JP2000197182

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DESCRIPTION JP2000197182
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method and apparatus for controlling loudness in an audio apparatus such as an on-vehicle
apparatus, a household apparatus, a portable apparatus and the like.
[0002]
2. Description of the Related Art In a conventional sound device, a capacitor and a resistor are
simply connected to a part of a volume adjuster, and bass and treble are changed according to
the volume using this filter characteristic. The volume controller had little effect at adjustment
positions above a certain volume, and at adjustment positions below a certain volume, it was
common for the frequency characteristics of the same pattern to translate according to the
volume. .
[0003]
However, in the above-described conventional system, only an adjustment amount of about +6 to
12 dB can be obtained, and it is desirable to sufficiently obtain sound quality as a loudness
characteristic when an adjustment amount larger than this is required. If the request could not be
answered adequately.
Moreover, in the case of the on-vehicle apparatus, in the conventional two-channel loudness
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control, the aperture of the speaker is often limited due to the restriction of the mounting
position, and a normal listening point may not be equidistant from the speaker Most of them,
even if the left and right, front and rear speakers at the listening point have the same loudness
characteristic, the difference in distance from each speaker is not sufficient in the effect of the
loudness characteristic. In addition, since sound sources with different reproduction bands may
exist at four or more places such as radios, televisions, tapes, CDs, etc., there is a problem that
auditory sensitivity correction including consideration to sound image localization, phase and
sound quality is difficult. The In particular, when the bass is emphasized by loudness control, the
speaker is often set at a low position, and the sound image becomes low. Furthermore, there is a
problem that the roundness effect when adopting a multi-speaker system or a multi-amplifier
system does not differ much from the two-channel system.
[0004]
The present invention solves such conventional problems, and an object of the present invention
is to provide a loudness control method and apparatus that can obtain loudness characteristics
sufficiently effectively.
[0005]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
divides the audio signal of each channel into bands and makes the volume of each divided band
follow the overall volume change to obtain loudness characteristics. The sound quality, balance
control, and fader control are linked to the overall volume change to construct an optimal sound
system.
As a result, control of sound quality and sound image localization can be performed while
securing a sufficient variable amount, and auditory sensitivity correction can be performed in
consideration of special reproduction conditions such as in-vehicle use.
[0006]
According to the first aspect of the present invention, the frequency is divided into bands in
order to correct the auditory sensitivity of the input audio signal, and the volume of each banddivided frequency is divided into an audio signal. This is a loudness control method that changes
in accordance with the overall volume change of the output, and since the volume is adjusted for
each band in the prior art in which the loudness effect has been limited, the theoretical
adjustment of the main volume It has the effect that the loudness effect can be given to the
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range.
[0007]
The invention according to claim 2 of the present invention is the loudness control method
according to claim 1, wherein the cutoff frequency of each frequency is changed following the
entire volume change at the time of band division. By changing the cutoff frequency in
accordance with the above, it is possible to improve the connection between the divided bands.
[0008]
The invention according to claim 3 of the present invention is the loudness control method
according to claim 1, wherein the cutoff characteristics of each frequency are switched in a
plurality of stages at the time of band division, and the preferred loudness characteristic is
selected according to the application. It has the effect of being able to
[0009]
The loudness control method according to claim 1, wherein the invention according to claim 4 of
the present invention takes out an audio signal of each frequency which is band-divided and
volume-adjusted, and outputs it from independent power amplifiers and speakers. It has the
effect that the optimal loudness characteristic in a listening point can be acquired.
[0010]
The invention according to claim 5 of the present invention changes the position of the sound
image by changing a specific frequency region of the band-divided frequencies in accordance
with the overall volume change. The loudness control method according to the present invention
has the effect of improving the position of a sound image particularly in an on-vehicle acoustic
system in which the speaker arrangement is restricted.
[0011]
The invention according to claim 6 of the present invention is an acoustic system having
speakers arranged at the front, back, left, and right, interlocking balance control and fader
control in accordance with overall volume change, and optimizing at a listener's listening point
The loudness control method according to claim 1, which has the effect of improving the sense of
stereo in a car-mounted audio system in which the position of the viewer is not located at the
center of the front and rear speakers.
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[0012]
According to a seventh aspect of the present invention, in the vehicle-mounted acoustic system,
the level of the frequency-divided mid-range audio signal is attenuated when the audio guidance
signal of another device is input during the audio signal output. The loudness control method
according to claim 1, wherein the level of the voice guidance signal is increased, and the clarity
of the guidance voice signal is improved while maintaining the optimum loudness characteristic
even when the voice guidance signal is input. It has the effect of being able to
[0013]
The invention according to claim 8 of the present invention is a means for band dividing a
frequency for correcting auditory sensitivity, and changing the volume of each band-divided
frequency in accordance with the volume change of the entire audio signal output. And a
loudness control device having a means for controlling the loudness effect for each band, which
has conventionally been limited to the loudness effect, so that the loudness effect can be
theoretically provided to the adjustment range of the main volume It has the effect of
[0014]
The invention according to claim 9 of the present invention is a loudness control apparatus
according to claim 8, further comprising means for changing the cutoff frequency of each
frequency in accordance with the overall volume change at the time of band division. By
changing the cut-off frequency in accordance with the level, the connection between the divided
bands can be improved.
[0015]
The invention according to claim 10 of the present invention is the loudness control apparatus
according to claim 8, further comprising means for switching the cut-off characteristics of each
frequency in a plurality of steps at the time of band division. It has the effect of being selectable.
[0016]
The invention according to claim 11 of the present invention is a loudness control apparatus
according to claim 8, further comprising means for taking out an audio signal of each frequency
band-divided and outputting it from independent power amplifiers and speakers. It has the effect
of being able to obtain the optimum loudness characteristic at the listening point.
[0017]
The invention according to claim 12 of the present invention is the loudness control apparatus
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according to claim 8, further comprising means for changing the volume of a specific frequency
region of the band-divided frequencies in accordance with the overall volume change. In
particular, it has the effect of being able to improve the position of the sound image in the onvehicle acoustic system in which the speaker arrangement is restricted.
[0018]
The invention according to claim 13 of the present invention, in an acoustic system provided
with speakers on the front, rear, left and right, synchronizes balance control and fader control in
accordance with overall volume change, and optimizes at a listener's listening point The loudness
control apparatus according to claim 8, further comprising: means for improving the sense of
stereo in a car-mounted audio system in which the position of the viewer is not located at the
center of the front and rear speakers.
[0019]
The invention according to claim 14 of the present invention is a vehicle-mounted audio system,
comprising means for mixing an audio signal and an audio guidance signal of another device, the
audio guidance signal of the other device being an audio signal being output. 9. A loudness
control apparatus according to claim 8, further comprising means for attenuating the level of the
frequency-divided mid-range audio signal when it is input, and controlling to raise the level of the
audio guidance signal. It has the effect of being able to improve the intelligibility of the guidance
voice signal while maintaining the optimum loudness characteristic even at the time of signal
input.
[0020]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
Embodiment 1 First, the entire loudness control method and apparatus according to the present
invention will be described with reference to FIG.
In FIG. 1, reference numeral 11 denotes an input selector unit for switching an input source of an
audio signal, and assuming a CD, a tape, a radio and others as the input source, shows a case
where only the left channel is input.
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In total, this control block is provided for four or six channels.
Reference numeral 12 denotes a band division unit which performs band division of the input
audio frequency, and in this case, it is divided into three parts, a low band, a middle band, and a
high band.
A level control unit 13 changes the volume of each frequency band-divided in accordance with
the volume change of the main volume 17, and is composed of a VCA (Voltage Controlled
Amplifier) having an attenuation characteristic as shown in FIG. .
Reference numeral 14 denotes a buffer for each level-adjusted frequency, and reference numeral
15 denotes a mixing circuit which mixes the outputs of the buffers 14 and combines them into
one channel signal (here, the left channel).
A level control unit 16 inputs a voice guidance signal for navigation and follows the volume
change of the main volume 17 to set an optimal mixing level, and is constituted by a VCA similar
to the level control unit 13 There is.
Reference numeral 17 is a main volume for adjusting the volume of the entire input audio signal,
and as shown in FIG. 2, the control voltage V controls the amount of attenuation of each VCA.
Reference numeral 18 denotes a multi-amplifier output terminal for independently controlling
the output of the control level unit 13 by an external multi-amplifier.
The band dividing unit 12 and the level control unit 13 are integrally formed as a DSP (Digital
Signal Processor) 19.
[0021]
Next, the operation in the above embodiment will be described.
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When the sound source is selected by the input selector unit 11, the frequency of the audio
signal is divided into three, low, middle and high, by the band dividing unit 12, and the level
control unit 13 changes the main volume 17 variablely. It is variable according to the amount.
As shown in FIG. 2, the variable resistor of each VCA in the level control unit 13 has a large
attenuation amount as the control voltage V of the main volume 17 becomes high, but the
attenuation amount is loudness controlled so as to differ depending on the band. The necessary
loudness characteristics as shown by 20 can be obtained by combining by the mix circuit 15.
Here, the loudness effect can be further enhanced by enabling the adjustment by the main
volume 17 to linearly vary the audibility sensitivity in, for example, ± 2 dB steps.
[0022]
(Second Embodiment) FIG. 3 shows another configuration of the band division unit 12 and the
level control unit 13 in the roundness control apparatus of the present invention.
The band dividing unit 12 and the level control unit 13 have VCAs, and the variable resistors
VR1 to VR11 in each VCA change the attenuation according to the control voltage V from the
main volume 17. By using the variable resistor VR in the resistive part of the filter in the band
dividing unit 12 and changing the cutoff frequency of each frequency in accordance with the
overall volume change of the main volume 17 at the time of band division, the volume control in
each band Not only can the crossover frequency between bands be controlled simultaneously to
create a smooth loudness characteristic. FIG. 4 (a) shows the case where only the level
adjustment of each band is performed, and FIG. 4 (b) shows the characteristic in the case where
the cutoff frequency is varied according to the level of each band, and the crossover frequency is
adjusted. By doing this, it is shown that the loudness characteristic can be smoothed.
[0023]
(Third Embodiment) FIG. 5 shows still another configuration of the band division unit and the
level control unit in the roundness control apparatus of the present invention. Although FIG. 5
shows only the low band part, the same configuration is provided in the mid band and high band
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parts. The band division unit 31 includes a fixed resistor and an amplifier, and the level control
unit 32 has the same configuration as that shown in FIG. Reference numeral 33 denotes a filter
circuit composed of a variable resistor VR12 and a capacitor C9. The band division unit 31 and
the level control unit 32 are connected via the switch SW1, the band division unit 31 and the
filter circuit 33 are connected via the switches SW1 and SW2, and the level control unit 32 and
the filter The circuit 33 is connected via the switches SW3 and SW2, and the outputs of the level
control unit 32 and the filter circuit 33 are selected by the switch SW4.
[0024]
Now, when the switch SW1 is connected to the a side, the switch SW3 to the b side, and the
switch SW4 to the a side, a cutoff characteristic of 18 dB / oct can be obtained as indicated by.
Next, when the switch SW1 is connected to the a side, the switch SW3 to the a side, the switch
SW2 to the b side, and the switch SW4 to the b side, a cutoff characteristic of 12 dB / oct is
obtained. When the switch SW1 is connected to the b side, the switch SW2 to the a side, and the
switch SW4 to the b side, a cutoff characteristic of 6 dB / oct can be obtained. As described
above, by switching the cutoff characteristics of each band-divided frequency to a plurality of
steps, it is possible to obtain a loudness characteristic suitable for the user's preference
depending on the application.
[0025]
(Fourth Embodiment) FIG. 6 shows the configuration of the main part of a loudness control
device according to a fourth embodiment of the present invention, and the configuration of the
loudness control device main body is the same as that shown in FIG. This embodiment utilizes the
multi-amplifier output terminal 18 of FIG. The left channel low band multi amplifier output
terminal 41a, the left channel middle band multi amplifier output terminal 41b, and the left
channel high band multi amplifier output terminal 41 c are connected via power amplifiers 42a,
42b and 42c, respectively. The speakers 43a, 43b, 43c are connected. Similarly, power amplifiers
45a, 45b, and 45c are respectively applied to the right side channel low band multi amplifier
output terminal 44a, the right channel middle band multi amplifier output terminal 44 b, and the
right channel high band multi amplifier output terminal 44 c. The speakers 46a, 46b, 46c are
connected through the same. The audience listening point 47 is located at a position surrounded
by the speakers.
[0026]
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The audio signals from the multi-amplifier output terminals divided into bands and adjusted to
appropriate volume levels are respectively amplified by the power amplifier, and then sound is
output from the speakers dedicated to each band disposed at predetermined positions. Thus, in
the multi-amplifier system and the multi-speaker system, the viewer can obtain the optimum
loudness characteristic 48 at the listening point 47 thereof.
[0027]
(Fifth Embodiment) FIG. 7 schematically shows loudness control in a vehicle-mounted acoustic
system in a fifth embodiment of the present invention.
As shown in FIG. 7A, in the acoustic system in the vehicle, the high-midrange speaker unit 52 is
disposed above the instrument panel in front of the front seat 51, and the low-range speaker unit
53 is disposed below the door panel. In many cases, when viewed from the driver's listening
point 54, the sound image position 55 of the sound from the speaker units 52, 53 is at a
relatively low position, so that sound can be heard from below. For this reason, as shown in FIG.
7B, when the loudness effect is exerted by adjusting the volume adjustment volume knob 56, the
midrange becomes low, and the sound image position 55 is further lowered. Therefore, as shown
in FIG. 7C, in the loudness control, the fall of the sound image position 55 is prevented by
changing from 1 kHz to about 8 kHz in the middle range following the volume change of the
main volume 17 in FIG. can do.
[0028]
Sixth Embodiment FIG. 8 shows another example of loudness control in a vehicle-mounted
acoustic system according to a sixth embodiment of the present invention. The normal driver's
listening point is usually not equidistant from the speakers, and in the conventional 2-channel
control loudness control, even if the left and right, front and back speakers at the listening point
have the same loudness characteristics, Due to the difference in distance from each speaker, the
effect of the loudness characteristic was not sufficiently obtained. Therefore, as shown in FIG. 8,
the audio signals of the four channels of front, rear, left and right are amplified by the power
amplifiers 61, 62, 63, 64 through the variable resistors VR13, 14, 15, 16 respectively, and the
speakers 65, 66, In the configuration of outputting from 67, 68, the resistance value of each of
the variable resistors VR13, 14, 15, 16 is set individually, and individually controlled by the
control voltage V for level adjustment from the main volume 17 of FIG. Controls the balance
control (right and left volume) and the fader control (front and back volume) to virtually listen to
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the driver's actual listening point 69 located at the center of each speaker 65, 66, 67, 68 It can
be set to point 70, and even real listening point 69 while improving the sense of stereo It can be
obtained optimal loudness effect.
[0029]
(Seventh Embodiment) FIG. 9 is for explaining the operation of the loudness control system in the
seventh embodiment of the present invention, and the configuration of the system itself is the
same as that shown in FIG. In the in-vehicle system, when the voice guidance for navigation is
performed using the in-vehicle acoustic system, when the voice guidance for navigation jumps in
while the acoustic system is operating and listening to music, in the conventional system The
sound of the front channel was muted and voice guidance was inserted there, but with this
method the localization of the sound became unstable and the discomfort when muting was
large. Therefore, in the seventh embodiment, the output levels of VCA1 to VCA3 are lowered as
in 71 by the control voltage V for level control from the main volume 17 for the two channels on
the left and right of the front, and By controlling the voice guidance signal to increase the output
level by the VCA 4 as in 72, the output mixed by the mixing circuit 15 is a combination of the
voice signal and the voice guidance signal at the time of voice guidance signal input as in 73. The
clarity of the voice guidance signal can be secured without changing the volume of the signal,
and the user can hear easy-to-hear voice guidance without a sense of discomfort.
[0030]
As is apparent from the above embodiments, the present invention divides the audio signal of
each channel into bands and controls the change in volume of each band to the overall volume
for each band to control the loudness characteristic. It is realized, and sound quality, balance, and
fader control can be linked to construct an optimal sound system. As a result, control of sound
quality and sound image localization can be performed while securing a sufficient variable
amount, and auditory sensitivity correction can be performed in consideration of special
reproduction conditions such as in-vehicle use.
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