JP2005150797A - Method of driving thermal induction type sound wave radiating element - Google Patents
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Abstract
Description
本発明は熱誘起型音波放射素子の駆動方法に関する。 The present invention relates to a method for driving a thermally induced acoustic wave radiating element.
従来、下記非特許文献1に記載されているように、熱誘起型音波放射素子を用いた音波の放射が知られている。
Conventionally, as described in
熱誘起型音波放射素子は、気体(多くの場合に空気)に接触している状態の電気抵抗体に交流電流を流し、通電によるジュール熱の発生によって、電気抵抗体に周期的な温度変化を起こさせ、それによって、電気抵抗体に接触している気体に周期的な密度変化を起こさせ、気体の粗密波すなわち気体中を伝わる音波を放射する素子である。 A heat-induced acoustic wave radiating element applies an alternating current to an electric resistor in contact with a gas (in many cases, air), and generates a periodic temperature change in the electric resistor by generating Joule heat by energization. This is an element that causes a periodic density change in the gas in contact with the electric resistor, thereby emitting a dense wave of the gas, that is, a sound wave transmitted in the gas.
このような熱誘起型音波放射素子は、下記非特許文献1に記載されているように、超音波放射素子として利用される。
Such a heat-induced acoustic radiation element is used as an ultrasonic radiation element as described in Non-Patent
しかしながら、熱誘起型音波放射素子を、電流信号を音波信号に変換する信号変換手段として見た場合に、その忠実度は低い。すなわち、熱誘起型音波放射素子に流す交流電流を交流信号として見たとき、その基本周波数と同じ周波数の音波成分は、素子から放射される音波には含まれていない。これをさらに詳しく説明するとつぎのようになる。 However, the fidelity of the heat-induced acoustic wave radiating element is low when viewed as signal conversion means for converting a current signal into a sonic signal. That is, when an alternating current flowing through the heat-induced acoustic wave radiating element is viewed as an alternating current signal, a sonic component having the same frequency as the fundamental frequency is not included in the sonic wave emitted from the element. This will be described in more detail as follows.
素子に流す交流電流を、I0sin(ωt)とする。ここに、I0(I0>0とする)は電流の振幅であり、ωは角周波数すなわち2πf(fは周波数)であり、tは時間である。この場合に、fがこの交流電流の基本周波数である。素子の電気抵抗体の抵抗値をRとすれば、この抵抗体で単位時間当たりに発生する熱量は
R(I0sin(ωt))2 = RI0 2(1−cos(2ωt))/2
= RI0 2/2 −(RI0 2/2)cos(2ωt)
となり、上式の最右辺中には、交流成分として、基本周波数fの2倍で振動する項((RI0 2/2)cos(2ωt))のみが含まれ、基本周波数fで振動する項は含まれていない。したがって、このような発熱によって誘起される音波の中にも基本周波数fを持つ成分は含まれないことになる。
The alternating current that flows through the element is defined as I 0 sin (ωt). Here, I 0 (I 0 > 0) is an amplitude of current, ω is an angular frequency, that is, 2πf (f is a frequency), and t is time. In this case, f is the fundamental frequency of this alternating current. If the resistance value of the electric resistor of the element is R, the amount of heat generated per unit time by this resistor is
R (I 0 sin (ωt)) 2 = RI 0 2 (1-cos (2ωt)) / 2
= RI 0 2/2 - (
Next, during the rightmost side of the above equation, as the AC component, contains only the term which oscillates at twice the fundamental frequency f ((RI 0 2/2 ) cos (2ωt)), term which oscillates at the fundamental frequency f Is not included. Therefore, the component having the fundamental frequency f is not included in the sound wave induced by such heat generation.
図4は、熱誘起型音波放射素子を従来の駆動方法、すなわち、素子の電気抵抗体に交流電流(この場合は正弦波電流)を流す方法によって動作させた場合の、電流波形(「入力」で表示)、電気抵抗体の温度変化波形(「熱変化」で表示)および放射される音波の音圧波形(「出力」で表示)を示している。この場合には、すでに説明したように、交流電流の基本周波数と同じ周波数をもつ音波は放射されない。 FIG. 4 shows a current waveform (“input”) when a heat-induced acoustic wave radiating element is operated by a conventional driving method, that is, a method in which an alternating current (in this case, a sine wave current) is passed through the electric resistor of the element. ), A temperature change waveform of the electric resistor (displayed as “thermal change”), and a sound pressure waveform of the radiated sound wave (displayed as “output”). In this case, as already described, sound waves having the same frequency as the fundamental frequency of the alternating current are not emitted.
本発明の主たる目的は、上記の、熱誘起型音波放射素子を信号変換手段として見た場合の忠実度が低い問題を解決し、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することにある。 The main object of the present invention is to solve the above-mentioned problem of low fidelity when the heat-induced acoustic radiation element is viewed as a signal conversion means, and the sound wave emitted from the thermally-induced acoustic radiation element is thermally induced. An object of the present invention is to provide a method for driving a heat-induced acoustic wave radiating element that includes a sonic wave component having the same frequency as the fundamental frequency of the alternating current component of the current flowing through the sonic wave radiating element.
上記課題を解決するために、本発明においては、請求項1に記載のように、
熱誘起型音波放射素子の駆動方法において、交流電流に直流のバイアス電流を重ねて前記熱誘起型音波放射素子に流すことによって、前記交流電流の基本周波数と同じ周波数の音波成分を有する音波を前記熱誘起型音波放射素子から放射させることを特徴とする熱誘起型音波放射素子の駆動方法を構成する。
In order to solve the above problems, in the present invention, as described in
In the method for driving a heat-induced acoustic wave radiating element, a sound wave having a sound wave component having the same frequency as the fundamental frequency of the alternating current is obtained by superimposing a direct current bias current on an alternating current and passing the current through the thermally induced acoustic wave radiating element. A driving method for a heat-induced acoustic wave radiating element, characterized by radiating from a heat-induced acoustic wave radiating element, is configured.
また、本発明においては、請求項2に記載のように、
熱誘起型音波放射素子の駆動方法において、交流電気信号に直流のバイアスを重ねてバイアス付加電気信号とし、該バイアス付加電気信号に比例する電流を前記熱誘起型音波放射素子に流すことによって、前記交流電気信号の基本周波数と同じ周波数の音波成分を有する音波を前記熱誘起型音波放射素子から放射させることを特徴とする熱誘起型音波放射素子の駆動方法を構成する。
In the present invention, as described in
In the method for driving a thermally induced acoustic radiation element, a direct current bias is superimposed on an alternating current electrical signal to form a biased electrical signal, and a current proportional to the biased electrical signal is caused to flow through the thermally induced acoustic radiation element. A driving method for a heat-induced acoustic wave radiating element, characterized in that a sound wave having a sound wave component having the same frequency as the fundamental frequency of an AC electrical signal is emitted from the heat-induced acoustic wave radiating element.
また、本発明においては、請求項3に記載のように、
熱誘起型音波放射素子の駆動方法において、交流電気信号に正の値のバイアスを重ねて、負の値をとらないバイアス付加電気信号とし、nは1/2以上1以下の数であるとし、前記バイアス付加電気信号のn乗に比例する電流を前記熱誘起型音波放射素子に流すことによって、前記交流電気信号の基本周波数と同じ周波数の音波成分を有する音波を前記熱誘起型音波放射素子から放射させることを特徴とする熱誘起型音波放射素子の駆動方法を構成する。
In the present invention, as described in
In the driving method of the heat-induced acoustic wave radiating element, a positive bias is superimposed on the AC electrical signal to obtain a biased electrical signal that does not take a negative value, and n is a number of 1/2 or more and 1 or less, By causing a current proportional to the nth power of the biased electrical signal to flow to the heat-induced sound wave emitting element, a sound wave having a sound wave component having the same frequency as the fundamental frequency of the AC electric signal is generated from the heat-induced sound wave emitting element. A driving method of a heat-induced acoustic wave radiating element, characterized by radiating, is configured.
本発明の実施により、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することが可能となる。 By implementing the present invention, the sound wave radiated from the thermally induced sound wave radiating element includes a sound wave component having the same frequency as the fundamental frequency of the alternating current component of the current flowing through the heat induced sound wave radiating element. It is possible to provide a method for driving a sound wave radiating element.
本発明においては、交流電流に直流のバイアス電流を重ねて熱誘起型音波放射素子に流すことによって、交流電流の基本周波数と同じ周波数をもつ音波成分が熱誘起型音波放射素子から放射される音波に含まれるようにする。 In the present invention, a sound wave component having the same frequency as the fundamental frequency of the alternating current is radiated from the heat-induced sound radiation element by superimposing a direct current bias current on the alternating current and flowing it through the heat-induced sound radiation element. To be included.
交流電流を、上記と同じく、I0sin(ωt)とし、直流のバイアス電流をIBとする。ここで、電流の向きを適当にとってIB>0とする。この場合に、ωがこの交流電流の基本角周波数であり、f=ω/(2π)がこの交流電流の基本周波数である。素子の電気抵抗体の抵抗値をRとすれば、この抵抗体で単位時間当たりに発生する熱量は
R(I0sin(ωt) + IB)2
=R(I0 2sin(ωt)2 + 2I0IBsin(ωt)+IB 2)
=RI0 2/2+RIB 2−(RI0 2/2)cos(2ωt)+2RI0IBsin(ωt)
となり、上式の最右辺に基本周波数fで振動する項(2RI0IBsin(ωt))が現われ、したがって、熱誘起型音波放射素子から放射される音波にも基本周波数fと同じ周波数をもつ音波成分が含まれるようになる。
An alternating current, the Like, and
R (I 0 sin (ωt) + I B ) 2
= R (I 0 2 sin ( ωt) 2 + 2I 0 I B sin (ωt) + I B 2)
= RI 0 2/2 + RI B 2 - (
Next, appeared term which oscillates at the fundamental frequency f to the rightmost side of the above equation (2RI 0 I B sin (ωt )) is, therefore, to sound waves radiated from the heat-induced wave emitting element of the same frequency as the fundamental frequency f The sound wave component is included.
上式には基本周波数fの2倍で振動する項((RI0 2/2)cos(2ωt))も含まれている。基本周波数fで振動する項(2RI0IBsin(ωt))に起因して発生する基本周波数fと同じ周波数をもつ音波の振幅と、基本周波数fの2倍で振動する項((RI0 2/2)cos(2ωt))に起因して発生する基本周波数fの2倍の周波数をもつ音波の振幅とは、それぞれ、2RI0IBとRI0 2/2とに比例すると考えられる。音波の強さは振幅の2乗に比例するから、基本周波数fと同じ周波数をもつ音波の強さに対する基本周波数fの2倍の周波数をもつ音波の強さの比は
(RI0 2/2)2/(2RI0IB)2 = (I0/IB)/16
となる。たとえば、I0 = IBとすれば、この比の値は1/16となり、良好な忠実度が得られていることがわかる。これよりもIBの値を大きくすれば、この比の値は1/16よりも小さくなり、さらに忠実度が向上する。ただし、IBをI0よりも大きくすると、無効に消費される電力が増加するので、具体的には、IBをI0の1倍以上3倍以下、または、1.5倍以上3倍以下にするのがよい。
Term which oscillates at twice the fundamental frequency f in the above equation ((RI 0 2/2) cos (2ωt)) are also included. Term that vibration and amplitude of the sound wave with the same frequency as the fundamental frequency f generated due to the term (2RI 0 I B sin (ωt )) which oscillates at the fundamental frequency f, at twice the fundamental frequency f ((RI 0 the 2/2) cos (amplitude of sound waves having a frequency twice the fundamental frequency f generated due to 2.omega.t)), respectively, believed to be proportional to the 2RI 0 I B and RI 0 2/2. Since the intensity of a sound wave is proportional to the square of the amplitude, the ratio of the intensity of a sound wave having a frequency twice the fundamental frequency f to the intensity of a sound wave having the same frequency as the fundamental frequency f is
(RI 0 2/2) 2 / (
It becomes. For example, if I 0 = I B, the value of this ratio is found to be 1/16, good fidelity is obtained. If this increasing the value of I B than, the value of this ratio is smaller than 1/16, more fidelity is improved. However, if I B is made larger than I 0 , the power consumed ineffectively increases. Specifically, I B is 1 to 3 times, or 1.5 to 3 times that of I 0. The following is recommended.
以下に、図面を用いて、本発明の実施の形態を詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(実施の形態1)
図1に、熱誘起型音波放射素子の一例を示す。図の(a)は正断面図、(b)は平面図である。図において、1はシリコン単結晶基板であり、シリコン単結晶基板1の1つの面には、多孔質シリコン層2が形成されている。多孔質シリコン層2の表面にはタングステン層3が形成され、タングステン層3に通電するための1対の金属電極4が形成されている。1対の金属電極4の間にあるタングステン層3の部分(5mm×5mm)が熱誘起型音波放射素子の電気抵抗体として機能する。
(Embodiment 1)
FIG. 1 shows an example of a thermally induced acoustic wave radiating element. (A) of a figure is a front sectional view, (b) is a top view. In the figure,
図2は、図1に示した熱誘起型音波放射素子を本発明の駆動方法、すなわち、素子の電気抵抗体となるタングステン層3に、交流電流に直流のバイアス電流を重ねて流す方法によって動作させた場合の、電流波形(「入力」で表示)、電気抵抗体の温度変化波形(「熱変化」で表示)および放射される音波の音圧波形(「出力」で表示)を示している。この場合に、交流電流は正弦波電流とし、その振幅の0.5倍、1.0倍、1.5倍のバイアス電流を重ねた場合を、それぞれ、(a)、(b)、(c)に示す。すでに、式を用いて説明したように、バイアス電流値の増加に伴って、交流電流の基本周波数fと同じ周波数をもつ音波成分の割合が増加していることがわかる。なお、電気抵抗体の発熱の変化に追従する電気抵抗体の温度変化の追従速度は十分に速いので、電気抵抗体の温度変化は電気抵抗体の発熱の変化に比例するとして温度変化波形を描き、放射される音波の音圧波形は、実測結果に基づいて描いてある。
FIG. 2 shows the operation of the thermally induced acoustic wave radiating element shown in FIG. 1 according to the driving method of the present invention, that is, the method in which a direct current bias current is superimposed on the
以上に説明したように、本実施の形態によって、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することが可能となる。 As described above, according to the present embodiment, the sound wave radiated from the heat-induced sound wave radiating element has a sound wave component having the same frequency as the fundamental frequency of the alternating current component of the current flowing through the heat-induced sound wave radiating element. It is possible to provide a method for driving a heat-induced acoustic wave radiating element as described above.
本実施の形態においては、交流電流に直流のバイアス電流を重ねて熱誘起型音波放射素子に流す電流としたが、別の方法によって、熱誘起型音波放射素子に流す電流を得てもよい。すなわち、交流電気信号(交流電流信号または交流電圧信号)に直流のバイアス(電流信号の場合にはバイアス電流、電圧信号の場合にはバイアス電圧)を重ねて、バイアス付加電気信号を得、このバイアス付加電気信号に比例する電流を作りだして、その電流を熱誘起型音波放射素子に流す電流としても、本実施の形態と全く同じ効果が得られ、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することが可能となる。 In the present embodiment, a direct current bias current is superimposed on an alternating current to flow through the heat-induced acoustic radiation element. However, a current that flows through the heat-induced acoustic radiation element may be obtained by another method. That is, a DC bias (bias current in the case of a current signal, bias voltage in the case of a voltage signal) is superimposed on an AC electric signal (AC current signal or AC voltage signal) to obtain a bias-added electric signal. Even if a current proportional to the additional electrical signal is created and the current is passed through the heat-induced acoustic radiation element, the same effect as in the present embodiment can be obtained, and the sound wave emitted from the heat-induced acoustic radiation element It is possible to provide a method for driving a heat-induced sound wave emitting element that includes a sound wave component having the same frequency as the fundamental frequency of the alternating current component of the current flowing through the heat-induced sound wave emitting element.
(実施の形態2)
熱誘起型音波放射素子による信号変換の忠実度を、上記の実施の形態1よりもさらに向上させる方法を以下に説明する。
(Embodiment 2)
A method for further improving the fidelity of signal conversion by the heat-induced acoustic wave radiating element as compared with the first embodiment will be described below.
この方法においては、交流電気信号に正の値のバイアスを重ねて、負の値をとらないバイアス付加電気信号とし、このバイアス付加電気信号の平方根に比例する電流を作りだして、その電流を熱誘起型音波放射素子に流す。交流電気信号が正弦波信号である場合を例として、以下に、この方法について説明する。 In this method, a positive bias is superimposed on the AC electrical signal to produce a biased electrical signal that does not take a negative value, and a current proportional to the square root of this biased electrical signal is created and the current is thermally induced. Flow through the acoustic wave emitting element. This method will be described below by taking as an example the case where the AC electrical signal is a sine wave signal.
音圧信号に変換しようとする電気信号をS0sin(ωt)とする。S0は電流値であっても電圧値であってもよく、いずれの場合においても正の値であるとする。この電気信号に、SB≧S0を満足するバイアスSBを重ねて、バイアス付加電気信号S0sin(ωt)+SBとする。このバイアス付加電気信号は、SB≧S0であるので、負の値をとらない。このバイアス付加電気信号の平方根すなわち(S0sin(ωt)+SB)1/2に比例する電流を作りだして、その電流を熱誘起型音波放射素子に流す。 An electric signal to be converted into a sound pressure signal is defined as S 0 sin (ωt). S 0 may be a current value or a voltage value, and is assumed to be a positive value in any case. This electrical signal, superimposed bias S B that satisfy the S B ≧ S 0, the bias added electrical signal S 0 sin (ωt) + S B. This biased electrical signal does not take a negative value because S B ≧ S 0 . A current proportional to the square root of the biased electric signal, that is, (S 0 sin (ωt) + S B ) 1/2 is created, and the current is passed through the heat-induced acoustic wave radiating element.
熱誘起型音波放射素子の電気抵抗体におけるジュール熱の発生速度は電気抵抗体に流れる電流の2乗に比例するから、上記の電流によるジュール熱の発生速度は
((S0sin(ωt)+SB)1/2)2 = S0sin(ωt)+SB、
すなわちバイアス付加電気信号に比例することになり、このジュール熱の発生速度の変化に比例して、熱誘起型音波放射素子から放射される音波は、元の電気信号S0sin(ωt)に比例する成分のみからなる。すなわち、この場合の忠実度は100%である。この場合に、SBはS0に等しければよく、それよりも大きくすると無効に消費される電力が増加する。
Since the generation rate of Joule heat in the electrical resistor of the heat-induced acoustic radiation element is proportional to the square of the current flowing through the electrical resistor, the generation rate of Joule heat due to the current is
((S 0 sin (ωt) + S B ) 1/2 ) 2 = S 0 sin (ωt) + S B ,
That is, it is proportional to the bias-added electric signal, and the sound wave radiated from the heat-induced sound wave radiating element is proportional to the original electric signal S 0 sin (ωt) in proportion to the change in the generation rate of Joule heat. It consists only of ingredients. That is, the fidelity in this case is 100%. In this case, it is sufficient that S B is equal to S 0, and if it is larger than that, the power consumed ineffectively increases.
図3は、S0=SBとした場合の、熱誘起型音波放射素子に流れる電流波形(「入力」で表示)、電気抵抗体の温度変化波形(「熱変化」で表示)および放射される音波の音圧波形(「出力」で表示)を示している。 3, in the case of the S 0 = S B, (indicated by "Input") current flowing through the heat-induced sound wave emitting element waveform (indicated by "thermal change") temperature change waveform of the electric resistor and the emitted The sound pressure waveform of the sound wave (indicated by “output”).
元の電気信号が、複数の周波数成分を含んでいる場合にも、本実施の形態の方法によって、元の電気信号をきわめて高い忠実度で音波に変換できることは、上記の説明によって明らかである。この場合には、交流電気信号にバイアスを重ねてなるバイアス付加電気信号の値が負にならないようにSBの値を選べばよい。この方法によって熱誘起型音波放射素子を駆動した場合には、その熱誘起型音波放射素子は高忠実度の音波出力素子としての機能を発揮する。 It is clear from the above description that the original electrical signal can be converted into a sound wave with extremely high fidelity by the method of the present embodiment even when the original electrical signal includes a plurality of frequency components. In this case, it may be selected values of S B so that the value of the bias-added electrical signal formed by superimposing a bias to the alternating electrical signal is not negative. When a heat-induced acoustic wave radiating element is driven by this method, the thermally-induced acoustic wave radiating element exhibits a function as a high-fidelity sound wave output element.
以上に説明したように、本実施の形態によって、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することが可能となる。 As described above, according to the present embodiment, the sound wave radiated from the heat-induced sound wave radiating element has a sound wave component having the same frequency as the fundamental frequency of the alternating current component of the current flowing through the heat-induced sound wave radiating element. It is possible to provide a method for driving a heat-induced acoustic wave radiating element as described above.
本実施の形態においては、バイアス付加電気信号の平方根に比例する電流を作りだして、その電流を熱誘起型音波放射素子に流しているが、一般に、1/2≦n≦1を満足する指数nを用いて、バイアス付加電気信号のn乗に比例する電流を作りだして、その電流を熱誘起型音波放射素子に流すことによっても、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することが可能となる。n=1の場合が実施の形態1の一部の場合(熱誘起型音波放射素子に流す電流の向きが反転しない場合)に相当し、nが1より小さくなって1/2に近づくにつれて忠実度は向上し、nが1/2に等しい場合に理想的状態が実現し、きわめて高い忠実度が得られる。すなわち、このような指数nを用いた場合においても、熱誘起型音波放射素子から放射される音波が、熱誘起型音波放射素子に流される電流の交流成分の基本周波数と同じ周波数をもつ音波成分を含むような、熱誘起型音波放射素子の駆動方法を提供することが可能となり、しかも、信号変換の忠実度は高い。 In the present embodiment, a current proportional to the square root of the bias-added electric signal is generated and the current is passed through the heat-induced acoustic wave radiating element. In general, an index n satisfying 1/2 ≦ n ≦ 1 is satisfied. Is used to generate a current proportional to the nth power of the bias-added electrical signal, and the current is passed through the heat-induced acoustic radiation element, so that the sound wave radiated from the heat-induced acoustic radiation element is also thermally induced. It is possible to provide a method for driving a thermally induced acoustic radiation element that includes a acoustic wave component having the same frequency as the fundamental frequency of the alternating current component of the current flowing through the acoustic radiation element. The case of n = 1 corresponds to a part of the first embodiment (the case where the direction of the current flowing through the heat-induced acoustic wave radiating element is not reversed), and faithful as n becomes smaller than 1 and approaches 1/2. The degree is improved and an ideal state is realized when n is equal to 1/2, resulting in very high fidelity. That is, even when such an index n is used, a sound wave component in which the sound wave radiated from the heat-induced sound wave radiating element has the same frequency as the fundamental frequency of the AC component of the current flowing through the heat-induced sound wave radiating element. It is possible to provide a method for driving a heat-induced acoustic wave radiating element including the above, and the fidelity of signal conversion is high.
1…シリコン単結晶基板、2…多孔質シリコン層、3…タングステン層、4…金属電極。
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WO2008029451A1 (en) | 2006-09-05 | 2008-03-13 | Pioneer Corporation | Thermal sound generating device |
JP2012054762A (en) * | 2010-09-01 | 2012-03-15 | Nippon Hoso Kyokai <Nhk> | Thin film sound wave outlet device |
US8162097B2 (en) | 2009-06-08 | 2012-04-24 | Panasonic Corporation | Sound wave generator and method for producing the same, and method for generating sound waves using the sound wave generator |
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WO2008029451A1 (en) | 2006-09-05 | 2008-03-13 | Pioneer Corporation | Thermal sound generating device |
US8094840B2 (en) | 2006-09-05 | 2012-01-10 | Pioneer Corporation | Thermal sound generating device |
US8162097B2 (en) | 2009-06-08 | 2012-04-24 | Panasonic Corporation | Sound wave generator and method for producing the same, and method for generating sound waves using the sound wave generator |
JP2012054762A (en) * | 2010-09-01 | 2012-03-15 | Nippon Hoso Kyokai <Nhk> | Thin film sound wave outlet device |
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