Flextensional transducers and methods of using flextensional transducers. The transducer includes a piezoelectric element and may include at least one endcap coupled with the piezoelectric element. The endcap may have an outer portion formed of a first material and an inner portion formed of a second material having a greater flexibility than the first material. The endcap may be coupled with an annular piezoelectric element near either its outer circumference or its inner circumference. The piezoelectric element may be a planar disk or have a curved bowl-shape. The transducer may be coupled with, and at least partially restrained by, a support structure. The transducer may also be configured to permit light to pass therethrough.

A display apparatus includes a display panel including configured to display an image and a sound generating device on a rear surface of the display panel, the sound generating device being configured to vibrate the display panel to generate sound. The sound generating device includes a first structure and a second structure over or under the first structure, the second structure including a first part having a piezoelectric characteristic and a second part between adjacent first parts to have flexibility.

An object is to provide an electroacoustic transducer consisting of a vibration plate and an exciter and having good flexibility. The object is solved by providing a vibration plate and an exciter, in which a maximal value of a loss tangent of the exciter at a frequency of 1 Hz according to dynamic viscoelasticity measurement is 0.08 or more in a temperature range of 0° C. to 50° C., and a product of a thickness of the exciter and a storage elastic modulus at a frequency of 1 Hz and 25° C. according to the dynamic viscoelasticity measurement is at most three times a product of a thickness of the vibration plate and a Young's modulus.

Provided are an electroacoustic transduction film capable of reproducing a sound with a sufficient sound volume at a high conversion efficiency, a manufacturing method thereof, an electroacoustic transducer, a flexible display, a vocal cord microphone, and a sensor for a musical instrument. The electroacoustic transduction film includes: a polymer composite piezoelectric body in which piezoelectric body particles are dispersed in a viscoelastic matrix formed of a polymer material having viscoelasticity at a normal temperature; two thin film electrodes laminated on both surfaces of the polymer composite piezoelectric body; and two protective layers respectively laminated on the two thin film electrodes, in which an intensity ratio α.sub.1=(002) plane peak intensity/((002) plane peak intensity+(200) plane peak intensity) between a (002) plane peak intensity and a (200) plane peak intensity derived from the piezoelectric body particles in a case where the polymer composite piezoelectric body is evaluated by an X-ray diffraction method is more than or equal to 0.6 and less than 1.

A transducer, a method of manufacturing a transducer, and a transducing device are provided. The transducer includes a receiving unit and a transmitting unit. The receiving unit includes a first receiving electrode, a first piezoelectric film, and a second receiving electrode which are sequentially stacked, and the receiving unit is configured to convert a first acoustic wave signal into an electrical signal by using a piezoelectric effect of the first piezoelectric film. The transmitting unit is configured to receive a control signal, which is based on the electrical signal, to transmit a second acoustic wave signal.

An object is to provide a piezoelectric film with good piezoelectricity. This object can be achieved by a piezoelectric film comprising a vinylidene fluoride/tetrafluoroethylene copolymer film and having a residual polarization amount of 40 mC/m.sup.2 or more.

There is provided a sound device used while being worn on the listener's ears.

The sound device includes a main body installed on a medial surface of an auricle, a holding portion having an annular hollow structure arranged to be coupled to an intertragic notch of an ear near an entrance of an ear canal, a sound guide portion formed as a pipe structure having one end communicating with the main body and another end communicating with the holding portion, an open/close operation unit configured to open or close an earhole, and a control unit configured to control driving of the open/close operation unit. The earhole open/close state is set for each user. The earhole open/close state can be switched depending on the type of application or content to be played, ambient noise level, user behavior, position information, or the like.

A mobile device includes one or more piezoelectric polymer layers underlying a display. The one or more piezoelectric polymer layers may be electrically driven to operate in either a d33 stretching mode or a d31 bending mode. The mobile device functions as an ultrasonic sensor in the d33 stretching mode and as an audio speaker/microphone or a proximity sensor in the d31 bending mode. The piezoelectric polymer layer operating in the d31 bending mode may be directly mechanically coupled to a display, indirectly mechanically coupled to the display and underlying an ultrasonic sensor stack, or integrated in the ultrasonic sensor stack. Signal performance of the piezoelectric polymer layer operating in the d31 bending mode may be enhanced or modulated by having a larger area, multiple layers, bi-pole or uni-pole driving with multiple layers, one or more stiff adhesives, a spacer layer, one or more mass features, a thin TFT layer, a thick piezoelectric polymer layer, or combinations thereof.

An audio reproduction apparatus includes an audio device in which a plurality of layer structures is formed by folding a thin film material having a capacitance layer sandwiched between a first electrode layer and a second electrode layer a plurality of times, and a vibrated portion which is bendable and to which one face of the audio device is fixed.

A vibration-generating apparatus, includes: a microphone apparatus disposed at an object including a plurality of regions, the microphone apparatus being configured to receive noise near the object, a sound processing circuit configured to: receive a sound source signal and a noise signal corresponding to the noise, generate a noise removal signal having an antiphase of the noise signal, and generate a vibration driving signal, based on the sound source signal and the noise removal signal, and a vibration apparatus disposed at the object to vibrate based on the vibration driving signal to vibrate the object.