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JPS61108292

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DESCRIPTION JPS61108292
[0001]
BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a
sound field correction apparatus that corrects a sound field generated by sound emitted from
sound output means such as a speaker. BACKGROUND ART As a sound field correction device
that corrects a sound field generated by sound emitted by sound output means such as a speaker,
frequency characteristics of the sound field are detected by signal levels of respective frequency
components in an electrical signal obtained by converting from the sound. A device for
substantially correcting the frequency characteristic of the sound field by changing the signal
level of each frequency component in the audio signal supplied to the speaker according to the
detection result by the frequency characteristic correction means having the same function as
the graphic equalizer. It has already been devised. When such a conventional sound field
correction apparatus corrects a sound field having characteristics as shown in FIG. 1 such as a
sound field frequency characteristic in a vehicle interior, the frequency characteristics of the
frequency characteristic correction means become as shown in FIG. You must do it. However,
since this frequency characteristic correction means is configured to change the signal level of
each frequency component in a plurality of bands which divide the audio frequency band
adjacent to each other similarly to the graphic equalizer, the frequency as shown in FIG. Even if it
becomes characteristic, as shown in FIG. 3, it becomes frequency characteristic with many peaks
and dips. In the conventional sound field correction apparatus, as shown in FIG. 1, the sound field
frequency characteristics changing in a fixed direction with a gentle slope in the high and low
bands are corrected as shown in FIG. There is a disadvantage that peaks and dips occur at high
and low frequencies. SUMMARY OF THE INVENTION An object of the present invention is to
provide a sound field correction apparatus capable of well correcting a sound field having a
frequency characteristic with a gradual change in a fixed direction in high and low bands. In the
sound field correction apparatus according to the present invention, for frequency components
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lower than the predetermined frequency, the gain gradually changes in the predetermined
direction at a change rate according to the supplied data as the frequency decreases, and the
frequency is higher than the predetermined frequency For the component, sound quality
adjusting means is provided to adjust the sound quality with a frequency characteristic so that
the gain gradually changes in a predetermined direction at a change rate according to the
supplied data as the frequency becomes higher. EXAMPLE Hereinafter, an example of the present
invention will be described in detail with reference to FIG. 5 to FIG. In FIG. 5, an audio signal is
supplied to a graphic equalizer (hereinafter referred to as GEQ) 2 as frequency characteristic
correction means via a tone control circuit 1 as sound quality adjustment means. The tone
control circuit 1 is configured such that the frequency characteristic changes in accordance with
the output data of the control circuit 3 as shown by the broken line in the range shown by the
solid line in FIG.
That is, the tone control circuit 1 responds to the output data of the control circuit 3 as the
frequency decreases for frequency components lower than the frequency f4 among the
frequencies f1 to f7 existing at predetermined intervals in the audio frequency band. The gain
gradually changes in a predetermined direction at a constant change rate, and the gain gradually
changes in a predetermined direction at a change rate according to the output data of the control
circuit 3 as the frequency increases for frequency components higher than the frequency f4. It
has such frequency characteristics. For GEQ 2, as indicated by the solid line in FIG. 7, the
components in each band centering on frequencies f and f 7 respectively are independently
enhanced or attenuated according to the control signal output from control circuit 3 It is
configured to let you When the gain in each band of GEQ2 is all maximized, the frequency
characteristic of GEQ2 is as shown by the broken line t in FIG. 7, when the gain in all bands of
GEQ2 is all minimized GEQ 2 The frequency characteristic of is as shown by a broken line. The
output of this GEQ 2 is one power of the adder 4. The output of the pink noise generator 5 is
supplied to the adder 4 as an individual input. The pink noise generator 5 is configured to
generate pink noise whose energy per octave is constant in response to a command from the
control circuit 3. The output of the adder 4 is applied to the speaker 7 via the power amplifier 6
and a sound is emitted from the speaker 7. The direct radiation sound of the speaker 7 and the
reflection sound thereof are converted into an electric signal by the microphone 8. The output of
the microphone 8 is supplied to a microphone amplifier 9. The microphone amplifier 9 is
configured to amplify the output of the microphone 8 with a gain corresponding to the control
voltage output from the control circuit 3. The output of the microphone amplifier 9 is supplied to
the frequency characteristic measurement circuit 10. The frequency characteristic measuring
circuit 10 includes, for example, seven band pass filters having the frequencies f1 to f7 as their
center frequencies, and a multiplexer which sequentially outputs the outputs of the seven band
pass filters according to the output data of the control circuit 3. The output of the multiplexer is
rectified and then integrated to convert it into a DC voltage according to the signal level, and this
DC voltage is converted to digital data by an A / D converter and output. The output data of the
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frequency characteristic measurement circuit 10 is supplied to the control circuit 3. The
following processing is performed by a processor which is formed of a control circuit, for
example, a microcomputer and which operates according to a program stored in advance in a
ROM (read only memory) in the microcomputer.
That is, first, in response to a command from a keyboard (not shown) or the like, control is made
so that the frequency characteristic of GEQ 2 becomes flat (FIG. 8 Sl). Next, a command is issued
to the pink noise generator 5 and the pink noise starts to be output (FIG. 8). At this time, if an
audio signal is not supplied to the 1-on control circuit 1, only pink noise is supplied to the
speaker 7 through the adder 4 and the power amplifier 6. In this state, by changing the data
supplied to the multiplexer in the frequency characteristic measuring circuit 10, data
corresponding to the signal level of the frequency component in each band centering on the
frequency f1-f7 is sequentially banded . Next, the average value of the captured data is
calculated, and the gain of the microphone amplifier 9 is adjusted so that the calculated average
value corresponds to the level near the center of the input range of the A / D converter in the
frequency characteristic measurement circuit 10. (FIG. 8). Then, again, data D1 ° D2...
Corresponding to the signal level of the frequency component in each band centering on the
frequencies f1 to f7. The measurement of the frequency characteristic of the sound field
produced by the radiation sound of the speaker 7 is completed by taking in D7 (FIG. 8). Next, an
average value Da (-D3 + D4 + D5 / 3) of data in the middle range, that is, a band ranging from the
frequency f3 to the frequency f5 among the measurement data D1 to D7 is calculated (Fig. 8 Ss).
Next, the difference ΔDn (−Dn−Da) between each measurement data and the average value Da
is calculated. The sign of .DELTA.Dn is inverted to derive correction data Dn '(=-. DELTA.Dn) (FIG.
86). Next, the gains of the tone control circuit 1 at fl and f7 are controlled to be D1 'and D7',
respectively (FIG. 8). As a result, the frequency characteristic of the tone control circuit 1 changes
as shown in FIG. However, assuming that a table indicating the relationship between the gain of
tone control circuit 1 and the control signal supplied from control circuit 3 is stored in advance
in the ROM in control circuit 3, f3. f4. The gain of the tone control circuit 1 at each of f5 can be
known. Now, this table is read out and f3. Assuming that the data representing the gain at each
of f5 is D3 ′ ′ and D5 ′, respectively, the correction amount G3 of GEQ2 at f3.f4.f5. G4. G
,, can be obtained as shown in the following equation. G3-D3'-D3 "· old · (1) G4-D41 · · · · · (2) G5D, /-D5" · · · correction amount calculated as described above (3) G3 ~ GEQ 2 is controlled based
on G 5 (FIGS. 8 to 8), and the frequency characteristic of GEQ 2 is as shown in FIG.
As a result, correction in the middle of the sound field frequency characteristic is performed
while canceling out the influence of the tone control circuit 1. After this, the generation of pink
noise is stopped (FIG. 8 811). FIG. 11 is a block diagram showing another embodiment of the
present invention; Adder 4. The pink noise generator 5, 7427, 7192 frequency characteristic
measurement circuit 10 is connected in the same manner as the device of FIG. However, in the
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present example, GEQ 2 is connected to the subsequent stage of adder 4, and these GEQ 2 and
control circuit 3. Adder 4. Pink noise generator5. A GEQ unit 11 is formed by the microphone
amplifier 9 and the frequency characteristic measurement circuit 10. The output of the control
amplifier unit 12 is supplied to the adder 4 as one person. The audio signal that has passed
through the main volume adjustment volume 13 and the balance volume 14 in the control
amplifier unit 12 is supplied to the tone control circuit 1, and the output of the tone control
circuit 1 is derived at the output end. These main volume adjustment volumes 13. The balance
volume 14 and the tone control circuit 1 are controlled by the control circuit 15. That is, the
control circuit 15 receives the supply of data for sound field correction from the control circuit 3
through the data communication path line 16 to control the frequency characteristics of the tone
control circuit 1 and a keyboard (not shown). The main volume adjustment volume 13. The
balance volume 14 and the tone control circuit 1 are controlled to perform volume adjustment,
left-right balance adjustment, and sound quality adjustment. Also in the above configuration, it is
apparent that the same operation as the device of FIG. 5 works. A table showing the
characteristics of the tone control circuit 1 is stored in the control circuit 15 in advance, and
when data for sound field correction is supplied to the control circuit 15, a midrange according
to the correction amount of the tone control circuit 1 is used. If data indicating gain is read out
from the table and supplied to control circuit 3, a single type of GEQ can be used regardless of
which of plural types of control amplifier units 12 having different frequency characteristics of
tone control circuit 1. A good sound field correction can be made by the unit 11. In the above
embodiment, the characteristics of the tone control circuit 1 are changed as shown in FIG. 6, but
if the characteristics of the tone control circuit 1 are not changed in the middle region as shown
in FIG. There is no need to consider the effect of 1.
Still, the characteristics of the tone control circuit 1 may be changed only in the direction of gain
gain. Although the number of bands of GEQ2 is seven in the above embodiment, the number of
bands of GEQ2 is not limited to seven. Although the GEQ 2 is able to enhance and attenuate the
low and high frequency components in the above embodiment, the GEQ 2 may be configured to
increase and attenuate only the mid frequency component. As described above, in the sound field
correction apparatus according to the present invention, for frequency components lower than
the predetermined frequency, the gain gradually changes in the predetermined direction at a
change rate corresponding to the supplied data as the frequency decreases. For frequency
components higher than the frequency, sound quality adjusting means having frequency
characteristics such that the gain gradually changes in a predetermined direction at a change
rate corresponding to the supplied data as the frequency increases is provided. Therefore, it is
possible to well correct a sound field having a frequency characteristic such as a car interior
sound field having a gradual change in a fixed direction in high and low frequencies.
[0002]
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Brief description of the drawings
[0003]
1 is a graph showing an example of sound field frequency characteristics, FIG. 2 is a graph
showing characteristics at the time of correction of ideal frequency characteristics correction
means, and FIG. 3 is characteristics at the time of correction of seven bands GEQ FIG. 4 is a graph
showing the characteristics of the sound field after correction by the conventional device, FIG. 5
is a block diagram showing an embodiment of the present invention, and FIG. A graph showing
an example of characteristics, FIG. 7 is a graph showing the characteristics of GEQ 2, FIG. 8 is a
flow chart showing the operation of the device of FIG. 5, and FIG. FIG. 10 is a graph showing
characteristics of GEQ 2 during correction, FIG. 11 is a graph showing another embodiment of
the present invention, and FIG. 12 is a graph showing another characteristic example of the tone
control circuit 1 It is.
Explanation of the code of the main part 1 ... tone control circuit 2 ... GEQ 3 ... control circuit 10 ...
frequency characteristic measurement circuit
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