target acoustic characteristic. Thus, when this target acoustic characteristic is recreated in the listening area, the viewer can also experience a feeling of actually being in the location.
After the target acoustic characteristic is obtained in advance, the control points 10-1 to 10-45 are next controlled using the speakers 7-1 to 7-50 in order for the reproduced sounds from the speakers 8-1 to 8-8 used for adjusting the listening points to be reduced in a quiet area 202 shown in
In
For example, the coefficient design unit 20-1 inputs the measurement input signal from the sound source 100 into Fx filters 40-1 to 40-3 where the input signals are convoluted with respective coefficients b11, b12, and b13 which are previously obtained. The coefficient b11 represents a transfer characteristic from the speaker 7-1 to the microphone 10-1. The coefficient b12 represents a transfer characteristic from the speaker 7-1 to the microphone 10-2. The coefficient b13 represents a transfer characteristic from the speaker 7-1 to the microphone 10-3. Then, the output signals from the Fx filters 40-1 to 40-3 are inputted into LMSs 30-1 to 30-3. Here, the signals detected by the microphones 10-1 to 10-3 (i.e., the detection signals) are also inputted into the LMSs 30-1 to 30-3. Based on these signals, the LMSs 30-1 to 30-3 update the coefficients w1, w2, and w3 of the control filters 5-1 to 5-3 to allow the detection signals of the microphones 10-1 to 10-3 to be minimum. This coefficient update arithmetic operation is similarly performed by the coefficient design units 20-2 and 20-3.
Note that the Fx filters and the LMSs of the coefficient design units 20-2 and 20-3 are simply omitted in
[Math. 10]
w1(i+1)=w1(i)+μ{r11(i)e1(i)+r12(i)e2(i)+r13(i)e3(i)}
w2(i+1)=w2(i)+μ{r21(i)e1(i)+r22(i)e2(i)+r23(i)e3(i)}
w3(i+1)=w3(i)+μ{r31(i)e1(i)+r32(i)e2(i)+r33(i)e3(i)}
rjk(i)=x(i)*bjk(i) Equation 10
In Equation 10, “w1 (i)” represents the coefficient (vector) of the filter 5-1, “w2 (i)” represents the coefficient (vector) of the filter 5-2, and “w3 (i)” represents the coefficient (vector) of the filter 5-3. Moreover, “x (i)” represents the measurement input signal (vector) outputted from the sound source 100, and “bjk (i)” represents the coefficients (vectors) of the Fx filters 40-1 to 40-3. Furthermore, “e1 (i)” represents the detection signal (scalar) of the microphone 10-1, “e2 (i)” represents the detection signal (scalar) of the microphone 10-2, and “e3 (i)” represents the detection signal (scalar) of the microphone 10-3. Moreover, “p” represents a step parameter (scalar) that is an update constant.
After the coefficients of the control filters 5-1 to 5-8 are obtained, the coefficient of the listening compensation filter is obtained using the control filters 5-1 to 5-8 as coefficient-fixed filters. The listening points 9-1 to 9-8 are controlled to recreate the target acoustic characteristics in the listening area 201 shown in
In
[Math. 11]
δ11(i)=c11(i)+w1−1(i)*g11(i)+w2−1(i)*g21(i)+w3−1(i)*g31(i)
δ12(i)=c12(i)+w1−1(i)*g12(i)+w2−1(i)*g22(i)+w3−1(i)*g32(i)
δ21(i)=c21(i)+w1−2(i)*g11(i)+w2−2(i)*g21(i)+w3−2(i)*g31(i)
δ22(i)=c22(i)+w1−2(i)*g12(i)+w2−2(i)*g22(i)+w3−2(i)*g32(i) Equation 11
In Equation 11, “c11 (i)” represents a transfer characteristic from the speaker 8-1 to the microphone 9-1, and “c12 (i)” represents a transfer characteristic from the speaker 8-1 to the microphone 9-2. Moreover, “c21 (i)” represents a transfer characteristic from the speaker 8-2 to the microphone 9-1, and “c22 (i)” represents a transfer characteristic from the speaker 8-2 to the microphone 9-2. Furthermore, “w1-1 (i)” represents the coefficient of the control filter 5-1-1, “w2-1 (i)” represents the coefficient of the filter 5-1-2, and “w3-1 (i)” represents the coefficient of the filter 5-1-3. Moreover, “w1-2 (i)” represents the coefficient of the control filter 5-2-1, “w2-2 (i)” represents the coefficient of the filter 5-2-2, and “w3-2 (i)” represents the coefficient of the filter 5-2-3. Furthermore, “g11 (i)” represents a transfer characteristic from the speaker 7-1 to the microphone 9-1, and “g12 (i)” represents a transfer characteristic from the speaker 7-1 to the microphone 9-2. Moreover, “g21 (i)” represents a transfer characteristic from the speaker 7-2 to the microphone 9-1, and “g22 (i)” represents a transfer characteristic from the speaker 7-2 to the microphone 9-2. Furthermore, “g31 (i)” represents a transfer characteristic from the speaker 7-3 to the microphone 9-1, and “g32 (i)” represents a transfer characteristic from the speaker 7-3 to the microphone 9-2.
In this way, the coefficients δ11, δ12, δ21, and δ22 of the Fx filters 70-1 to 70-4 are approximated, thereby assuring that the LMSs 80-1 to 80-4 converge normally. Thus, the LMSs 80-1 to 80-4 update the coefficients of the listening compensation filters 1-1 and 1-2 to minimize the signals from the subtracters 4-1 and 4-2, based on the signals from the Fx filters 70-1 to 70-4 and the signals from the subtracters 4-1 and 4-2. As a result, the target acoustic characteristics d1 and d2 are recreated at the microphones 9-1 and 9-2. The processing described thus far is understood to be based on the MEFX-LMS algorithm disclosed in Non Patent Literature 5, as indicated by Equation 12 below.
[Math. 12]
z1(i+1)=z1(i)+μ{r11(i)e1(i)+r12(i)e2(i)}
z2(i+1)=z2(i)+μ{r21(i)e1(i)+r22(i)e2(i)}
rjk(i)=x(i)*δjk(i) Equation 12
In Equation 12, “z1 (i)” represents the coefficient of the listening compensation filter 1-1, and “z2 (i)” represents the coefficient of the listening compensation filter 1-2. Moreover, “x (i)” represents the measurement input signal outputted from the sound source 100, and “δjk (i)” represents the coefficients of the Fx filters 70-1 to 70-4. Furthermore, “e1 (i)” represents the signal outputted from the subtracter 4-1, and “e2 (i)” represents the signal outputted from the subtracter 4-2. Moreover, “p” represents a step parameter that is an update constant.
Firstly, in
As described thus far, the reproduced sounds from the speakers 8-1 to 8-8 can be reduced in the quiet area 202 of the laboratory 300. This can be physically sensed in actual trial listening. Even when freely moving around in the quiet area 202, the listener can sense the same effect as described above.
Next,
It can be seen from
On the other hand, as can be seen from
In
Incidentally, this experiment resulted in that, while the control is being performed, the viewer U present in the quiet area sensed the sound lower by 10 dB to 20 dB at 100 Hz to 1000 Hz than the sound sensed by the viewer V present in the listening area.
Here, an experiment was carried out using the sound field control apparatus 3000 shown in
With this being the situation, the control filter 3001 is divided into a control filter 3001-1 in charge of listening compensation and a control filter 3001-2 in charge of quiet sound as shown in a sound field control apparatus 3100 in
In
It is clear from the result of the experiment that the sound field control apparatus 3000 cannot obtain the aforementioned effect achieved by the sound field control apparatus 101 in Embodiment 1. Moreover, it is also clear that the sound field control apparatus 3100 having the configuration obtained by simply changing the configuration of the sound field control apparatus 3000 cannot produce the effect achieved by the sound field control apparatus 101 in Embodiment 1. Hence, the effectiveness of the sound field control apparatus 101 shown in
As described thus far, the sound field control apparatus 101 in Embodiment 1 can reproduce the target sound (sound field) in the listening area of the laboratory 300. Thus, the audio of the TV 301, for example, can be properly previewed. Moreover, since this reproduced sound can be reduced in the quiet area, conversation can be carried out without interruption by, for example, the audio of the TV 301. At the same time, the audio of the TV 301 can be enjoyed in the listening area at high volume levels without concern for someone else present in the quiet area.
Alternatively, when two persons side by side would like to listen to different contents (such as classic music and popular music, or a movie program on TV and a baseball game live on TV), one person can listen to the desired content while reducing the reproduced content of the other person. Accordingly, the persons can enjoy the desired contents without the mutual adverse influences, that is, crosstalk. In addition, these desired contents can also be controlled to be reproduced virtually at any sound fields. Therefore, the presence can also be recreated as if the persons were in, for example, a concert hall and a baseball stadium.
Moreover, especially in the case where the speakers used for control are arranged, for example, in the same plane in front of the viewer without limiting the condition to arrange the acoustic devices such as the speakers and microphones used for control, the effect can be obtained for the entire frequency band to be controlled. On this account, the apparatus can be broadly applicable to not only a room in a home where a TV and audio devices are installed, but also shops such as a barber shop and a beauty salon, facilities such as a gallery and a museum, and transportation means such as a car and a train.
Furthermore, in the experiment shown in
In Embodiment 1, the control is performed to implement the quiet area 202 over a large area behind the listening area 201 as shown in
As an example of the basic control configuration of the sound field control apparatus in Embodiment 1, the sound field control apparatus 101 is shown in
In order for the control filters and the listening compensation filter to converge properly, the principle of cause and effect in the digital signal processing needs to be satisfied. Thus, as a technique for designing a coefficient, the delay units 13 and 13-1 to 13-n may be inserted as appropriate, as shown by the sound field control apparatus 102 and a system including the sound field control apparatus 102. The delay unit 13 may be included in the target characteristic unit 3. The delay unit 13 delays the transfer of the input signal from the sound source 100 to the target characteristic unit 3, and the delay units 13-1 to 13-n delay the transfer of the output signal from the listening compensation filter 1 to the speakers 8-1 to 8-n.
It should be noted that each of the systems shown in
As described, the sound field control apparatus in Embodiment 1 can appropriately implement any sound field characteristics at different areas in one space without any constraint on an arrangement of a configuration. For example, when the audio from audio-video (AV) equipment such as a TV or an audio device is listened to, the reproduced sound from the AV equipment can be precisely heard only in a specific listening area and the reproduced sound can be reduced in other areas.
A configuration of a sound field control apparatus in Embodiment 2 is described.
To be more specific, the system 201 in Embodiment 2 includes the listening compensation filter 1a, the listening compensation filter 1b, a coefficient design unit 2a, a coefficient design unit 2b, coefficient design units 20-1a to 20-na, coefficient design units 20-1b to 20-nb, a target characteristic unit 3a, a target characteristic unit 3b, a difference extraction unit 4a, a difference extraction unit 4b, the control filters 5-1a to 5-na, the control filters 5-1b to 5-nb, adders 6-1a-1 to 6-1a-n, adders 6-pa-1 to 6-pa-n, an adder 6-1b-1, an adder 6-pb-1, speakers 7-1 to 7-p, speakers 8-1a to 8-na, and speakers 8-1b to 8-nb. The sound field control apparatus in Embodiment 2 includes the listening compensation filter 1a, the listening compensation filter 1b, the control filters 5-1a to 5-na, the control filters 5-1b to 5-nb, the adders 6-1a-1 to 6-1a-n, the adders 6-pa-1 to 6-pa-n, the adder 6-1b-1, the adder 6-pb-1, the speakers 7-1 to 7-p, the speakers 8-1a to 8-na, and the speakers 8-1b to 8-nb. It should be noted that the sound field control apparatus in Embodiment 2 may not include the speakers 7-1 to 7-p, 8-1a to 8-na, and 8-1b to 8-nb.
The structural elements of the system 201 are identical to those of the system 101C in Embodiment 1. Therefore, the explanations of these structural elements are omitted, and only the operations are described as follows.
A sound field to be controlled by the sound field control apparatus of the system 201 recreates a different acoustic characteristic for each of viewers V and U as shown in
In this way, Embodiment 2 can recreate, in one space, the two sound fields having the individual acoustic characteristics. In Embodiment 2, the two areas to be controlled are adjacent to each other side by side as shown in
Furthermore, the sound field control apparatus in Embodiment 2 may include adders 14-1 to 14-n as shown by a sound field control apparatus of a system 202 shown in
Moreover, the sound field control apparatus in Embodiment 2 can be applied to different sound sources as shown by a sound field control apparatus of a system 203 shown in
As in the cases shown in
As described thus far, like the sound field control apparatus in Embodiment 2 for example, a sound field control apparatus in an aspect according to the present invention includes a first listening compensation filter and a first control filter that are the aforementioned listening compensation filter and control filter, and further includes a second listening compensation filter and a second control filter. The second listening compensation filter generates a third output signal by performing, according to a control characteristic that is previously set, signal processing on a current acoustic signal to be processed, and outputs the third output signal to a third speaker. The second control filter generates a fourth output signal by performing signal processing on the third output signal from the second listening compensation filter according to a control characteristic that is previously set, and outputs the fourth output signal to the first speaker. Here, the control characteristic of the second control filter is previously set as a third control characteristic that allows a reproduced sound from the third speaker to be reduced at the second control position by the reproduced sound from the first speaker. Moreover, the control characteristic of the second listening compensation filter is previously set as a fourth control characteristic that allows a sound having a predetermined target acoustic characteristic to be presented at the first control position by the reproduced sounds from the first and third speakers.
It should be noted that the first listening compensation filter, the second listening compensation filter, the first control filter, the second control filter, and the third speaker described above correspond, respectively, to the listening compensation filter 1a, the listening compensation filter 1b, any one of the control filters 5-1a to 5-na, any one of the control filters 5-1b to 5-nb, and at least one of the speakers 8-1b to 8-nb shown in
Moreover, as shown in
Although the sound field control apparatus according to the present invention has been described by way of Embodiments above, it should be obvious that the present invention is not limited to Embodiments described above. Moreover, each of the structural elements described above may be configured with a circuit, or with a system large scale integration (system LSI) in part or in whole. Furthermore, Embodiments described above may be combined.
The sound field control apparatus according to the present invention has an advantageous effect of appropriately presenting a desired sound in a listening area and sufficiently reducing the sound in a nearby area without any constraint on an arrangement of a configuration. For example, the sound field control apparatus can be applied to a facility in which an area where a person is present can be specified. To be more specific, the sound field control apparatus can be used for controlling a sound field in, for example, a barber shop, a beauty salon, a gallery, a museum, a car, or a train. More specifically, any sound can be reproduced for each of persons sitting on chairs in a barber shop or a beauty salon without any mutual adverse influences. Moreover, any sound can be reproduced for each of persons standing in front of different exhibits without any mutual adverse influences. Furthermore, an individual sound can be reproduced for each of seats in a car or a train.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-285007 | Dec 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2012/007330 | 11/15/2012 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/099093 | 7/4/2013 | WO | A |
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| 20140056431 A1 | Feb 2014 | US |
