JP3874749B2 - Target sound detection method and apparatus - Google Patents
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Description
本発明は、振動する物体の特定の音響放射面から放射される音だけを検出する対象音検出方法及びその装置に関する。 The present invention relates to a target sound detection method and apparatus for detecting only sound radiated from a specific acoustic radiation surface of a vibrating object.
従来、振動する物体の特定の音響放射面から放射される音を検出するために、２マイクロホン法による音響インテンシティ計測が用いられている。これは、ある距離だけ隔てて設置された２つのマイクロホンによって計測された音圧から空気粒子速度ベクトルと音圧を近似し、その積から空間を通過する音響エネルギーを表すベクトル量を算出する方法であり、そのベクトルの大きさおよび向きにより音を放射している放射面を特定することで振動する物体の特定の音響放射面から放射される音を検出する方法である（例えば、非特許文献１参照）。
しかし、２マイクロホン法による音響インテンシティ計測によって振動する物体の特定の音響放射面から放射される音を検出する場合、下記のような問題がある。 However, when detecting sound radiated from a specific acoustic radiation surface of a vibrating object by acoustic intensity measurement by the two-microphone method, there are the following problems.
（１）空間を通過するすべての音響エネルギーを計測するため、対象とする特定の放射面以外の放射面から放射される音の音響エネルギーを除去することができない。従って、特定の放射面からの放射音の音響エネルギーが、それ以外の放射面からの放射音の音響エネルギーと同等あるいは小さい場合、特定の放射面からの放射音を検出できない。 (1) Since all the acoustic energy passing through the space is measured, the acoustic energy of the sound radiated from the radiation surface other than the target specific radiation surface cannot be removed. Therefore, when the acoustic energy of the radiated sound from the specific radiation surface is equal to or smaller than the acoustic energy of the radiated sound from the other radiation surfaces, the radiated sound from the specific radiation surface cannot be detected.
（２）空間を通過するすべての音響エネルギーを計測するため、対象とする物体以外の物体からの放射音の音響エネルギーを除去することができない。従って、計測対象の物体からの放射音の音響エネルギーが、それ以外の物体からの放射音の音響エネルギーと同等あるいは小さい場合、計測対象の物体からの放射音を検出できない。 (2) Since all the acoustic energy passing through the space is measured, the acoustic energy of the sound radiated from an object other than the target object cannot be removed. Therefore, when the acoustic energy of the radiated sound from the measurement target object is equal to or smaller than the acoustic energy of the radiated sound from the other objects, the radiated sound from the measurement target object cannot be detected.
（３）空間を通過するすべての音響エネルギーを計測するため、対象とする特定の放射面からの放射音が他の物体で反射して伝搬する反射音の音響エネルギーを除去することができない。従って、正確な放射音の音響エネルギーを算出できず、放射面の特定に誤差が生じるため、振動する物体の特定の音響放射面から放射される音を検出することができない。 (3) Since all the acoustic energy passing through the space is measured, it is impossible to remove the acoustic energy of the reflected sound that is propagated by reflecting the sound emitted from the target specific radiation surface by another object. Therefore, accurate acoustic energy of the radiated sound cannot be calculated, and an error occurs in the specification of the radiating surface, so that the sound radiated from the specific acoustic radiating surface of the vibrating object cannot be detected.
（４）放射面からある距離はなれた２次元計測平面上の多数の点において、音響インテンシティを算出する必要があり、その上、１点の音響インテンシティを算出するためにマイクロホン、マイクロホンアンプおよび分析器などが２系列必要となる。従って、計測点数が増えるほど計測器に対するコストが増加する。 (4) It is necessary to calculate the sound intensity at a number of points on the two-dimensional measurement plane at a certain distance from the radiation surface. In addition, in order to calculate the sound intensity at one point, a microphone, a microphone amplifier, and Two analyzers are required. Therefore, the cost for the measuring instrument increases as the number of measurement points increases.
これらの問題を解決するためには、高い防音性能を有する無響室内に計測対象物体のみを設置し、音響インテンシティを計測する必要がある。従って、計測対象物が通常の使用状態または稼動状態での計測は不可能であり、複数の機器が組み合わされて使用または稼動している場合には、その一部の機器を対象とした計測は不可能である。また、計測器に対するコストを軽減するには、多数点での計測を少数のマイクロホンおよび分析器などで数回に分けて計測するなどの多大な作業と時間を必要とする。
本発明は、従来の技術が有するこのような問題点に鑑みてなされたものであり、その目的とするところは、計測系の簡素化によりコストを軽減し、計測対象物が通常使用または稼動している状態において、計測対象物の特定の音響放射面から放射される音の検出方法及びその装置を提供しようとするものである。
In order to solve these problems, it is necessary to install only the measurement target object in an anechoic room having high soundproof performance and measure the sound intensity. Therefore, the measurement object cannot be measured in the normal use state or operation state, and when multiple devices are used or operated in combination, the measurement for some of the devices is not possible. Impossible. Further, in order to reduce the cost for the measuring instrument, a great deal of work and time are required, such as measuring a number of points in several times with a small number of microphones and analyzers.
The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to reduce the cost by simplifying the measurement system, so that the measurement object is normally used or operated. The present invention is intended to provide a method and apparatus for detecting sound radiated from a specific acoustic radiation surface of a measurement object.
上記課題を解決すべく請求項１に係る発明は、振動する物体の特定の音響放射面から放射される可聴周波数域の音を検出する対象音検出方法であって、前記特定の音響放射面及びこの音響放射面近傍に設けた音圧検出手段に向けて波長掃引レーザ光を放射し、前記特定の音響放射面からの反射光及び前記音圧検出手段からの反射光を前記波長掃引レーザ光と干渉させ、前記特定の音響放射面からの反射光と前記波長掃引レーザ光との干渉強度及び前記音圧検出手段からの反射光と前記波長掃引レーザ光との干渉強度を同時に検出し、次いで前記特定の音響放射面からの反射光のドップラシフトによる周波数変化を前記特定の音響放射面の振動速度に変換すると共に、前記音圧検出手段からの反射光のドップラシフトによる周波数変化を前記音圧検出手段の振動速度に変換し、次いで前記特定の音響放射面の振動速度と前記音圧検出手段の振動速度のクロススペクトルを求め、前記特定の音響放射面からの可聴周波数域の放射音が他の物体で反射して伝搬する反射音と、前記特定の音響放射面以外の音響放射面及び前記振動物体以外の物体からの可聴周波数域の放射音を除去して前記特定の音響放射面から放射される可聴周波数域の音だけを検出するようにした。 In order to solve the above-mentioned problem, the invention according to claim 1 is a target sound detection method for detecting sound in an audible frequency range radiated from a specific acoustic radiation surface of a vibrating object, the specific acoustic radiation surface and A wavelength swept laser beam is emitted toward the sound pressure detecting means provided in the vicinity of the acoustic radiation surface, and the reflected light from the specific acoustic radiation surface and the reflected light from the sound pressure detecting means are converted to the wavelength swept laser light. Detecting the interference intensity between the reflected light from the specific acoustic radiation surface and the wavelength swept laser light and the interference intensity between the reflected light from the sound pressure detecting means and the wavelength swept laser light at the same time; The frequency change due to the Doppler shift of the reflected light from the specific acoustic radiation surface is converted into the vibration speed of the specific acoustic radiation surface, and the frequency change due to the Doppler shift of the reflected light from the sound pressure detecting means is converted into the sound. It is converted into the vibration speed of the detection means, and then the cross spectrum of the vibration speed of the specific acoustic radiation surface and the vibration speed of the sound pressure detection means is obtained. The reflected sound that is reflected and propagated by the object and the radiated sound in the audible frequency range from the sound emitting surface other than the specific sound emitting surface and the object other than the vibrating object are removed and emitted from the specific sound emitting surface. Only the sound in the audible frequency range is detected.
請求項２に係る発明は、振動する物体の特定の音響放射面から放射される可聴周波数域の音を検出する対象音検出装置であって、前記特定の音響放射面近傍の音圧を検出する音圧検出手段と、前記特定の音響放射面及び前記音圧検出手段に向けて波長掃引レーザ光を照射するレーザ照射手段と、前記特定の音響放射面からの反射光及び前記音圧検出手段からの反射光を夫々前記波長掃引レーザ光と干渉させる干渉手段と、前記特定の音響放射面からの反射光と前記波長掃引レーザ光との干渉強度及び前記音圧検出手段からの反射光と前記波長掃引レーザ光との干渉強度を同時に検出する干渉強度検出手段と、この干渉強度検出手段が検出した前記特定の音響放射面からの反射光のドップラシフトによる周波数変化を前記特定の音響放射面の振動速度に変換すると共に、前記音圧検出手段からの反射光のドップラシフトによる周波数変化を前記音圧検出手段の振動速度に変換する変換手段と、前記特定の音響放射面の振動速度と前記音圧検出手段の振動速度のクロススペクトルを求める演算手段を備える。 The invention according to claim 2 is a target sound detection device that detects sound in an audible frequency range radiated from a specific acoustic radiation surface of a vibrating object, and detects sound pressure in the vicinity of the specific acoustic radiation surface. From sound pressure detection means, laser irradiation means for irradiating the specific acoustic emission surface and the sound pressure detection means with wavelength-swept laser light, reflected light from the specific acoustic emission surface, and sound pressure detection means Interference light that interferes with the wavelength-swept laser light, interference intensity between the reflected light from the specific acoustic radiation surface and the wavelength-swept laser light, reflected light from the sound pressure detection means, and the wavelength. Interference intensity detection means for simultaneously detecting the interference intensity with the swept laser light, and frequency change due to Doppler shift of the reflected light from the specific acoustic emission surface detected by the interference intensity detection means is performed on the vibration of the specific acoustic emission surface. Conversion means for converting frequency change caused by Doppler shift of reflected light from the sound pressure detection means into vibration speed of the sound pressure detection means, and vibration speed and sound pressure of the specific acoustic radiation surface. Computation means for obtaining a cross spectrum of the vibration speed of the detection means is provided.
以上説明したように本発明によれば、従来技術が必要とする高い防音性能を有する無響室などを用いることなく、計測対象物が通常使用または稼動している状態において、計測対象物の特定の音響放射面から放射される音を検出することができる。 As described above, according to the present invention, it is possible to specify the measurement object in a state where the measurement object is normally used or operated without using an anechoic chamber having high sound insulation performance required by the prior art. The sound radiated from the acoustic radiation surface can be detected.
以下に本発明の実施の形態を添付図面に基づいて説明する。ここで、図１は本発明に係る対象音検出装置の実施例１の構成図、図２は信号発生器からレーザ発振器へ注入される電流の変化図、図３はレーザ発振器が照射するレーザ光の周波数の変化図、図４はレーザ受光器に入射する全反射鏡及び半反射薄膜鏡からのレーザ光の周波数の変化図、図５はレーザ受光器に入射する全反射鏡、半反射薄膜鏡及び音響反射面からのレーザ光の周波数の変化図、図６はレーザ受光器に入射する全反射鏡、半反射薄膜鏡及び音響反射面からのレーザ光の干渉によるビート信号の強度分布図、図７は本発明に係る対象音検出装置の実施例２の構成図、図８は本発明に係る対象音検出装置の実施例３の構成図である。 Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a block diagram of Example 1 of the target sound detection apparatus according to the present invention, FIG. 2 is a change diagram of a current injected from a signal generator to a laser oscillator, and FIG. 3 is a laser beam irradiated by the laser oscillator. FIG. 4 is a diagram showing changes in the frequency of laser light from a total reflection mirror and a semi-reflection thin film mirror incident on the laser receiver, and FIG. 5 is a diagram showing a total reflection mirror and a semi-reflection thin film mirror incident on the laser receiver. FIG. 6 is a diagram showing changes in the frequency of the laser light from the acoustic reflection surface, FIG. 6 is an intensity distribution diagram of the beat signal due to the interference of the laser light from the total reflection mirror, the semi-reflection thin film mirror and the acoustic reflection surface incident on the laser receiver. 7 is a configuration diagram of the second embodiment of the target sound detection device according to the present invention, and FIG. 8 is a configuration diagram of the third embodiment of the target sound detection device according to the present invention.
本発明に係る対象音検出装置の実施例１は、図１に示すように、信号発生器１、レーザ発振器２、ビームスプリッタ３、全反射鏡４、半反射薄膜鏡５、レーザ受光器６、周波数−電圧変換器７，８、Ａ／Ｄ変換器９，１０およびクロススペクトル演算部１１からなる。 As shown in FIG. 1, the target sound detection apparatus according to the first embodiment of the present invention includes a signal generator 1, a laser oscillator 2, a beam splitter 3, a total reflection mirror 4, a semi-reflection thin film mirror 5, a laser receiver 6, It consists of frequency-voltage converters 7 and 8, A / D converters 9 and 10, and a cross spectrum calculation unit 11.
信号発生器１は、レーザ発振器２への注入電流を時々刻々に変化させる電気信号を発生する。レーザ発振器２は、信号発生器１によって注入された電流の大きさに比例して周波数が変化するレーザ光（波長掃引レーザ光）を半反射薄膜鏡５及び音響放射面１２に照射する。 The signal generator 1 generates an electric signal that changes the injection current to the laser oscillator 2 every moment. The laser oscillator 2 irradiates the semi-reflective thin film mirror 5 and the acoustic emission surface 12 with laser light (wavelength-swept laser light) whose frequency changes in proportion to the magnitude of the current injected by the signal generator 1.
ビームスプリッタ３は、レーザ発振器２が照射したレーザ光を全反射鏡４の方向と半反射薄膜鏡５の方向に分ける機能と、全反射鏡４によって反射されたレーザ光をレーザ受光器６の方向に透過する機能と、半反射薄膜鏡５によって反射されたレーザ光をレーザ受光器６の方向に反射する機能を有している。全反射鏡４は、ビームスプリッタ３からのレーザ光をビームスプリッタ３の方向に完全反射する。ビームスプリッタ３と全反射鏡４により、音響放射面１２及び半反射薄膜鏡５からの反射光は、夫々レーザ発振器２からのレーザ光と干渉する。 The beam splitter 3 functions to divide the laser light irradiated by the laser oscillator 2 into the direction of the total reflection mirror 4 and the direction of the semi-reflection thin film mirror 5, and the direction of the laser light reflected by the total reflection mirror 4 to the laser receiver 6. And the function of reflecting the laser beam reflected by the semi-reflective thin film mirror 5 in the direction of the laser receiver 6. The total reflection mirror 4 completely reflects the laser beam from the beam splitter 3 in the direction of the beam splitter 3. By the beam splitter 3 and the total reflection mirror 4, the reflected light from the acoustic radiation surface 12 and the semi-reflective thin film mirror 5 interferes with the laser light from the laser oscillator 2, respectively.
音圧検出手段としての半反射薄膜鏡５は、ビームスプリッタ３からのレーザ光のうち半分を透過し、残りの半分をビームスプリッタ３の方向に反射すると共に、音響放射面１２から放射される音波の音圧に比例して振動する。なお、半反射薄膜鏡５は、例えば高分子膜に金属を蒸着させて形成される。 The semi-reflective thin film mirror 5 as sound pressure detecting means transmits half of the laser light from the beam splitter 3, reflects the other half in the direction of the beam splitter 3, and emits sound waves emitted from the acoustic radiation surface 12. Vibrates in proportion to the sound pressure. The semi-reflective thin film mirror 5 is formed by evaporating metal on a polymer film, for example.
そして、レーザ発振器２、ビームスプリッタ３、全反射鏡４およびレーザ受光器６は、振動しないように固定される。半反射薄膜鏡５は、振動物体１３の音響放射面１２の近傍に、音響放射面１２とは非接触で設置される。 The laser oscillator 2, the beam splitter 3, the total reflection mirror 4, and the laser receiver 6 are fixed so as not to vibrate. The semi-reflective thin film mirror 5 is installed in the vicinity of the acoustic radiation surface 12 of the vibrating object 13 without contact with the acoustic radiation surface 12.
この時、ビームスプリッタ３と全反射鏡４の距離、ビームスプリッタ３と半反射薄膜鏡５の距離、ビームスプリッタ３と音響放射面１２の距離には、差を設けておく。 At this time, a difference is provided in the distance between the beam splitter 3 and the total reflection mirror 4, the distance between the beam splitter 3 and the semi-reflective thin film mirror 5, and the distance between the beam splitter 3 and the acoustic radiation surface 12.
レーザ受光器６は、入射したレーザ光の強度に比例した電気信号を出力する。例えば、２つのレーザ光を干渉させてレーザ受光器６に入射させれば、レーザ受光器６は２つのレーザ光の周波数の差に等しい周波数のビート信号を出力する。周波数−電圧変換器７，８は、レーザ受光器６から出力される電気信号のうち、特定周波数範囲の周波数変化に比例した電圧を出力する。 The laser receiver 6 outputs an electrical signal proportional to the intensity of the incident laser beam. For example, when two laser beams interfere with each other and enter the laser receiver 6, the laser receiver 6 outputs a beat signal having a frequency equal to the difference between the frequencies of the two laser beams. The frequency-voltage converters 7 and 8 output a voltage proportional to a frequency change in a specific frequency range among the electrical signals output from the laser receiver 6.
Ａ／Ｄ変換器９，１０は、周波数−電圧変換器７，８が出力したアナログ電気信号を、ある一定時間間隔のデジタル信号に変換する。クロススペクトル演算部１１は、Ａ／Ｄ変換器９，１０から出力されるデジタル信号を演算処理してクロススペクトルを算出する。 The A / D converters 9 and 10 convert the analog electric signals output from the frequency-voltage converters 7 and 8 into digital signals at certain time intervals. The cross spectrum calculation unit 11 calculates the cross spectrum by calculating the digital signals output from the A / D converters 9 and 10.
以上のように構成した本発明に係る対象音検出装置の実施例１の動作及び対象音検出方法について説明する。 The operation and the target sound detection method of the first embodiment of the target sound detection apparatus according to the present invention configured as described above will be described.
信号発生器１は、図２に示すように、一定振幅で一定周期の鋸波になるように制御された電流をレーザ発振器２へ注入する。すると、レーザ発振器２は、注入された電流の変化に伴って、図３に示すように、照射するレーザ光の周波数を変化させる。 As shown in FIG. 2, the signal generator 1 injects a current controlled so as to be a sawtooth wave with a constant amplitude and a constant period into the laser oscillator 2. Then, the laser oscillator 2 changes the frequency of the irradiated laser light as shown in FIG. 3 in accordance with the change of the injected current.
次いで、ビームスプリッタ３は、レーザ発振器２が照射したレーザ光を全反射鏡４の方向と半反射薄膜鏡５の方向に分配する。半反射薄膜鏡５の方向に分配されたレーザ光は、半反射薄膜鏡５によってビームスプリッタ３の方向に反射するレーザ光と、振動物体１３の音響放射面１２へ照射するレーザ光に分けられる。また、音響放射面１２へ照射されたレーザ光は、音響放射面１２でビームスプリッタ３の方向に反射する。 Next, the beam splitter 3 distributes the laser light irradiated by the laser oscillator 2 in the direction of the total reflection mirror 4 and the direction of the semi-reflection thin film mirror 5. The laser light distributed in the direction of the semi-reflective thin film mirror 5 is divided into laser light reflected by the semi-reflective thin film mirror 5 in the direction of the beam splitter 3 and laser light irradiated to the acoustic radiation surface 12 of the vibrating object 13. Further, the laser light irradiated to the acoustic radiation surface 12 is reflected by the acoustic radiation surface 12 in the direction of the beam splitter 3.
この時、半反射薄膜鏡５は、音響放射面１２から放射される音波の音圧に比例して振動しており、半反射薄膜鏡５からの反射光の周波数は、ドップラ効果により、半反射薄膜鏡５の振動速度に比例して変化する。また、音響放射面１２も振動しているので、音響放射面１２からの反射光の周波数も、ドップラ効果により、音響放射面１２の振動速度に比例して変化する。 At this time, the semi-reflective thin film mirror 5 vibrates in proportion to the sound pressure of the sound wave emitted from the acoustic radiation surface 12, and the frequency of the reflected light from the semi-reflective thin film mirror 5 is semi-reflective due to the Doppler effect. It changes in proportion to the vibration speed of the thin film mirror 5. Further, since the acoustic radiation surface 12 is also oscillating, the frequency of the reflected light from the acoustic radiation surface 12 also changes in proportion to the vibration speed of the acoustic radiation surface 12 due to the Doppler effect.
次いで、半反射薄膜鏡５からの反射光は、ビームスプリッタ３で反射し、レーザ受光器６に入射する。この時、ビームスプリッタ３と全反射鏡４の距離と、ビームスプリッタ３と半反射薄膜鏡５の距離の差によって、レーザ発振器２から照射されたレーザ光が全反射鏡４を経てレーザ受光器６に到達するまでの時間と、半反射薄膜鏡５を経てレーザ受光器６に到達するまでの時間に差が生じる。 Next, the reflected light from the semi-reflective thin film mirror 5 is reflected by the beam splitter 3 and enters the laser receiver 6. At this time, the laser light irradiated from the laser oscillator 2 passes through the total reflection mirror 4 and the laser receiver 6 due to the difference between the distance between the beam splitter 3 and the total reflection mirror 4 and the distance between the beam splitter 3 and the semi-reflection thin film mirror 5. There is a difference between the time required to reach the laser light receiver 6 and the time required to reach the laser receiver 6 via the semi-reflective thin film mirror 5.
例えば、ビームスプリッタ３と全反射鏡４の距離よりも、ビームスプリッタ３と半反射薄膜鏡５の距離の方が長い場合には、図４に示すように、半反射薄膜鏡５からの反射光Ｌ２が全反射鏡４からの反射光Ｌ１よりも遅れてレーザ受光器６に入射する。 For example, when the distance between the beam splitter 3 and the semi-reflective thin film mirror 5 is longer than the distance between the beam splitter 3 and the total reflective mirror 4, the reflected light from the semi-reflective thin film mirror 5 is shown in FIG. L2 enters the laser receiver 6 later than the reflected light L1 from the total reflection mirror 4.
そこで、全反射鏡４からの反射光Ｌ１と半反射薄膜鏡５からの反射光Ｌ２を干渉させてレーザ受光器６に入射させることによって、図６に示すように、２つの反射光Ｌ１，Ｌ２の周波数の差に等しい周波数のビート信号Ｂ１がレーザ受光器６から出力される。 Therefore, the reflected light L1 from the total reflection mirror 4 and the reflected light L2 from the semi-reflective thin film mirror 5 are caused to interfere with each other and enter the laser receiver 6, thereby making the two reflected lights L1, L2 as shown in FIG. A beat signal B1 having a frequency equal to the difference between the frequencies is output from the laser receiver 6.
レーザ受光器６から出力されたビート信号Ｂ１は、ドップラ効果により、半反射薄膜鏡５の振動速度に比例して周波数が変化している。更に、周波数−電圧変換器７により、周波数の変化を電圧値の変化に変換することで、半反射薄膜鏡５の振動速度に比例した電気信号が得られる。 The beat signal B <b> 1 output from the laser receiver 6 changes in frequency in proportion to the vibration speed of the semi-reflective thin film mirror 5 due to the Doppler effect. Furthermore, the frequency-voltage converter 7 converts a change in frequency into a change in voltage value, whereby an electrical signal proportional to the vibration speed of the semi-reflective thin film mirror 5 is obtained.
同時に、ビームスプリッタ３と全反射鏡４の距離及びビームスプリッタ３と半反射薄膜鏡５の距離よりも、ビームスプリッタ３と振動物体１３の音響放射面１２の距離が長い場合には、図５に示すように、音響放射面１２からの反射光Ｌ３が全反射鏡４及び半反射薄膜鏡５からの反射光Ｌ１，Ｌ２よりも遅れてレーザ受光器６に入射する。 At the same time, when the distance between the beam splitter 3 and the total reflection mirror 4 and the distance between the beam splitter 3 and the semi-reflective thin film mirror 5 is longer than the distance between the beam splitter 3 and the acoustic radiation surface 12 of the vibrating object 13, FIG. As shown, the reflected light L3 from the acoustic radiation surface 12 enters the laser receiver 6 later than the reflected lights L1 and L2 from the total reflection mirror 4 and the semi-reflection thin film mirror 5.
そこで、全反射鏡４からの反射光Ｌ１と音響放射面１２からの反射光Ｌ３を干渉させてレーザ受光器６に入射させることによって、図６に示すように、２つの反射光Ｌ１，Ｌ３の周波数の差に等しい周波数のビート信号Ｂ２がレーザ受光器６から出力される。 Therefore, the reflected light L1 from the total reflection mirror 4 and the reflected light L3 from the acoustic radiation surface 12 are caused to interfere with each other and enter the laser receiver 6 to obtain two reflected lights L1 and L3 as shown in FIG. A beat signal B 2 having a frequency equal to the frequency difference is output from the laser receiver 6.
ここで、音響放射面１２からの反射光Ｌ３と全反射鏡４からの反射光Ｌ１の周波数の差は、半反射薄膜鏡５からの反射光Ｌ２と全反射鏡４からの反射光Ｌ１の周波数の差よりも大きいため、半反射薄膜鏡５によるビート信号Ｂ１よりも高い周波数のビート信号Ｂ２がレーザ受光器６から出力される。 Here, the difference in frequency between the reflected light L3 from the acoustic radiation surface 12 and the reflected light L1 from the total reflection mirror 4 is the frequency of the reflected light L2 from the semi-reflective thin film mirror 5 and the reflected light L1 from the total reflection mirror 4. Therefore, a beat signal B2 having a higher frequency than the beat signal B1 from the semi-reflective thin film mirror 5 is output from the laser receiver 6.
レーザ受光器６から出力されたビート信号Ｂ２は、ドップラ効果により、音響放射面１２の振動速度に比例して周波数が変化している。更に、周波数−電圧変換器８により、周波数の変化を電圧値の変化に変換することで、音響放射面１２の振動速度に比例した電気信号が得られる。 The beat signal B2 output from the laser receiver 6 changes in frequency in proportion to the vibration speed of the acoustic radiation surface 12 due to the Doppler effect. Further, the frequency-voltage converter 8 converts a change in frequency into a change in voltage value, thereby obtaining an electrical signal proportional to the vibration speed of the acoustic radiation surface 12.
このように、２つのビート信号Ｂ１，Ｂ２の周波数の変化は、２つの周波数−電圧変換器７，８を用いて、別々に電圧の変化に変換されるので、半反射薄膜鏡５の振動速度に比例した電気信号と音響放射面１２の振動速度に比例した電気信号を別々に取り出すことができる。 Thus, the change in frequency of the two beat signals B1 and B2 is separately converted into a change in voltage using the two frequency-voltage converters 7 and 8, so that the vibration speed of the semi-reflective thin film mirror 5 is increased. And an electric signal proportional to the vibration speed of the acoustic radiation surface 12 can be taken out separately.
周波数−電圧変換器７，８から出力されたアナログ電気信号は、２つのＡ／Ｄ変換器９，１０によって、別々に、ある一定時間間隔のデジタル信号に変換され、それらのクロススペクトルがクロススペクトル演算部１１において算出される。このような演算処理により、振動物体１３の音響放射面１２近傍の音圧に比例した半反射薄膜鏡５の振動速度に含まれるスペクトル成分うち、音響放射面１２の振動速度には含まれていないスペクトル成分が除去される。 The analog electric signals output from the frequency-voltage converters 7 and 8 are separately converted into digital signals at certain time intervals by the two A / D converters 9 and 10, and their cross spectrums are cross spectrums. Calculated in the calculation unit 11. By such calculation processing, out of the spectral components included in the vibration velocity of the semi-reflective thin film mirror 5 that is proportional to the sound pressure in the vicinity of the acoustic radiation surface 12 of the vibrating object 13, it is not included in the vibration velocity of the acoustic radiation surface 12. Spectral components are removed.
また、計測対象の音響放射面１２の近傍で計測しているため、計測対象の音響放射面１２からの放射音が他の物体に反射して伝搬する反射音と、計測対象の音響放射面１２の振動速度との間には、大きな時間差が生じるため、クロススペクトル演算時に反射音は除去される。 In addition, since measurement is performed in the vicinity of the acoustic radiation surface 12 to be measured, the reflected sound from the acoustic radiation surface 12 to be measured is reflected by other objects and propagated, and the acoustic radiation surface 12 to be measured. Since there is a large time difference between the vibration speed and the reflected sound, the reflected sound is removed during the cross spectrum calculation.
従って、計測対象の音響放射面１２からの放射音が他の物体に反射して伝搬する反射音と、計測対象の音響放射面１２以外の放射面および振動物体１３以外の物体からの放射音を除去し、計測対象の音響放射面１２が振動することにより放射されている音だけを検出することができる。 Therefore, the reflected sound from the sound radiation surface 12 to be measured is reflected and propagated to another object, and the sound emitted from the radiation surface other than the sound radiation surface 12 to be measured and the object other than the vibration object 13 is reflected. It is possible to detect only the sound radiated by removing and vibrating the acoustic radiation surface 12 to be measured.
また、ビームスプリッタ３からのレーザ光を光ファイバで半反射薄膜鏡５まで導くと共に、半反射薄膜鏡５を光ファイバの先端に装着してセンサプローブを構成することができる。このセンサプローブを産業用ロボットに把持させて計測対象物の特定の音響放射面に位置決めすることにより、家電製品などの製造ラインにおいて行うオンライン検査に適用することができる。 Further, the laser beam from the beam splitter 3 can be guided to the semi-reflective thin film mirror 5 by an optical fiber, and the semi-reflective thin film mirror 5 can be attached to the tip of the optical fiber to constitute a sensor probe. The sensor probe is gripped by an industrial robot and positioned on a specific acoustic radiation surface of a measurement object, whereby the sensor probe can be applied to an on-line inspection performed on a production line for home appliances.
次に、本発明に係る対象音検出装置の実施例２では、図７に示すように、レーザ受光器６からのアナログ電気信号をＡ／Ｄ変換器１４によって、ある一定時間間隔のデジタル信号に変換する。更に、デジタル処理を行う周波数−電圧変換部１５，１６によって、半反射薄膜鏡５の振動速度に比例したデジタル信号と音響放射面１２の振動速度に比例したデジタル信号を抽出する。 Next, in Example 2 of the target sound detection apparatus according to the present invention, as shown in FIG. 7, the analog electric signal from the laser receiver 6 is converted into a digital signal at a certain time interval by the A / D converter 14. Convert. Further, digital signals proportional to the vibration speed of the semi-reflective thin film mirror 5 and digital signals proportional to the vibration speed of the acoustic radiation surface 12 are extracted by the frequency-voltage conversion units 15 and 16 that perform digital processing.
このように、周波数−電圧変換部１５，１６をデジタル信号処理技術によって実現することで、クロススペクトル演算部１１を含めて１台の計算機で処理を行うことができ、計測器に対するコストの軽減が実現できる。なお、図１と同符号の構成要素については、実施例１と同様なので説明を省略する。 As described above, by realizing the frequency-voltage conversion units 15 and 16 by the digital signal processing technique, the processing can be performed by one computer including the cross spectrum calculation unit 11, and the cost for the measuring instrument can be reduced. realizable. The components having the same reference numerals as those in FIG. 1 are the same as those in the first embodiment, and thus the description thereof is omitted.
次に、本発明に係る対象音検出装置の実施例３では、図８に示すように、実施例２の構成に加えて、ビームスプリッタ３と半反射薄膜鏡５の間にビームスプリッタ１７を設置し、更に全反射鏡１８と半反射薄膜鏡１９を設けている。また、半反射薄膜鏡１９及びこれに対向する音響放射面１２の振動速度を夫々算出する周波数−電圧変換部２０，２１と、これらの振動速度のクロススペクトルを算出するクロススペクトル演算部２２を設けている。 Next, in the third embodiment of the target sound detection apparatus according to the present invention, as shown in FIG. 8, in addition to the configuration of the second embodiment, a beam splitter 17 is installed between the beam splitter 3 and the semi-reflective thin film mirror 5. In addition, a total reflection mirror 18 and a semi-reflection thin film mirror 19 are provided. Further, there are provided frequency-voltage converters 20 and 21 for calculating the vibration speeds of the semi-reflective thin film mirror 19 and the acoustic radiation surface 12 opposed thereto, and a cross spectrum calculation unit 22 for calculating a cross spectrum of these vibration speeds. ing.
半反射薄膜鏡１９及びこれに対向する音響放射面１２の振動速度を、周波数−電圧変換部２０，２１により、夫々算出し、これらの振動速度のクロススペクトルをクロススペクトル演算部２２により求める。このような周波数−電圧変換部とクロススペクトル演算部の組み合わせを増やすことで、一組のレーザ発振器２とレーザ受光器６によって音響放射面１２の多点の同時計測が可能になる。なお、図１と同符号の構成要素については、実施例１と同様なので説明を省略する。 The vibration speeds of the semi-reflective thin film mirror 19 and the acoustic radiation surface 12 facing the semi-reflective thin film mirror 19 are calculated by the frequency-voltage converters 20 and 21, respectively, and the cross spectrum of these vibration speeds is obtained by the cross spectrum calculator 22. By increasing the number of combinations of the frequency-voltage conversion unit and the cross spectrum calculation unit, it is possible to simultaneously measure multiple points on the acoustic radiation surface 12 by the set of the laser oscillator 2 and the laser receiver 6. The components having the same reference numerals as those in FIG. 1 are the same as those in the first embodiment, and thus the description thereof is omitted.
本発明は、従来技術が必要とする高い防音性能を有する無響室などを使用することなく、計測対象物が通常使用または稼動している状態において、計測対象物の特定の音響放射面から放射される音を検出することができる。 The present invention radiates from a specific acoustic radiation surface of a measurement object in a state where the measurement object is normally used or operated without using an anechoic chamber having high sound insulation performance required by the prior art. Sound can be detected.
また、半反射薄膜鏡を光ファイバの先端に装着してセンサプローブを構成し、このセンサプローブを産業用ロボットに把持させて計測対象物の特定の音響放射面に位置決めすることにより、家電製品などの製造ラインにおいて行うオンライン検査に適用することができる。 In addition, a semi-reflective thin film mirror is attached to the tip of an optical fiber to form a sensor probe, and this sensor probe is gripped by an industrial robot and positioned on a specific acoustic radiation surface of a measurement object, thereby allowing home appliances, etc. It can be applied to on-line inspection performed in the production line.
また、周波数−電圧変換部をデジタル信号処理技術によって実現することで、クロススペクトル演算部を含めて１台の計算機で処理を行うことができ、計測器に対するコストの軽減が実現できる。 In addition, by realizing the frequency-voltage conversion unit using a digital signal processing technique, it is possible to perform processing with a single computer including the cross spectrum calculation unit, and it is possible to reduce the cost for the measuring instrument.
更に、周波数−電圧変換部とクロススペクトル演算部の組み合わせを増やすことで、一組のレーザ発振器とレーザ受光器によって音響放射面の多点の同時計測が可能になる。 Furthermore, by increasing the number of combinations of the frequency-voltage conversion unit and the cross spectrum calculation unit, it is possible to simultaneously measure multiple points on the acoustic radiation surface with a set of laser oscillators and laser receivers.
１…信号発生器、２…レーザ発振器、３…ビームスプリッタ、４，１８…全反射鏡、５，１９…半反射薄膜鏡、６…レーザ受光器、７，８，１５，１６，２０，２１…周波数−電圧変換器、９，１０，１４…Ａ／Ｄ変換器、１１，２２…クロススペクトル演算部、１２…音響放射面、１３…振動物体。 DESCRIPTION OF SYMBOLS 1 ... Signal generator, 2 ... Laser oscillator, 3 ... Beam splitter, 4,18 ... Total reflection mirror, 5, 19 ... Semi-reflection thin film mirror, 6 ... Laser receiver, 7, 8, 15, 16, 20, 21 ... frequency-voltage converter, 9, 10, 14 ... A / D converter, 11, 22 ... cross spectrum calculation unit, 12 ... acoustic radiation surface, 13 ... vibrating object.
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