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JPH08107600

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DESCRIPTION JPH08107600
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound image localization apparatus suitable for a three-dimensional virtual reality system or the
like.
[0002]
2. Description of the Related Art A sound image localization apparatus is known which generates
a three-dimensional sound field by localizing a virtual sound source at an arbitrary position in a
sound field space in a sound reproduction system, an electronic musical instrument, a game or
the like. There is. Also in the three-dimensional virtual reality system, this kind of sound image
localization apparatus is used as a means for improving the sense of reality in a virtual
experience. In this case, the sound image localization apparatus generates a sense of sense of
direction, a sense of distance and a sense of distance by generating signals of a plurality of
channels having time difference, amplitude difference and frequency characteristic difference
based on a binaural method from monaural sound source. A three-dimensional sound field is
generated, and an acoustic signal is generated as if sound is emitted from each part in the threedimensional virtual space.
[0003]
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1
By the way, in the sound image localization apparatus of this type, various types of delay control,
filtering, amplitude control, etc. are required on the premise that the listener's head always faces
the front. Control parameters are calculated, and the audio output signal of each channel is
controlled based on these control parameters. For this reason, there is a problem that the sound
image can not be properly localized at the designated virtual sound source position when the
listener's head deviates from the front. For example, in a sound image localization apparatus
using headphones, the virtual sound source position is localized at a position different from the
desired position to be localized according to the change (rotation) of the head position of the
listener. That is, for example, when it is desired to localize the sound behind the listener, there is
no problem when the normal listener's head is directed to the front, but when the listener's head
is rotated 90 ° to the right, for example Naturally, the headphones are also turned 90 °, so the
listener feels that the sound is localized on the left side of the listener (localized behind the head
of the listener). Moreover, in the sound image localization apparatus using the speaker system
installed in a fixed manner, problems like headphones do not occur, but the transfer
characteristic etc. from the left and right speakers to both ears of the listener changes due to the
change of the head position of the listener In particular, processing of the crosstalk component is
difficult, and sounds that are undesirable for hearing may be generated. Such changes interfere
with the stable localization of the virtual sound source. In an advanced virtual reality system in
which a three-dimensional image is panned according to the movement of the viewer's head or
line of sight, such movement of the virtual sound source position interferes with the matching
between the image and the virtual sound source position. Cause a decline in
[0004]
Although this is an example of two-dimensional sound image localization, a method for solving
the above-mentioned problems has been proposed (Japanese Patent Application Laid-Open No. 417500). In this example, sound image localization control is performed based on left and right
rotation of the entire listener, that is, left and right rotation of a chair. However, even in this
method, the movement of the listener's head is not taken into consideration, and as a result, the
same problem as the above-described conventional example occurs. The present invention has
been made in view of such a problem, and it is possible to stably localize a sound image at a
designated position in an absolute coordinate system even if a change (rotation) of the head
position of the listener occurs. It aims at providing a localization device.
[0005]
A sound image localization apparatus according to the present invention calculates control
parameters based on position information indicating a virtual sound source position designated
in advance in a sound field space, and is supplied from the sound source. Virtual sound source
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position control for generating audio output signals of a plurality of channels for localizing a
sound image at the virtual sound source position by performing delay control, filtering and / or
amplitude control on the audio input signal based on the calculated control parameter Means for
detecting the rotation angle of the head of the listener in a sound image localization apparatus
comprising: means; and a plurality of electroacoustic conversion means for respectively
electroacoustically convert audio output signals of a plurality of channels output from the virtual
sound source position control means. The virtual sound source position control means may
include angle detection means, and the virtual sound source position control means may The
control parameter is corrected based on the rotation angle of the head of the head, and the audio
output signal is controlled so that the virtual sound source is always localized at the designated
position in the absolute coordinate system regardless of the head position of the listener. It is
characterized by being.
[0006]
When the electro-acoustic conversion means is a headphone worn on both ears of the listener,
the virtual sound source position control means sets the rotation angle of the head of the listener
detected by the rotation angle detection means. Based on the position of the virtual sound source
position in the coordinate system after conversion, coordinate conversion is performed centering
on the position on the neck of the listener, which is vertically lowered from the center position of
both ears of the listener. It is desirable to calculate the control parameter as position information.
[0007]
When the electro-acoustic conversion means is a speaker fixedly installed in the sound field
space, the virtual sound source position control means rotates the head of the listener detected
by the rotation angle detection means. Based on the angle, coordinate conversion is performed
centering on the position on the neck of the listener, which is vertically lowered from the center
position of the listener's ears, and the virtual sound source in which the virtual sound source
position in the coordinate system after conversion is corrected Preferably, the control parameter
is corrected based on a change in the position of the speaker with respect to the position of the
listener as well as the position.
[0008]
According to the present invention, the control parameter for sound image localization is
corrected based on the rotation angle of the head of the listener detected by the rotation angle
detection means, and the corrected control parameter is used. Since delay control, filtering,
amplitude control and the like are applied to the audio input signal, the audio output signal can
be controlled so that the virtual sound source is always localized at the designated position in the
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absolute coordinate system.
[0009]
Since the listener's head usually rotates in each direction (x-axis, y-axis, z-axis) about the
approximate center of the neck, coordinate conversion is required to correct the position
information indicating the virtual sound source position. By setting the center position of the
above to the position on the neck of the listener, accurate correction of the virtual sound source
position can be performed.
[0010]
When the electroacoustic transducer is a headphone, the headphone always keeps a fixed
position with respect to the listener's head, so the virtual sound source position is always moved
by the same amount on the opposite side of the head's moving direction. If control is performed
as described above, the virtual sound source position in the absolute coordinate system is fixed at
the set position.
Therefore, if the control parameters are calculated using the position information of the virtual
sound source position in the coordinate system after coordinate conversion based on head
rotation as the position information after correction, the sound image is always localized at a
constant position regardless of the listener's head rotation. It will be done.
[0011]
Further, in the case where the electroacoustic conversion means is a speaker fixedly installed in
the sound field space, it is sufficient that the virtual sound source position in the coordinate
system after the coordinate conversion is the corrected virtual sound source position. Absent.
This is because the position of the speaker with respect to the positions of both ears of the
listener changes.
This change affects control parameters and the like that give the transfer function of the
crosstalk component from each speaker.
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In one aspect of the present invention, it is possible to localize the virtual sound source at a fixed
position by modifying these control parameters based on the change in the position of the
speaker with respect to the both-ear position of the listener.
[0012]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a view showing the configuration of a three-dimensional virtual reality system to which
a sound image localization apparatus according to an embodiment of the present invention is
applied. The head gear 1 is attached to the head of the listener 2, and the speakers 3 and 4 are
embedded at positions corresponding to both ears of the listener 2. Further, a rotation angle
sensor 5 for detecting a rotation angle in a three-dimensional direction from a reference position
of the head gear 1 is attached to a part of the head gear 1. The speakers 3 and 4 and the rotation
angle sensor 5 are connected to the controller 6 via a signal line 7. The controller 6 is provided
with a display device 8, and while the listener 2 looks at the three-dimensional graphics screen
displayed on the display device 8, the user can operate a joystick or the like (not shown) to
perform a game or simulation, etc. There is. Then, the controller 6 executes sound image
localization control so that the position corresponding to each part of the screen displayed on the
display device 8 is set as the virtual sound source position.
[0013]
FIG. 2 is a block diagram showing a more detailed configuration of the above system. An audio
source 11 and a virtual sound source position control device 12 are provided in the controller 6.
The audio source 11 is a sound source such as a computer, a disk reproducing device, a video
reproducing device, etc. In this embodiment, a monaural audio signal SI and position information
r, θ, φ in a three-dimensional absolute coordinate system indicating a virtual sound source
position. And output. The virtual sound source position control device 12 receives the audio
input signal SI and the position information r, θ, φ, and the angle information α, β, γ from the
rotation angle sensor 5, and based on the position information and the angle information, an
audio input signal Each processing such as delay control, filtering and amplitude control is
applied to SI to generate audio output signals SOR and SOL of two channels. The audio output
signals of the two channels are supplied to the speakers 3 and 4 to supply acoustic waves to both
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ears of the listener 2.
[0014]
FIG. 3 is a block diagram showing an example of a concrete configuration of the virtual sound
source position control device 12. As shown in FIG. The monaural audio input signal SI is
supplied to the notch filter 22 through the amplifier 21. The notch filter 22 attenuates specific
frequency components of the audio signal SI based on the human auditory characteristics to give
the input signal SI a sense of vertical direction. The output of the notch filter 22 is subjected to
delay processing by a delay circuit 23 for giving a propagation time difference of sound from the
virtual sound source position to both ears, and converted to a two-channel signal having a time
difference. These signals are supplied to FIR (finite impulse response) filters 24 and 25
respectively. The FIR filters 24 and 25 measure in advance the impulse response (head-related
transfer function) when the sound image is localized in the front, rear, left, and right directions of
the listener 2 by using, for example, a dummy head, and stores the result as FIR coefficients.
From the input signals, signals for four directions are generated. The outputs of the FIR filters 24
and 25 control the amplitudes of the signals of the directional components so that the sound
comes from the designated virtual sound source position by the amplifiers 26 and 27,
respectively. The outputs of the amplifiers 26 and 27 are added by the adders 28 and 29,
respectively, and then the left and right amplitude balance based on the direction of the virtual
sound source is adjusted by the amplifiers 30 and 31, and the distance to the virtual sound
source is adjusted by the amplifiers 32 and 33. Based on amplitude control. The signal of each
channel is output as an audio output signal SOR, SOL through these processes.
[0015]
On the other hand, the positional information r, θ, φ given from the audio source 11 is
corrected by the sensor information α, β, γ in the positional information correction unit 35.
The parameter calculation unit 36 generates control parameters Nt, T, VRx, VLx, VR, VL, Vr based
on the corrected position information α ′, β ′, γ ′ and supplies the control parameters to
each unit.
[0016]
Next, the operating principle of this system will be described. FIG. 4 is a diagram for describing
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position information r, θ, and φ that indicate virtual sound source positions. Now, as shown to
the figure (a), the listener in the case where the middle point of both ears of the listener 2 is
made into the center point P0 of a three-dimensional coordinate, and the head of the listener 2
faces the reference direction (front direction). The rightward direction, the frontward direction,
and the upper direction of 2 are set as the X axis, Y axis, and Z axis of the absolute coordinate
system, respectively. The position information of the virtual sound source Ps is the horizontal
angle of the virtual sound source Ps viewed from the front (Y-axis direction) of the listener 2 and
the distance r from the center point P0 to the virtual sound source Ps as shown in FIG. It is given
by (azimuth) θ and an angle (elevation) φ in the vertical direction viewed from the direction of
the angle θ with respect to the front of the listener 2.
[0017]
On the other hand, as shown in FIG. 5, the rotation angle associated with the head movement of
the listener 2 is a rotation angle α about the Z axis, a rotation angle β about the X axis, and a
center about the Y axis. It can be represented by three types of rotation angles γ. The rotation
angles α, β and γ are detected by the rotation angle sensor 5. Although a known direction
detector such as a gyro sensor, a magnet type sensor, or an electromagnetic wave receiving type
sensor using an orthogonal three-way receiving unit can be applied as the rotation angle sensor
5, for example, as shown in FIG. The one shown in 6 can be used. That is, the flywheel 42 is
rotated by the motor 41, the shaft 43 is stabilized in a fixed direction by the inertia of the
flywheel 42, and the arm 44 supporting the shaft 43 and the head gear 1 rotate around the
horizontal direction HR and HL. The rotation angle α between the arm 45 supported thereby is
detected by the encoder 46. Further, the rotation angle β having the left and right directions HR
and HL of the head gear 1 as axes is detected by the encoder 47 interlocked with the rotation
axis of the arm 45. Furthermore, a weight 49 is slidably provided on an arm 48 rotatably
supported about the longitudinal direction HF, HB of the head gear 1 as an axis, and the encoder
50 interlocked with the rotation axis of the arm 48 makes the weight 49 gravity direction The
rotation angle γ about the longitudinal direction HF and HB, which is generated by the
movement to the direction of movement, is detected.
[0018]
As in this embodiment, in the case of the headphone-type sound image localization apparatus, for
rotational movement of the head of the listener, if the virtual sound source position is
rotationally moved in the opposite direction, the virtual sound source in the absolute coordinate
system The position of Ps can be kept constant. This means that the position information r, θ, φ
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of the virtual sound source Ps given by the absolute coordinate system X, Y, Z is converted
position in the conversion coordinate system X ', Y', Z 'based on the head of the listener It is
equivalent to converting into information r ′, θ ′, φ ′ and using this as given positional
information.
[0019]
Now, each axis coordinate value Xs, Ys, Zs of the position Ps of the virtual sound source can be
expressed as Equation 1 using the given position information r, θ, φ.
[0020]
Xs = r sin θ cos φ Ys = r cos θ cos φ Zs = r sin φ
[0021]
On the other hand, as shown in FIG. 7, since the head movement of the listener 2 is centered on
the neck, the center of coordinate rotation is the distance m along the neck of the listener 2 with
the coordinate origin P0 described above. Set to the position moved downward only.
m is set to about 15 cm as an average value.
The axis coordinate values Xs ′, Ys ′, Zs ′ of the virtual sound source Ps ′ in the
transformed coordinate system X ′, Y ′, Z ′ can be expressed as the following formula 2.
[0022]
[Equation 2]
[0023]
Here, M is a transformation matrix, which is defined as in Eq. 3 by transformation matrices M
(α), M (β) and M (γ) based on the rotation angles α, β and γ in each axial direction. Ru.
[0024]
M = M (α) M (β) M (γ)
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[0025]
From the coordinate values Xs', Ys' and Zs' of the virtual sound source Ps' thus determined, the
conversion position information r ', .theta.' And .phi. 'Can be determined by the equation (4).
[0026]
R ′ = √ (Xs′2 + Ys′2 + Zs′2) θ ′ = tan−1 (Xs ′ / Ys ′) φ ′ = tan−1 [Zs ′ / √
(Xs′2) + Ys' 2)]
[0027]
The position information correction unit 35 in FIG. 3 executes the above processing to convert
the position information r ', θ' from the position information r, θ, φ and the sensor outputs α,
β, γ by coordinate conversion processing. , Φ 'are generated and output.
FIG. 8 is a flowchart showing the contents of coordinate conversion processing in the position
information correction unit 35.
When the position information r, θ, φ is given to the position information correction unit 35,
first, axis coordinate values Xs, Ys, Zs in the absolute coordinate system are obtained (S1).
However, the Zs axis is shifted (+ m) in advance to the motion coordinate system of the head.
Next, the outputs α, β and γ of the rotation angle sensor 5 are sampled (S2), and coordinate
conversion processing is performed by the conversion matrix M (S3), and the Zs ′ axis is shifted
to match the original coordinates (−m ) (S4).
Then, converted position information r ', .theta.' And .phi. 'Are calculated from the obtained
converted coordinates Xs', Ys 'and Zs' (S5) and output (S6). The conversion position information
can be obtained in real time by performing the sampling of the sensor output and the conversion
processing at a constant interval.
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[0028]
The converted position information r ′, θ ′, φ ′ is supplied to the parameter calculation unit
36, and the following control parameters are calculated. First, the attenuation frequency Nt of the
notch filter 22 is determined. As shown in FIG. 9, it is known that the dead band frequency shifts
to a high frequency region as the angle (elevation) φ in the height direction of the sound source
increases, that is, as the sound source position is positioned higher. ing. Therefore, the parameter
calculation unit 36 determines the attenuation frequency Nt by the elevation φ ′ and controls
the notch filter 22.
[0029]
The propagation time difference T between the left and right channels in the delay circuit 23 is
obtained from the difference in the distance from the virtual sound source Ps' to each ear. That
is, as shown in FIG. 10, assuming that the distance from the coordinate center point P0 'to both
ears of the listener 2 is h, from the position Ps' (Xs', Ys', Zs') of the virtual sound source, the right
ear (h) , 0, 0) and the distance DL to the left ear (−h, 0, 0) can be expressed as Equation 5.
[0030]
DR = √ (r′2 −2 r′h sin θ ′ sin φ ′ + h2) DL = √ (r′2 +2 r′h sin θ ′ sin φ ′ + h2)
[0031]
Therefore, if the sound velocity is Vs,
[0032]
T = (DR−DL) / Vs
[0033]
However, the propagation time difference when the sound signal arrives from the virtual sound
source Ps' to both ears is shown.
[0034]
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Parameters VRx and VLx for controlling the amplitudes of the directional component outputs of
the FIR filters 26 and 27 (where R is for the right ear, L is for the left ear, x is F (front), R (right),
B (After), L (left).
] Is determined by the azimuths θR, θL and elevation φ of the left and right ears and the sound
source Ps'.
Each ear azimuth θR, θL is determined as follows.
[0035]
ΘR = tan-1 [(r'sin φ'sin θ'-h) / r'sin φ'cosθ '] θL = tan-1 [(r'sin φ'sin θ' + h) / r'sin φ 'cosθ']
[0036]
FIG. 11 is a diagram showing the relationship between the ear azimuths θR and θL and the
control parameters VRx and VLx. In FIG. 11A, the elevation φ ′ is 0 ° (horizontal), and FIG.
Shows the values when the elevation φ 'is ± 90 ° (vertical).
At this time, although each gain is set to 1⁄4 in the drawing, it is not necessarily limited to this.
The parameter calculation unit 36 determines the control parameters VRx and VLx based on
these relationships, and controls the amplifiers 26 and 27.
[0037]
The control parameters VR and VL of the amplifiers 30 and 31 for controlling the amplitudes of
the left and right channels are determined by the difference in the distance from the virtual
sound source Ps' to the ears.
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11
Furthermore, the control parameter Vr of the amplifiers 32, 33 controlling the overall amplitude
of both channels is determined by the distance r 'from the virtual sound source Ps'.
[0038]
The above is a sound image localization apparatus using headphones, and FIG. 12 shows the
configuration of a system in which the present invention is applied to a sound image localization
apparatus using speakers fixedly arranged. Also in this embodiment, in order to install the
rotation angle sensor 5 on the head of the listener 2, some kind of headgear is required. In the
case of the fixed type speaker, in addition to the fact that the virtual sound source position for
the listener 2 changes due to the rotation of the head of the listener 2, the relative position of the
speakers 3 and 4 for the listener 2 also changes. . For this reason, it is necessary to re-correct the
converted position information r ′, θ ′, φ ′ again to the vicinity of the position of the first
position information r, θ, φ based on the relative position change of the speakers 3 and 4 .
Further, as a simpler method, the control parameters may be obtained by using the first position
information r, θ, φ as it is. However, the crosstalk problem specific to fixed speakers requires
some measures.
[0039]
That is, as shown in FIG. 12, in the case of a sound image localization apparatus using a fixed
type speaker, the crosstalk of the sound of the right speaker 3 is supplied to the left ear and the
sound of the left speaker 4 is supplied to the right ear. Occurs. For this reason, as shown in FIG.
13, in the virtual sound source position control device 12, a crosstalk canceller 61 is disposed,
for example, between the amplifiers 30, 31 and the amplifiers 32, 33.
[0040]
Cross talk can be represented, for example, by the model of FIG. Now, assuming that the path
along which acoustic waves propagate from the right (left) speaker to the right (left) ear is the
main path, and the path along which acoustic waves propagate from the right (left) speaker to
the left (right) ear is defined as the crosstalk path , D is the time difference between the time the
acoustic wave propagates in the main path and the time it propagates the crosstalk path, and k is
the time when the crosstalk path is propagated to the amount of attenuation when the acoustic
wave propagates in the main path It is a ratio of the amount of attenuation.
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[0041]
The detail of the crosstalk canceller 61 based on this model is shown in FIG. Here, although the
propagation time difference d and the ratio k of attenuation amounts are calculated as that the
listener 2 is directed to the front with respect to the speakers 3 and 4, when the head of the
listener 2 rotates, the values d and k are also calculated. It changes in relative symmetry.
Therefore, the parameter calculation unit 62 calculates the propagation time differences dr and
dl and the attenuation ratio kr and kl from the sensor outputs α, β and γ. The propagation
time differences dr and dl are calculated using the positions of the speakers 3 and 4 as the sound
source positions and the above-mentioned coordinate conversion processing, calculate the
distance from both ears to each speaker in the head coordinate system of the listener 2, and
divide by the speed of sound. It can be obtained from the difference in propagation time
obtained. Further, the ratio of attenuations kr and kl is previously obtained by determining the
ratio k of attenuations from several points around the head of the listener 2, and according to the
direction of the speaker in the coordinate system of the head of the listener 2, It is sufficient to
calculate the value of R by interpolation processing as appropriate. The propagation time
differences dr, dl, kr, kl thus determined become control parameters for determining the
operation of the crosstalk canceller 61.
[0042]
As described above, according to the present invention, the control parameter for sound image
localization is corrected based on the rotation angle of the head of the listener detected by the
rotation angle detection means, and Since the audio input signal is subjected to delay control,
filtering, amplitude control, etc. using the modified control parameter, the audio output signal is
always localized so that the virtual sound source is located at the designated position in the
absolute coordinate system. Can be controlled.
[0043]
Brief description of the drawings
[0044]
FIG. 1 is a view showing the configuration of a system to which a headphone type sound image
localization apparatus according to the present invention is applied.
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13
[0045]
2 is a more detailed block diagram of the system.
[0046]
3 is a block diagram of a virtual sound source position control device in the same system.
[0047]
FIG. 4 is a diagram for explaining position information.
[0048]
FIG. 5 is a diagram for explaining the rotation direction of the head of the listener.
[0049]
6 is a perspective view showing an example of a rotation angle sensor.
[0050]
FIG. 7 is a diagram showing the motion of the head of the listener and a transformed coordinate
system.
[0051]
FIG. 8 is a flowchart showing processing of a position information correction unit.
[0052]
9 is a diagram showing the characteristics of the notch filter.
[0053]
It is a figure for demonstrating the procedure which calculates | requires the time difference in
the delay circuit.
[0054]
FIG. 11 is a diagram for explaining amplitude control of an FIR filter output.
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[0055]
FIG. 12 is a view showing the configuration of a system to which the fixed speaker type sound
image localization apparatus of the present invention is applied.
[0056]
13 is a block diagram of a virtual sound source position control device in the same system.
[0057]
FIG. 14 is a block diagram showing a crosstalk model in the same system.
[0058]
FIG. 15 is a block diagram showing details of a crosstalk canceller in the same system.
[0059]
Explanation of sign
[0060]
DESCRIPTION OF SYMBOLS 1 ... Head gear, 2 ... Listener, 3, 4 ... Speaker, 5 ... Rotation angle
sensor, 6 ... Controller, 7 ... Signal line, 8 ... Display apparatus, 11 ... Audio source, 12 ... Virtual
sound source position control apparatus, 21, 26 , 27, 30 to 33: amplifier, 22: notch filter, 23:
delay circuit, 24, 25: FIR filter, 28, 29: adder, 35: position information correction unit, 36, 62:
parameter calculation unit, 61: Crosstalk canceller.
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