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DESCRIPTION JP2018182480

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DESCRIPTION JP2018182480
Abstract [Problem] It is necessary to raise the volume when listening in an environment where
noise changes significantly. Depending on the noise, it is necessary to change not only the
volume but also the sound quality. The control system needs to know only the intensity of the
noise, since the reproduction sound corresponding to the increased volume is mixed into the
microphone for detecting the mixed sound in which the noise and the reproduction sound are
mixed. SOLUTION: A band division filter having the same characteristic is applied to each of a
mixed sound signal and a reproduction signal. Detect the maximum value of the time interval
from 200 mmsec to 1 second of each filter output. For each band, the difference between the
mixed sound signal and the reproduction signal, and the maximum value of the noise are
obtained. Apply the low speed attack time constant and the high speed release time constant to
the noise maximum value. With the obtained signal for each band, the gain of the reproduced
sound is corrected for each band. [Selected figure] Figure 1
Noise spectrum distribution detection method and noise volume control method
[0001]
The terms described in the claims are the same in the specification. For addition, + means
addition-means addition of sign inversion. Adaptive filter Stabilization of feedback loop Predictive
filter Sound propagation Noise properties of subway and aircraft cabins Vehicle structural
specifications and nature of driver's seat noise due to road surface condition and wind noise
traveling speed Statistical properties of acoustic signals No mutual Probability distribution of the
addition signal of two correlated signals. Probability distribution of each of the two uncorrelated
signals and the probability distribution of the added signal. Relationship between auditory noise
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and signal.
[0002]
Active noise canceller for earphones and headphones Active noise canceller for driver's seat
[0003]
SUMMARY OF THE INVENTION The present invention relates to a method of detecting a
maximum value of a noise signal and correcting a reproduction signal with the maximum value
of the noise signal.
There are multiple descriptions on how to calculate the amount of correction for the playback
sound, but none of them describes how to calculate the magnitude of the noise from the
synthetic sound of the noise and the playback sound and the playback sound. Although there is a
description of the analysis for each frequency band of the noise signal, regarding the analysis
result, the magnitude of the noise in the same band is calculated from both noise and the
synthetic sound of the noise and the reproduction signal, and the result is used to calculate There
is no description to control the playback sound of.
[0004]
The invention relates to a method of detecting a maximum value of a reproduction signal and
correcting the reproduction signal based on the maximum value and the magnitude of the
detected noise signal. The present invention relates to a method of controlling the magnitude of a
reproduced signal to match the intensity of the reproduced signal to the ambient noise. There is
no description that the magnitude of noise is calculated from both the signal where the noise and
the playback sound are mixed and the playback signal.
[0005]
The terms and symbols defined in the claims are the same in the specification. First, under strong
noise such as driving, commuting to the subway, in the passenger seat, etc., it is necessary to
increase the volume to listen to music, lectures and entertainment programs. Furthermore, in
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2
order to minimize the volume, it is necessary to change not only the volume but also the sound
quality. The microphone for detecting the sound wave in which the noise and the reproduced
sound are mixed is mixed with the reproduced sound as much as the volume is increased, which
becomes an unstable factor. To stabilize the control loop it is necessary to know the pure noise
maxima. Of course, it is necessary to detect a pure noise maximum value for anti-noise and tone
volume control.
[0006]
Second, in recent years, the control technology of sound field has been improved, and the
application products of the active noise canceller, which mutes noise in a specific area, are
coming to the market. However, achieving satisfactory performance in a strong noise
environment is difficult or requires a structure or cost that is not practical, and at the product
level, it must be within the range that can be achieved due to the relationship between
performance, cost and usability.
[0007]
Thirdly, when it is necessary to control the optimum sound quality according to the noise, it is
necessary to increase the sound volume according to the detected noise, but since the noise and
the reproduced sound are mixed, the reproduced sound is detected from the detected mixed
volume The volume of the must be deducted. Since the relationship between the volume of both
the reproduced sound and the noise changes relatively randomly with time, it is difficult to
accurately estimate the volume of the noise in the mixed sound.
[0008]
The first relates to a method of determining the maximum value of noise, and to a method of
estimating the maximum amplitude of noise from a signal in which noise and a reproduction
signal are mixed. Table 1 below is a sample of calculated values showing that it is possible to
accurately detect the maximum value of the noise from a mixture of the noise and the
reproduction signal. Table 1 relates to uncorrelated sine waves. The probability density near the
maximum amplitude obtained by adding the two uncorrelated signals to each other can be
estimated that the value obtained by adding the maximum values of the original two signals is
generated by the product of the probability densities near the both maximum amplitudes. .
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[0009]
Table 1 shows the relationship between two mutually uncorrelated sine waves (X) and sine waves
(Y) and the signal (X + Y) which is the addition signal of them. Table 1 shows the values
calculated for the evaluation items of each horizontal axis at every 5 degrees of angle. The
evaluation range is 2160 degrees or 6 cycles for the sine wave X. Indicates that the difference
between the maximum value of sine wave (X) and the maximum value of sine wave (X + Y) is
equal to the difference of the maximum value of sine wave (Y). Table 1 is a sampling of the
instantaneous values every 5 degrees of angle, so there is some degradation in accuracy, but it is
still quite exactly in line with the theoretical values. The sine wave (X) and the sine wave (Y) have
a frequency of 1 vs. root (2). Regarding the evaluation items on the horizontal axis, PK ()
indicates the maximum amplitude of the signal in (), AVG () indicates the average value of the
signal in (), and RMS () indicates the effective value of the signal in (). The vertical axis shows the
result in the case where the maximum amplitude PK (Y) of the sine wave (Y) is changed from
0.01 times to 30 times the maximum amplitude PK (X) of X. Here, assuming that sine wave (X) is
reproduction sound and sine wave (Y) is noise, the value in the column of PK (X + Y) -PK (X) is
less than the maximum value of PK (Y) by 0.2%. It shows that it agrees within the error of. The
calculated values are obtained by sampling the sine wave (X) at every 5 degrees of 360 degrees,
and calculating the range of 2160 degrees, that is, the range of 6 periods. 6The cycle is a time
interval of 200 msec assuming a relatively good regeneration system with a minimum
regeneration frequency of 30 Hz. AVG (X + Y) -AVG (X) and RMS (X + Y) -RMS (X) are the
difference of the average value and the difference of the effective value, respectively, but none of
them agree with PK (Y) I understand.
[0010]
Table 2 shows the same evaluation results as Table 1 for the case where the frequencies of the
sine wave (X) and sine wave (Y) are one pair (root (route (2))). The sampling angles and the
evaluation for six cycles are the same as in Table 1. Although the relationship between both
frequencies is 1 to 2 ^ 0.125, PK (X + Y) -PK (X) and PK (Y) have an error of 0.2% or less within
the evaluation interval of 200 msec under this condition. I understand that I do.
[0011]
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The evaluation items on the horizontal axis are the same as in Table 1. The vertical axis is also
the same as in Table 1.
[0012]
Table 3 shows that the maximum amplitude can be detected by detecting the maximum
amplitude as in Tables 1 and 2 when the two uncorrelated signals are M-sequence signals with
an acoustic band sampling frequency of 44.1 kHz. The results obtained by measurement are
shown. On the horizontal axis, WN (20%) is the M-sequence signal of the reference acoustic band,
WN (20% + 4%) is uncorrelated with the reference signal of 4% maximum relative to the
reference M-sequence signal The M-sequence signal of FIG. 100% Is the maximum value of
signed 16 bits. For LEVEL, the numerical value (%) on the vertical axis indicates the range of
magnitude of the absolute value of the signal. 0.00% The horizontal axis of is the sum of time
intervals in which the signal amplitude is in the range of 0.00% to 0.50%. The total evaluation
time is 3 seconds. 4% The blanks from to 16% are the intervals where the indication is omitted
because there is no change in the probability density of the amplitude. The maximum value of
the amplitude for which the probability density of the standard M-sequence signal is present is
19.0%, and the signal combining the 4% M-sequence signal is 22.5%, so the difference is 3.50%,
and the ratio is The rate is 3.68%. 4% Since noise is a considerable amount, it is possible to
measure the noise maximum value with an error of 8%, which is practically sufficient for
controlling the acoustic system, even under conditions where it is difficult to detect the M series
of reproduced signals and noise. Is shown. Since at least the reproduced signal is an acoustic
signal, and the probability near the maximum value is much higher than that of the M series, it
can be easily estimated that the noise maximum value can be measured with higher accuracy
than the result of Table 3. The above indicates that the maximum amplitude of noise can be
detected from the combined signal and the reference signal.
[0013]
Table 4 shows the maximum value of the running noise by subtracting the maximum value of the
playback signal from the maximum value of the signal where the running noise of the car and the
playback sound of the car audio are mixed 14% in terms of the maximum value of the playback
signal and the noise signal This is an example of the actual measurement results showing that
detection is performed with an error of. The running noise of the car and the reproduced sound
of the car audio are generally uncorrelated because they are independent sound sources. MUSIC
is a substitute for the playback signal and is an M-sequence signal assuming the worst case.
LOAD-Nise is a recording signal of an example driving noise of the driver's seat of an example
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car. MUSIC + LoadNoise is a composite signal of both. For LEVEL, the numerical value (%) on the
vertical axis indicates the range of magnitude of the absolute value of the signal. 0.00% The
horizontal axis of is the sum of time intervals in which the signal amplitude is in the range of
0.00% to 0.50%. The total time is 300 msec. Since the maximum value of the amplitude at which
the Music probability density exists is 29.5% and the maximum value of the composite signal is
55.5%, the maximum amplitude of the noise estimated from the measured value is 26%, but Since
the maximum amplitude of LoadNoise is 31%, the difference is an error of 1.3dB in -16% decibel
conversion at a 5% ratio. Since the amount of volume control to noise is at most about 10 dB, an
error of 16% does not cause the volume feedback system to become unstable due to the
divergence of the gain. The fact that the maximum noise amplitude can be calculated with an
error of 1.3 dB from the synthesized signal and the reference signal indicates that this detection
result is sufficient for practical use.
[0014]
The calculation and measurement results of Tables 1 and 2 and Tables 3 and 4 above are pure
noises by subtracting the maximum value of the reproduced signal from the maximum value of
the mixed sound signal corresponding to the synthetic sound of the noise and the reproduced
sound. Indicates that the maximum value of can be detected. However, in order to make the
maximum values of the mixed sound signal and the reproduction signal coincide with each other
in the absence of noise, it is necessary to make a process of combining the maximum values of
both.
[0015]
Secondly, regarding the relation between the spectral distribution of noise components and the
control of sound volume quality, the following calculates the maximum value of each noise
frequency band, and controls the volume sound quality of the reproduced signal for each band
according to the maximum value. On the way. As described above, it is possible to calculate the
maximum value of the noise, but the problem remains how to reflect the maximum value of the
obtained noise in the correction of the volume sound quality of the reproduction signal.
[0016]
In the case of the driver's seat noise of a car, road noise and engine noise are biased to the bass,
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and wind noise is biased to the treble. In such a case, it is not appropriate to control the volume
and the sound quality simply with uniform parameters in all bands. At low speeds, wind noise
hardly occurs, but depending on the road surface conditions, even at low speeds, road noise
biased to low tones is generated. In the case of a large passenger aircraft used for international
flights, the wind noise is stronger at the front seats than the engine noise, and the wind noise is
large at the rear seats and the engine noise is large. In addition, window side seat and center seat
are different. In the case of subways, there are strong broadband noise from railways and echoes
in tunnels, sometimes with bass, sometimes mid-span, sometimes high-pitched, with a deviation
from the intensity, and a noisy environment It is. In homes, vacuum cleaners and speech become
noise. In the case of a vacuum cleaner, the tone range is wide, and the speaking voice has an
intensity distribution in the middle sound. When listening to music, lectures or news in a noisy
environment, it is desirable to be finely controlled according to the spectral distribution of the
noise, but roughly divided into bass, mid and treble, and environmental noise in each band By
correcting the volume according to, it is possible to satisfy the volume sound quality correction
of the entire band.
[0017]
Third, with regard to the combination with noise cancellation technology that has become
popular in recent years, the following relates to the use of the residual signal of the noise
canceller. In noise cancellation, the physical phenomenon is to use the phenomenon of
wavebreaking or reflection, not muffling or wavebreaking. Since sound waves are energy,
injecting waves of the opposite phase does not cause wave breaking, and although the waves are
canceled in the noise traveling direction, the phenomenon that they are repulsed in the
approaching direction occurs. . This is phenomenologically the same as reflection. Wave
reduction is to convert sound waves, which are energy propagating in the air, into heat, but
active control of wave reduction is theoretically and technically difficult, and as of April 2017, it
is practically Technology has not been established.
[0018]
When the control amount is voltage or current, it is relatively easy to cause cancellation.
Speakers and microphones are energy conversion systems that generate or capture waves, but
electrical systems that are the other side of sound waves usually handle either voltage or current
signals. Control signals for control systems that control waves including energy conversion
systems are often handled with voltage or current, and there are many equally difficult issues.
Due to such reasons, the function of the noise canceller is not always perfect, and it is difficult to
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increase the degree of perfection to a state in which human hearing is satisfied.
[0019]
In particular, unlike the earphones and headphones, the car audio noise canceller is in a listening
environment in a state closer to an arbitrary space, so in the stage of March 2017, the state of
increasing satisfaction to the consumer level It has not been reached. For the above reasons, it is
effective to improve the listening environment of car audio by extracting the maximum value of
the noise component from the residual signal of the noise canceller and reflecting this value on
the volume sound quality control of the reproduced signal. The noise canceller system already
has resources for hybrid sound microphones and advanced signal processing, so that it is
possible to use the excess resources of the signal processing system without requiring an
increase in the cost of the extra hardware of the detection system. Enables effective sound
volume control of anti-noise.
[0020]
The level of the extracted noise is the maximum value of the noise, from which the frequency
component of the noise can not be identified. Therefore, by providing filters for the required
band on both the reproduction signal side and the mixed sound signal side and calculating the
noise maximum value from the signal after passing through the band filter, the noise maximum
value for each band is obtained by that value. Correct the playback volume according to. As a
method of applying signal processing to each divided band, there are a method of time division
and a method of parallel processing.
[0021]
Fourth, with regard to the averaging of the control amount of sound volume control
corresponding to noise, it is possible to control the volume and the sound quality corresponding
to noise as described above, but it is possible to say that it is listening in a noise environment.
Because the human hearing is sharp, it is uncomfortable to immediately change the volume and
sound quality of the reproduced sound in response to the noise, which causes another stress for
the listener other than the noise. On the other hand, if the averaging process in a long time
interval is reflected, there is no problem with some time to notice that the noise is stronger than
the reproduced sound when the noise becomes stronger, but the noise becomes sharply weaker.
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Sometimes there will be a strong playback sound that has been dealing with strong noise until
then. This feels a lot of discomfort in actual use. As it is a sensory problem, it is a task that also
has individual differences, but generally there is a strong sense of discomfort in the loud
playback sound in the absence of noise, and the listener is strongly stressed by repeating the
number of times. For this reason, the sound volume control of the playback sound corresponding
to the detected noise maximum value is appropriate for low-speed attack operation in the
direction of increasing noise intensity and high-speed release operation in the direction of
decreasing noise intensity. is there. Experiments applied to passenger cars have confirmed that
the combination of low-speed attack and high-speed release is the best when the road surface is
moving from a good place to a bad place while traveling on an expressway and vice versa. In the
case of a low-speed attack, the time constant is less than 1 second with discomfort, 2 to 4
seconds is good, and 10 seconds is too long because the contents of the radio broadcast can not
be heard. In the case of high-speed release, with a time constant of 3 seconds or more, it is
uncomfortable and 1 second is good. For shorter 0.3 seconds to 0.1 seconds, if the running noise
is unstable, it will be adjusted to the weak running noise, so the correction amount will be too
small to perform the function. With regard to the relationship between the control amount
obtained in low-speed attack and high-speed release and the volume correction amount, the
optimum condition for the listener is determined depending on the characteristics of the car if
the object is an earphone, a passenger car or a passenger car. Determined by design.
[0022]
Fifth, it is important to relate the amplitude ratio of the reproduced sound component to the
reproduced sound signal and the mixed sound signal. The coefficients of the reproduced signal to
be subtracted from the mixed sound signal are determined so that the maximum amplitude of the
reproduced sound and the maximum amplitude of the detection signal in a fixed time interval in
the noise-free state coincide with each other. There are the following three methods as this
method. These choices and specific methods will be determined by design. 5-1. The listener
operates the switch in the absence of noise to match the maximum value of the reproduction
signal with the maximum value of the detection signal. 5-2. In the case of car audio, an
acceleration sensor is provided to match the maximum value of the reproduction signal and the
mixed sound signal when the output of the acceleration sensor falls below a predetermined value.
5-3. In the case of a car audio system, the maximum value of the reproduction signal and the
mixed sound signal is matched when the vehicle is stopped or the engine is stopped and the
accessory power is on. 5-4. By making the level of the reproduction signal shorter than noise for
a short time, the maximum value of the reproduction signal and the maximum value of the
detection signal are matched.
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[0023]
First, since the noise component can be accurately measured and calculated from the signal in
which the noise and the reproduction signal are mixed, and the spectrum distribution can be
obtained, it is possible to finely determine the volume sound quality of the reproduction signal
optimum for the noise.
[0024]
Secondly, as a first result, even if the volume of the reproduction signal is increased according to
the noise, the maximum noise value is accurately detected and detected from the synthesized
signal of the reproduction sound and the noise being detected. Since the intensity of the noise
does not include or is small in the intensity of the reproduced sound, the volume control of the
reproduction system is accurate, and the closed loop operation of the volume control system
does not become unstable.
[0025]
Third, it is possible to determine an error signal when the noise canceller can not satisfactorily
cancel the noise, that is, the maximum amplitude of the noise component that can be heard from
the residual signal.
Therefore, the volume sound quality of the reproduced sound can be corrected according to the
noise maximum value reaching the hearing beyond the limit performance of the noise canceller.
[0026]
An explanatory diagram for detecting the spectrum of noise, an explanatory diagram of a basic
configuration of the present invention, an explanatory diagram of sound volume control of
reproduced sound by the detected noise signal, an explanatory diagram of a configuration
example using a residual signal of the noise canceller for mixed sound signal And illustration of
high-speed release Relationship between noise intensity and sound quality control and duration
of noise
[0027]
A portable terminal with a sound quality control function for noise response A car audio with a
sound quality control function for noise response A TV system with a sound quality control
function for noise A PA system with a volume sound quality control function for noise
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[0028]
Application of the noise distribution of noise calculated from the reproduction signal when the
reproduction signal is known and the mixed sound signal in which noise and reproduction sound
are mixed.
Volume sound quality control program for earphones, headphones, passenger cars, TVs, and PA
systems, in response to environmental noise.
Anti-noise sound quality control program as an added improvement function of the noise
canceller function used in earphones, headphones, and passenger cars.
[0029]
FIG. 1 is an explanatory view corresponding to claim 1 of the basic configuration of the present
invention, of the function of detecting the noise maximum value for each band from the
reproduction signal and the mixed sound signal.
+ And-indicate positive and negative polarities, respectively. INPUT is a signal input, and a
reproduction signal of music or broadcast is input. source is a reproduction signal, SAMP is an
amplification function of the reproduction signal, and SP is a speaker. MUSIC (source) is the
reproduced sound that reaches the mixed sound microphone, en is the noise source, NOISE (en)
is the noise that reaches the mixed sound microphone, MR is the mixed sound microphone for
detecting the synthesized sound of noise and reproduced sound, MRAMP Is an electromotive
force amplification function of the mixed sound microphone, and EN + SOURCE is an amplified
mixed sound signal. GAIN is a gain adjustment function for matching the maximum value of the
reproduction signal to the maximum value of the reproduction signal component contained in
the mixed sound signal, and is controlled by CONDITIOBNER. CTRLGAIN is a control signal of
GAIN. This function is necessary to accurately detect the maximum value of the noise component
when subtracting the maximum value of the reproduction signal from the maximum value of the
mixed sound signal. BPF- and BPF + are band-pass filters of the reproduction signal and the
mixed sound signal respectively, and both have the same characteristics. The characteristics of
BPF- and BPF + are controlled by CONDITIONEDR described later, and the necessary spectrum is
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detected by time division or parallel division of noise spectral distribution with necessary
resolution. The division method, division characteristics, and number of divisions are determined
by design. The BPF- and BPF + inputs are SOURCE and EN + SOURCE, respectively. BPF (SOURCE)
and BPF (EN + SOURCE) are the band pass filter output, and PEAK-and PEAK + are the maximum
value detection functions, respectively, and PK (BPF (S)) and PK (BPF (EN, S) Each is an output of
the maximum value detection function. The maximum value detection is the maximum value
within a fixed time, for example, 200 mmsec to 1 sec. This time width is determined in design
according to the specific purpose. PEAK- and PEAK + are controlled by CONDITIONER by control
signal CTRLPK. The specific detection method of the maximum value is determined by design.
ADD is an addition function, and the maximum value of the noise level can be obtained by
subtracting PK (BPF (S)) from PK (BPF (EN, S)) as shown in the agreement. PK (BPF (EN)) is the
maximum value of the detected noise. It is as explanation of Table 1, Table 2, Table 3, and Table
4 that PK (BPF (EN)) corresponds to the maximum value of noise.
CONDITIONER is a control function of the entire system, CTRLGAIN is a gain control signal of a
reproduction signal, CTRLBPF is a control signal of a band pass filter, and CTRLPK is a control
signal of a maximum value detection function. CTRLGAIN is adjusted to match the maximum
values of SOURCE and EN + SOURCE when noise is negligibly small, and when the playback
sound is large and noise can be ignored. Generally, it is desirable to update the characteristics of
the acoustic system manually or automatically as needed, because drift occurs due to
environmental conditions such as temperature and aging. The conditions under which the GAIN
gain is adjusted are determined by design. NOISE_PATTERN is a spectral pattern of the detected
noise. How to divide into a plurality of bands including one division of the entire range of bands
is determined in design according to the purpose. As an application example of the detected
noise spectrum pattern, there is volume sound quality control of reproduced sound according to
the noise maximum value. Since the control amount of the volume sound quality is only the noise
component excluding the error of the configuration system, the reproduction volume control
according to the noise maximum value, and further, the volume control of reproduction sound for
each band according to the noise maximum value for each band Is possible.
[0030]
FIG. 2 shows an example of a simple and effective system configuration that performs volume
sound quality control in response to noise when the basic configuration of FIG. 1 is divided into
three sections: low band, mid band, and high band for all bands. . It corresponds to claim 3. The
same symbols as those in FIG. 1 have the same functions. COMP (B), COMP (M), and COMP (T)
are volume correction functions for bass, mid, and treble, respectively. In the volume correction
function, the correction amount is controlled by the maximum noise value detected for each
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band. SUM_INP is an addition function. BASS- and BASS + are bass band filters, MID- and MID +
are mid band filters, and TREBLE- and TREBLE + are treble band filters. In FIG. 1, although the
number of band pass filters is arbitrary, FIG. 2 is a three-division simultaneous measurement of a
bass range, a mid range and a high range. This is an example of the most practical configuration.
GAINB, GAINM, and GAINT are gain adjustment functions to match the maximum values of the
low range, mid range, and high range components of both the source signal and mixed tone
signal. The outputs of the gain adjustment function are SOURCEB, SOURCEM and SOURCET,
respectively. The control of each gain is determined by CONDITIONER, and its control signal is
CTRLGAIN. BASS (SOURCEB) and BASS (EN + SOURCE) are the output of the bass band filter, MID
(SOURCE) and MID (EN + SOURCE) are the output of the mid band filter, TREBLE (SOURCE) and
TREBLE (EN) respectively. + SOURCE) Each is the output of the high band filter. PEAKB- and
PEAKB + are functions for detecting the maximum value of bass, PEAKM- and PEAKM +,
functions for detecting mid-range and PEAKT- and PEAKT + are functions for detecting maximum
of treble. CTRLPK is a control signal of the maximum value detection function. PK (B (S)) and PK
(B (EN, S)) are detection maximum values of the bass range, PK (M (S)) and PK (M (EN, S)) are
detection maximum values of the midrange, PK (T (S)) and PK (T (EN, S)) are detection maximum
values of the high range. ADDB, ADDM, ADDT are addition functions, PK (B (EN)), PK (M (EN)), PK
(T (EN)) are the noise maximum values in the mid-high range, respectively, and the mixed side It
is a value obtained by subtracting the detection maximum value on the signal side from the
detection maximum value.
S / Q_B, S / Q_M, S / Q_T are PK (B (EN)), PK (M (EN)), PK (T (EN)) described in Table 1 to Table
4, and slow attack time and It is an averaging function of the low range, mid range, and high
range, respectively, where the high-speed release time function is applied. Control the volume
correction of bass, middle and high tones by the output of the averaging function. The specific
method of averaging, attack time and release time are determined by design according to the
application. CONDITIONER is a control function of the whole system, and CTRL is a control signal
of volume sound quality correction.
[0031]
FIG. 3 is an explanatory diagram corresponding to claim 2 when the residual signal of the noise
canceller is a mixed tone signal. As the noise canceller is out of the scope of the present
invention, the detailed configuration and the description of this mechanism will be omitted. In the
case of FIG. 2, the mixed sound signal utilizes the amplified signal of the mixed sound
microphone, but in the case of FIG. 3, the mixed sound signal uses the remaining signal without
being able to cancel out the noise. This signal is a mixed sound signal because the remaining
signal contains a component of reproduced sound and a component of noise. The microphones
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are shown in two cases, one for detecting the noise of the noise source and the other for
detecting mixed sounds near the hearing. When there are many noise sources, multiple source
noise detection microphones are generally used for multiple noise sources, but FIG. 3 shows one
case. There are many noise canceller systems, and some systems do not have a noise source
microphone, but the presence and number of noise source microphones are beyond the scope of
the present invention.
[0032]
The source noise microphone is MN. MNAMP is its signal amplification function. TRN is the
transfer constant of the path from the noise source to the hybrid microphone. EN is the output.
ITRS is an inverse constant of the transfer constant until it is amplified by SAMP and converted
to sound wave by SP to reach MR. This loop is responsible for canceling the noise from the sound
source that reaches the hybrid microphone. The more precise the TRN and ITRS, the higher the
noise cancellation performance, but this loop contains a sound energy propagation system and is
affected by the presence of standing waves and the resonance of mechanical parts, so there is
always a solution It is not always the case. In particular, it is difficult to improve the accuracy of
the inverse transfer constant ITRS, and when there are many noise sources, it is difficult to solve
this problem under the conditions of low cost and low power consumption. FEEDBACK is the
output of ITRS, and the noise cancellation system is configured so that the sound reaching MR
via SAMP and SP offsets NOISE (en). NOISE (en) is the noise detected by the source noise
reaching the hybrid microphone through the propagation path.
[0033]
SAMP is an amplification function of the synthetic signal of the reproduction signal and the noise
cancellation signal. The difference from SAMP in Figure 1 or Figure 2 is that the integrity signal
of the reproduction signal and the noise cancellation signal is input. TRS is the transfer constant
until the reproduction signal source reaches the hybrid microphone. SOURCE is its output signal.
If the accuracy of the TRS is high enough, its output will match the SOURCE contained in the
output of the MRAMP. ADDSS is an addition function whose output is the residual component
ERR of the system. The noise cancellation function controls TRN and ITRS so that this residual
signal ERR is minimized. GAINB, GAINM, and GAINT are gain adjustment functions to match the
maximum values of the low, mid, and high range reproduction signal components included in
SOURCE and ERR, respectively. CTRLGAIN is its control signal. The outputs of GAINB, GAINM,
and GAINT are SOURCEB, SOURCEM, and SOURCET, respectively. SOURCEB, SOURCEM and
SOURCET are the input of BASS-, MID- and TREBLE-band division filters respectively. ERR is the
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input of the band splitting filter of BASS +, MID +, TREBLE +. The subsequent signal processing is
the same as that of FIG. Claim 3 uses this residual signal as a mixed tone signal. The mixed sound
signal contains the components of reproduced sound and noise that reach the hearing.
[0034]
FIG. 4 is a function to reduce the sense of discomfort to the auditory sense of the change of the
volume sound quality when changing the volume sound quality of the reproduced sound in
response to the change of the noise maximum value, the average by the low speed attack time
and the high speed release time FIG. The horizontal axis TIME is the time axis, the vertical axis
E_NOISE is the noise maximum value, and the COMPENSATION is the volume sound quality
correction amount. Hereinafter, the correction amount is simply the volume sound quality
correction amount. t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10 and t11 are noise change points,
respectively, P0, P1, P2, P3a, P4, P5a, P6, P7, P8, P9, P10a and P11 indicate the change points
of the control amount. The noise increases rapidly from t1 to t2 over 9 and decreases rapidly
from t2 to t3. In response to this change, the amount of correction gradually increases from P1
to P2, but the amount of correction falls sharply from P2 to P3a. Therefore, the correction
responds slowly to noise changes that return to the original state in a short time. The noise
increases rapidly from t4 to t5, and if it continues until t6, the amount of correction gradually
increases from P4 to P5a, and the condition continues to P6. Furthermore, the noise increases for
a short time from t6 to t7 t8, but the correction amount does not change much like p6 p7 p8a.
The noise decreases sharply from t9 to t10, but the correction amount returns sharply from p9
to p10a. The above-mentioned correction amount for noise due to the averaging function with
low-speed attack time and high-speed release time is experimentally confirmed to be a control
method with less discomfort for hearing in comparison with other methods. . The attack time and
release time, or time constant or averaging method and parameters thereof are determined by
design according to the purpose. Also, the attack time and release time in the low range, mid
range, and high range are not necessarily the same.
[0035]
FIG. 5 is an explanatory view of the tendency of the relationship between the magnitude of noise
and the correction amount according to noise duration time. (A) is the low range, (b) is the
middle range, and (c) is the high range. The horizontal axis E_NOISE is the noise maximum value,
the vertical axis COMPENSATION is the correction amount, and BGN is the background noise
maximum value. BASS, MID and TREBLE show that the graph is the control amount for each
duration corresponding to the maximum noise value in the low range, mid range and high range
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respectively. 2The duration of the noise is sec, 5 sec, 10 sec, 20 sec. In any case, the shorter the
duration of the noise, the smaller the correction amount, and naturally, the smaller the noise, the
smaller the correction amount.
[0036]
Fig. 1 +,-Positive and negative polarity INPUT signal input Source Reproduction signal SAMP
Reproduction signal amplification function SP Speaker MUSIC (source) Reproduction sound
reaching mixed sound microphone en Noise source NOISE (en) noise reaching mixed sound
microphone MR Mixed sound microphone MRAMP Mixed sound microphone EMF amplification
function EN + SOURCE Mixed sound signal GAIN Gain adjustment function CTRL GAIN GAIN
control signal BPF-, BPF + Band filter for reproduced signal and mixed sound signal SOURCE, EN
+ SOURCE BPF-, BPF + output BPF (SOURCE), BPF (EN + SOURCE) Band-pass filter output PEAK-,
PEAK + maximum value detection function PK (BPF (S)), PK (BPF (EN, S) maximum value
detection function output ADD Add Function PK (BPF (EN)) Maximum value of noise
CONDITIONER Control function of entire system CTRLGAIN Gain control signal of maximum
value of reproduced signal CTRLBPF Control signal of band-pass filter CTRLPK Control signal of
maximum value detection function NOISE_PATTERN Spectrum pattern of detected noise The
[0037]
Figure 2 COMP (B), COMP (M), COMP (T) Low-pitched, mid-pitched, high-pitched volume
correction function SUM_INP Addition function BASS-, BASS + Bass band filter MID-, MID + Mid
band filter TREBLE-, TREBLE + Treble band filter GAINB, GAINM, GAINT Gain adjustment function
SOURCEB, SOURCEM, SOURCET GAINB, GAINM, and GAINT output CTRLGAIN GAINB, GAINM,
Gaint gain control signal BASS (SOURCEB), BASS (EN + SOURCE) Bass band filter Output of MID
(SOURCE), MID (EN + SOURCE) Mid band filter output TREBLE (SOURCE), TREBLE (SOURCE),
TREBLE (EN + SOURCE) High band filter output PEAKB-, PEAKB + bass maximum detection
function PEAKM-, PEAKM + midrange maximum detection function PEAKT-, PEAKT + treble
maximum detection function CTRLPK Control signal for maximum detection function PK (B (S)),
PK (B (EN, S)) detection maximum of bass range PK (M (S)), PK (M (EN, S)) Detection maximum
value of midrange PK (T (S)), PK (T (EN, S)) Detection maximum value of high range ADDB,
ADDM, ADDT adder PK (B (EN)), PK (M (EN)), PK (T (EN)) Maximum noise in the middle to high
range of bass S / Q_B, S / Q_M, S / Q_T Slow attack time and fast release time Averaging function
CONDITIONER Control function of the whole system CTRL Control signal of volume sound
quality correction
[0038]
Fig. 3 MN Source noise microphone MNAMP amplification function EN Output FEEDBACK ITRS
output NOISE (en) Noise reaching the mixed sound microphone SAMP Amplitude function of
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totality of reproduced sound and noise cancellation signal TRS reproduced signal reaches mixed
sound microphone The transfer constant of the path from the noise source to the mixed sound
microphone SOURCE The transfer constant of the path from the noise source to the mixed sound
microphone SOURCE The inverse arrival constant of the output signal ITRS TRN ADDSS Addition
function ERR The residual component of the system GAINB, GAINM, GAINT gain adjustment
Function CTRLGAIN Output of its control signals SOURCEB, SOURCEM, SOURCET GAINB, GAINM,
and GAINT BASS-, MID-, TREBLE-band split filters BASS +, MID +, TREBLE + band split filters
[0039]
Fig. 4 TIME Time axis E_NOISE Noise maximum value axis COMPENSATION Volume sound
quality correction amount axis t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11 Change point of noise
P0, P1, P2, P3a , P4, P5a, P6, P7, P8a, P9, P10a, P11 Change point of control amount
[0040]
Fig. 5 E_NOISE Maximum noise axis COMPENSATION Correction amount axis for playback sound
BGN Maximum background noise BASS, MID, TREBLE Control amount for low, middle and high
range respectively 2sec, 5sec, 10sec, 20sec Noise duration
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