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JPH09215085

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH09215085
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
audio reproduction apparatus for providing reproduction sound such as a stereo sound
reproduction apparatus, and to a method of correcting the listening frequency characteristics of
the audio reproduction apparatus.
[0002]
2. Description of the Related Art When listening to music or the like using a relatively large
sound reproducing apparatus called component stereo system, the listener listens to the
reproduced sound with his / her favorite sound quality, so a graphic equalizer or parametric
equalizer is used. The frequency characteristic correction means called "etc." adjusts the
frequency characteristic of the reproduced voice.
[0003]
In this case, the listener needs to adjust the frequency characteristics in consideration of the
characteristics of the sound reproduction device and the speaker, the state of the room in which
the speaker is installed, the installation position and the listening position of the speaker, and the
like.
[0004]
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By the way, when a large luggage is carried into a room in which a speaker is installed, the
positional relationship between the speaker and the listener changes, and the listening
environment or the listening conditions change, the reproduced voice becomes Due to the
influence of this change, the frequency characteristic at the listener's ear changes.
In this case, the listener can not hear the reproduced sound with the desired sound quality.
[0005]
For this reason, every time the listening environment or the listening conditions change, the
listener needs to operate the equalizer to adjust the sound quality of the reproduced sound again.
However, it is very bothersome to adjust the sound quality often.
[0006]
Also, the change in the frequency characteristics of the reproduced sound at the listener's ear can
only be perceived by the listener in his own hearing. For this reason, the adjustment work of the
equalizer takes time and effort because it is performed by listening to one's own hearing while
listening to the reproduced sound.
[0007]
In view of the above, the present invention provides an audio reproduction apparatus and an
audio listening frequency characteristic correction method capable of easily providing
reproduced audio of a sound quality preferred by the listener even when the listening
environment or the listening conditions change. The purpose is
[0008]
SUMMARY OF THE INVENTION In order to solve the above problems, the sound reproducing
apparatus according to the present invention comprises means for generating a test signal which
can be regarded as having a flat frequency characteristic, and the test signal emitted from a
speaker. A microphone for picking up the sound, an analysis means for frequency analysis of an
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audio signal from the microphone, a filter circuit for controlling frequency characteristics of the
audio signal, and a parameter to be given to the filter circuit from a frequency analysis result
from the analysis means And means for calculating so that the frequency characteristic of the
output voice signal of the filter circuit becomes flat at the listening position, and means for
holding the calculation result of the calculating means and providing the result to the filter
circuit. It is characterized by
[0009]
According to the sound reproducing apparatus according to the present invention, the test signal
emitted from the speaker is collected by the microphone and subjected to frequency analysis.
As a result, the transfer characteristic of the reproduced sound from the speaker to the
microphone is acquired.
Based on this transfer characteristic, parameters to be set in the filter circuit are obtained by
calculation. By this parameter, the filter circuit is made to have a frequency characteristic
opposite to the transfer characteristic.
[0010]
The reproduction characteristic outputted through the filter circuit cancels the transfer
characteristic, and the frequency characteristic of the reproduction sound at the position where
the microphone picks up the test signal is made flat.
[0011]
In the state where the frequency characteristic is flat, it is also easy to correct to a desired
frequency characteristic by using the above-mentioned equalizer.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the sound reproducing
apparatus and the listening frequency characteristic correction method according to the present
invention will be described below with reference to the drawings.
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[0013]
FIG. 1 is a block diagram for explaining an embodiment in the case where the sound reproducing
apparatus according to the present invention is applied to a so-called pre-main amplifier of a
stereo sound reproducing apparatus.
Although the pre-main amplifier of this embodiment has reproduction paths for audio signals of
the left and right two channels, one of the channels is shown in FIG. 1 for the sake of simplicity.
[0014]
An audio signal from, for example, a cassette deck unit or a CD (compact disc) player unit of a
stereo sound reproducing apparatus is supplied to an A / D conversion circuit 2 through an input
terminal 1.
The A / D conversion circuit 2 converts an input analog audio signal into a digital audio signal
and supplies the digital audio signal to the filter circuit 3.
[0015]
The filter circuit 3 is configured as a DSP (digital signal processor) in this example.
As described later, the filter circuit 3 receives the supply of the control signal formed in the
control circuit 100 in accordance with the set parameters and the instruction of the listener to
control the frequency characteristic of the audio signal, thereby Form an audio signal of desired
sound quality. The audio signal from the filter circuit 3 is supplied to the input terminal a of the
switch circuit 4, and is supplied to the D / A conversion circuit 5 through the switch circuit 4.
[0016]
The D / A conversion circuit 5 converts the digital audio signal into an analog audio signal and
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supplies the analog audio signal to the power amplifier 6. The power amplifier 6 amplifies the
audio signal to a predetermined level and supplies this to the speaker 20 via the output terminal
7. As a result, from the speaker 20, the reproduced sound with the sound quality desired by the
listener is emitted.
[0017]
In this embodiment, the control circuit 100 is configured as a microcomputer (not shown) having
a CPU, a ROM, and a RAM. Then, a control signal is formed based on instruction information or
the like input via the key operation unit 101 that receives an instruction input from the listener,
and is supplied to the related units. Thus, processing according to the instruction of the listener
can be performed by the pre-main amplifier of this embodiment.
[0018]
Then, as described above, the pre-main amplifier of this embodiment has the frequency
characteristic of the reproduced voice at the position where the listener listens to the reproduced
voice (hereinafter referred to as the listening position) even if the listening environment or the
listening conditions change. In order to make it flat, it has the following composition.
[0019]
That is, as shown in FIG. 1, the pre-main amplifier of this embodiment includes a test signal
oscillator 8, a microphone 9, an input terminal 10 of an audio signal from the microphone 9, an
A / D conversion circuit 11, a frequency analysis circuit 12, coefficients. A calculation circuit 13
is provided.
Further, although not shown, the key operation unit 101 includes a test key. The frequency
analysis circuit 12 and the coefficient calculation circuit 13 can be realized by software of a
microcomputer including the control circuit 100.
[0020]
The test signal oscillator 8 generates a test signal for detecting the transfer characteristic of the
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audio signal from the speaker 20 to the listening position. In this embodiment, TSP (Time Stretch
Pules) waves are used as test signals. TSP waves are used when determining various frequency
characteristics and phase characteristics, etc., with a constant level, wide frequency
characteristics, and not single phase characteristics.
[0021]
In this embodiment, the test signal oscillator 8 is configured as a ROM in which digitized TSP
waves are stored. The TSP wave from the test signal oscillator 8 is supplied to the input end b of
the switch circuit 4 described above.
[0022]
In this embodiment, the switch circuit 4 is replaced by a switching control signal from the control
circuit 100. The switch circuit 4 is normally switched to the input end a side, and is switched to
the input end b side when the test key of the key operation unit 101 is turned on. Then, the
switch circuit 4 is switched to the input end b side, and then switched to the input end a side by
the control of the control circuit 100 when the processing to flatten the frequency characteristic
at the listening position to be described later ends.
[0023]
When the test key of the key operation unit 101 is turned on, a signal indicating this is notified
from the key operation unit 101 to the control circuit 100. Thus, the control circuit 100 activates
the test signal oscillator 8, the frequency analysis circuit 12, and the coefficient calculation
circuit 13. Then, the TSP wave from the test signal oscillator 8 is supplied to the speaker 20 via
the switch circuit 4, the D / A conversion circuit 5, and the power amplifier 6, and the test voice
by the TSP wave is emitted.
[0024]
At this time, the microphone 9 is disposed at the listening position, and picks up the test sound
emitted from the speaker 20. The collected test voice is converted into a digital signal in the A /
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D conversion circuit 11 and supplied to the frequency analysis circuit 12.
[0025]
The frequency analysis circuit 12 performs orthogonal transformation by, for example, FFT (Fast
Fourier Transform), performs spectrum analysis of the collected test speech, and obtains
frequency characteristics.
[0026]
This frequency characteristic indicates the transfer characteristic of the reproduced sound from
the speaker 20 to the listening position, and indicates how much the frequency of the test sound
whose level is fixed (flat) changes at the listening position. .
Then, the frequency characteristic at the listening position as the analysis result is notified to the
coefficient calculation circuit 13.
[0027]
The coefficient calculation circuit 13 calculates a parameter for giving the reverse frequency
characteristic to the above-mentioned filter circuit 3 based on the notified frequency
characteristic. Then, the obtained parameter is supplied to the filter circuit 3 and set.
[0028]
When parameters are set in the filter circuit 3, the control circuit 100 switches the switch circuit
4 to the input end a side.
[0029]
Therefore, the input sound from the input terminal 1 is supplied to the speaker 20 through the
filter circuit 3 set to the reverse frequency characteristic as described above and emitted.
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In this case, since the parameter is set so that the filter circuit 3 has the inverse characteristic of
the frequency characteristic at the listening position, the reproduction sound emitted from the
speaker 20 is transmitted from the speaker 20 to the listening position. The characteristic is
canceled. Thereby, the frequency characteristic of the reproduced sound from the speaker 20 at
the listening position becomes flat.
[0030]
As described above, the listener can arrange the microphone 9 at the listening position and turn
on the test key to flatten the frequency characteristic at the listening position.
[0031]
As described above, after the frequency characteristic is made flat, it is also easy to obtain
desired characteristics by the graphic equalizer and the parametric equalizer.
[0032]
The process for flattening the frequency characteristic at the listening position in the pre-main
amplifier of this embodiment configured as described above will be further described using the
flowchart of FIG.
[0033]
The process shown in the flowchart of FIG. 2 is repeatedly executed in the control circuit 100
each time a key is operated by the key operation unit 101 after the pre-main amplifier is
powered on.
That is, first, the control circuit 100 determines whether the test key has been operated by the
listener (step 201).
[0034]
If the operation key is not the test key, other processing, for example, processing such as sound
quality adjustment according to the instruction of the listener is performed (step 210), and this
routine is ended.
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[0035]
When it is determined in the determination process of step 201 that the test key is turned on, the
switch circuit 4 is switched to the input end b side, and each part is controlled as described above
to control the frequency characteristics of the audio signal at the listening position. Start
processing to flatten (step 202).
[0036]
That is, when the switch circuit 4 is switched to the input end b side, a test voice corresponding
to the TSP wave is emitted and collected by the microphone 9 set at the listening position.
The collected test voice is brought into operation with the frequency analysis circuit 12 (step
203).
[0037]
When the test speech is taken, the frequency analysis circuit 12 is then controlled to analyze the
frequency of the test speech (step 204).
The analysis result in the frequency analysis circuit 12 is the transfer characteristic of the audio
signal from the speaker 20 to the listening position.
Then, the coefficient calculation circuit 13 receiving this analysis result calculates a parameter
for giving the filter circuit 3 the reverse characteristic of the transfer characteristic (step 205).
[0038]
Next, the control circuit 100 completes the calculation in the coefficient calculation circuit 13
and determines whether or not the parameter has been obtained (step 206). If the calculation has
not been completed yet, the control circuit 100 enters a waiting state.
[0039]
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If it is determined in the determination process of step 206 that the calculation is completed, the
obtained parameter is supplied to the filter circuit 3 and is set (step 207).
After that, the switch circuit 4 is returned to the input end a side (step 208), so that the audio
signal from the filter circuit 3 is emitted.
This is the end of the routine.
[0040]
As described above, since the inverse characteristic of the transfer characteristic from the
speaker 20 to the listening position is set in the filter circuit 3, when the audio signal is emitted
from the speaker 20, the reproduced voice whose transfer characteristic has already been
canceled. As the sound is emitted, the frequency characteristic of the reproduced sound at the
listening position becomes flat.
[0041]
In the above embodiment, one of the audio reproduction paths having two channels has been
described, but the frequency characteristic of the reproduced speech emitted from the other
speaker can be listened to by similarly configuring the other channel. In position, it can be flat in
character.
[0042]
In this case, the input terminal 1 for audio signal, the A / D conversion circuit 2, the filter circuit
3, the switch circuit 4, the D / A conversion circuit 5, the power amplifier 6, the output terminal
7 and the speaker 20 are separate for each channel. Although the control circuit 100, the key
operation unit 101, the frequency analysis circuit 12, the coefficient calculation circuit 13, and
the test signal oscillator 8 can be shared by two channels.
[0043]
Further, in the above embodiment, since the TSP wave is used as the test signal, the phase
characteristic of the reproduced voice at the listening position is also made to be the desired
good characteristic in the same manner as the frequency characteristic. Can.
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In this case, parameters for adjusting the phase characteristic are set in the filter circuit 3 and
the phase of each frequency is adjusted.
[0044]
Further, in the above embodiment, although the case where the sound reproducing apparatus
according to the present invention is applied to the pre-main amplifier of the stereo sound
reproducing apparatus has been described, not only such pre-main amplifier but also cassette
tape recorders and speaker systems The present invention can be applied to a sound
reproduction apparatus that provides reproduction sound.
[0045]
The test signal is not limited to the TSP wave, but may be a signal having a constant level and
wide frequency characteristics.
[0046]
In the above embodiment, by turning on the test key of the key operation unit 101, the control
circuit 100 automatically measures the frequency characteristic of the listening position and sets
the parameter of the filter. However, the switch circuit 4 may be used as a switch key to a test
mode by manual operation, and the switch circuit 4 may be switched to the input terminal b side
for a predetermined time to perform measurement of frequency characteristics and parameter
setting.
[0047]
As described above, according to the sound reproducing apparatus and the listening frequency
characteristic correction method of the present invention, the frequency characteristic of the
reproduced voice at the listening position is flat even when the listening environment or the
listening conditions change. Can be
[0048]
Then, by changing the equalizer characteristics after changing the frequency characteristics to be
flat, even when the listening position is changed, the listener can easily adjust the sound quality
to his / her preference and listen to the reproduced voice. .
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[0049]
The effect is particularly great if the microphone is set near the ear of the listener.
[0050]
Brief description of the drawings
[0051]
1 is a block diagram for explaining an embodiment of the sound reproduction apparatus
according to the present invention.
[0052]
2 is a flow chart for explaining the process of correcting the frequency characteristic of the
reproduced sound at the listening position in the sound reproducing apparatus according to the
embodiment of the present invention.
[0053]
Explanation of sign
[0054]
DESCRIPTION OF SYMBOLS 1 ... Input terminal, 2 ... A / D conversion circuit, 3 ... Filter circuit
(DSP), 4 ... Switch circuit, 5 ... D / A conversion circuit, 6 ... Power amplifier, 7 ... Output terminal,
8 ... Test signal oscillator, 9: Microphone, 10: Input terminal, 11: A / D conversion circuit, 12:
Frequency analysis circuit, 13: Coefficient calculation circuit, 20: Speaker, 100: Control circuit,
101: Key operation unit
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