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DESCRIPTION JPH0787590

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DESCRIPTION JPH0787590
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
loudspeaker apparatus capable of controlling directivity.
[0002]
2. Description of the Related Art In the case where different explanations are given at adjacent
booths in exhibition halls or when different announcements are made at homes next to a station,
etc., when using a general speaker system, the respective voices are mixed and it is very difficult.
It may be difficult to hear. This is because a typical speaker system is designed to reproduce
sound in any direction in the same way, that is, to have wide directivity. In such a case, in order
to make it easy to hear individual voices, there is a demand for a directional speaker system that
can obtain strong sound pressure only in a specific place.
[0003]
Conventionally, as one of the means for realizing narrow directivity of sound, a method of
configuring a speaker array by arranging a plurality of speaker units in a line or plane and
controlling a signal input to each speaker unit is known. Are known. The configuration will be
described below with reference to FIGS. 8 to 12.
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[0004]
FIG. 8 is a block diagram showing a directional speaker device disclosed in, for example,
Japanese Patent Laid-Open No. 2-239798. As constituent elements, 1 in the figure is a signal
source, 17 is an A / D converter, 18 is an FIR filter, 19 is a D / A converter, 10 is an amplifier,
and 101 is a plurality of speaker units 11 linearly arranged. It is a speaker array.
[0005]
The relationship between these components and their operation will be described. The output of
the signal source 1 is A / D converted and then branched into a plurality of components, which
are controlled in phase / amplitude characteristics by the FIR filter 18. Furthermore, after being
D / A converted, the signal is amplified by the amplifier 10, and the same signal is input to the
pair of speaker units 11 located at symmetrical positions with respect to the symmetry axis of
the speaker array 101.
[0006]
Here, by controlling the phase / amplitude characteristics of the signal input to each speaker unit
11 constituting the speaker array 101, the directivity is sharpened, broadened, or the
directionality of directivity is changed (pointing axis It is well known that the
[0007]
FIG. 9 shows a directional speaker apparatus including a speaker array 107 in which 12
loudspeaker units 11 (9.4 in aperture diameter) are arranged in a grid of 25 cm intervals, a
signal source 1, and an amplifier 10.
[0008]
FIG. 10 shows the sound pressure distribution in the anechoic chamber when all the speaker
units constituting this speaker array are driven at the same phase and level.
That is, the equal sound pressure lines in a plane parallel to the speaker array are displayed at a
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distance of 1.5 m from the speaker array, and the equal sound pressure line interval is every 3
dB.
The sound pressure is highest at a point where the coordinate of the horizontal axis is 1 m and
the coordinate of the vertical axis is 1.5 m directly below the center of the speaker array. In FIG.
10, the sound pressure level at this point is normalized to 0 dB and displayed.
[0009]
Further, FIG. 11 is in a horizontal plane 1.5 m below the speaker array when the directional
speaker device of FIG. 9 is mounted on a ceiling of a room 3.8 m high × 6.8 m wide × 3.0 m
high. Sound pressure distribution is shown similarly to FIG.
[0010]
However, the conventional directional speaker apparatus as described above has the following
problems.
When FIG. 10 and FIG. 11 are compared, it can be seen that the directivity in the anechoic room
and the directivity in the actual room are greatly different even with the same speaker device. In
general, even in a speaker apparatus which can obtain a considerably sharp directivity in an
anechoic chamber, the high sound pressure level range is considerably expanded when this is
mounted and used in an actual room. For example, the sound pressure level at 500 Hz and 2 m
away from the highest sound pressure point is only −9 dB in FIG. 11 as opposed to −28 dB in
FIG.
[0011]
FIG. 12 schematically shows the reason for this. The walls in the anechoic chamber do not reflect
sound, so when the directivity of the sound source is sharp, concentrated in a narrow range, a
strong sound pressure can be obtained. In contrast, the wall surface of the actual room reflects
sound, and the sound pressure level in the room is averaged to diffuse the sound wave, and it is
difficult to limit the range in which strong sound pressure can be obtained.
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[0012]
In order to solve this, it is necessary to control the phase / amplitude characteristics of the signal
input to each of the speaker units constituting the speaker array after considering in advance the
reflected wave from the wall surface. However, since the positional relationship between the
speaker and the wall in the room and the sound absorption coefficient in the room differ from
each other, when the configuration as shown in FIG. 8 is adopted, the optimal control method is
calculated for each room in which the speaker is installed. The filter characteristics need to be
changed each time, which causes a problem of lack of versatility.
[0013]
The present invention solves the above-mentioned problems and sharp directivity is obtained
even when a directional speaker device is used in an actual room having a reflected wave, and it
is pointed regardless of the place where the speaker device is used. The purpose is to get sex.
[0014]
According to the directivity control speaker device of the present invention, in order to achieve
the above object, there is provided a speaker array comprising a plurality of speaker units
arranged in a line or plane, a line or a speaker array. A microphone array consisting of a plurality
of microphones arranged in a plane, a plurality of signal adjustment means for adjusting input
signals to the plurality of speaker units, and output signals from the plurality of microphones are
taken in And control means for controlling the signal adjustment means based on this.
[0015]
In the directivity control speaker device of the above configuration, sound waves radiated from
the speaker array become direct waves or reflected waves from the wall surface, floor surface
and ceiling surface, and reach each microphone.
The control means first takes in the output signal from each microphone and detects the state of
the sound pressure distribution in the room.
Next, based on this, a control method of the signal adjustment means is determined so as to
obtain a desired sound pressure distribution, and the signal adjustment means is controlled
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thereby.
[0016]
Through this process, the phase and amplitude characteristics of the signal input to each speaker
unit are controlled in consideration of the reflected wave from the wall surface, and sharp
directivity is obtained regardless of the location where the speaker device is used. It becomes
possible.
[0017]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be
described below based on the drawings showing the embodiments.
FIG. 1 is a block diagram of a directivity control speaker device according to a first embodiment
of the present invention. The output of the signal source 1 is first divided into bands by the low
pass filter 6 and the high pass filter 7 and branched for each speaker unit (or set of speaker
units) to be controlled. Be done. The branched signal is set in level by the signal level attenuator
8. A signal whose level is set for each band is mixed by the mixer 9 for each (set of) speaker units
to be controlled, then amplified by the amplifier 10 and input to each speaker unit 11 in the
speaker array 101. Ru. The signal adjustment means 104 is composed of the low pass filter 6
and the high pass filter 7, the signal level attenuator 8, the mixer 9, and the amplifier 10.
[0018]
The microphone 2 collects the direct wave radiated from the speaker array 101 and the reflected
wave from the wall surface and the like, and converts it to an electric signal. The signal is divided
into bands by the low pass filter 3 and the high pass filter 4, and is input to the level setter
control device 5. The control means 103 comprises a low pass filter 3, a high pass filter 4 and a
level setter control unit 5.
[0019]
The level setter control device 5 receives the band-divided signal of each microphone 2 and
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detects the sound pressure distribution in the room in each frequency band. Furthermore, based
on the detected sound pressure distribution, the signal level attenuator 8 is set so as to obtain a
desired sound pressure distribution.
[0020]
FIG. 2 shows an example of using the directivity control speaker device of the present
embodiment indoors. The speaker array 101 is attached to the ceiling, and the microphone array
is two-dimensionally arranged on the floor to detect the sound pressure distribution in the room.
[0021]
With such a configuration, in each frequency band, the level of the signal input to each speaker
unit is controlled in consideration of the reflected wave from the wall surface, and sharp
directivity is obtained regardless of the place where the speaker device is used. Is possible.
[0022]
Although the above embodiment has described the case where the signal is divided into two
bands by the low pass filter and the high pass filter, the present invention is not limited thereto,
and finer control is possible when the signal is divided into three or more bands. It becomes.
Further, the arrangement of the speaker unit and the microphone is not limited to the illustrated
arrangement.
[0023]
Next, a directivity control speaker device according to a second embodiment of the present
invention will be described with reference to FIG. FIG. 3 is a block diagram of the directivity
control speaker device of this embodiment. In FIG. 3, the speaker array 101, the microphone
array 102, and the signal adjusting means 104 have the same configuration as in the first
embodiment.
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[0024]
The microphone 2 collects the direct wave / reflected wave and converts it into an electric signal.
The signal is band-divided by low-pass filter 3 and high-pass filter 4, and voltmeter 12 measures
the voltage of the band-divided signal (that is, the sound pressure value for each band at the
position of the microphone) and calculates the measurement value Send to The calculator 13
performs the following calculation to calculate the set value of the signal level attenuator 8 in
each frequency band, sets the signal level attenuator 8 and stores the set value in the storage
device 14.
[0025]
The actual sound pressure at the position of the i-th microphone (i = 1,..., M) is Pi, and the sound
pressure value preset for each microphone is Ti. Further, the set value of the j-th signal level
setter (j = 1,..., N) in the k-th step is set as Xj (k). Although the square of the difference between Pi
and Ti is multiplied by a predetermined weighting factor Wi, the total sum E for i is expressed by
(Expression 1). Here, E is a function of X j (k), where the setting value X j (k -1) of the j-th signal
level setter in the immediately preceding step k-1 is stored in the storage device 14 The new set
value Xj (k + 1) can be calculated so that E will be smaller with reference to this. For this purpose,
for example, an algorithm of quasi-Newton method may be used.
[0026]
By repeating this step, the set value Xj of the signal level setter converges, the value of E
gradually decreases, and the actual sound pressure value in each frequency band approaches the
set value. Therefore, if the set sound pressure value Ti at the position of the microphone is set so
that strong sound pressure can be obtained only at a specific location, sharp directivity can be
obtained even in an actual room.
[0027]
Note that, instead of (Equation 1), Pi represents the actual sound pressure as expressed by
(Equation 2), and the set sound pressure value is Ti, and the absolute value of the difference
between Pi and Ti has a predetermined weighting factor Wi It is the same even if it uses the total
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E about i of what multiplied by. This is expressed as (Equation 2). Although a voltmeter is used to
read the output level of the filter in this embodiment, the present invention is not limited to this,
and an arithmetic device is configured such that the above calculation is performed according to
the output level of each filter. Just do it.
[0028]
Next, a directivity control speaker device according to a third embodiment of the present
invention will be described with reference to FIG. FIG. 4 is a block diagram of the directivity
control speaker device of the third embodiment. The output of the signal source 1 is converted
into a digital signal by the A / D converter 17 and branched for each speaker unit (or a set of
speaker units) to be controlled. The branched signals are controlled by the FIR filter 18,
converted into an analog signal by the D / A converter 19, amplified by the amplifier 10, and
input to each speaker unit 11. The signal adjustment means 104 is constituted by the whole of
the A / D converter 17, the FIR filter 18, the D / A converter 19, and the amplifier 10.
[0029]
The microphone 2 collects the direct wave radiated from the speaker array 101 and the reflected
wave from the wall surface and the like, and converts it to an electric signal. The signal is
converted to a digital signal by the A / D converter 15 and input to the FIR filter control unit 16.
The control means 103 comprises an A / D converter 15 and an FIR filter controller 16.
[0030]
The FIR filter control unit 16 receives the digitally converted signal of each microphone and
detects the sound pressure distribution in the room in each frequency band. Furthermore, based
on the detected sound pressure distribution, the coefficients of the FIR filter 18 are set so as to
obtain a desired sound pressure distribution.
[0031]
The above configuration is the same as that of the first embodiment except that digital signal
processing is used as the control means and signal adjustment means, and sharp directivity can
be obtained regardless of the place where the speaker device is used. It becomes possible.
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[0032]
Next, a directivity control speaker device according to a fourth embodiment of the present
invention will be described with reference to FIG.
FIG. 5 is a block diagram of the directivity control speaker device of the fourth embodiment. In
FIG. 5, the speaker array 101, the microphone array 102, and the signal adjusting means 104
have the same configuration as the third embodiment.
[0033]
The microphone 2 collects the direct wave / reflected wave and converts it into an electric signal.
The signal is A / D converted, frequency analyzed by the FFT unit 20, and the result is sent to the
calculation unit 21. The calculating unit 21 performs the same calculation as that performed by
the calculating unit 13 in the second embodiment to calculate the transfer function of the FIR
filter 18. The calculation result is sent to the inverse FFT unit 23, and the transfer function value
is stored in the storage unit 22. The inverse FFT unit 23 obtains the coefficient value of the FIR
filter 18 from the transfer function value, and sets the FIR filter 18.
[0034]
The above configuration is the same as that of the second embodiment except that digital signal
processing is used as the control means and signal adjustment means, and sharp directivity can
be obtained regardless of the place where the speaker device is used. It becomes possible.
Further, by using digital signal processing, even a filter that can not be realized by analog signal
processing can be easily configured, so precise and accurate control can be performed at each
frequency.
[0035]
Finally, a directivity control speaker device according to a fifth embodiment of the present
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invention will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a block diagram of the
directivity control speaker device of the fifth embodiment. In FIG. 6, the speaker array 101, the
microphone array 102, the control means 103, and the signal adjustment means 104 have the
same configuration as in the first embodiment. Between the speaker array 101 and the
microphone array 102, a detection device 107 for detecting the presence or absence of a listener
in the service area is installed.
[0036]
The detector 107 comprises an infrared source and its receiver. When the listener stands
between the infrared source and the receiver, the infrared is blocked and the receiver detects the
presence of the listener. FIG. 7 shows an example of using the directivity control speaker device
of the present embodiment indoors. The speaker array 101 is attached to the ceiling, and the
microphone array is two-dimensionally arranged on the floor surface to detect the sound
pressure distribution in the room. Moreover, the detection apparatus 107 is installed in the wall
surface.
[0037]
When the detection device 107 detects the presence of a listener in the service area, the level
setter control device changes the control method of the signal adjustment means 104. For
example, when a plurality of directivity control speaker devices are used, the directivity is
sharpened and the volume is raised when the listener is present, and the directivity is broadened
and the volume is lowered when the listener is not present. It is effective.
[0038]
In the present embodiment, the case where an infrared ray source and its receiving device are
used for the detection device has been described, but the detection device is not limited to this.
For example, even when an internal monitoring camera, a pyroelectric sensor or an ultrasonic
sensor is used for the detection device, the same effect can be obtained.
[0039]
As is apparent from the description of each of the above embodiments, the present invention can
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obtain sharp directivity even when using a directivity control speaker device in an actual room
having a reflected wave, and further, the speaker device Sharp directivity can be obtained
regardless of the place where it is used.
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