JPS61106000A - Automatic anti-howling device - Google Patents

Automatic anti-howling device

Info

Publication number
JPS61106000A
JPS61106000A JP22676484A JP22676484A JPS61106000A JP S61106000 A JPS61106000 A JP S61106000A JP 22676484 A JP22676484 A JP 22676484A JP 22676484 A JP22676484 A JP 22676484A JP S61106000 A JPS61106000 A JP S61106000A
Authority
JP
Japan
Prior art keywords
signals
signal
pair
gain
branched
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP22676484A
Other languages
Japanese (ja)
Inventor
Takayoshi Hirata
平田 能睦
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to JP22676484A priority Critical patent/JPS61106000A/en
Publication of JPS61106000A publication Critical patent/JPS61106000A/en
Pending legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00Circuits for transducers, loudspeakers or microphones
    • H04R3/02Circuits for transducers, loudspeakers or microphones for preventing acoustic reaction, i.e. acoustic oscillatory feedback

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  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

PURPOSE:To suppress oscillation, i.e. singing of a loudspeaker system by automatically detecting howling caused in the loudspeaker device and controlling the loudspeaker gain. CONSTITUTION:Among a pair of signals (a) and (b) branched from the signal transmission line by the branching means 1, the signal (b) is delayed 5 to make a certain time difference between both signals. Furthermore, the signal (a) is branched 2 and between a pair of signals branched by phase shifting means 3, 4 and a phase difference of 90 deg. or about 90 deg. is given and then each is multiplied by the other signal branched 1 by the multipliers 6 and 7. The output signals of the multipliers 10 and 11 are integrated at a specified attenuation factor by the integrators 8 and 9. And with the arithmetic units 10 and 11, the absolute value or squared value of the output signal of the integrator is outputted. Then, with the adder 12, the outputs of the arithmetic units are added. By controlling the gain of the gain control circuit Q inserted in the signal transmission line by means of the output signal of the adder 12, the singing generated in the electroacoustic system including the signal transmission line L is suppressed.

Description

【発明の詳細な説明】 ホールや会議室において、電気音響設備を用いて拡声を
行なう場合、マイクロホン、増幅器、スピーカなどで構
成される伝送系は、スピーカとマイクロホンの音響的結
合によって帰還ループが生じ、伝送系の利得が一定量を
越えると鳴音(ハウリング)が発生する。このようなハ
ウリングを回避するために、マイクロホンおよびスピー
カの指向特性をハウリングの生じにくいように設定した
り、更に電気的方法を取入れて、ハウリングの生じる周
波数の利得を下げることが行われている。
[Detailed Description of the Invention] When amplifying sound using electroacoustic equipment in a hall or conference room, the transmission system consisting of microphones, amplifiers, speakers, etc. creates a feedback loop due to acoustic coupling between the speaker and microphone. Howling occurs when the gain of the transmission system exceeds a certain amount. In order to avoid such howling, the directional characteristics of microphones and speakers are set so that howling is less likely to occur, and electrical methods are also used to lower the gain at frequencies where howling occurs.

しかしながら、電気的方法とはいっても、ノ1ウリング
の検出は人の耳に頼り、これと思われる周波数の利得を
グラフィック・イボライザなど用いて手動で下げるか、
実際に拡声を行なっている最中では、周波数の区別なく
マイクロホンとスピーカ間の利得をハウリンクの発生に
応じて手動で下げるということが行なわれており、しか
もこれらの操作はある程度の専門的知識や経験を必要と
するということなどから、更に勝った方法、手動に依ら
ない方法が望まれてきた。
However, even though it is an electrical method, the detection of noise ringing relies on the human ear, and the gain of the frequency that seems to be affected must be manually lowered using a graphic equalizer or the like.
During actual sound amplification, the gain between the microphone and speaker is manually lowered according to the occurrence of howling, regardless of frequency, and these operations require a certain degree of specialized knowledge. Since this method requires a lot of experience and experience, there has been a desire for a more efficient method that does not rely on manual methods.

本発明は上記の要求に答えるためになされた。The present invention has been made in response to the above needs.

即ち本発明の目的は拡声設備に生じるハウリングを自動
的に検出し、拡声利得を制御することによって、拡声系
の発振すなわち鳴音を抑圧する自動ハウリング防止装置
を提供することにある。
That is, an object of the present invention is to provide an automatic howling prevention device that suppresses oscillation, that is, ringing, of a public address system by automatically detecting howling occurring in a public address system and controlling the public address gain.

以下、本発明の実施例を図に従って詳細に説明する。Embodiments of the present invention will be described in detail below with reference to the drawings.

図1は本発明による自動ハウリング防止装置の第1の実
施例を示すブロック図である。図1に於いて、(1)は
信号伝送路りから一対の信号a、bを取り出す第1の分
岐手段である。従って信号a、bは同じものである。(
2)は信号aを分岐する第2の分岐手段である。(8)
および(4)は分岐された一対の信号間に位相差90度
もしくは約90度を与える移相手段であり、ここで信号
伝送路りがグラフィック・イコライザのある1つのチャ
ネルで1/3ないし1オクターブに帯域制限された信号
を伝送するようにされている場合ならば、1次OCR回
路で得られる一対のバイパス・フィルタとローパスψフ
ィルタをそれぞれ(8)、(4)の移相手段として使用
することができる。ただし、その場合には各フィルタの
3 dB減衰する周波数を信号周波数帯域の中間に合せ
ることが必要である。(5)は信号aとbの間に一定の
時間差を与えるために、信号すを遅らせるようにした遅
延手段である。遅延手段はアナログ回路ならば電荷転送
素子(例えばBBD)を用いることができる。(6)お
よび(7)は乗算手段であり、乗算器によって実現でき
る。(8)および(9)は積分手段であり、積分された
信号が時間経過に比例して減衰する一定の減衰率(時定
数)をもった積分器で実現できる。αQおよびa力は、
入力信号の自乗値もしくはその代用として絶対値を得る
ための演算手段であり、乗算器、自乗器もしくは絶対値
回路を用いることができる。(121はC0)およびa
℃の出力を加え合せる加算手段であり、加算器によって
実現できる。Qは(至)の出力の大小に応じてその利得
が制御される利得制御回路である。図1において、分岐
手段(1)以後% (2)% (81、・・・、(2)
までが、鳴音を検出して出力する、正弦波検出回路を構
成するものである。
FIG. 1 is a block diagram showing a first embodiment of an automatic howling prevention device according to the present invention. In FIG. 1, (1) is a first branching means for taking out a pair of signals a and b from a signal transmission path. Therefore, signals a and b are the same. (
2) is a second branching means for branching the signal a. (8)
and (4) is a phase shift means that provides a phase difference of 90 degrees or approximately 90 degrees between a pair of branched signals, where the signal transmission path is 1/3 to 1 in one channel with a graphic equalizer. If an octave band-limited signal is to be transmitted, a pair of bypass filters and low-pass ψ filters obtained from a primary OCR circuit are used as phase shifting means in (8) and (4), respectively. can do. However, in that case, it is necessary to match the frequency at which each filter is attenuated by 3 dB to the middle of the signal frequency band. (5) is a delay means that delays the signal in order to give a certain time difference between the signals a and b. If the delay means is an analog circuit, a charge transfer device (eg, BBD) can be used. (6) and (7) are multiplication means, which can be realized by a multiplier. (8) and (9) are integrating means, which can be realized by an integrator having a constant attenuation rate (time constant) in which the integrated signal attenuates in proportion to the passage of time. αQ and a force are
It is an arithmetic means for obtaining the square value of an input signal or an absolute value as a substitute thereof, and a multiplier, a squarer, or an absolute value circuit can be used. (121 is C0) and a
This is an addition means that adds together the outputs of degrees Celsius, and can be realized by an adder. Q is a gain control circuit whose gain is controlled depending on the magnitude of the output. In FIG. 1, after branching means (1) % (2)% (81, ..., (2)
The above constitutes a sine wave detection circuit that detects and outputs a sound.

次に、図1に従って、本発明の動作原理を説明する。Next, the principle of operation of the present invention will be explained according to FIG.

音声信号や音楽信号は、物理的に見れば時間的に不規則
に変動する信号であり、時間軸上のある時率で生じた信
号と、それから十分離れた時点で生じた信号は互に無相
関となる。従って、それら異る時点で生じた信号を掛け
合せて積分した結果は、平均値がOとなるゆらぎとして
表わされる。
From a physical perspective, audio and music signals are signals that fluctuate irregularly over time, and a signal that occurs at a certain rate on the time axis and a signal that occurs at a sufficiently distant point are mutually exclusive. It becomes a correlation. Therefore, the result of multiplying and integrating the signals generated at different times is expressed as a fluctuation whose average value is O.

一方、発振音は周波数が一定でその振幅が時間的に増大
するような正弦波と見なすことができ、異る時点で観測
されたその正弦波、すなわち図1のaおよびeで得られ
る波形を、それぞれA(t)sin(2πf t ) 
       式IA(t−T)sin(2πf(t−
T))    式2とすれば、移相器(8’l、(4)
を経て互に位相差90度の関係、を持ったCおよびdの
波形にeの波形をそれぞれ乗算器(+5)%(テ)を用
いて掛け合せ、得られたgおよびhの波形をそれぞれ積
分器(8)、(9)で積分した結果は、各々 K(t)(Crs(2πfT)+5in(2yr、fT
))     式3K(t)(as(2πfT)−si
n(2・πfT))   式4となる。ただし、上記の
式において、tは時間、Tは遅延時間1.fは周波数を
表わし、K(t)=澁−A(t)A(t −T ) d
 t     式5従りて、演算器(10)、C11)
を自乗器とすれば、加算器(2)の出力G(t)は、 G (tl= −K(t)2         弐6と
なる。G (t)は時間と共に増加し、仮りに鳴音が時
間1=0から一定の振幅で生じた正弦波とすれば、式5
および式6より、 G(t)= A4を臀/4        式7となる
。ただしA=A(t)−A (t−T)。
On the other hand, the oscillated sound can be considered as a sine wave whose frequency is constant and whose amplitude increases over time. , respectively A(t)sin(2πf t )
Formula IA(t-T) sin(2πf(t-
T)) If Equation 2 is used, the phase shifter (8'l, (4)
The waveforms of C and d, which have a phase difference of 90 degrees, are multiplied by the waveform of e using a multiplier (+5)% (te), and the obtained waveforms of g and h are integrated, respectively. The results of integration by the instruments (8) and (9) are respectively K(t)(Crs(2πfT)+5in(2yr, fT
)) Equation 3K(t)(as(2πfT)−si
n(2·πfT)) Equation 4 is obtained. However, in the above formula, t is time and T is delay time 1. f represents the frequency, K(t)=澁−A(t)A(t−T) d
t Equation 5 Therefore, arithmetic unit (10), C11)
If G(t) is a squarer, the output G(t) of adder (2) becomes G(tl=-K(t)2 26.G(t) increases with time, and if the sound is If it is a sine wave generated with a constant amplitude from time 1 = 0, then Equation 5
From Equation 6, G(t)=A4=hip/4 Equation 7. However, A=A(t)-A(t-T).

尚、音声信号あるいは音楽信号(持続する正弦波は含ま
ないものとする)に対しては、G(t)= N(t)<
 (ある一定値〕    弐8と表わされる。
Note that for audio signals or music signals (not including sustained sine waves), G(t)=N(t)<
(A certain constant value) It is expressed as 28.

従って、G(t)がある一定値を越えた時に、利得制御
回路の利得を下げるようにすれば、図1の信号伝送路を
含んだ拡声系に鳴音が生じた場合、自動的にその系の利
得が下がり、鳴音が抑圧されることになる。
Therefore, if the gain of the gain control circuit is lowered when G(t) exceeds a certain value, if a sound occurs in the loudspeaker system including the signal transmission path shown in Figure 1, it will automatically be suppressed. The gain of the system decreases and the noise is suppressed.

以上の説明では、計算の繁雑さを避ける為に、積分器の
時定数を無限大としたが、実用上からは数秒程度の時定
数を与えた方がよい。それはマイクロホンが移動する場
合に、スピーカとマイクロホン間の音響的結合の程度が
時々刻々変化することもあり、拡声系の利得を最初の鳴
音で下げた状態に保ち続ける必要はないからである。ま
た、鳴音によらず、なんらかの正弦波が信号として加わ
った場合、それによって下げられた系の利得は、時定数
に応じた時間経過をもって元に復帰することができるか
らである。
In the above explanation, the time constant of the integrator was set to infinity in order to avoid the complexity of calculation, but from a practical standpoint, it is better to give a time constant of about several seconds. This is because when the microphone moves, the degree of acoustic coupling between the speaker and the microphone may change from moment to moment, and it is not necessary to keep the gain of the amplification system at a lower level at the first sound. Furthermore, if some kind of sine wave is added as a signal, regardless of the sound, the gain of the system that has been lowered by it can be restored to its original value with the passage of time according to the time constant.

図1の演算器(101、αηに絶対値回路を用いた場合
には、式6は式3および式4の絶対値の和で表わされる
。更に式7は、 G(t)= kA” t/2         式9と
なる。kはfTに依存し%  1 <、 k < ?2
の範囲の値をとる係数である。
When an absolute value circuit is used for the arithmetic unit (101, αη) in FIG. /2 becomes Equation 9. k depends on fT and % 1 <, k < ?2
It is a coefficient that takes values in the range of .

音声信号に対しては、純音成分の多い母音の場合でも、
その基本周波数が一定とみなせる時間は高々数十ミリ秒
であるから、Tは数十ミリ秒以上あればよい。音楽の場
合(ハウリング防止の対象としては2次的であるが)、
演奏する楽器によっては定常的な正弦波を発生すること
もあるので、音声に対するよりもTを大きくとる必要が
ある。
For audio signals, even in the case of vowels with many pure tone components,
Since the time period during which the fundamental frequency can be considered constant is several tens of milliseconds at most, T may be at least several tens of milliseconds. In the case of music (although it is a secondary target for howling prevention),
Depending on the instrument being played, a stationary sine wave may be generated, so it is necessary to set T larger than that for voice.

特に電子楽器で一定の音程を鳴らしたときは、物理的に
鳴音と区別できなくなり、本発明による自動ハウリング
防止装置はそれを鳴音と判断して、拡声系の利得を下げ
ることになる。
In particular, when an electronic musical instrument plays a certain pitch, it becomes physically indistinguishable from a ringing sound, and the automatic howling prevention device according to the present invention determines this to be a ringing sound and lowers the gain of the amplification system.

図2はIKHzを中心周波数とした1オクターブの不規
則雑音を用いて、異る時点での二つの波形を掛け合せ積
分した出力波形の実測値Rと、一方の波形を自乗して積
分した出力波形の実測値Sを示したものである。Rは弐
8に相当し、無相関な二つの信号を掛けて積分した出力
波形は、平均値がOなるゆらぎとなることがわかる。S
は正弦波を掛け合せて積分したものではないので、直接
的ではないが、式9に相当する。正弦波であればSは時
間と共になめらかに増加する波形となる。(日本音響学
会講演論文集、昭和57年3月、煮1−1−17参照)
Figure 2 shows the actual measured value R of the output waveform obtained by multiplying and integrating two waveforms at different times using one octave irregular noise with a center frequency of IKHz, and the output waveform obtained by squaring and integrating one waveform. The actual measured value S is shown. R corresponds to 28, and it can be seen that the output waveform obtained by multiplying and integrating two uncorrelated signals has a fluctuation with an average value of O. S
is not the result of multiplying and integrating sine waves, so it corresponds to Equation 9, although it is not direct. If it is a sine wave, S will have a waveform that increases smoothly over time. (Refer to Proceedings of the Acoustical Society of Japan, March 1981, Ni 1-1-17)
.

図3は本発明による自動ハウリング防止装置の第2の実
施例を示すプロ7り図である。図3に於いて、(1)は
第1の分岐手段、(2)は第2の分岐手段を示す。(1
5)は位相差90度をもった一対の正弦波Cおよびdを
出力する発振器、(4)、(5)、(6’)は乗算器を
表わし、(2)で分岐された一対の信号は、位相差90
度をもった一対の正弦波とそれぞれ掛け合されることに
より、位相差90度をもった変調信号gおよびhに変換
される。他方、第1の分岐手段で分岐された信号すは、
遅延手段(3)によって遅延され、乗算器(4)で発振
器部)の出力Cと掛け合され変調信号eに変換され、更
に帯域フィルタ(γ)によって単側帯波信号」が取り出
される。ここて、(4)〜(7)および@耳よ、第1の
実施例である図1の(3)と(4)の処理、即ち位相差
90度なる一対の信号を得るためのものであるが、図3
の方法は信号の全帯域に渡り90度の位相差を与えるの
に適したものである。(8)および(9)は乗算手段、
(10)および(11Jは積分手段、(2)および03
)は演算手段、(14)は加算手段であり、それぞれ図
1の(6)〜(彼で示されたものに対応する。
FIG. 3 is a schematic diagram showing a second embodiment of the automatic howling prevention device according to the present invention. In FIG. 3, (1) shows the first branching means, and (2) shows the second branching means. (1
5) represents an oscillator that outputs a pair of sine waves C and d with a phase difference of 90 degrees, (4), (5), and (6') represent multipliers, and a pair of signals branched at (2). is a phase difference of 90
By multiplying them with a pair of sine waves having different angles, they are converted into modulated signals g and h having a phase difference of 90 degrees. On the other hand, the signal branched by the first branching means is
The signal is delayed by the delay means (3), multiplied by the output C of the oscillator (oscillator section) by the multiplier (4), and converted into a modulated signal e, and further extracted by the bandpass filter (γ) into a single sideband signal. Here, (4) to (7) and @ear, the processing of (3) and (4) in FIG. 1, which is the first embodiment, is to obtain a pair of signals with a phase difference of 90 degrees. There is, but Figure 3
This method is suitable for providing a 90 degree phase difference over the entire signal band. (8) and (9) are multiplication means;
(10) and (11J are integrating means, (2) and 03
) is an arithmetic means, and (14) is an addition means, which correspond to (6) to (1) in FIG. 1, respectively.

発振器(ロ))の出力信号Cおよびdを、それぞれfB
匹(2πFt)、(B sin (2πFt)とし、信
号a(およびb)が式1で表わせるものとすれば、図3
における加算器(14)の出力は、弐6で表わされる。
The output signals C and d of the oscillator (b) are respectively fB
(2πFt), (B sin (2πFt), and if the signal a (and b) can be expressed by Equation 1, then Fig. 3
The output of the adder (14) in is represented by 26.

よって鳴音の抑圧原理は図1での説明と同様であるので
省略する。
Therefore, the principle of suppressing noise is the same as that explained in FIG. 1, so the explanation thereof will be omitted.

尚、図3に於いて、正弦波検出回路は第1の分岐手段(
1)以後、(2)、(3)・・・(15)で構成され、
信号伝送路りに挿入された利得制御回路はQで示されて
いる。同図に於いて帯域フィルタ(7)は、信号gおよ
びhに対して用いてもよい。更に遅延回路(3)は信号
aに対して用いてもよく、これは図1に於いても同様で
ある。
In addition, in FIG. 3, the sine wave detection circuit is connected to the first branching means (
1) Thereafter, it consists of (2), (3)...(15),
A gain control circuit inserted into the signal transmission path is indicated by Q. In the figure, a bandpass filter (7) may be used for signals g and h. Further, the delay circuit (3) may be used for the signal a, which is also the case in FIG.

以上、本発明によれば拡声系で生じる鳴音を自動的に検
出し抑圧することが可能となる。
As described above, according to the present invention, it is possible to automatically detect and suppress noise generated in a public address system.

なお、本発明は上記の実施例に限定されるものではなく
、例えば図1の構成全体あるいは一部をデジタル回路で
実現してもよい。その場合、位相器はアナログ回路と同
様に、−次の巡回型、非巡回型フィルタの直列接続によ
る一対のローパス・フィルタおよびバイパス中フィルタ
を用いて得ることができる。また積分器は一次の巡回型
フィルタによって実現できる。
Note that the present invention is not limited to the above-described embodiment, and for example, the entire or part of the configuration shown in FIG. 1 may be realized by a digital circuit. In that case, the phase shifter can be obtained using a pair of low-pass filters and a filter in bypass formed by series connection of -order cyclic and acyclic filters, similar to analog circuits. Further, the integrator can be realized by a first-order recursive filter.

【図面の簡単な説明】[Brief explanation of drawings]

図1は本発明に係る第1の実施例を示すプロ。 り図、図2は本発明の詳細な説明する実測例、図3は本
発明に係る第2の実施例を示すブロック図である。図1
および図2に於いて、(1)は分岐手段(分岐部)、L
は信号伝送路、Mは正弦波検出回路、Qは利得制御回路
を表わす。
FIG. 1 is a diagram showing a first embodiment of the present invention. FIG. 2 is a measured example for explaining the present invention in detail, and FIG. 3 is a block diagram showing a second embodiment of the present invention. Figure 1
And in FIG. 2, (1) is the branching means (branching part), L
is a signal transmission path, M is a sine wave detection circuit, and Q is a gain control circuit.

Claims (1)

【特許請求の範囲】[Claims] 信号伝送路から第1の分岐手段によって分岐された一対
の信号間に一定の時間差を与える遅延手段と、前記一対
の信号の一方を更に分岐する第2の分岐手段と、該第2
の分岐手段によって分岐された一対の信号間に90度も
しくは約90度の位相差を与える移相手段と、該移相手
段によって位相差を与えられた一対の信号それぞれに前
記第1の分岐手段で分岐された他方の信号を掛け合せる
乗算手段と、該乗算手段の出力信号を一定の減衰率をも
って積分する一対の積分手段と、該積分手段の出力信号
の絶対値もしくは自乗値を出力する一対の演算手段と、
該演算手段の各出力を加え合せる加算手段とを少なくと
も有して成る正弦波検出回路を用いて、前記信号伝送路
に挿入された利得制御回路の利得を前記正弦波検出回路
の出力信によって制御することにより、前記信号伝送路
を含んだ電気音響系に発生する鳴音を抑圧すること特徴
とする自動ハウリング防止装置。
a delay means for providing a certain time difference between the pair of signals branched from the signal transmission path by the first branching means; a second branching means for further branching one of the pair of signals;
phase shifting means for providing a phase difference of 90 degrees or about 90 degrees between the pair of signals branched by the branching means; and the first branching means for each of the pair of signals to which the phase difference is given by the phase shifting means. a pair of integrating means that integrates the output signal of the multiplying means at a constant attenuation rate; and a pair of integrating means that outputs the absolute value or square value of the output signal of the integrating means. calculation means,
Controlling the gain of a gain control circuit inserted in the signal transmission path by the output signal of the sine wave detection circuit, using a sine wave detection circuit comprising at least addition means for adding together the respective outputs of the calculation means. An automatic howling prevention device characterized by suppressing noise generated in an electroacoustic system including the signal transmission path.
JP22676484A 1984-10-30 1984-10-30 Automatic anti-howling device Pending JPS61106000A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP22676484A JPS61106000A (en) 1984-10-30 1984-10-30 Automatic anti-howling device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP22676484A JPS61106000A (en) 1984-10-30 1984-10-30 Automatic anti-howling device

Publications (1)

Publication Number Publication Date
JPS61106000A true JPS61106000A (en) 1986-05-24

Family

ID=16850246

Family Applications (1)

Application Number Title Priority Date Filing Date
JP22676484A Pending JPS61106000A (en) 1984-10-30 1984-10-30 Automatic anti-howling device

Country Status (1)

Country Link
JP (1) JPS61106000A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003032780A (en) * 2001-07-16 2003-01-31 Matsushita Electric Ind Co Ltd Howling detecting and suppressing device, acoustic device provided therewith and howling detecting and suppressing method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003032780A (en) * 2001-07-16 2003-01-31 Matsushita Electric Ind Co Ltd Howling detecting and suppressing device, acoustic device provided therewith and howling detecting and suppressing method
JP4681163B2 (en) * 2001-07-16 2011-05-11 パナソニック株式会社 Howling detection and suppression device, acoustic device including the same, and howling detection and suppression method

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