EP2023672A1

EP2023672A1 - Speaker system

Info

Publication number: EP2023672A1
Application number: EP07744260A
Authority: EP
Inventors: Takahiro c/o Panasonic Corp. IPROC HAYAKAWA; Junichi c/o panasonic Corp. IPROC MATSUDA
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2006-05-31
Filing date: 2007-05-28
Publication date: 2009-02-11
Also published as: JP2007324907A; WO2007139066A1; CN101461256A

Abstract

A speaker system capable of providing a listening environment without giving audience the feeling of wrongness is described. A speaker system (100) includes a first speaker unit configured to include first and second speakers (101) and (102), the first and second speakers (101) and (102) being arranged in symmetry each other with respect to a first standard plane (d) including a first listening point. The speaker system (100) further includes a second speaker unit configured to include third and fourth speakers (103) and (104), the third and fourth speakers being arranged in symmetry each other with respect to a second reference plane (c) including a second listening point, and to be arranged in symmetry with the first speaker unit with respect to a predetermined median plane (e).

Description

Technical Field

The present invention relates to a speaker system that includes two pairs of speaker units each including at least two speakers.

Background Art

A conventional speaker system includes, for example, an L channel speaker unit, an R channel speaker unit and a center speaker unit (for example, see Patent Document 1). Each of the above three speaker units is arranged in the center of positions ahead of the driver' s seat and passenger seat of a vehicle. The L channel speaker unit is directed toward a direction in which the directivity axis of the L channel speaker unit is rotated counterclockwise in the horizontal direction with respect to the traveling direction of the vehicle and in which the directivity axis is inclined at a predetermined angle to the vertical direction with respect to the traveling direction of the vehicle. The R channel speaker unit is directed toward a direction in which the directivity axis of the R channel speaker unit is rotated clockwise in the horizontal direction with respect to the traveling direction of the vehicle and in which the directivity axis is inclined at a predetermined angle in the vertical direction with respect to the traveling direction of the vehicle. The center speaker unit outputs an -L-R signal obtained by adding an -L signal which is a reverse phase signal of an L channel signal and an -R signal which is a reverse phase signal of the R channel signal.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-289341

Disclosure of Invention

Problems to be Solved by the Invention

With such a conventional speaker system mounted in a vehicle, given that a difference (path length difference) is caused between the lengths of the paths for the L and R channel signals through which the Both signals reaches the listener in the driver' s seat, a phase difference and delay are caused between the both channel signals before they reach the listener. The same applies to the listener in the front passenger seat. There is a problem that listeners feel a sense of discomfort listening to audio due to the above phase difference and delay.
In view of the above, it is therefore an object of the present invention to provide a speaker system that makes it possible to provide a listening environment which does not give a sense of discomfort to a plurality of listeners.

Means for Solving the Problem

To realize the above object, A speaker system includes: a first speaker unit configured to include first and second speakers, the first and second speakers being arranged in symmetry each other with respect to a first reference plane including a first listening point; and a second speaker unit configured to include third and fourth speakers, the third and fourth speakers being arranged in symmetry each other with respect to a second reference plane including a second listening point, and to be arranged in symmetry with the first speaker unit with respect to a predetermined median plane.

Advantageous Effect of the Invention

Thanks to the symmetry of speakers according to the present invention, it is easier to provide sound without a phase difference and delay to the first and second listening points. Consequently, it is possible to provide a listening environment which does not give a sense of discomfort to listeners at the first and second listening points.

Brief Description of Drawings

FIG.1 shows the interior of a vehicle mounting a speaker system from above, according to an embodiment of the present invention;
FIG.2 shows the lateral side of the driver's seat in the speaker system, according to the above embodiment;
FIG.3 shows a configuration of a signal processing block of the speaker system according to the embodiment;
FIG.4 is a plan view illustrating positions of the speaker unit of the speaker system and the listener according to the embodiment; and
FIG.5 is a schematic view illustrating the relationship between the direction of the speaker unit of the speaker system and the position of the listener according to the embodiment.

Best Mode for Carrying Out the Invention

An embodiment of the present invention will be described in detail below with reference to the drawings.
FIG.1 shows an interior of a vehicle mounting the speaker system from above, according to the embodiment of the present invention and FIG.2 shows the lateral side of the driver's seat.
In FIG.1, a speaker system 100 includes a first R channel speaker 101, a second R channel speaker 102, a the third L channel speaker 103 and a fourth L channel speaker 104 that each output sound of the middle and high frequency band (about 200 Hz to 20 kHz).
The first R channel speaker 101 is substantially arranged in front of the driver's seat of the vehicle (for example, in/on a dashboard 200) and outputs sound based on an in-phase signal of the R channel signal (hereinafter referred to as "in-phase signal (R)") from a sound source.
Further, the second R channel speaker 102 is arranged in a location in symmetry with the first R channel speaker 101 with respect to the first virtual plane and is substantially arranged in front of the driver's seat, and outputs sound based on the reverse phase signal (hereinafter referred to as "reverse phase signal (R)") that inverts has a reverse phase with respect to above in-phase signal (R).
Furthermore, the above first virtual plane will be referred to as the "first reference plane c" in the following description. With the present embodiment, this first reference plane c is parallel or substantially parallel to longitudinal median plane e of the vehicle, includes a listening point (hereinafter referred to as "the first listening point") for the listener sitting in the driver's seat and passes the center of the first and second R channel speakers 101 and 102. Further, in the present embodiment, the first listening point is exemplarily determined in advance around the head of the listener sitting in the driver's seat.
Furthermore, the third L channel speaker 103 is substantially arranged in front of the front passenger seat next to the driver's seat (for example, in/on dashboard 200), and outputs sound based on the in-phase signal of the L channel signal (hereinafter referred to as "in-phase signal (L)") from the same sound source as above.
The fourth L channel speaker 104 is arranged in a location in symmetry with the third L channel speaker 103 with respect to the second virtual plane and is substantially arranged in front of the front passenger seat, and outputs sound based on the reverse phase signal (hereinafter "reverse phase signal (L)") that has a reverse phase with respect to the above in-phase signal (L).
The above second virtual plane will be referred to as the "second reference plane d" in the following description. With the present embodiment, this second reference plane d is parallel or substantially parallel to the longitudinal median plane e of the vehicle, includes the listening point for the listener sitting in the front passenger seat (hereinafter referred to as "the second listening point") and passes the center of third and fourth L channel speakers 103 and 104. Further, in the present embodiment, the second listening point is exemplarily determined in advance around the head of the listener sitting in the front passenger seat.
As described above, the first R channel speaker 101 outputs sound based on the in-phase signal (R) and the second R channel speaker 102 outputs sound based on the reverse phase signal (R). Consequently, above and near the first reference plane c, sound based on the in-phase signal (R) and sound based on the reverse signal (R) cancel each other and the listener sitting in the driver's seat feels like sound does not come from the front. Given that the same phenomenon occurs in the first L channel speaker 103 and the second L channel speaker 104, the listener sitting in the front passenger seat feels like sound does not come from the front of the listener.
Further, the speaker system 100 includes a sound input section 110 in which a sound source composed of two-channel signal (composed of L channel and R channel), and a signal processing block 120 for applying signal processing to the two-channel signal from the sound input section 110 to generate an in-phase signal (R), a reverse phase signal (R), a in-phase signal (L) and a reverse phase signal (L). The in-phase signal (R), the reverse phase signal (R), the in-phase signal (L) and the reverse phase signal (L) generated, are outputted to the first R channel speaker 101, the second R channel speaker 102, the third L channel speaker 103 and the fourth L channel speaker 104, respectively.
The sound input section 110 is an input terminal in which a sound source from an audio device and a speech input device, the audio device being one of a CD player, DVD player, MD player, cassette deck, radio, television receiver and semiconductor memory audio device and a speech input apparatus being a microphone, for example. Further, the sound input section 110 as such may be an audio device or speech input apparatus.
As shown in FIG.2, the speaker system 100 includes a low band (less than about 200 Hz) speaker (woofer) 180 under dashboard 200 of the driver's seat side. Further, although not shown in FIG.2, a low band speaker 181 (see FIG.3) similar to the speaker 180, is provided under dashboard 200 of the front passenger seat side.
The directivity axes of the low band speakers 180 and 181 are not directed toward the listener P1 in the driver's seat (i.e. driver) and the listener in the front passenger seat. Preferably, the low band speakers 180 and 181 are installed so as to be directed downward from the respective locations of installation. Consequently, the sounds having a low frequency band radiated from the low band speakers 180 and 181 do not reach the listeners directly, and, instead reflected sounds reach the listeners.
Further, the first R channel speaker 101, the second R channel speaker 102, the third L channel speaker 103 and the fourth L channel speaker 104 reproduce sound of a middle and high frequency band and the low band speakers 180 and 181 reproduce sound of a low frequency band. Consequently, to the middle and high band speakers 101, 102, 103 and 104, middle and high band audio signals obtained by performing band division of the audio signal from the sound source are supplied as the in-phase signal (R), the reverse phase signal (R), the in-phase signal (L) and the in-phase signal (L), respectively. Supplied to the low band speakers 180 and 181 are the low band audio signals obtained by performing band division of the audio signal from the above sound source.
A pair of the first R channel speaker 101 and the second R channel speaker 102 compose speaker unit SP1 (see FIG.2) for the driver' s seat, and a pair of the third L channel speaker 103 and the fourth L channel speaker 104 compose a speaker unit SP2 (not shown) for the front passenger seat. In this way, the speaker units SP1 and SP2 are arranged in the driver's seat side and in the front passenger seat of dashboard 200, respectively. Further, the first R channel speaker 101 and the third L channel speaker 103 compose a speaker set for the listener (i.e. driver) in the driver' s sea, and the second R channel speaker 102 and the fourth L channel speaker 104 compose another speaker set for the listener in the front passenger seat.
The first R channel speaker 101 and the second R channel speaker 102 are mounted in dashboard 200 of the driver's seat side such that an opening angle and elevation angle as described below are formed. Similarly, the third L channel speaker 103 and the fourth L channel speaker 104 are mounted in the dashboard 200 of the front passenger seat side such that an opening angle and elevation angle described below are formed.
(1) The first speaker unit SP1 is arranged in a location where an extension line of a bisector 150 of the opening angle, formed by the directivity axis of the first R channel speaker 101 and the directivity axis of the second R channel speaker 102, is parallel or substantially parallel to the longitudinal median line of the vehicle and passes the first listening point. Note that the extension line of the bisector 150 is included in the first reference plane c where the in-phase signal (R) and reverse phase signal (R) cancel each other. Similarly, the second speaker unit SP2 is arranged in a location where an extension line of a bisector 160 of the opening angle, formed by the directivity axis of the third L channel speaker 103 and the directivity axis of the fourth L channel speaker 104, is parallel or substantially parallel to the longitudinal median line of the vehicle and passes the second listening point. The extension line of the bisector 160 is included in the second reference plane d where the in-phase signal (L) and reverse phase signal (L) cancel each other. By this means, the first R channel speaker 101 and the second R channel speaker 102 are arranged in front of the driver, and the third L channel speaker 103 and the fourth L channel speaker 104 are arranged in front of the listener in the front passenger seat. Consequently, as described above, each listener sitting in the driver's seat and the front passenger seat feels like sound does not come from the front.
(2) The directions of the first R channel speaker 101 and the third L channel speaker 103 (preferably, the directions of the directivity axis) are determined such that the distance of a path 151 through which sound is reflected by a right side glass 210 and reaches from the first R channel speaker 101 the right ear of the driver and the distance of a path 152 through which sound reaches from the third L channel speaker 103 directly the left ear of the driver, are equal. Similarly, the directions of the third L channel speaker 103 and the fourth L channel speaker 104 (preferably, the directions of the directivity axes) are determined such that the distance of a path 153 through which sound reaches from the second R channel speaker 102 directly the right ear of the listener in the front passenger seat and the distance of a path 154 through which sound is reflected by a left side glass 220 and reaches from the fourth L channel speaker 104 the left ear of the driver, are equal.
(3) The first speaker unit SP1 and the second speaker unit SP2 are arranged in locations in symmetry with each other with respect to the longitudinal median plane e including the longitudinal median line of the vehicle.
Depending on the size of the interior of the vehicle, the location of the seat and the shape of the dashboard, there are cases where all of the above (1) to (3) arrangement requirements are not necessarily satisfied. In these cases, the first R channel speaker 101, the second R channel speaker 102, the third L channel speaker 103 and the fourth L channel speaker 104 are mounted by adjusting the arrangement and directions such that the above (1) to (3) arrangement conditions are satisfied as much as possible. What important matters to hearing is the requirement (2) that the distance of the path through which sound is reflected by the side glasses 210 and 220 and reaches the listener and the distance of the path through which sound reaches directly the listener are equal. To prioritize this requirement, a method of arranging the first R channel speaker 101 and the second R channel speaker 102 and the third L channel speaker 103 and the fourth L channel speaker 104 on the dashboard 200 by shifting these speakers slightly to the right, left, forward or backward with respect to the front of the driver or the listener in the front passenger seat, may be adopted. In this case, a set of the first R channel speaker 101 and the second R channel speaker 102 and a set of the third L channel speaker 103 and the fourth L channel speaker 104 may not face the listener in the driver's seat (i.e. driver) and the listener in the front passenger seat, respectively.
If the first R channel speaker 101, the second R channel speaker 102, the third L channel speaker 103 and the fourth L channel speaker 104 are suitably arranged on the dashboard 200 such that the above (1) and (2) arrangement requirements are satisfied, the driver does not hear the sound from the first channel speaker 101 directly but hears the sound reflected by the side glass 210. Consequently, the listener feels like sound based on the in-phase signal (R) comes from a virtual image 105 of the first R channel speaker 101 at the front right outside the vehicle. The listener sitting in the driver' s seat feels like the virtual image 105 of the first R channel speaker 101 is in a location in symmetry with the third L channel speaker 103 with respect to the first reference plane c. By hearing sound from the virtual image 105 of the first R channel speaker 101 and sound from the third L channel speaker 103, the listener sitting in the driver' s seat is able to hear sound wide stereo feeling in the narrow space in the vehicle in which installation of speakers is considerably restricted.
Given that the second speaker unit SP2 is arranged in a location in symmetry with the first speaker unit SP1 with respect to the longitudinal median plane e of the vehicle, the listener in the front passenger seat recognizes that there is a virtual image 106 of the fourth L channel speaker 104 at the front left outside the vehicle. Consequently, the listener sitting in the front passenger seat is able to hear sound with wide stereo feeling, like the listener sitting in the driver's seat.
In this way, the speaker system 100 includes the speaker unit SP1 composed of the first R channel speaker 101 that radiates the in-phase signal of the R channel signal and the second R channel speaker 102 that radiates the reverse phase signal of the R channel signal, and the speaker unit SP2 composed of the third L channel speaker 103 that radiates the in-phase signal of the L channel signal and the fourth L channel speaker 104 that radiates the reverse phase signal of the L channel signal. In the speaker unit SP1, the first R channel speaker 101 and the second R channel speaker 102 are in symmetry with respect to the first reference plane c including the listening point for the listener, and are arranged such that sound outputted from the first R channel speaker 101 is reflected by the side glass 210 and reaches to the first listening point. The speaker unit SP2 is arranged in a location in symmetry with the first speaker unit SP1 with respect to the longitudinal median plane e of the vehicle, the third L channel speaker 103 and the fourth L channel speaker 104 are in symmetry with respect to the second reference plane d including the listening point for the listener and are arranged such that sound outputted from the fourth L channel speaker 104 is reflected by the side glass 220 and reaches to the second listening point.
Further, the first R channel speaker 101 and the third L channel speaker 103 are arranged such that the distance through which sound outputted from the first R channel speaker 101 is reflected by the side glass 210 and reaches the first listening point and the distance through which sound outputted from the third L channel speaker 103 reaches directly the first listening point, are equal. The second R channel speaker 102 and the fourth L channel speaker 104 are arranged according to the same relationship between the positions of the first R channel speaker 101 and the third L channel speaker 103.
As described above, it is possible to provide to the listeners, the sound of the R channel and the sound of the L channel with substantially no phase difference and delay. The listeners do not feel a sense of discomfort listening to audio. Further, the listener sitting in the front passenger seat is able to hear sound with wide stereo feeling like the listener sitting in the driver's seat.
FIG.3 shows a configuration of the signal processing block 120.
In FIG.3, the signal processingblock 120 includes amplifiers 301 to 304, inverters 311 to 314, delay units 321 to 324 and band division sections 325 to 328.
The amplifiers 301 and 302 adjust the levels of the R and L channel signals from a sound source (not shown), respectively. Further, the amplification factors in amplifiers 301 and 302 are set such that, for example, as to the levels of the first R channel speaker 101 and the third L channel speaker 103, a listener at the first listening point hears sounds therefrom with the same levels each other. The inverters 311 and 312 invert the R and L channel signals from the sound source (not shown) to adjust the level thereof, respectively. Further, the amplification factors in the amplifiers 311 and 312 are set such that, for example, as to the levels of the second R channel speaker 102 and the fourth L channel speaker 104, another listener at the second listening point hears sounds outputted therefrom with the same levels each other.
The amplifiers 303 and 304 adjust the level of the center signal to be applied to R channel speakers 101 and 102 from the sound source (not shown), respectively. The inverters 311 and 312 invert the center signal to be applied to L channel speakers 103 and 104 to adjust the levels thereof, respectively. The center signal of the present embodiment is a center channel signal used for multi-channel signals use such as 5.1 ch signals. For example, voices of actors/actresses in the center of a movie reproduced with DVD are assigned in the center channel. Alternatively, the vocal sound is assigned in the center channel in case that the source is music.
A signal, in which the output signal of the amplifier 301 and the output signal of the amplifier 303 are combined, is applied to the delay unit 321 and given a predetermined delay in the delay unit 321. The output signal of the delay unit 321 is inputted to the band division section 325. The band division section 325 includes ahighpass filter and lowpass filter (not shown), and the high pass filter passes the signal components of the signal inputted to the band division section 325, included in a passband of about 200 Hz to about 20 kHz. The output signal of this high band filter includes the above-described in-phase signal (R) and is applied to the first R channel speaker 101. Further, the low pass filter passes the signal components of the input signal to the band division section 325, included in a passband of about 200 Hz or lower. The output signal of the low pass filter is applied to the low band speaker 180.
A signal, in which the output signal of the inverter 311 and the output signal of the amplifier 304 are combined, is applied to the delay unit 322, given a predetermined delay in the delay unit 322 and then is inputted to the band division section 326. The band division section 326 includes a high pass filter (not shown), and the high pass filter passes signal components of the signal inputted to the band division section 326, included in a passband of about 200 Hz to about 20 kHz. The output signal of this high band filter includes the above-described reverse phase signal (R) and is applied to the second R channel speaker 102.
Further, a signal, in which the output signal of the amplifier 302 and the output signal of the inverter 313 are combined, is applied to the delay unit 323, given a predetermined delay in the delay unit 323 and then is inputted to the band division section 327. The band division section 327 includes a high pass filter (not shown), and the high pass filter passes signal components of the signal inputted to the band division section 327, included in a passband of about 200 Hz to about 20 kHz. The output signal of this high band filter includes the above-described in-phase signal (L) and is assigned to the third L channel speaker 103.
A signal, in which the output signal of the inverter 312 and the output signal of the inverter 314 are multiplexed, is applied to the delay unit 324, and given a predetermined delay in the delay unit 324. The output signal of the delay unit 324 is inputted to the band division section 328. The band division section 328 includes a high pass filter and low pass filter (not shown), and the high pass filter passes signal components of the signal inputted to the band division section 328, included in a passband of about 200 Hz to about 20 kHz. The output signal of this high band filter includes the above-described reverse phase signal (L) and is applied to the fourth L channel speaker 104. Further, the low pass filter passes signal components of the signal inputted to the band division section 328, included in the passband of about 200 Hz or lower. The output signal of the low pass filter is applied to the low band speaker 181.
The amplifiers 301 to 304 and the inverters 311 to 314 have functions as level adjusters that adjust the output levels to the speakers by adjusting gain, and the output levels for speakers 101 to 104 can be adjusted by the amplifiers 301 to 304 and the inverters 311 to 314. In this case, the level of the center signal applied to speakers 101 to 104 can be adjusted by the amplifiers 303 and 304 and the inverters 313 and 314, respectively.
Further, the in-phase signals of the center signals are added through the amplifiers 303 and 304 to the signals toward the first R channel speaker 101 and the second R channel speaker 102, respectively. The reverse signal of the center signals are added through the inverters 313 and 314 to the signals toward the third L channel speaker 103 and the fourth L channel speaker 104, respectively. By this means, it is possible to locate sound image of the center channel in the front of the listener in the driver's seat (i.e. driver) and the listener in the front passenger seat.
The delay units 321 to 324 can give different phase shifts between the outputs of the first R channel speaker 101 and the second R channel speaker 102 or between the outputs of the third L channel speaker 103 and the fourth L channel speaker 104. As described above, the first R channel speaker 101 that makes the in-phase sound of the R channel signal reach to the right ear of the driver via reflection using the right side glass 210, the second R channel speaker 102 that makes the reverse phase sound of the R channel signal reach directly to the right ear of the listener in the front passenger seat, the third L channel speaker 103 that makes the in-phase sound of the L channel signal reach directly the left ear of the driver, and the fourth L channel speaker 104 that makes the reverse phase sound of the L channel signal reach the left ear of the listener in the front passenger seat via reflection using the left side glass 220, are provided, so that the in-phase and reverse phase of the R channel signal can cancel each other in the locations of the listener in the driver's seat (driver) and the in-phase and reverse phase of the L channel signal can cancel each other in the locations of the listener in the passenger seat. It is possible to finely adjust the angle, at which silence occurs, by adjusting the phase difference with the delay units 321 and 324.
FIG.4 is a plan view illustrating the positions of the speaker unit and the listener, employing an example of the relationship between the positions of the speaker unit SP1 of the driver's seat side and the listener P1 in the driver's seat (i.e. driver).
As shown in FIG.4, the speaker unit SP1 and the listener P1 in the driver's seat face each other. Further, reference numeral "a" is assigned to the directivity axis of the first R channel speaker 101 that radiates sound based on the in-phase signal (R) and reference numeral "b" is assigned to the directivity axis of the second R channel speaker 102 that radiates sound based on the reverse phase signal (R). Reference numeral "c" is assigned to the above-described first reference plane. Further, assuming that the angle formed by the directivity axis a and the first reference plane c is rv1 and the angle formed by the directivity axis b and the first reference plane c is rv2, the condition of following equation (1) for providing an effect that the listener P1 sitting in the driver's seat feels like sound does not come from the front, is formed.
$rv 1 = rv 2$

Note that the speaker unit SP1 and the listener P1 need not to face each other if above equation (1) is satisfied.
Although the positions of the speaker unit SP1 of the driver's seat side and the listener P1 in the driver's seat (i.e. driver) have been described above, the same applies to the listener in the front passenger seat and the speaker unit SP2 of the passenger seat side, that is, the in-phase signal (L) and reverse phase signal (R).
FIG. 5 is a schematic view showing the relationship between the direction of the speaker unit and the position of the listener, employing an example of the relationship between the positions of the speaker unit SP1 of the driver's seat side and the listener P1 in the driver's seat (i.e. driver) and the listener P2 of the passenger seat side.
In FIG.5, the speaker unit SP1 of the driver's seat side is installed on the dashboard 200 shown in FIG.1 and FIG.2. Further, the reflection plane A of FIG.5 is the side glass 210 of FIG.1. This interior space of the vehicle is defined with X and Y coordinates. In the width X in the interior space of the vehicle, to the reference point of the reflection plane A, there are the distance x3 from the speaker unit SP1 of the driver's seat side, the distance X1 from the listener P1 in the driver's seat and the distance x2 from the listener P2 in the front passenger seat. Further, in the depth Y in the interior space of the vehicle, there are the distance y1 from the listener P1 in the driver's seat to the reference point of the speaker unit SP1 and the distance y2 from the listener P2 in the front passenger seat to the reference point of the speaker unit SP1.
Reference numeral "α" (see the dotted line) is assigned to the path through which the sound outputted from the first R channel speaker 101 composing the speaker unit SP1 (the in-phase signal (R)) is reflected by the reflection plane A and reaches the listener P1 in the driver's seat, and reference numeral "β" (see the dotted line) is assigned to the path through which the sound outputted from the second R channel speaker 102 (the reverse phase signal (R)) reaches directly the listener P2 in the front passenger seat. Further, in case of FIG.5, the speaker unit SP1 and the listener P1 in the driver's seat face each other as described in FIG.4, and, given that sounds radiated from the first R channel speaker 101 and the second R channel speaker 102 cancel each other near the first reference plane c, the listener P1 sitting in the driver's seat feels like sound does not come from the front.
In the interior space of the vehicle defined with X and Y coordinates, the distance y1 to the listener P1 in the driver's seat and the distance y2 to the listener P2 in the front passenger seat are equal. The distance of the path α through which sound is reflected by the reflection plane A and reaches the listener P1 in the driver's seat from the first R channel speaker 101 of the speaker unit SP1 and the distance of the path β through which sound reaches directly the listener P2 in the front passenger seat from the second R channel speaker 102 are equal. These relationships can be represented as follows.
Condition 1: y1 = y2 = y
Condition 2: path α = path β $Path 1 = {({(x 1 + x 3)}^{2} + {(y 1)}^{2})}^{0.5}$
$Path 2 = {({(x 2 - x 3)}^{2} + {(y 2)}^{2})}^{0.5}$

Following equation (4) can be derived from the condition 2 and above equations (2) and (3). Equation (5) can be obtained by applying the condition 1 to equation 4 and figuring out x3.
${({(x 1 + x 3)}^{2} + {(y 1)}^{2})}^{0.5} = {({(x 2 - x 3)}^{2} + {(y 2)}^{2})}^{0.5}$
$x 3 = 0.5 * (x 2 - x 1)$

According to above equation (5), the speaker unit SP1 needs to be preferably arranged at the distance x3 which is apart from the wall A by a half of the distance between the two listeners P1 and P2.
Although the positions of the speaker unit SP1 of the driver's seat side, the listener P1 in the driver's seat and the listener P2 in the front passenger seat are described above, the same applies to the arrangement of the speaker unit SP2 of the front passenger seat side.
The positions of the speaker units SP1 and SP2, the listener P1 in the driver's seat and the listener P2 in the front passenger seat in the horizontal direction have been described. Next, the elevation angle formed by the speaker units SP1 and SP2, the listener P1 in the driver's seat and the listener P2 in the front passenger seat will be described with reference to FIG.2.
As shown in FIG.2, it is preferable to mount the speaker unit SP1 with the elevation angle rh such that the directivity axis a of the first R channel speaker 101 (that radiates reflected sound to the listener P1) of the speaker units SP1 and SP2 (in FIG.2, speaker unit SP1 and the listener P1 are represented and shown) come at the height of the ears of the listener P1. By setting the elevation angle rh in this way, the listener P1 would hear the sound radiated from the speakers 101 and 102 better.
As described above in detail, according to the present embodiment, the speaker system 100 includes the speaker unit SP1 composed of the first R channel speaker 101 that radiates the in-phase R channel signal and the second R channel speaker 102 that radiates the reverse phase R channel signal and the speaker unit SP2 composed of the third L channel speaker 103 that radiates the in-phase L channel signal and the fourth L channel speaker 104 that radiates the reverse phase L channel signal, and the first R channel speaker 101 and the second R channel speaker 102 are in symmetry with respect to the first reference plane c including the first listening point for the listener and are arranged such that sound from the first R channel speaker 101 is reflected by the side glass 210 which is the reflection plane and reaches the first listening point. The same relationship holds between the third L channel speaker 103 and the fourth L channel speaker 104.
Further, speakers composing the speaker units SP1 and SP2 are arranged such that the distance through which sound from one speaker is reflected by the side glasses 210 and 220 and reaches the listeningpoint for the listener and the distance through which sound from the other speaker reaches directly the listening point for the listener, are equal. Further, the listening point for the listener is arranged on the axis in which the in-phase sound signal from above one speaker and the sound signal from the above other speaker cancel each other. By this means, it is possible to realize a speaker system that makes it possible to provide a listening environment that does not give a sense of discomfort to listeners. That is, in an environment in which there are two listeners in the interior of the vehicle, it is possible to produce excellent effects that, at the same time, (1) the sound image is located in the front, (2) the opening angles of the left side and the right side are the substantially same each other and (3) the sound paths of the left side and the right side are the substantially same each other, for the two listeners, so that an optimal acoustic environment is possible.
Further, in the above description, the first and second listening points are determined in advance and are located near the heads of the listeners sitting in the driver's seat and the front passenger seat. More preferably, in case where the vehicle is a car with a right-hand steering wheel, the first listening point is set near the left ear of the listener sitting in the driver's seat and the second listening point is set near the right ear of the listener sitting in the front passenger seat. In case where the vehicle is a car with a left-hand steering wheel, the first listening point is set near the right ear of the listener sitting in the driver's seat and the second listening point is set near the left ear of the listener sitting in the front passenger seat.
The above description is an illustration of a preferred embodiment of the present invention and the scope of the present invention is not limited to this.
Further, although an example has been described with the present embodiment where the present invention is applied to a speaker system arranged on the dashboard in a vehicle, the speaker system may be mounted in other locations in the vehicle. Furthermore, the present invention is applicable to the speaker system arranged in, for example, a narrow room other than in the passenger compartment.
Further, although the term "speaker system" is used with the present embodiment for ease of description, other terms are certainly possible, including, for example, "audio system," "audio playback system," "speaker apparatus mounted in the vehicle" and "audio devices mounted in the vehicle."
Furthermore, each circuit section forming the above speaker system , for example, the type, number and connecting method of signal processing sections are not limited to the above described embodiment.
The disclosure of Japanese Patent Application No. 2006-152550, filed on May 31, 2006 , including the specification, drawings and abstract, is incorporated herein by reference in its entirety.

Industrial Applicability

The speaker system according to the present invention is useful as a speaker system installed in the interior of the vehicle. The present invention is also applicable for use in, for example, products having a plurality of speaker units. Further, the present invention is preferable for the speaker system installed in a narrow space other than in the interior of the vehicle.

Claims

A speaker system comprising:
a first speaker unit configured to include first and second speakers, the first and second speakers being arranged in symmetry each other with respect to a first reference plane including a first listening point; and

a second speaker unit configured to include third and fourth speakers, the third and fourth speakers being arranged in symmetry each other with respect to a second reference plane including a second listening point, and to be arranged in symmetry with the first speaker unit with respect to a predetermined median plane.
The speaker system according to claim 1, wherein:
an in-phase signal from a sound source is inputted to one of the first and second speakers;

a reverse phase signal of the in-phase signal is inputted to the other one of the first and second speakers;

the in-phase signal from the sound source is inputted to one of the third and fourth speakers; and

the reverse phase signal of the in-phase signal from the sound source is inputted to the other one of the third and fourth speakers.
The speaker system according to claim 1, wherein:
a directivity axis of the first speaker is configured to be directed toward a first reflection plane;

a directivity axis of the second speaker is configured to be directed toward the second listening point;

a directivity axis of the third speaker is configured to be directed toward the first listening point; and

a directivity axis of the fourth speaker is configured to be directed toward a second reflection plane.
The speaker system according to claim 3, wherein:
a path length through which sound outputted from the first speaker is reflected by the first reflection plane and reaches the first listening point, and a path length through which sound outputted from the third speaker reaches the first listening point, are substantially equal; and

a path length through which sound outputted from the second speaker reaches the second listening point, and a path length through which sound outputted from the fourth speaker is reflected by the second reflection plane and reaches the second listening point, are substantially equal.