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DESCRIPTION JPS60126998

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DESCRIPTION JPS60126998
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
apparatus comprising microphones, amplifiers, speakers and the like, which prevents howling in
a loudspeaker system used for meetings, lectures and the like. Configuration of Conventional
Example and Problems Thereof FIG. 1 shows a block diagram of a conventional howling
suppression apparatus. In the figure, 1 is an input terminal, 2.3 ░ 4 is a band pass filter, 5, 6.7 is
a measuring circuit for measuring the magnitude of the signal, and 8 is a comparison of the
magnitudes of a plurality of divided signals to detect howling And control circuits for controlling
signal attenuation, 9, 10, 11 are attenuators for attenuating signals passing through the
respective bands, 12 is an adder, and 13 is an output terminal. In this figure, first, the input
signal is divided into a plurality of frequency bands by band pass filters 2 and 3.4, and the output
is branched into two. One of the branched signals is measured for the magnitude of the signal by
the measuring circuit 5.6.degree. 7, the measured signal is taken into the control circuit 8, and
the magnitude comparison of the signals is performed. Here, for each band signal, a comparison
is made between the signal of both bands and-, and if the difference exceeds a certain threshold,
it is detected that /% wringing has occurred, and the corresponding attenuation 9.10.degree. 11
is controlled, and the signal passing through the band in which howling is detected is attenuated,
and the output of each attenuator 9.10. Howling is suppressed by this configuration. FIG. 2 is a
phase diagram showing howling processing algorithm of the conventional howling suppressor. In
this figure, i is the number of the band divided into a plurality, Ei is the signal size in the i band, q
is the attenuator for attenuating the signal passing through the i band at 9 ░ 10.11. Is a
predetermined attenuation amount (the amount to attenuate the signal) given by control to
attenuator 9, 10.11. S, Si is the magnitude of the signal of i-1st and i + 1st bands for both i-bands
Difference. That is, assuming that the magnitudes of the pass signals in the i-1, i and i-11 bands
are E knee 1 + B1 + E1 +, respectively, Si??Ei?Di?1Si = El?E1 + 1. TH indicates a threshold
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for detecting howling occurrence. In this figure, the magnitude E ? (i = 1 to n) of each signal
frequency-divided into a plurality is taken, and first, for the i band, an attenuator corresponding
to that band (any of 9 ░ 10.11. The amount of attenuation is checked, and if the predetermined
amount of attenuation G has already been given, the howling process of the band i is not
performed, and the process proceeds to the process of the next band i + 1.
However, if a predetermined attenuation amount is not given to the corresponding attenuator
here, howling processing is performed, and the signal magnitude E knee 11 Ei + 1 of the bothend band i-1 ░ i + 1 of the band i If the difference S ?, sH is obtained and their values exceed a
certain threshold TH, it is recognized that howling has occurred in the band i, and the attenuation
amount ? of the attenuator corresponding to the band i is The attenuation amount G is added,
the signal passing through the band i is attenuated, and howling is suppressed. Then, the howling
suppression processing is performed by repeating such processing for each band. However, in
the case of the above configuration, since the attenuation adjustment is performed only once for
each signal, the howling limit (limit level of howling occurrence) is reached in a certain frequency
band when the processing is finally finished. In the actual use, it may be necessary to lower the
loudness level to some extent after the processing. Further, the amount of howling suppression is
given only a certain amount at a rate to all the bands where howling occurs, so there are cases
where the suppression is performed more than necessary or the amount of suppression is
insufficient as described above. Furthermore, the number of howling suppressions is not limited,
and this number has the disadvantage of having to be performed manually. SUMMARY OF THE
INVENTION It is an object of the present invention to solve the above-mentioned conventional
drawbacks and to provide a howling suppressor capable of performing an appropriate amount of
howling suppression and therefore responding promptly to the condition of a varying sound
field. The howling suppression apparatus according to the present invention includes band
dividing means for dividing an input signal into a plurality of frequency bands, and one divided
signal of each of a plurality of divided plural signals divided into two. Howling is detected based
on a comparison of the sizes of the signals measured by the measuring means, measuring means
for measuring the size, attenuating means for attenuating the size of each of the other divided
divided signals, and this detection When the attenuation means of the band corresponding to the
signal is controlled to increase its attenuation stepwise and the number of bands in which such
stepwise increased attenuation reaches a predetermined value reaches a predetermined number.
Control means for terminating the process, and addition means for adding the output signals
from the respective attenuation means. That is, the input signal is divided into a plurality of
frequency bands, and by comparing the magnitudes of the signals in the respective bands, the
band in which the howling has occurred is detected, and the signal passing through that band is
attenuated stepwise When the number of bands in which the total amount of attenuation reaches
a predetermined amount reaches a predetermined number, the process of the howling is ended,
and the howling is appropriately suppressed.
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Description of the Embodiment FIG. 3 shows a block diagram of an embodiment of the present
invention. In FIG. 3, 14 is an input terminal, 15 ░ 16.17 is a band pass filter that divides an input
signal into a plurality of frequency bands, and 18.19.20 is a measurement circuit for adjusting
the signal size, 21 is a control circuit for detecting howling and controlling an individual
attenuator 22.23.24 and an overall attenuator 26, 22, 23 ░ 24 an individual attenuator for
attenuating a signal, 25 an adder, 26 an overall A total attenuator 27 which attenuates the signal
level is an output terminal. In the figure, the signal input from the input terminal 14 is frequency
divided by a plurality of band pass filters 15.16.17. Then, the output of each band pass filter
15.16.17 is branched into two, and one signal is input to the measuring circuit 18, 19.20, and
the other signal is input to the individual attenuator 22.23.24. Ru. Measurement port!
????????? The signals input to 20 have their respective signal magnitudes taken into
control circuit 21. In this control circuit 21, the magnitudes of the signals of the respective bands
are compared with the magnitudes of the signals of the respective bands of the two bands, and if
the difference exceeds a certain threshold, howling occurs in the bands. It is recognized as Then,
any attenuator 22 ░ 23.24 corresponding to the band recognized as howling occurs is
controlled to give a certain amount of attenuation. Also, if rehearing occurs in the same band,
howling is recognized in the same manner as above, and a certain amount of attenuation is
applied to the attenuator corresponding to that band, and the signal passing through that band is
attenuated. Be done. Then, howling suppression is performed until the sum of the attenuation
sounds reaches a certain value, and when there are a limited number of bands in which the
attenuation amount reaches a certain value, the noise reduction is When the process is
completed and the total attenuator 26 is further controlled, the overall signal level is attenuated
by a fixed amount, and finally howling suppression is completed. The above operation will be
described in more detail according to the flowchart of FIG. In this figure, i is the number of
frequency-divided bands, E is the magnitude of the signal in the i band, 9 ? is the original
attenuation of the attenuator that attenuates the signal passing through the i band, G 2 is this
Sum of attenuations given to attenuators, S ?, Sj are differences in the magnitude of the signal of
both bands i-1 and i + 1 to i band, TH is considered that howling has occurred t [t, o The amount
of attenuation added to the amount of attenuation g1 when it is recognized that howling has
occurred, Hn is the number of bands where the total amount of attenuation G applied to the
attenuator has become 02, 9t attenuates the overall signal level The original attenuation of the
integrated attenuator 26, G3 indicates the attenuation applied thereto.
As shown in this figure, first, the number of bands in which the howling suppression amount has
reached 02 is checked, and when the number is a certain number m, the attenuation amount ft of
the total attenuator 26 is a fixed amount G3 To attenuate the overall signal level and complete
the howling suppression process completely. Note that gl and 9t as initial values may be O. If the
number of bands for which the howling suppression amount has reached 02 is less than m:
howling processing is performed from the i band to check whether the attenuation amount of the
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attenuator corresponding to the i band has reached 02, to G2 If it has reached, the feedback
processing in the gate band will not be performed, and the processing will be transferred to the
next band i + 1. If the amount of attenuation does not reach G, howling processing is performed,
and both bands i-1 and! If the difference S1, 8'x from the magnitude of the +1 signal is taken and
that value exceeds a certain threshold TH, it is recognized that howling has occurred in that band
i, and the attenuation of the attenuator corresponding to that band i A certain amount of
attenuation G ? is added to the amount q1 to shift to processing of the next band i + 1. Then, by
continuing this processing until the number of birds reaches a predetermined number m,
howling can be optimally suppressed. A more specific operation example will be described. (1)
When the first signal of the first band-1 = 1 is taken in, step NO is normally NO, and step 1 is
normally NO. Then, after the process of step 2, the determination is made in step 3. When the
howling is performed, a whistle is performed in step 4 and when the howling is not performed,
+0 (no change) is performed in step 4. Next, i is counted by 1 in step 1 and NO is obtained in step
1. ????????????????? {Circle over (2)} The first signal of the second band i: = 2
is taken, and the same processing as the above (1) is performed. Thus, the first signal of the last
band i = n is acquired, and the same processing as (1) is performed. (3) Then, YES is obtained in
step 1 and initialization of i is performed in step 2 and processing for the second signal is
performed in each band order. Then, i is initialized again in the same manner as above, and the
third signal. It is processed with the 411st signal. (4) During this time, with respect to the signal
of a certain band, G process is added several times in each step ?, it becomes YBS in step ? in
the next cycle, and in the subsequent cycles, steps ?, ?, ?, ? It is omitted.
Each time YBS is obtained in {circle over (1)}, +1 is added to Hn. (5) While the cycle is repeated
several times, ? reaches m and the answer in step {circle over (4)} is YES, and the howling
suppression processing is finished and G is given in step [stock] to complete all 6 rules. In
addition, this invention includes the thing without step [stock], ie, the thing without the total
subtractor 26, in an Example. Also, the number of divisions of the signal by the band is arbitrary.
According to the howling suppressor of the present invention, since the signal of the band in
which the howling is generated is attenuated stepwise, there is an effect that appropriate howling
suppression can be performed without causing excess or deficiency in the howling suppression
amount.
[0002]
Brief description of the drawings
[0003]
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FIG. 1 is a block diagram of a conventional example, FIG. 2 is a 7-row chart, FIG. 3 is a block
diagram of an embodiment of the present invention, and FIG. 4 is a flowchart thereof.
15.16.17 иии Band-pass filter (band division means), 18.19.2 o и и и Measurement circuit
(measurement means), 22.23.24.26 иии Attenuator (attenuation means), 21 ... Control circuit
(control means), 25 ... Adder (addition means)
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