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JP2006197076

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DESCRIPTION JP2006197076
PROBLEM TO BE SOLVED: To provide a loudspeaker capable of effectively preventing howling.
SOLUTION: A loudspeaker apparatus 1 connected to a microphone 2 and a speaker 3, which
amplifies a speech signal and inputs the same to the loudspeaker 3; a speech circuit unit 6, 8;
The adaptive filter 92 has a filter coefficient that simulates a feedback transfer system from the
speaker 3 to the microphone 2 based on the signal and has an adaptive filter 92, and the
microphone signal is a simulation signal obtained by processing an audio signal input to the
speaker 3 by the adaptive filter 92. Howling canceller 9 supplies residual signals, which are
subtracted from the audio signal input from Sb, to loudspeaker circuits 6, 8; internal sound
source 5 generating audio signal and inputting it to speaker 3; audio signal input from
microphone 2 In addition to the audio signal returned from the speaker 3, it is determined
whether the audio signal input from the external sound source is included or not, according to
the determination result. And sound source determination means 10 for controlling updating of
the filter coefficient of the response filter 92. [Selected figure] Figure 1
Loudspeaker
[0001]
The present invention relates to a loudspeaker having a howling canceller for preventing
howling.
[0002]
The loudspeaker amplifies the audio signal input from the microphone and inputs it to the
speaker. In this loudspeaker, a closed loop is formed in the path from the speaker to the
microphone, and the loudspeaker outputs and is input to the microphone It is well known that
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howling occurs when the feedback sound signal is repeatedly amplified.
[0003]
In order to prevent such feedback, it has been proposed in the prior art to use an adaptive filter
for generating a simulation signal simulated to a feedback sound signal and using a howling
canceller for removing the simulation signal from the input signal from the microphone for a
loudspeaker. (See Non-Patent Document 1).
In this howling canceller, a signal input to the speaker is input to the delay unit, and this signal is
delayed by the delay unit by a delay time corresponding to the delay time from the speaker to
the microphone.
By performing a convolution operation of the delayed signal with an adaptive filter coefficient, a
simulation signal is generated by the adaptive filter. Then, a residual signal obtained by removing
the simulation signal from the input signal from the microphone by the addition unit is output to
the amplification unit. Then, the residual signal amplified by the amplification unit is input to the
speaker and emitted from the speaker. Here, in the adaptive filter, the residual signal is input as a
reference signal, and the adaptive filter coefficients are calculated using a known adaptive
algorithm (for example, LMS (Least Mean Square) algorithm) such that the residual signal is
minimized. Will be updated. Thus, howling is prevented by approximating the simulated signal to
the feedback sound signal.
[0004]
Also, in a karaoke apparatus as a loudspeaker apparatus, correlation calculation is performed
between a sound signal from a sound source such as a CD and an input signal from a microphone
to obtain a correlation function of a feedback transfer system from a speaker to the microphone.
It is known to monitor the degree of risk of In this karaoke apparatus, when the risk of howling
occurs is higher than a predetermined level, the danger is notified to the user, or the gain of a
frequency with a high risk of howling occurs is lowered (for example, Patent Document 1) See).
Inazumi, Imai, Konishi: "Howling prevention of a loudspeaker system using LMS algorithm",
Proceedings of the Acoustical Society of Japan pp. 417-418 (1991, 3) JP-A-8-33091
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[0005]
In the conventional howling canceller using an adaptive filter, as described above, the adaptive
filter coefficient is calculated using the residual signal so as to minimize the error between the
simulation signal and the feedback sound signal, thereby using the simulation signal as the
feedback sound. Close to the signal. However, since the speech signal input from the microphone
includes the speech signal of the speaker, the residual signal input as a reference to the adaptive
filter includes the speech signal as well as the difference between the feedback sound signal and
the simulation signal. Be When such a residual signal is used as a reference, it is difficult to
improve the calculation accuracy for calculating a simulation signal that approximates the
feedback sound signal. For this reason, there was a case where howling could not be prevented
sufficiently.
[0006]
On the other hand, the conventional karaoke apparatus that monitors the risk of howling can not
prevent howling because it is configured only to notify the degree of risk of howling. Further, in
the configuration in which the gain of the frequency having the risk of howling is lowered, the
sound quality of the reproduction sound emitted from the speaker may be deteriorated.
[0007]
Then, in order to solve the said subject, an object of this invention is to provide the loud-speaking
apparatus which can prevent howling more effectively.
[0008]
In order to solve the above-mentioned subject, the following means are adopted in the present
invention.
[0009]
(1) The present invention is a loudspeaker system connected to a microphone and a speaker,
wherein the loudspeaker circuit amplifies a speech signal and inputs the speech signal to the
loudspeaker, and the loudspeaker based on the speech signal and residual signal inputted to the
loudspeaker Has an adaptive filter that sets up a filter coefficient that simulates a feedback
transfer system from a speaker to a microphone, and a residual signal obtained by subtracting a
simulation signal obtained by processing an audio signal input to a speaker by an adaptive filter
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from an audio signal input from a microphone Audio signal input from an external sound source
in addition to the audio signal fed back from the speaker to the internal sound source generating
the audio signal and input to the speaker, and the audio signal input from the microphone Is
determined, and updating of the filter coefficient of the adaptive filter is controlled according to
the determination result. A source determination means, characterized in that it comprises a.
[0010]
When a signal is input to the microphone, the simulation signal is subtracted from the input
signal by the howling canceler, and is supplied as a residual signal to the loudspeaker circuit unit,
amplified by the loudspeaker circuit unit, and input to the speaker, from the loudspeaker It is
emitted.
Here, the simulated signal is processed by an adaptive filter.
The adaptive filter is for self setting the filter coefficients simulating the feedback transfer system
from the speaker to the microphone based on the audio signal and the residual signal input to
the speaker. The feedback sound to be fed back is simulated, and howling is prevented by
subtracting the simulation signal from the input signal.
[0011]
Here, the residual signal is an ideal state in order to accurately identify the filter coefficient that
only the difference between the feedback sound signal and the simulation signal is included.
Therefore, when the signal input from the external sound source to the microphone includes the
audio signal input from the external sound source, the residual signal whose audio signal is input
to the adaptive filter is the difference between the feedback sound signal and the simulation
signal. In addition, since it is included, it is not an ideal state in order to perform identification of
an adaptive filter precisely.
[0012]
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In the above configuration, it is determined by the external sound source determination unit
whether or not the audio signal input from the external sound source is included in addition to
the audio signal returned from the speaker, and the filter coefficient of the adaptive filter is
updated according to the determination result. It is controlled. Therefore, it is possible to update
the adaptive filter while reflecting whether or not it is an ideal state in order to accurately
identify the adaptive filter, and it becomes possible to preferably identify the adaptive filter.
[0013]
For example, when it is determined that the sound source determination means does not include
an audio signal input from the external sound source other than the audio signal returned from
the speaker, the source of the adaptive filter is compared with the case where the determination
is not performed. By adopting a configuration that increases the adaptation speed, it is possible
to perform adaptation at a high adaptation speed when the adaptation filter is in an ideal state
for accurate identification of the adaptive filter, which makes it possible to use filter coefficients.
It is possible to improve the adaptation accuracy of
[0014]
(2) In the above-described loudspeaker system, the adaptive filter calculates an adaptive filter
coefficient by adding the product of the pre-updated adaptive filter coefficient and the forgetting
factor and the product of the correction amount and the step size. When it is determined that the
calculated adaptive filter coefficient is updated and the sound source determination unit does not
include the sound signal input from the external sound source in the sound signal input from the
microphone, the sound source determination unit does not perform the determination. In
comparison, the value of the step size is set larger.
[0015]
Here, the larger the step size, the more the correction amount is reflected on the adaptive filter
coefficient.
Therefore, the larger the step size, the faster the adaptation speed of the adaptive filter.
According to the above configuration, when it is determined that the audio signal input from the
microphone does not include the audio signal input from the external sound source, a step size
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larger in value is used as compared with the case where the determination is not performed. The
adaptive filter coefficient is calculated. For this reason, in such a case, the adaptation speed of the
adaptive filter is faster than when it is determined that the audio signal from the external sound
source is included in the audio signal input from the microphone.
[0016]
(3) The above-described loudspeaker apparatus is characterized by being a karaoke apparatus in
which a performance processing unit for playing a karaoke song is an internal sound source and
a singer of the singer is an external sound source. According to this configuration, in the karaoke
apparatus, it is possible to reflect in the update of the adaptive filter whether the audio signal
input from the microphone includes the audio signal of the singer's singing.
[0017]
(4) In the above-described karaoke apparatus, the performance processing unit outputs, to the
display unit, lyric data for displaying the lyrics in accordance with the progress of the karaoke
music, and the sound source determination unit is the lyrics data It is characterized in that it is
determined that the voice signal inputted from the microphone includes the voice signal of the
singing of the singer who is the external sound source when outputting the voice signal. Here,
since the singer sings while watching the usually displayed lyrics, if the lyric data for displaying
the lyrics in accordance with the progress of the karaoke song is not output to the display unit,
the singing person's singing There is a high probability that the audio signal is not included in
the audio signal input from the microphone. In the configuration of the present invention, the
sound source determination unit determines that the singing voice signal is included in the audio
signal input from the microphone when the lyric data corresponding to the accompaniment
sound signal input to the speaker is output to the display unit. When it is determined that the
lyrics data is not output to the display unit, it is determined that the voice signal of singing is not
included in the voice signal input from the microphone. Therefore, it is possible to determine
whether the voice signal of singing is included in the voice signal input from the microphone,
using a simple process of determining the presence or absence of the output of the lyric data to
the display unit.
[0018]
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(5) In the above-described loudspeaker system, the sound source determination unit determines
that the signal level of the audio signal input from the microphone exceeds the predetermined
level even when the performance processing unit does not output the lyric data. If the voice
signal is present, it is determined that the voice signal input from the microphone includes the
voice signal of the song. According to this configuration, even if the lyric data is not output to the
display unit, if the signal level of the signal input from the microphone exceeds the
predetermined level, the singing voice signal is input from the microphone Is determined to be
included in Even if the lyrics are not displayed, for example, depending on the singer, the voice
may be input to the microphone by singing or the listener of the singing around the singer
having a conversation. In this case, it is not an ideal state in order to perform identification of the
adaptive filter with high accuracy as in the case where the voice of singing is input. By
determining that there is an input of an audio signal of singing when the audio signal input from
the microphone exceeds a predetermined level, such a case can be handled in the same way as
when there is an input of an audio signal of singing. . In addition, since it is sufficient to
determine the signal level only when the lyric data is not output, the processing load is relatively
light and it is possible to determine the presence or absence of the singing voice signal.
[0019]
According to the present invention, the external sound source determination unit determines
whether the audio signal from the external sound source is included in the signal input from the
microphone, and the adaptive filter is updated based on the determination result. Here, when the
audio signal from the external sound source is not included in the signal input from the
microphone, the residual signal does not include the audio signal from the external sound source
and substantially approaches the difference between the feedback sound signal and the
simulation signal. Therefore, the residual signal is in an ideal state to accurately identify the
adaptive filter. According to the present invention, the adaptive filter can be updated by
reflecting whether or not it is an ideal state in order to accurately identify the adaptive filter, and
adaptive filter identification can be suitably performed. This can provide a loudspeaker that can
more effectively prevent howling.
[0020]
Therefore, in the present embodiment, the adaptive voice filter is positively identified during a
period in which the singing voice signal is not input to the microphone, that is, a period ideal for
accurately identifying the adaptive filter. While the singing voice signal is input from the
microphone, the degree of identification is lowered (the value of the step size is lowered).
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[0021]
First Embodiment FIG. 1 is a block diagram showing a schematic configuration of a karaoke
apparatus 1 according to a first embodiment of the present invention.
The karaoke apparatus 1 is connected to the microphone 2, the speaker 3 and the display unit 4
disposed indoors, and the performance processing unit 5, the processing unit 6, the adding unit
7, the audio reproduction processing unit 8, the howling canceller 9 And a singing voice judging
unit 10, and an image reproduction processing unit 11.
[0022]
The microphone 2 inputs sound from the outside of the device as a microphone input signal. The
microphone input signal is A / D converted by an A / D (Analog / Digital) converter (not shown).
The A / D converted signal is output to the processing unit 6 through the howling canceller 9.
The sound input to the microphone 2 includes a singing sound when the singer (corresponding
to an external sound source) sings, and a singing voice signal obtained by converting the singing
sound into an electric signal (a voice signal input from the external sound source Is included in
the input signal.
[0023]
The speaker 3 converts an analog audio signal input from the karaoke apparatus 1 into a sound
and emits the sound. The display unit 4 is realized by, for example, a cathode ray tube (CRT)
display, a liquid crystal display (LCD), or the like.
[0024]
The performance processing unit 5 is realized by a CPU (Central Processing Unit), a memory, a
storage unit such as a hard disk, and executes a control program for karaoke performance.
Specifically, the performance processing unit 5 stores karaoke accompaniment sound data D1
and lyric data D2. The performance processing unit 5 corresponds to the internal sound source
of the present invention, generates the karaoke accompaniment sound signal based on the
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karaoke accompaniment sound data D1 and sequentially outputs it to the addition unit 7, and
outputs the karaoke accompaniment sound signal. In synchronization, the lyrics data D2 are
sequentially output to the image reproduction processing unit 11. The karaoke accompaniment
sound data D1 is data for reproducing the accompaniment sound of the karaoke song. The lyric
data D2 is data for displaying the lyrics of the karaoke song played using the karaoke
accompaniment sound signal, thereby displaying the lyrics on the display unit 4 and changing
the character color according to the progress of the karaoke accompaniment song Go on. That is,
the lyric data D2 includes character data of the lyric and character color change data.
[0025]
The processing unit 6 includes an equalizer and the like, adjusts the frequency characteristic of
the signal input to the microphone input signal input through the A / D converter (not shown) howling canceller 9, or digitally It performs signal processing such as amplification.
[0026]
The addition unit 7 executes processing (mixing processing) of mixing the karaoke
accompaniment sound signal output from the performance processing unit 5 with the signal
processed by the processing unit 6.
The adder 7 outputs the audio signal (synthetic audio signal x (k)) subjected to the mixing
process to the audio reproduction processor 8 and the howling canceller 9.
[0027]
The audio reproduction processing unit 8 performs D / A (Digital / Analog) conversion on the
synthesized audio signal x (k) input from the addition unit 7, amplifies the analog audio signal
after this conversion, and Enter in The processing unit 6 and the voice reproduction processing
unit 8 constitute a loudspeaker circuit unit of the present invention.
[0028]
The howling canceller 9 includes a delay unit 91, an adaptive filter 92, and an addition unit 93.
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The delay unit 91 and the adaptive filter 92 simulate a feedback transmission system 100 which
is an acoustic transmission path from the speaker 3 to the microphone 2. That is, the delay unit
91 simulates the delay time τ of the feedback sound through the feedback transfer system 100,
and the adaptive filter 92 simulates the transfer function that is the sound propagation
characteristic of the feedback transfer system 100.
[0029]
Specifically, the delay unit 91 delays the input synthetic speech signal x (k) by the delay time τ,
and outputs the delayed synthetic speech signal x (k−τ) to the adaptive filter 92. The adaptive
filter 92 includes a digital filter 92a (typically, an FIR (Finite Impulse Response Filter)) and a filter
coefficient calculator 92b that determines the filter coefficient of the digital filter 92a. The digital
filter 92a generates a simulation signal do (k) by performing convolution operation of the input
synthetic speech signal x (k−τ) with filter coefficients. The digital filter 92a outputs the
generated simulation signal do (k) to the addition unit 93.
[0030]
The filter coefficient calculation unit 92 b estimates the transfer function of the feedback transfer
system 100 based on the residual signal, which is a signal output from the addition unit 93, and
the synthetic speech signal x (k−τ) input from the delay unit 91. Then, the filter coefficients are
self-set by correcting (simulating) the filter coefficients of the digital filter 92a in accordance with
this transfer function. This correction is performed so that the residual signal is as small as
possible, and is performed every predetermined time interval (for example, every several
microseconds to several hundreds of microseconds). The estimation of the transfer function of
the feedback transfer system 100 and the correction of the filter coefficients are performed using
an adaptive algorithm (described in detail later). As an adaptive algorithm, for example, a
learning identification method, an LMS method, a projection method, an RLS method or the like
can be applied. As described above, the synthetic speech signal x (k) is supplied to the delay unit
91-adaptive filter 92 in parallel with the output from the speaker 3, so that the simulation signal
do (k) is output from the adaptive filter 92. Can be approximated to the feedback sound signal d
(k).
[0031]
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The adder unit 93 receives the simulation signal do (k) and the microphone input signal. The
addition unit 93 outputs a residual signal obtained by removing the simulation signal do (k) from
the microphone input signal to the processing unit 6, and outputs the residual signal as a
reference signal to the filter coefficient calculation unit 92b. By this, it is possible to remove the
feedback component from the microphone input signal, and it is possible to prevent howling.
[0032]
The singing voice judging unit 10 is realized, for example, by a judgment program executed by a
CPU (Central Processing Unit) or the like, and executes a process (judging process) of judging
whether the microphone signal includes a singing voice signal. is there. The singing voice
determining unit 10 determines whether the lyrics data D2 corresponding to the karaoke
accompaniment sound signal output to the adding unit 7 is output from the performance
processing unit 5 to the display unit 4 via the image reproduction processing unit 11. It detects
and when the lyric data D2 is output, it determines with a singing voice signal being contained in
a microphone input signal. Usually, the singer sings while watching the displayed lyrics.
Therefore, when there is no output of the lyric data D2 corresponding to the karaoke
accompaniment sound signal, there is a high possibility that the singing voice signal is not
inputted to the microphone 2, and it can be determined that the singing voice signal is not
included in the microphone input signal.
[0033]
The singing voice determination unit 10 controls the update of the adaptive filter 92 based on
the determination result. When the singing voice signal is not included in the microphone input
signal, the residual signal input to the filter coefficient calculating unit 92b does not include the
singing voice signal, and therefore the feedback sound signal d (k) and the simulation signal do
(k) It is close to the difference of Here, as the residual signal is closer to the difference between
the feedback sound signal d (k) and the simulation signal do (k), it is ideal to reduce the
identification error of the adaptive filter 92. When it is determined that the singing voice signal is
not included in the microphone input signal, the singing voice determination unit 10 raises the
degree of identification of the adaptive filter 92 as compared to the case where it is determined
to be included, and the adaptive filter 92 is positively implemented. Update the Therefore,
identification error can be reduced and identification of the adaptive filter 92 can be performed.
[0034]
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The image reproduction processing unit 11 includes, for example, a video memory, a video
processing circuit, etc., and the lyrics data D2 corresponding to the karaoke accompaniment
sound signal output to the addition unit 7 is input from the performance processing unit 5. The
image reproduction processing unit 11 generates a character pattern based on the lyric data D 2
output from the performance processing unit 5, and displays the lyrics synchronized with the
contents of the karaoke accompaniment emitted from the speaker 3 on the display unit 4. When
the background image corresponding to the lyric data D2 is stored in the performance
processing unit 5 and this background image is input from the performance processing unit 5,
the input background image is synthesized with the lyric data D2 Display a composite image.
[0035]
FIG. 2 is a block diagram showing the configuration of the filter coefficient calculation unit 92b
shown in FIG. 1 and the periphery thereof. The filter coefficient calculation unit 92 b includes a
pre-update filter coefficient acquisition unit 921, a forgetting coefficient multiplication unit 922,
a correction amount calculation unit 923, a step size multiplication unit 924, and an addition unit
925.
[0036]
The pre-update filter coefficient acquisition unit 921 stores the adaptive filter coefficient before
update, and outputs the pre-update adaptive filter coefficient to the forgetting factor
multiplication unit 922 at predetermined time intervals. The forgetting factor multiplication unit
922 multiplies the forgetting factor by the pre-update adaptive filter coefficient output from the
pre-update filter coefficient acquisition unit 921 and outputs the result to the adding unit 925.
[0037]
The correction amount calculation unit 923 calculates a correction amount from the residual
signal output from the addition unit 93 and the synthetic speech signal x (k−τ) output from the
delay unit 91 using a known adaptive algorithm. It is. The correction amount calculation unit 923
outputs the correction amount to the step size multiplication unit 924 every predetermined time
interval synchronized with the output interval of the pre-update filter coefficient acquisition unit
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921. The step size multiplication unit 924 performs multiplication of the input correction
amount and the step size, and outputs a value obtained by this multiplication to the addition unit
925.
[0038]
Here, the step size can be set to at least two types of values. As the step size, the smaller value is
set by the singing voice determination unit 10 when the singing voice determination unit 10
determines that the microphone input signal includes a singing voice signal. On the other hand,
when the singing voice determination unit 10 determines that the microphone input signal does
not include the singing voice signal, the singing voice determination unit 10 sets the larger value.
[0039]
The adding unit 925 adds the value output from the forgetting factor multiplying unit 922 and
the value output from the step size multiplying unit 924 to obtain an adaptive filter coefficient.
That is, the adaptive filter coefficient is obtained by adding a value obtained by multiplying the
adaptive filter coefficient before updating by the forgetting coefficient and a value obtained by
multiplying the correction amount obtained from the residual signal and the input signal by the
step size.
[0040]
As described above, the larger the step size is set, the more the correction amount is reflected,
and the adaptive filter coefficient is actively updated. Further, when it is determined by the
singing voice determination unit 10 that the microphone input signal does not include a singing
voice signal, the step size is set to a larger value than in the case where this determination is not
made. For this reason, if it is determined that the singing voice signal is not included in the
microphone input signal by the singing voice determination unit 10, that is, if it is in an ideal
state for suitably identifying the adaptive filter 92, The adaptive filter coefficient is updated.
[0041]
The addition unit 925 updates the value of the adaptive filter coefficient of the filter 92a with the
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calculated adaptive filter coefficient, and updates the value of the pre-update adaptive filter
coefficient stored in the pre-update filter coefficient acquisition unit 921.
[0042]
FIG. 3 is a flowchart showing an example of the determination process performed by the karaoke
apparatus 1 shown in FIG.
The present process is started, for example, when the singing voice judging unit 10 detects that
the karaoke accompaniment sound signal of the sound reproduction processing unit 8 is read out
to the adding unit 7. First, the singing voice judging unit 10 judges whether the lyrics data D2
corresponding to the outputted karaoke accompaniment sound signal is outputted from the
performance processing unit 5 to the display unit 4 (S1).
[0043]
When it is determined that the lyric data D2 corresponding to the output karaoke
accompaniment sound signal is output to the display unit 4 (YES in S1), the singing voice
determination unit 10 determines that the singing voice signal is a microphone input signal. It is
determined that it is included (S2). Thereafter, the singing voice judging unit 10 sets the step size
of the step size multiplying unit 924 to the smaller one (S3). Thereafter, the singing voice judging
unit 10 executes step 6 described later.
[0044]
On the other hand, when it is not determined that the lyrics data D2 corresponding to the
outputted karaoke accompaniment sound signal is outputted to the display unit 4 (NO in S1), the
singing voice judging unit 10 inputs the singing voice signal into the microphone It is determined
that the signal is not included (S4). Then, the singing voice determination unit 10 sets the step
size of the step size multiplication unit 924 to the larger one (S5).
[0045]
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By execution of this step S1, it is judged whether or not the lyric data D2 corresponding to the
outputted karaoke accompaniment sound signal is outputted to the display unit 4, and if the lyric
data D2 is outputted, the singing voice signal Is determined to be included in the microphone
input signal. When the lyrics data D2 is not output, it is determined that the singing voice signal
is not included in the microphone input signal. Usually, the singer sings while watching the
displayed lyrics, and when the lyrics data is not output to the display unit 4, there is no display of
the lyrics, so the singer sings Absent. Therefore, it is possible to determine with relatively high
accuracy whether the microphone input signal includes a singing voice signal by a simple
configuration that only determines whether the lyrics data D2 is output to the display unit 4. .
[0046]
Thereafter, the singing voice judging unit 10 judges whether the output of the karaoke
accompaniment sound signal has ended (S6). If it is not determined that the output of the
karaoke accompaniment sound signal has ended (NO in S6), the singing voice determination unit
10 returns the process to step S1, and if it is determined that the output of the karaoke
accompaniment sound signal has ended ( YES in S6), this processing ends.
[0047]
With this configuration, in the present embodiment, when it is determined that the singing voice
signal is included in the microphone input signal, the step size is set smaller than in the case
where the singing voice signal is not determined. Here, the larger the step size is set, the more
the component of the correction amount is reflected, the adaptive filter coefficient is updated,
and the adaptive filter 92 is positively updated (the adaptation speed of the adaptive filter is
faster). become.
[0048]
As described above, when the singing voice signal is not included in the input signal, the residual
signal input to the adaptive filter 92 as the reference signal is the feedback sound signal d (k)
and the simulation signal do (k). It is only a difference. Therefore, the residual signal is ideal for
calculating an adaptive filter coefficient for bringing the simulated signal do (k) close to the
feedback sound signal d (k), and the error in identification of the adaptive filter 92 should be
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reduced. Can. In this embodiment, the simulation signal do (k) can be brought close to the
feedback sound signal d (k) with high accuracy by actively updating the adaptive filter 92 in such
a case. This can enhance the howling prevention effect.
[0049]
Second Embodiment Hereinafter, a second embodiment of the present invention will be described
using FIGS. 1 and 4. In the first embodiment, when the lyrics data D2 corresponding to the
output karaoke accompaniment sound signal is not output to the display unit 4, the singing voice
determination unit 10 includes the singing voice signal in the microphone input signal. Although
it is not determined, in the second embodiment, even in such a case, if the microphone input
signal exceeds the predetermined level, it is determined that a singing voice signal is included.
[0050]
Referring to FIG. 1, a microphone input signal is output to singing voice determination unit 10 as
indicated by a broken arrow, and singing voice determination unit 10 uses the signal level of this
microphone input signal to make a singing voice signal as a microphone input signal. Determine
if it contains.
[0051]
FIG. 4 is a flowchart showing an example of the determination process according to the second
embodiment.
In the figure, steps in which the same process as the process shown in FIG. 3 is performed are
denoted by the same reference numerals. If it is not determined that the lyrics data D2
corresponding to the output karaoke accompaniment sound signal is output to the display unit 4
in step S1 (NO), the singing voice determination unit 10 determines that the signal level of the
microphone input signal is It is determined whether it is larger than the threshold (S11). If it is
determined that the signal level is greater than the threshold (YES in S11), it is determined in
step S2 that a singing voice signal is included in the microphone input signal, and thereafter, step
S3 and step S3 similar to the process shown in FIG. Step S6 is performed. On the other hand,
when it is not determined that the signal level is higher than the threshold (NO in S11), it is
determined in step S4 that the singing voice signal is not included in the microphone input
signal, and thereafter the step is the same as the process shown in FIG. S5 and step S6 are
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performed.
[0052]
With the above configuration, in the second embodiment, when it is not determined that the
lyrics data D2 corresponding to the output karaoke accompaniment sound signal is output from
the performance processing unit 5 to the display unit 4, the input signal level If is greater than
the threshold value, it is determined that the microphone input signal includes a singing voice
signal. Some singers may sing even if the lyrics are not displayed, or viewers around the singer
may speak loudly. In such a case, the microphone input signal includes the singing signal and the
speech signal of the speaking voice, which is not an ideal state for the adaptive filter 92 to be
accurately adapted. In the second embodiment, in this case, by setting the threshold so that the
microphone input signal exceeds the threshold, it is determined that the singing voice signal is
included in the microphone input signal, and the singing voice signal is included in the
microphone input signal. It can be handled in the same way as in By this, the identification
accuracy of the adaptive filter 92 can be further improved as compared with the first
embodiment.
[0053]
Then, only when the lyrics data D2 corresponding to the output karaoke accompaniment sound
signal is not output, the processing load is relatively light since the determination of the signal
level of the microphone input signal may be performed, and the singing voice signal is a
microphone input signal It can be determined whether it is included in
[0054]
The following modifications can be employed in the present embodiment.
[0055]
(1) In the above-described embodiment, only the step size is set so that the value differs
depending on whether the microphone input signal includes the singing voice signal or not, but
the forgetting factor is also set similarly in addition to the step size It may be configured as
In such a case, for example, two values of large and small can be set for the forgetting factor.
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When it is determined by the singing voice determination unit 10 that the microphone input
signal includes a singing voice signal, the singing voice determination unit 10 sets the larger
value. On the other hand, when it is determined by the singing voice determination unit 10 that
the microphone input signal does not include the singing voice signal, the smaller value is set. As
the forgetting factor is set larger, more filter factor components before updating are reflected,
and the adaptive filter factor is updated in a negative manner.
[0056]
(2) In the embodiment described above, although the same signal as the synthetic speech signal x
(k) outputted to the speech reproduction processor 8 is outputted to the delay unit 91, the
present invention is not limited to this. In the embodiment, the karaoke accompaniment sound
signal generated by the performance processing unit 5 is output to the howling canceller 9, but
the adding unit 7 is disposed on the rear side (speaker 3 side) of the howling canceller 9 and the
karaoke accompaniment signal is The speaker 3 may be made to emit sound without being input
to the howling canceller 9.
[0057]
(3) In the embodiment described above, the karaoke apparatus 1 is configured to externally
attach the microphone 2, the speaker 3 and the display unit 4, but may be integrally provided.
Further, in the present embodiment, the present invention is applied to the karaoke apparatus 1.
However, the present invention is not limited to this. For example, an audio signal is generated as
an internal sound source and input to a speaker like an audio device or an AV device. It may be a
loudspeaker having a function.
[0058]
(4) Further, the audio signal generated by the internal sound source of the performance
processing unit 5 or the like is not limited to the karaoke music accompaniment sound signal,
and if it is an audio signal generated inside the device, the performance sound of singing or
musical instrument, chorus sound Or the like. Further, the audio signal input from the external
sound source is not limited to the singing voice signal, and for example, the voice, the
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performance sound of a musical instrument (corresponding to the external sound source), the
audio generated by an audio device or an AV device (corresponding to the external sound source)
The voice signal may be any voice signal input through the microphone 2. In this case, since the
lyric data is not output to the display unit 4, for example, by comparing the signal level of the
microphone input signal with a threshold, the audio signal input from the external sound source
to the microphone 2 is the microphone input signal It should be determined that it is included in.
[0059]
(5) In the embodiment described above, when it is determined that the microphone input signal
does not include the singing voice signal, the step size is increased and the forgetting factor is
decreased as compared with the case where the microphone input signal is not determined.
Although the adaptation speed of the filter 92 is increased, the present invention is not limited to
this, and the updating interval of the adaptive filter 92 may be increased.
[0060]
(6) In this specification, it is determined whether the signal level of the microphone input signal
is larger than the threshold (larger than the threshold), but instead, the signal level of the
microphone input signal is higher than the threshold It may be determined whether it is "."
[0061]
It is a block diagram which shows schematic structure of the karaoke apparatus concerning the
1st Embodiment of this invention.
It is a block diagram which shows the filter coefficient calculation part shown in FIG. 1, and the
structure of the periphery of it.
It is a flowchart which shows an example of the determination processing which the karaoke
apparatus shown in FIG. 1 performs. It is a flowchart which shows an example of the
determination processing concerning 2nd Embodiment.
Explanation of sign
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[0062]
DESCRIPTION OF SYMBOLS 1 karaoke apparatus (corresponding to a loud speaker) 2
microphone 3 speaker 5 performance processing unit (corresponding to an internal sound
source) 9 howling canceller 92 adaptive filter 10 singing voice judging unit (an example of an
external sound source judging means) D2 lyric data do simulation signal d feedback Sound signal
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