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JP2008160265

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DESCRIPTION JP2008160265
A portable information terminal is used with the hand held by the listener, often used by tilting it
back and forth with respect to the listener, causing a difference in the distance between the two
speakers and the listener, and the crosstalk cancellation effect Can not be obtained, can not
provide a three-dimensional sound field, and crosstalk cancellation processing with head-related
transfer functions according to the tilt of the portable information terminal requires a large
number of head-related transfer functions, resulting in an increase in circuit size . SOLUTION:
The display screen for displaying an image and two speakers are provided on the same plane,
and the inclination can be changed, and the crosstalk cancellation processing is performed to
present two-dimensional sound reproduction system for presenting a three-dimensional sound
field to a listener. The speakers are arranged so that the straight line connecting the two
speakers is non-horizontal with respect to the vertical direction of the display screen, and the
means for detecting the tilt of the sound reproduction system housing changes the positions of
the two speakers according to the tilt Are detected, and a delay corresponding to the position
change is inserted into the output signal to the speaker. [Selected figure] Figure 1
Sound reproduction system
[0001]
The present invention relates to a device such as a portable information terminal having a sound
signal reproducing function, a desktop monitor, a liquid crystal monitor, etc., in which the display
screen and the two speakers are on the same plane and the tilt can be changed by the tilt
function. The present invention relates to a sound reproduction system used.
[0002]
10-05-2019
1
Conventionally, various methods have been conceived for presenting a virtually threedimensional sound field to a listener using two speakers.
For example, in JP-A-9-233600, transfer characteristics (hereinafter referred to as head-related
transfer functions) from the sound source position to be virtually localized to the listener's ears
(hereinafter referred to as head-related transfer function) By calling the processing) and
suppressing the crosstalk reproduced from the two speakers from reaching the listener's ear
(hereinafter referred to as the crosstalk cancellation processing), the sound source is located at
the desired position around the listener. The method of making the listener illusion as if there is
[0003]
In recent years, even with portable information terminals such as mobile phones using such
methods, it has become possible to enjoy contents delivered from the center and contents stored
in advance in a memory card etc. in a three-dimensional sound field. ing.
[0004]
On the other hand, for example, in Japanese Patent Application Laid-Open No. 2005-295382,
focusing on the fact that the localization position of the sound image can be changed in the
reproduction of the sound signal by two speakers, In a mobile phone equipped with a speaker, a
method of operating a localization position of a sound image with respect to an image is shown.
[0005]
Specifically, assuming that the portable information terminal is used in the vertical or horizontal
state, according to the relationship between the two loudspeakers for the listener at the same
time as the display unit provided in the portable information terminal rotates. Direction
localization processing is switched to localize the sound image of one or both of the speakers at a
virtual position.
[0006]
JP-A-9-233600 JP-A-2005-295382
[0007]
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2
The sound reproduction system which can provide a three-dimensional sound field by the
conventional method is considered on the premise that the positional relationship between the
two speakers and the listener is fixed, and the head transfer function in the positional
relationship is considered. The crosstalk cancellation processing is performed using
When a plurality of positional relationships exist, it is necessary to prepare a head related
transfer function corresponding to each.
[0008]
In addition, while using the portable information terminal either vertically or horizontally, this
positional relationship is considered to be unchanged.
However, a portable information terminal characterized by small size and light weight is often
used while being held by the listener while holding the hand, or installed on a desk or the like,
and even when used in a specific orientation, In many cases, the listener may be tilted in the
front-rear direction and used.
In such a case, if the two speakers are disposed asymmetrically as described above, the positional
relationship between the two speakers and the listener, that is, the distance, is different.
Due to this, there is a problem that the crosstalk cancellation effect can not be obtained, and the
three-dimensional sound field can not be presented to the listener.
[0009]
Moreover, when considering crosstalk cancellation processing using a head transfer function that
is uniquely obtained according to the tilt of the sound reproduction system housing, it is
necessary to prepare a large number of head transfer functions in advance. is there. When the
crosstalk cancellation processing is realized by a configuration using a filter, a huge memory is
required to store all the filter coefficients, and there is also a problem that the circuit scale
increases.
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3
[0010]
The present invention has been made to solve the problems as described above, and it is an
object of the present invention to provide an acoustic reproduction system capable of presenting
a highly effective three-dimensional sound field to a listener.
[0011]
According to the sound reproduction system of the present invention, a display screen for
displaying an image and two speakers are provided on the same plane, the inclination of the
display screen can be varied, and crosstalk cancellation processing is applied to the listener for
three-dimensionality. Sound reproduction system for presenting a typical sound field, wherein
the two speakers are arranged so that the straight line connecting the two speakers is nonhorizontal and non-vertical when the vertical direction of the display screen is vertical; A means
for detecting the posture of the reproduction system case to detect an inclination of the case, a
means for detecting changes in the positions of the two speakers according to the detected
inclination, and to the speakers according to the change in the position. A means is provided for
inserting a delay into the output signal system.
[0012]
According to the sound reproduction system of the present invention, the inclination of the
sound reproduction system casing causes a difference in the sound source signal arrival time
from the two speakers to the listener, and the effect of crosstalk cancellation can not be obtained.
By inserting the delay into the output signal to the speaker, the characteristic of the head related
transfer function is corrected. Therefore, even if the sound reproduction system case is greatly
inclined, precise crosstalk cancellation processing is possible. The listener hears the sound image
localized at the intended position.
[0013]
Hereinafter, an embodiment showing a sound reproduction system of the present invention will
be described as a representative example in the case of a portable information terminal with
reference to the drawings.
The present invention is not limited to application to only the portable information terminals
described below. For example, as in a desktop monitor and a liquid crystal monitor, the display
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4
screen and the speaker are on the same plane and the tilt is changed by the tilt function. It is
possible to apply to the device etc which can do.
[0014]
Embodiment 1
FIG. 1 is a block diagram showing a configuration of a sound reproduction system of a portable
information terminal according to a first embodiment of the present invention.
In FIG. 1, reference numeral 10 denotes a sound source unit, and 100 denotes a sound image
localization processing unit, which includes a direction localization unit 20 and a crosstalk
cancellation unit 30. Reference numeral 40 denotes a reproduction unit, which includes two
speakers.
[0015]
First, an outline of the operation will be described. The sound reproduction system of the
portable information terminal according to the present embodiment has a single or a plurality of
sound source signals in the sound source unit 10, and an input from the sound source unit 10 in
the direction localization unit 20 constituting the sound image localization processing unit 100.
Direction localization processing to localize the sound image to a desired virtual position for each
of the single or plural sound source signals to be added, and the plural sound source signals
subjected to the direction localization processing are added to finally obtain two channels Output
as a stereo signal of Further, in the crosstalk cancellation unit 30 constituting the sound image
localization processing unit 100, the stereo signal obtained as a result of performing the
direction localization processing is subjected to filter processing for canceling crosstalk. The
output signal of the crosstalk cancellation unit 30 is reproduced by the two speakers constituting
the reproduction unit 40, whereby a three-dimensional sound field is reproduced to the listener.
[0016]
Next, details of the operation will be described. The sound source unit 10 has a single or a
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5
plurality of monaural sound sources, a general two-channel stereo sound source, and a so-called
5.1 channel surround sound source. These sound sources may be stored in advance in a memory
or may be downloadable by a music distribution service or the like. These sound sources are
output to the sound image localization processing unit 100 as sound source signals of M
channels (M> 0).
[0017]
The sound image localization processing unit 100 includes a direction localization unit 20 and a
crosstalk cancellation unit 30. First, the direction localization processing is performed by the
direction localization unit 20 on the sound source signals of M channels input from the sound
source unit 10 in order to localize a sound image at desired virtual positions. The direction
localization process performed here is a process for making the listener feel the sound source in
a specific direction or distance by giving characteristics such as the level difference and time
difference of the signal in both ears of the listener, and is publicly known. There are many ways.
For example, there is a method of synthesizing binaural sound.
[0018]
The binaural sound is, for example, a microphone attached near the human ear canal to record
the sound of that place, and reproducing this recorded sound with headphones at different
places, so that the listener is as if the listener were at the recorded place. Sound can be
presented, and the recorded sound at this time is called binaural sound. It is known that binaural
sound is characterized by the head-related transfer function from the sound source to both ears,
and if the head-related transfer function from any direction and distance is determined, the
sound image is localized at that position. Can.
[0019]
For example, in the case where the sound source signal stored in the sound source unit 10 is a
stereo signal, the concept of the virtual position where the sound image is localized in the
direction localization unit 20 is, for example, compared with the actual distance between two
speakers provided in the portable information terminal. The localization position is a position
that results in a wide arrangement.
[0020]
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6
Alternatively, if the sound source signal is a 5.1 channel surround signal, virtual localization of
the general 5.1 channel speaker arrangement (left front, center, right front, left rear, right rear)
Position.
The direction localization process can be omitted because the signal of 0.1 channel is a low
frequency signal with a small sense of localization.
[0021]
The signals obtained as a result of the direction localization processing in this way are a group of
signals considered to have reached the left ear from respective virtual localization positions (L
channel signals) and a signal considered to have reached the right ear The signal is divided into
groups (R channel signals), subjected to addition processing for each signal group, and then
output from the direction localization unit 20 as signals of two channels.
[0022]
Here, although the method of synthesizing binaural sound by the head related transfer function
is mentioned, the direction localization processing in the present invention does not depend on a
specific method, and other methods may be applied.
[0023]
By the way, it is premised that the acoustic signal outputted by the direction localization
processing unit 20 is a sound such as a binaural sound when it is heard at the ear of the listener
like the above.
For example, if reproduced by headphones, it is possible to deliver two channels of audio signals
directly to the listener's ear, respectively.
However, when reproduction is performed by the speaker as in the sound reproduction system of
the portable information terminal according to the present embodiment, the left speaker reaches
the right ear of the listener and the right speaker reaches the left ear of the listener So-called
crosstalk occurs.
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7
[0024]
FIG. 2 is a view showing how an acoustic signal reproduced from a speaker disposed in front of
the listener's left reaches the listener's ears. The speaker reproduces a signal considered to have
reached the left ear of the listener, and at this time, the signal SC reaching the right ear of the
listener is crosstalk. The presence of this crosstalk is a factor that greatly impairs the sense of
localization of the sound image, and it is necessary to cancel this. The signal SM reaching the left
ear of the listener is affected by the propagation characteristic from the speaker to the left ear of
the listener.
[0025]
The crosstalk cancellation unit 30, which is another block constituting the sound image
localization processing unit 100, generates a signal for canceling the above-mentioned crosstalk
and adds it to the output signal of the direction localization unit 20. Details of the crosstalk
cancellation unit 30 will be described later.
[0026]
The reproduction unit 40 includes two speakers for presenting the sound signals of two channels
output from the sound image localization processing unit 100 to the listener. In an actual device,
a D / A conversion unit, an amplifier, etc. are connected to the front stage of the speaker, but the
explanation is omitted because it does not affect the operation of the present invention.
[0027]
FIG. 3 shows an example of the appearance of the portable information terminal according to the
present embodiment. The portable information terminal 200 includes a screen display unit 201,
an antenna unit 202, and two speakers 4a and 4b. The screen display unit 201 has a rectangular
shape, and is formed on the operation surface of the portable information terminal 200 so that
each side of the screen display unit 201 is perpendicular or parallel to the vertical direction of
the operation surface. Although the operation part etc. which are not illustrated other than this
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8
are provided, since it is not related to the essence of this invention, it is abbreviate | omitted.
[0028]
Here, the arrangement of the two speakers 4a and 4b will be mentioned. In the portable
information terminal according to the present embodiment, the direction of the straight line
connecting the two speakers does not perpendicularly intersect and is not parallel to the vertical
direction of the image displayed on the screen display unit 201. In FIG. 3A, the speaker 4a for
reproducing the L channel signal is disposed at the lower left portion of the screen display unit
201, and the speaker 4b for reproducing the R channel signal is disposed at the upper right
portion of the screen display unit 201. By arranging in this manner, even when the portable
information terminal 200 is rotated 90 degrees to the right as shown in FIG. 3B, two speakers are
not arranged on a straight line in the vertical direction, and hence the stereo speakers There is no
loss of the function of Such an arrangement is referred to as an asymmetric arrangement of
speakers.
[0029]
In general, the portable information terminal 200 may be used while being held by a listener
with one hand or both hands, or installed in a holder that also serves as a charger and placed on
a desk and used. In such a case, the position of the reference between the two speakers 4a and
4b and the ears of the listener changes.
[0030]
For example, FIG. 4 is a view showing a state in which the portable information terminal 200 is
used by being inclined at an inclination θ from the vertical direction, and is a viewpoint from the
right side to the portable information terminal 200. At this time, since the speakers are arranged
asymmetrically, a difference in distance dL occurs in the distance between the listener and the
two speakers 4a and 4b, and the speaker 4b that reproduces the R channel signal reproduces the
L channel signal It becomes farther than the speaker 4a. Hereinafter, in order to facilitate the
description, the position of the speaker 4a is assumed to be at the same position with respect to
the listener in the case where the speaker 4a is inclined and in the case where the speaker 4a is
not inclined. Also, the case of not tilting, that is, the case of θ = 0 ° is considered as the
reference position.
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9
[0031]
Consider the head related transfer function in the state as described above. FIG. 5 is a view
showing a case where the portable information terminal 200 is used at the reference position. At
this time, the two speakers 4a and 4b arranged asymmetrically in the portable information
terminal 200 are located at approximately equal distances from the listener. Here, hLL is a headrelated transfer function from the speaker 4a located on the left front of the listener to the left
ear of the listener, and hLR is also a head-related transfer from the speaker 4a to the right ear of
the listener. Also, hRR is a head-related transfer function from the speaker 4b located to the right
front of the listener to the right ear of the listener, and hRL is also a head-related transfer
function from the speaker 4b to the left ear of the listener.
[0032]
FIG. 6 is a plan view from the upper viewpoint showing a case where the portable information
terminal 200 is used in a state of being inclined by an angle θ. At this time, the two speakers 4a
and 4b arranged asymmetrically in the portable information terminal 200 are at different
positions from the listener by the distance dL.
[0033]
Here, since the head-related transfer function from the speaker 4a located on the left front of the
listener to both ears of the listener is the same as in the case of the reference position, the
positional relationship between the speaker 4a and both ears of the listener is the same. The
head-related transfer function from the speaker 4a to the left ear is hLL, and the head-related
transfer function from the speaker 4a to the right ear is hLR. On the other hand, in the speaker
4b located on the right front of the listener, the distance to the listener is changed by dL
compared to the reference position shown in FIG. Regarding the head related transfer function at
this time, let hRR 'be the head related transfer function from the speaker 4b to the listener's right
ear, and hRL' be the head related transfer function from the speaker 4b to the listener's left ear.
[0034]
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10
In a state in which the portable information terminal 200 is inclined by the angle θ, the
direction (azimuth angle) of the speaker 4b viewed from the listener is also changed strictly, and
there is also a variation in distance associated with this. However, the variation of this distance is
very small compared to the aforementioned distance dL and can be ignored.
[0035]
The head related transfer function is characterized by the transfer system in the space where the
listener is present and the transfer system by reflection, diffraction, and resonance by the
listener's own head, face, pinnacle, shoulder, etc. The characteristics of the head related transfer
functions hRR 'and hRL' at that time were experimentally examined while changing the
inclination θ of the portable information terminal 200 little by little, and it was found that the
delay characteristics are most remarkably changed There is. Therefore, in the crosstalk
cancellation processing in the present embodiment, when the head related transfer functions hRR
and hRL at the reference inclination are defined and the portable information terminal 200 is
used in an inclined manner, the reference is made according to the inclination θ. The delay is
added based on the head transfer functions hRR and hRL of
[0036]
FIG. 7 shows a circuit configuration of the crosstalk cancellation unit 30 in the present
embodiment. Reference numerals 1a and 1b denote input terminals for inputting the two-channel
acoustic signals from the direction localization unit 20. Here, it is assumed that 1a is an input
terminal of an L channel signal and 1b is an input terminal of an R channel signal.
[0037]
Reference numerals 2a, 2b, 2c and 2d denote filter units having different filter characteristics.
Each filter characteristic HLL, HLR, HRL, RRR is as follows using a head related transfer function
as a reference. HLL = hRR / (hLL · hRR-hLR · hRL) (Expression 1) HLR = hLR / (hLL · hRR-hLR ·
hRL) (Expression 2) HRL = hRL / (hLL · hRR-hLR · hRL) (Expression 3) HRR = hLL / (hLL · hRRhLR · hRL) (Equation 4)
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[0038]
The signal addition unit 3a subtracts the output signal of the filter unit 2c from the output signal
of the filter unit 2a. The signal addition unit 3 b subtracts the output signal of the filter unit 2 b
from the output signal of the filter unit 2 d.
[0039]
The inclination θ of the portable information terminal 200 is detected by the sensor 7 as
inclination detection means. The sensor 7 is used to detect a so-called attitude angle, and is also
called an inertial sensor, and includes a three-axis acceleration sensor, a three-axis geomagnetic
sensor, and a three-axis gyro.
[0040]
The distance correction unit 5 as the speaker position change detection means determines the
distance dL between the two speakers 4a and 4b according to the value of the inclination θ
detected by the sensor 7 to obtain the time difference between the sound reaching the listener
from the speaker Calculate From this calculation result, an instruction signal for performing time
adjustment is output to time adjustment units 6a and 6b as delay insertion means provided at the
front stage of each of the speakers 4a and 4b.
[0041]
The time adjustment units 6a and 6b delay the sound source signals input from the signal
addition units 3a and 3b according to the instruction signal from the distance correction unit 5
and output the delayed sound source signals to the speakers 4a and 4b of the reproduction unit
40 in the subsequent stage. Here, 9 a and 9 b are output terminals for outputting an acoustic
signal to the reproduction unit 40.
[0042]
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12
The specific example of a sound source signal delay process is shown. In the case of inclination
θ = 30 °, the distance dL to which the speaker 4b varies with respect to the reference position
is dL = 1/2 * L (Equation 5) where L is between the speakers in the vertical direction determined
at the stage of mounting the speaker on the body It will be the distance. The speaker 4b is
located farther from the listener than the speaker 4a. At this time, a time difference dT
corresponding to the distance dL occurs, and the sound reproduced simultaneously by the two
speakers 4a and 4b is delayed in the time when the sound from the speaker 4b arrives. Assuming
that the sound velocity is c [m / s], this time difference dT is as follows: dT = dL / c (Equation 6)
[0043]
FIG. 8 shows the distance L in the vertical direction when two speakers are mounted in
asymmetrical arrangement in the portable information terminal 200. In FIG. Assuming that the
linear distance between the two speakers is Lsp, and the angle between the vertical direction and
the straight line connecting the two speakers is θsp, the distance L can be obtained by L = Lsp *
cos (θsp) (Expression 7). As can be seen from Equations 5 to 7, when the distance Lsp is large
and the angle θsp is small, the time difference dT becomes large. This is true in the case where
the speakers are arranged above and below the display screen, respectively.
[0044]
The distance correction unit 5 instructs the time adjustment unit 6a and the time adjustment unit
6b to insert a delay in consideration of the time difference dT obtained as described above and
the positional relationship between the two speakers 4a and 4b. Output a signal. In the above
case, since the time when the sound from the speaker 4b arrives is delayed, an instruction signal
is output to the time adjustment unit 6a to insert a delay corresponding to the time difference dT.
At the same time, an instruction signal is output to the time adjustment unit 6b to make the delay
to be inserted zero.
[0045]
Further, the distance correction unit 52 shown in FIG. 13 configured to allow the user to make
fine adjustments to the time difference dT obtained as described above may be substituted. When
the user operates the user input unit 70, an offset with respect to the time difference dT is given
to the distance correction unit 52. After adding the given offset to the time difference dT, the
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distance correction unit 52 outputs an instruction signal so as to insert a delay to the time
adjustment units 6a and 6b.
[0046]
The crosstalk cancellation unit 30 is not limited to the filter configuration as described above,
and any other configuration may be appropriately used as long as it can cancel crosstalk
generated during reproduction of an audio signal by two speakers. can do.
[0047]
In the above description, the case where the portable information terminal is used vertically is
described, but in the case of horizontal use, the speaker interval in the horizontal direction seen
from the listener is largely different. The head related transfer functions to both ears of the
subject may be obtained, and the filter characteristics HLL, HLR, HRL, and HRR may be switched.
[0048]
As described above, according to the sound reproduction system of the portable information
terminal in the present embodiment, the inclination of the main body of the portable information
terminal is detected, and the characteristic of the head transfer function from the two speakers at
that time to the listener's ears is corrected. As a result, the listener can hear a sound image
localized at the intended position without degrading the crosstalk cancellation effect.
[0049]
In addition, since the characteristic of the head-related transfer function is corrected by inserting
a delay to the sound source signal according to the inclination of the portable information
terminal, a head-related transfer function assuming all inclinations is prepared. It is not
necessary to store the filter coefficients, and the memory size for storing the filter coefficients
does not increase, and the increase in circuit scale can be suppressed.
[0050]
Second Embodiment
FIG. 9 is a block diagram showing the configuration of the crosstalk cancellation unit 31 of the
sound reproduction system of the portable information terminal according to the second
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embodiment of the present invention, which has a different crosstalk cancellation unit from the
first embodiment.
The configuration, functions, and operation of the sound source unit 10, the direction localization
unit 20, and the reproduction unit 40 shown in the first embodiment do not change even in the
sound reproduction system of the portable information terminal according to the second
embodiment. I omit it.
[0051]
The crosstalk cancellation unit 31 according to the present embodiment newly includes a
determination unit 8 as crosstalk cancellation calculation means, and receives information from
the sensor 7 on the tilt of the portable information terminal, and based on this, the filter unit 21a,
Control of selection and switching of filter coefficients used in 21b, 21c and 21d.
[0052]
For example, the inclination θ of the portable information terminal is divided into a plurality of
divisions, and a filter coefficient corresponding to an angle representing the inclination θ is
prepared for each division.
FIG. 10 and FIG. 11 are examples of the classification table showing the relationship between the
inclination θ and the division and representative angles.
FIG. 10 shows the case where the range of 0 ° to 90 ° is equally divided into three divisions
with respect to the inclination θ.
The filter coefficients used in division 1 are obtained from the head related transfer function
when the inclination of the main body is 0 °. FIG. 11 shows the case where the range of 0 ≦ dL
≦ L is equally divided into three sections for the distance dL. The filter coefficients used in
division 1 are obtained from the head related transfer function when the inclination of the main
body is 0 °.
[0053]
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Regarding the classification table, the distance correction unit 51 and the determination unit 8
have the same classification table. The division setting method is not limited to the abovedescribed method, and the number of divisions set is not limited to three, and can be set to N (an
integer such that N> 0).
[0054]
The determination unit 8 determines the corresponding classification from the classification table
according to the value of the inclination θ detected by the sensor 7. Furthermore, the
information of this division is output to the filter units 21a, 21b, 21c, and 21d. Each filter unit
selects a filter coefficient based on the classification information and executes filter processing.
The configurations and operations of the respective filter units are the same, so here, the filter
unit 21a will be described as a representative.
[0055]
FIG. 12 is a diagram showing the configuration of the filter unit 21a. When a division is given by
the determination unit 8, the filter unit 21a switches to the filter processing using the
corresponding filter coefficient with the division information as an index. When the index is 1,
HLL_1 is selected, and when the index is 2, HLL_2 is selected.
[0056]
Further, the information of the inclination θ from the sensor 7 in FIG. 9 is also input to the
distance correction unit 51. The distance correction unit 51 obtains the distance dL between the
two speakers 4 a and 4 b according to the value of the inclination θ. At the same time, based on
the classification table, the difference in distance at the slope representative of the division is
obtained, and this difference is regarded as a substantial difference in distance. Based on this
substantial distance difference, the time difference in which the sound reaches the listener from
the speaker is calculated. From this calculation result, an instruction signal for performing time
adjustment is output to the time adjustment units 6a and 6b provided at the front stage of each
of the speakers 4a and 4b.
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[0057]
The time adjustment units 6a and 6b delay the sound source signals input from the signal
addition units 3a and 3b according to the instruction signal from the distance correction unit 51,
and output the delayed sound source signals to the speakers 4a and 4b of the reproduction unit
40 in the subsequent stage. Here, 9a and 9b are output terminals for outputting a signal to the
reproduction unit 40.
[0058]
A concrete example is shown. In the case of inclination θ = 30 °, the distance dL between the
two speakers with respect to the listener is as shown in (Equation 5). When this inclination θ =
30 °, for example, in FIG. And at the boundary of Category 2. When the detected inclination is at
the boundary, it is defined that the division 2 which is the division having a large inclination is
selected. The information of the section output from the determination unit 8 is 2, and at this
time, the filter unit 21a uses the filter coefficient HLL_2. The filter coefficients are similarly
selected in the filter units 21b, 21c, and 21d.
[0059]
At the same time as obtaining the distance dL, the distance correction unit 51 obtains a
difference in distance in the case of an inclination of 30 ° representing the category 2 based on
the sorting table, and calculates a substantial distance difference dL ′. In the case of θ = 30 °,
since it is the same as the representative slope of 30 °, dL ′ is zero, and the corresponding
time difference is also zero. As a result, an instruction signal is output to the time adjustment
units 6a and 6b to make the delay to be inserted zero.
[0060]
On the other hand, in the case of the inclination θ = 45 °, for example, in the case of applying
the classification table of FIG. The determination unit 8 outputs classification information to all
filter units. According to this information, the filter unit 21a uses the filter coefficient HLL_2. The
filter coefficients are similarly selected in the filter units 21b, 21c, and 21d.
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[0061]
The distance correction unit 51 obtains the distance dL between the two speakers with respect to
the listener. dL = 1 / √2 * L (Equation 8) At the same time, the distance in the case of the
inclination of 30 ° representing the division 2 of θ = 45 ° is determined from the classification
table, and the substantial distance difference dL ′ is calculated. It becomes as follows from
(Formula 5) and (Formula 8). dL '= (1 / √2-1/2) L (Equation 9)
[0062]
Then, in consideration of the time difference dT 'corresponding to the substantial distance
difference dL' and the positional relationship between the two speakers 4a and 4b, an instruction
signal is provided to insert a delay into each of the time adjusting units 6a and 6b. Output The
method of determining the time difference dT 'is the same as that of the first embodiment. In the
above case, since the time when the sound from the speaker 4b reaches the listener is delayed,
an instruction signal is output to the time adjustment unit 6a so as to insert a delay
corresponding to the time difference dT '. At the same time, an instruction signal is output to the
time adjustment unit 6b to make the delay to be inserted zero. As described in the first
embodiment, the distance correction unit 51 may be configured to allow the user to adjust the
time difference dT '.
[0063]
In the above description, the case where the portable information terminal is used vertically is
described, but in the case of horizontal use, the speaker interval in the horizontal direction seen
from the listener is largely different. The head related transfer functions to both ears of the
subject may be obtained, and the filter characteristics HLL, HLR, HRL, and HRR may be switched.
[0064]
As described above, according to the sound reproduction system of the portable information
terminal in the present embodiment, a plurality of filter coefficients are switched according to the
inclination of the main body of the portable information terminal divided into a plurality of
divisions, and Since the correction of the characteristic of the head related transfer function due
to the difference between the angle and the actual inclination is performed by inserting a delay to
the sound source signal, even if the portable information terminal is greatly inclined, the
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crosstalk cancellation is finely performed. Processing becomes possible, and the listener hears
the sound image localized at the intended position.
[0065]
In the above embodiment, the timing at which the inclination θ is determined is, for example,
when the switch operated by the listener is turned on to enable three-dimensional sound
reproduction, or when the fluctuation of the inclination is within the specified range Although the
time when it is contained within, etc. may be mentioned, it can be determined variously
according to the usage of using the portable information terminal according to the present
invention.
[0066]
Third Embodiment
FIG. 14 is a diagram showing an asymmetric arrangement of two speakers in a sound
reproduction system of a portable information terminal according to a third embodiment of the
present invention.
The two speakers 4a and 4b are arranged such that the angle θsp between the vertical direction
of the screen display unit 201 and the linear direction connecting the two speakers 4a and 4b is
45 °.
[0067]
FIG. 14 (a) shows a state in which the portable information terminal according to the present
embodiment is used vertically, and FIG. 14 (b) shows a state in which the portable information
terminal according to the present embodiment is used horizontally. .
In both of these cases, the distance Lh between the speakers in the left-right direction is equal to
the vertical direction of the screen display unit 201, and Lh = 1/2 * Lsp.
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[0068]
When the two speakers are arranged in this way, the distance between the left and right speakers
as viewed from the listener does not change, so it is not necessary to obtain different head
related transfer functions in the vertical orientation and the horizontal orientation. It is not
necessary to switch between HLL, HLR, HRL, and HRR in the vertical orientation and in the
horizontal orientation.
[0069]
As described above, according to the sound reproduction system of the portable information
terminal in the present embodiment, even when the portable information terminal is used
vertically or horizontally, the distance between the speakers in the horizontal direction viewed
from the listener can be made the same. It is not necessary to apply different head related
transfer functions in the talk cancellation process, it is possible to avoid an increase in memory
size for storing filter coefficients, and it is possible to suppress an increase in circuit scale.
[0070]
Although the above embodiments have described the case where the sound reproduction system
according to the present invention is applied to a portable information terminal, the application
is not limited to only the portable information terminal as described above. For example, a
desktop monitor, a liquid crystal monitor, etc. It is needless to say that the present invention can
be applied to an apparatus or the like in which the display screen and the two speakers are on
the same plane and the tilt can be changed by the tilt function.
[0071]
The sound reproduction system according to the present invention can finely carry out crosstalk
cancellation processing even when the housing of the device is used in an inclined manner, and
the housing is often used in an inclined state. Such as a portable information terminal device
such as a portable game machine capable of playing the game, a desktop monitor, a liquid crystal
monitor, etc., a device having a display screen and a speaker on the same surface and whose tilt
can be changed by a tilt function It is possible.
[0072]
It is a structure block diagram of the sound reproduction system of the portable information
terminal which is Embodiment 1 of this invention.
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It is explanatory drawing of a mode that a reproduction | regeneration acoustic signal arrives at a
listener's both ears from a speaker.
FIG. 1 is an external view showing an example of a portable information terminal according to
Embodiment 1.
It is a right side view of a state where a personal digital assistant is used with inclination.
It is a use condition explanatory view in a reference (standard) position of a portable information
terminal. It is a top view of a state where a personal digital assistant is used with inclination. FIG.
6 is a circuit diagram of a crosstalk cancellation unit in the first embodiment. It is explanatory
drawing of the distance of the top-and-bottom direction between two speakers asymmetrically
arrange | positioned at a portable information terminal. It is a circuit diagram of the crosstalk
cancellation part in Embodiment 2 of this invention. It is explanatory drawing of the inclination
which divided the inclination of a portable information terminal into equal division, and the
relationship of a representative value. It is explanatory drawing of the relationship of the
inclination and representative value which divided the distance difference to the listener which
arises at the time of inclination of a portable information terminal equally. FIG. 8 is a block
diagram showing the configuration of a filter unit according to a second embodiment. FIG. 7 is a
block diagram of a distance correction unit configured to allow a user to adjust the amount of
acoustic signal delay. It is asymmetrical arrangement | positioning explanatory drawing of two
speakers in the sound reproduction system of the portable information terminal by Embodiment
3 of this invention.
Explanation of sign
[0073]
2a, 2b, 2c, 2d, 21a, 21b, 21c, 21d; filter unit, 3a, 3b; signal addition unit, 4a, 4b; speaker, 5, 51,
52; distance correction unit, 6a, 6b; time adjustment unit , 7; sensor 8; determination unit 9a, 9b;
output terminal 10; sound source unit 20; direction localization unit 30; 31 crosstalk cancellation
unit 40 reproduction unit 70 user input unit 100; Sound image localization processing unit, 200;
portable information terminal, 201; screen display unit, 202; antenna unit.
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