JPH0313997A - Electronic sound deadening system - Google Patents
Electronic sound deadening systemInfo
- Publication number
- JPH0313997A JPH0313997A JP1150275A JP15027589A JPH0313997A JP H0313997 A JPH0313997 A JP H0313997A JP 1150275 A JP1150275 A JP 1150275A JP 15027589 A JP15027589 A JP 15027589A JP H0313997 A JPH0313997 A JP H0313997A
- Authority
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- Japan
- Prior art keywords
- sound
- divided
- sound waves
- propagation
- sensor
- 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.)
- Granted
Links
- 230000001902 propagating effect Effects 0.000 claims description 28
- 230000030279 gene silencing Effects 0.000 claims description 20
- 238000013016 damping Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 6
- 230000000644 propagated effect Effects 0.000 abstract description 5
- 238000011144 upstream manufacturing Methods 0.000 abstract description 3
- 230000001743 silencing effect Effects 0.000 description 9
- 238000012546 transfer Methods 0.000 description 7
- 238000005192 partition Methods 0.000 description 4
- 238000009434 installation Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 101000640753 Danio rerio Tryptophan 2,3-dioxygenase A Proteins 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000003584 silencer Effects 0.000 description 1
Landscapes
- Soundproofing, Sound Blocking, And Sound Damping (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は電子消音システムに係り、特に音波の伝播通路
を改善して高い消音効果を得るようにした電子消音シス
テムに関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic silencing system, and more particularly to an electronic silencing system that improves the propagation path of sound waves to obtain a high silencing effect.
従来、管内騒音に対する消音を管構造による干渉や管に
内貼りした多孔質材による吸音等の現象を利用して行う
受動型消音器は広く実用されている。しかし、このよう
な受動型消音器は、消音器のサイズ、圧力損失等の点で
、その改善に対する要求が多い。BACKGROUND ART Conventionally, passive silencers have been widely used, which muffle noise inside a pipe by utilizing phenomena such as interference by the pipe structure or sound absorption by a porous material attached to the inside of the pipe. However, there are many demands for improvements in such passive silencers in terms of the size, pressure loss, etc. of the silencer.
一方、これに対して管内騒音を消音するもう一つの方法
として、古くから提案されていた能動型消音器、即ち音
源から伝播してきた騒音に対し、同一音圧、逆位相の付
加音を放射し、音波干渉によって消音効果を強制的に生
じさせる電子消音システムが着目されつつある。On the other hand, as another method for silencing pipe noise, an active muffler has been proposed for a long time. In other words, it emits additional sound of the same sound pressure and opposite phase to the noise propagating from the sound source. Electronic silencing systems that forcibly produce a silencing effect through sound wave interference are attracting attention.
前記電子消音システムは電子デバイス、信号処理技術等
の急速な発達に伴って、最近様々な観点からの研究成果
が次々と発表されている。With the rapid development of electronic devices, signal processing technology, etc., research results regarding the electronic silencing system from various viewpoints have recently been published one after another.
この電子消音システムについて、本出願人は既に特願昭
６１−７１１５号明細書等に於いて実用化の為のシステ
ム構成を開示してきた。Regarding this electronic silencing system, the present applicant has already disclosed a system configuration for practical use in Japanese Patent Application No. 7115/1983.
かかる電子消音システムは、第２図に示すように音波の
伝播通路２２内に於いて騒音源からの伝播音波を検出す
る２つのセンサマイクＭｔ 、Ｍｔが付加音源（スピー
カ）Ｓを基準にして、その上流側と下流側の位置に夫々
設置されている。As shown in FIG. 2, this electronic silencing system includes two sensor microphones Mt for detecting propagating sound waves from a noise source in a sound wave propagation path 22, with Mt as a reference to an additional sound source (speaker) S. They are installed at the upstream and downstream positions, respectively.
一方、コントローラ２４は、主として加算回路２６、Ａ
／Ｄ変換１ｓ２８．３０、Ｄ／Ａ変換部３２、アダプテ
ィブディジタルフィルタ３４及び制御部３６から構成さ
れ、前記２つのセンサマイクＭ＋ 、Ｍａ からの入力
に基づいてスピーカＳを制御する信号を出力する。On the other hand, the controller 24 mainly includes an adder circuit 26, A
It is composed of a /D converter 1s28.30, a D/A converter 32, an adaptive digital filter 34, and a controller 36, and outputs a signal for controlling the speaker S based on inputs from the two sensor microphones M+ and Ma.
即ち、伝播通路２２内に於いて騒音源より発せられた伝
播音波がセンサマイクＭｔ 、Ｍｉ によって検出され
ると、センサマイクＭ＋、Ｍａ の出力信号はＡ／Ｄ変
換部２８を介してディジタルフィルタ３４、制御Ｒ３６
に夫々入力される。制御部３６では、伝播通路２２の外
乱による伝播特性の変化及び各電気音響変換器自体の特
性変化等を考慮して、これらの特性を示す伝達関数を求
め、これらの伝達関数に基づいて消音効果、即ち騒音源
からの伝播音波とスピーカＳから放射された音波との干
渉状態を検出するセンサマイクＭ、の出力信号が最小に
なるようにディジタルフィルタ３４に付与すべき伝達関
数を決定し、この伝達関数を特定する為の制御パラメー
タをディジタルフィルタ３４に設定する。尚、制御部３
６は、伝播通路２２の伝播特性の変化及び制御系の特性
変化に応じて前記制御パラメータの修正を随時行う。こ
の結果、センサマイクＭＩＳＭｔ によって検出された
騒音源からの伝播音波は電気信号に変換され、加算回路
２６、Ａ／Ｄ変換部２８を介してディジタルフィルタ３
４に入力される。この入力信号は、ディジタルフィルタ
３４によって、制御部３６から与えられた伝達関数に基
づいて所定の振幅特性及び位相特性を有するディジタル
信号に変換される。前記ディジタル信号は、Ｄ／Ａ変換
部３２によってＤ／Ａ変換され、スピーカＳの駆動信号
としてスピーカＳの駆動コイルに印加する。これによっ
て、スピーカＳからは、騒音源から発せられた伝播音波
を打ち消す為の音波が放射される。この結果、センサマ
イクＭ２の設置位習に於いて、音波の干渉により騒音源
からの伝播音波は消去され、伝播通路２２中に於けるセ
ンサマイクＭ２ の設置位習より下流側では騒音源から
の伝播音波は伝播されなくなる。That is, when the propagating sound waves emitted from the noise source in the propagation path 22 are detected by the sensor microphones Mt, Mi, the output signals of the sensor microphones M+, Ma are sent to the digital filter 34 via the A/D converter 28. , control R36
are input respectively. The control unit 36 takes into account changes in propagation characteristics due to disturbances in the propagation path 22 and changes in the characteristics of each electroacoustic transducer itself, calculates transfer functions representing these characteristics, and calculates the silencing effect based on these transfer functions. In other words, the transfer function to be given to the digital filter 34 is determined so that the output signal of the sensor microphone M that detects the interference state between the propagating sound wave from the noise source and the sound wave radiated from the speaker S is minimized. Control parameters for specifying the transfer function are set in the digital filter 34. Furthermore, the control section 3
6 modifies the control parameters as needed in response to changes in the propagation characteristics of the propagation path 22 and changes in the characteristics of the control system. As a result, the propagating sound waves from the noise source detected by the sensor microphone MISMt are converted into electrical signals, which are sent to the digital filter 3 via the adder circuit 26 and the A/D converter 28.
4 is input. This input signal is converted by the digital filter 34 into a digital signal having predetermined amplitude characteristics and phase characteristics based on a transfer function given from the control section 36. The digital signal is D/A converted by the D/A converter 32 and applied to the drive coil of the speaker S as a drive signal for the speaker S. As a result, the speaker S emits sound waves for canceling the propagating sound waves emitted from the noise source. As a result, in the installation position of the sensor microphone M2, the propagating sound waves from the noise source are canceled due to the interference of the sound waves, and the propagating sound waves from the noise source are canceled downstream from the installation position of the sensor microphone M2 in the propagation path 22. Propagating sound waves are no longer propagated.
このように、前記電子消音システムでは、第３図に示す
ように伝播通路２２を線形システムと扱い、固有の伝達
関数Ｇで表している。殆どの管路では、これを線形シス
テムとして扱うことが、可能である。尚、同図に於いて
、ｌ（ｅはコントローラ２４０制御特性を示す伝達関数
であり、ｘｌＹはセンサマイクＭ＋ −Ｍｍ に於ける
騒音を示す信号、Ｅは残留騒音を示す信号である。In this way, in the electronic silencing system, the propagation path 22 is treated as a linear system and expressed by a unique transfer function G, as shown in FIG. For most conduits it is possible to treat this as a linear system. In the figure, l(e is a transfer function indicating the control characteristics of the controller 240, xlY is a signal indicating noise in the sensor microphone M+ -Mm, and E is a signal indicating residual noise.
また、電子消音システムは、一次元音場の制御を前提と
しているので、消音可能帯域は伝播通路２２０口径で決
まる平面波伝播周波数以下まで消音可能である。これに
ついては、本出願人らが特開昭６２−１６４４００号公
報明細書に於いて既に開示している。しかし、伝播通路
の口径が大きくなるに伴い、前述した平面波伝播周波数
が低下するので、広帯域層・波数の消音効果を十分に得
ることができない。Further, since the electronic silencing system is based on the control of a one-dimensional sound field, the silencing band can be silencing up to a plane wave propagation frequency determined by the diameter of the propagation path 220 or less. This has already been disclosed by the present applicants in the specification of Japanese Patent Application Laid-Open No. 164400/1983. However, as the diameter of the propagation path increases, the plane wave propagation frequency described above decreases, making it impossible to obtain a sufficient silencing effect for broadband layers and wave numbers.
この問題を解消する為に、大口径伝播通路を゛仕切板に
よって一次元音場を形成できる小口径伝播通路に分割し
、この分割伝播通路にセンサマイク、スピーカを夫々取
付は消音効果を図ることが考えられるが、各分割伝播通
路にセンサマイク、スピーカを夫々取付けると、仕切板
の末端から他の分割伝播通路に伝播する音による影響で
個々の分割伝播通路内で安定した消音効果を得ることが
できないという欠点がある。In order to solve this problem, the large-diameter propagation passage is divided into small-diameter propagation passages that can form a one-dimensional sound field using a partition plate, and a sensor microphone and a speaker are installed in each of these divided propagation passages to achieve a silencing effect. However, if a sensor microphone and a speaker are installed in each divided propagation path, a stable sound silencing effect can be obtained within each divided propagation path due to the influence of sound propagating from the end of the partition plate to other divided propagation paths. The disadvantage is that it cannot be done.
本発明はこのような事情に鑑みてなされたもので、分割
伝播通路内を伝播する音波が相互に伝播通路に回り込む
ことにより生じる、各々の制御系に与える影響をなくし
、広帯域周波数の消音効果を安定して得ることのできる
電子消音システムを提供することを目的とする。The present invention has been made in view of the above circumstances, and eliminates the influence on each control system caused by the sound waves propagating in the divided propagation paths mutually going around the propagation paths, and improves the silencing effect of wide band frequencies. The purpose is to provide an electronic silencing system that can be stably obtained.
本発明は、前記目的を達成する為に、音波の伝播通路内
に於ける騒音源からの伝播音波を第一第二のセンサマイ
クによって検出し、この検出した伝播音波によって逆位
相で且つ同一音圧の音波をスピーカから発生させ、前記
伝播通路内の前記第二のセンサマイクの位置で騒音が最
小になるようにその音波干渉により消音を行う電子消音
システムに於いて、前記伝播通路（１０）内を、一次元
音場を形成する口径の伝播通路（１０ａ、１０ｂ）に分
割し、該分割した各伝播通路（ｌ Ｏａ。In order to achieve the above object, the present invention detects a propagating sound wave from a noise source in a sound wave propagation path using a first and second sensor microphone, and uses the detected propagating sound wave to generate the same sound with opposite phase. In the electronic sound damping system, the sound waves of pressure are generated from a speaker, and the sound waves are silenced by the interference of the sound waves so that the noise is minimized at the position of the second sensor microphone in the propagation path, the propagation path (10) The inside is divided into propagation passages (10a, 10b) having apertures that form a one-dimensional sound field, and each divided propagation passage (lOa).
１０ｂ）毎に該伝播通路（１０ａ、１０ｂ）の入口から
伝播音波の進行方向に向かって前記第一のセンサマイク
（１２ａ、１２ｂ）、スピーカ（１６ａ、１６ｂ）を夫
々取付け、分割した伝播通路（１０ａ、１０ｂ）の合流
後の通路に共通の第二のセンサマイク（１４）を取付け
たことをｒｆ微とする。10b), the first sensor microphones (12a, 12b) and speakers (16a, 16b) are respectively attached from the entrance of the propagation path (10a, 10b) in the traveling direction of the propagating sound wave, and the divided propagation path ( The installation of a common second sensor microphone (14) in the path after the merging of the two sensors 10a and 10b) is referred to as RF micro.
本発明によれば、伝播通路（１０）内を一次元音場とな
る口径の伝播通路（１０ａ、１０ｂ）に分割し、この分
割伝播通路（１０ａ、１ｏｂ）の入口（上流）側から伝
播音波の進行方向に向かって第一のセンサマイク（１２
ａ、１２ｂ）、スピーカ（１６ａ、 １６ ｂ）を取付
け、分割伝播通路＜１０ａ、１０ｂ）の合流後の通路に
共通の第二のマイクセンサ（１４）を取付けて、分割伝
播通路（１０ａ、１０ｂ）内を伝播する音波が相互に伝
播通路（１０ａ、１０ｂ）に回り込むことによって生じ
る、各々の制御系に与える影響をなくしたので、広帯域
周波数の消音効果を安定して得ることができる。According to the present invention, the inside of the propagation passage (10) is divided into propagation passages (10a, 10b) having a diameter constituting a one-dimensional sound field, and the propagating sound waves are The first sensor microphone (12
a, 12b), speakers (16a, 16 b) are attached, a common second microphone sensor (14) is attached to the path after the merging of the divided propagation paths <10a, 10b), and the divided propagation paths (10a, 10b) are connected. ) The effects on each control system caused by the sound waves propagating through the propagation paths (10a, 10b) are eliminated, so it is possible to stably obtain a wide-band frequency silencing effect.
以下添付図面に従って本発明に係る電子消音システムの
好ましい実施例を詳説する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the electronic silencing system according to the present invention will be described in detail below with reference to the accompanying drawings.
第１図は本発明に係る電子消音システムの実施例を示す
要部斜視図が示され、電子消音システム用ダクトｌＯに
はセンサマイク１２ａ、１２ｂ。FIG. 1 is a perspective view of a main part showing an embodiment of an electronic silencing system according to the present invention, and a duct 10 for the electronic silencing system includes sensor microphones 12a and 12b.
１４、スピーカ１６ａ、１６ｂが配設されている。14, speakers 16a and 16b are provided.
尚、ここでは第２図に示したコントローラ部分の作用を
省略し、またセンサマイク１２ａ、１２ｂ。Note that the operation of the controller portion shown in FIG. 2 is omitted here, and the sensor microphones 12a and 12b are illustrated.
１４、スピーカ１６ａ、１６ｂの各作用についても省略
する。14 and the functions of the speakers 16a and 16b will also be omitted.
一般に、前記ダク）１０は亜鉛鉄板で断面矩形状に構成
され、図示しない騒音源から発せられる伝播音波が矢印
入方向に伝播している。また、ダクト１００口径は、前
記伝播音波に対して一次元音場とならない大口径に形成
されている。Generally, the duct 10 is made of a galvanized iron plate and has a rectangular cross section, and propagating sound waves emitted from a noise source (not shown) propagate in the direction indicated by the arrow. Further, the diameter of the duct 100 is formed to a large diameter that does not create a one-dimensional sound field for the propagating sound waves.
前記ダクト１０内には矩形状の仕切板１８が取付けられ
、ダクト１０を２分割している。これによって、ダク）
１０は一次元音場を形成することができる口径の分割ダ
クトｔｏ−ａ、ｔａｂに分割されている。A rectangular partition plate 18 is attached within the duct 10 to divide the duct 10 into two. By this, Dak)
10 is divided into divided ducts TO-A and TAB having a diameter capable of forming a one-dimensional sound field.
前記分割ダク）１０ａ、１０ｂの上面中央部には、スピ
ーカ１６ａ、１６ｂが取付けられている。Speakers 16a and 16b are attached to the center portions of the upper surfaces of the divided ducts 10a and 10b.
また、スピーカ１６ａ、１６ｂの上部にはコントローラ
２０ａ、２０ｂが夫々設置されている。Furthermore, controllers 20a and 20b are installed above the speakers 16a and 16b, respectively.
前記センサマイク１２ａ、１２ｂは、前記スピーカ１６
ａ、１６ｂを基準にして分割ダクト１０ａ、１０ｂに於
ける伝播音波の上流側に設けられ、分割ダク）１０ａ、
１０ｂ内に於ける騒音源からの伝播音波を検出している
。また、センサマイク１４は、前記スピーカ１６ａ、１
６ｂを基準にして分割ダク）１０ａ、１０ｂに於ける伝
播音波の下流側後方で分割ダク）１０ａ、１０ｂが合流
する位置に設けられている。これによって、前記センサ
マイク１４は、ダクト１０ａＳ１０ｂの下流側に夫々設
けられていた従来のセンサマイクと比較し、分割ダク）
１０ａ、１０ｂ内を伝播する音波が相互に分割ダク）１
０ａ、１０ｂ内に回り込んできても制御に影響されるこ
となく伝播音波を検出することができる。The sensor microphones 12a and 12b are connected to the speaker 16.
a, 16b, provided on the upstream side of the propagating sound waves in the divided ducts 10a, 10b, divided ducts) 10a,
A propagating sound wave from a noise source within 10b is detected. Further, the sensor microphone 14 is connected to the speakers 16a, 1
It is provided at a position where the divided ducts 10a and 10b join at the rear of the downstream side of the propagating sound waves in the divided ducts 10a and 10b with respect to the dividing duct 6b. As a result, the sensor microphone 14 is installed in a divided duct (compared to conventional sensor microphones that are respectively provided on the downstream side of the duct 10aS10b).
The sound waves propagating in 10a and 10b are mutually divided) 1
Even if the propagating sound waves go around inside 0a and 10b, the propagating sound waves can be detected without being affected by the control.
また、本実施例ではダクト１０を２分割するとしたが、
この分割数に限られるものではなく分割したダクトの口
径が一次元音場を形成できる大きさに、ダクト１０の口
径に応じて適宜に分割すれば良い。また、分割したダク
トの口径形状は矩形状に限られるものではなく、例えば
三角形状等にしても良い。Furthermore, in this embodiment, the duct 10 is divided into two parts, but
The number of divisions is not limited to this number, and the division may be made as appropriate depending on the diameter of the duct 10 so that the diameter of the divided duct can form a one-dimensional sound field. Further, the diameter shape of the divided duct is not limited to a rectangular shape, and may be, for example, a triangular shape.
以上説明したように本発明に係る電子消音システムによ
れば、大口径のダクトを一次元音場となる小口径ダクト
に分割し、この分割ダクトの上流側から伝播音波の進行
方向に向かって第一のセンサマイク、スピーカを夫々取
付け、分割ダクトの合流後のダクトに共通の第二のセン
サマイクを取付け、分割ダクト内を伝播する音波が相互
に伝播通路に回り込むことによって生じる、各々の制御
系に与える影響をなくしたので、広帯域周波数の消音効
果を安定して得ることができる。As explained above, according to the electronic silencing system of the present invention, a large-diameter duct is divided into small-diameter ducts that form a one-dimensional sound field. Each control system is generated by installing one sensor microphone and speaker respectively, and installing a common second sensor microphone in the duct after the merging of the divided ducts, so that the sound waves propagating in the divided ducts mutually wrap around the propagation path. Since the effect on noise is eliminated, it is possible to stably obtain a wide-band frequency silencing effect.
第１図は本発明に係る電子消音システムの実施例を示す
要部斜視図、第２図は従来の電子消音システムの基本構
成図、第３図は電子消音システムの概念を示す図である
。
１０・・・ダクト、 １．Ｏａ、１０ｂ・・・分割ダ
クト、１２ａ、１２ｂ％ １４−・・センサマイク、
１６ａ、１５ｂ・・・スピーカ、 １８・・・仕切
板。FIG. 1 is a perspective view of a main part showing an embodiment of an electronic silencing system according to the present invention, FIG. 2 is a basic configuration diagram of a conventional electronic silencing system, and FIG. 3 is a diagram showing the concept of an electronic silencing system. 10...Duct, 1. Oa, 10b...Divided duct, 12a, 12b% 14-...Sensor microphone,
16a, 15b...Speaker, 18...Partition plate.
Claims (1)
、第二のセンサマイクによって検出し、この検出した伝
播音波によって逆位相で且つ同一音圧の音波をスピーカ
から発生させ、前記伝播通路内の前記第二のセンサマイ
クの位置で騒音が最小になるようにその音波干渉により
消音を行う電子消音システムに於いて、 前記伝播通路内を、一次元音場を形成する口径の伝播通
路に分割し、該分割した各伝播通路毎に該伝播通路の入
口から伝播音波の進行方向に向かって前記第一のセンサ
マイク、スピーカを夫々取付け、分割した伝播通路の合
流後の通路に共通の第二のセンサマイクを取付けたこと
を特徴とする電子消音システム。[Claims] First and second sensor microphones detect propagating sound waves from a noise source in a sound wave propagation path, and the detected propagating sound waves send sound waves of opposite phase and the same sound pressure to a speaker. In an electronic sound damping system that generates sound from a sound source and muffles the sound by its sonic interference so that the noise is minimized at the position of the second sensor microphone in the propagation path, a one-dimensional sound field is created in the propagation path. The first sensor microphone and the speaker are respectively attached to each of the divided propagation passages from the entrance of the propagation passage in the direction in which the propagating sound waves travel, and the divided propagation passages are joined together. An electronic silencing system characterized by having a common second sensor microphone installed in the rear aisle.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1150275A JP2596127B2 (en) | 1989-06-12 | 1989-06-12 | Electronic silencing system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1150275A JP2596127B2 (en) | 1989-06-12 | 1989-06-12 | Electronic silencing system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0313997A true JPH0313997A (en) | 1991-01-22 |
| JP2596127B2 JP2596127B2 (en) | 1997-04-02 |
Family
ID=15493401
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1150275A Expired - Fee Related JP2596127B2 (en) | 1989-06-12 | 1989-06-12 | Electronic silencing system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2596127B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1992017936A1 (en) * | 1991-04-05 | 1992-10-15 | Applied Acoustic Research | Active noise control |
| US5452362A (en) * | 1994-01-26 | 1995-09-19 | Sun Microsystems, Inc. | Apparatus and method for cooling with noise control |
| US5606622A (en) * | 1994-09-29 | 1997-02-25 | The Boeing Company | Active noise control in a duct with highly turbulent airflow |
| US5689572A (en) * | 1993-12-08 | 1997-11-18 | Hitachi, Ltd. | Method of actively controlling noise, and apparatus thereof |
| US7114274B2 (en) | 2003-07-22 | 2006-10-03 | Matsushita Electric Industrial Co., Ltd. | Ironing apparatus |
-
1989
- 1989-06-12 JP JP1150275A patent/JP2596127B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1992017936A1 (en) * | 1991-04-05 | 1992-10-15 | Applied Acoustic Research | Active noise control |
| US5511127A (en) * | 1991-04-05 | 1996-04-23 | Applied Acoustic Research | Active noise control |
| US5689572A (en) * | 1993-12-08 | 1997-11-18 | Hitachi, Ltd. | Method of actively controlling noise, and apparatus thereof |
| US5452362A (en) * | 1994-01-26 | 1995-09-19 | Sun Microsystems, Inc. | Apparatus and method for cooling with noise control |
| US5606622A (en) * | 1994-09-29 | 1997-02-25 | The Boeing Company | Active noise control in a duct with highly turbulent airflow |
| US7114274B2 (en) | 2003-07-22 | 2006-10-03 | Matsushita Electric Industrial Co., Ltd. | Ironing apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2596127B2 (en) | 1997-04-02 |
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