Conversation is one of the most important channels for human beings. To help communications, speech recognition technologies have been developed. Above all, in a conversation, not only contents of utterances but also intonations and tones include important information regarding a speaker’s intention. To study the sphere of human speech, microphones are typically used to record voices. However, since microphones have to be set around a space, their existences affect a physical behavior of the sound field. To challenge this problem, we have suggested a recording method using a high-speed camera. By using a high-speed camera for recording sound vibrations, it can record two or more points within the range of the camera at the same time and can record from a distance, without interfering with the sound fields. In this study, we extract voice information using high-speed videos, which capture both a face and a cervical part of the subject. This method allows recording skin vibrations, which contain voices with individuality and extrapolating sound waves by using an image processing method. The result of the experiment shows that a high-speed camera is capable of recording voice information.

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Aerodynamic sounds are one of the noises of high-speed trains, automobiles, and wind turbines. To understand the characteristics of those noises, measuring sound sources is important. In general, microphones are used for measuring aerodynamic sounds. However, measuring the sound fields inside flow fields is difficult for microphones because they disturb flows. Thus, optical measurement methods have been applied to visualize aerodynamic sounds. The optical method can measure the sound fields without installing devices inside measurement fields. Therefore, it can capture the sound around sources. In this paper, we performed visualization and spatio-temporal analysis of sound sources of edge tones using parallel phase-shifting interferometry (PPSI). We experimentally confirmed the difference in pressure fluctuations near the sound source depending on the frequency of the edge tones.

The piezoelectric actuators have been applied to various electrical devices such as piezoelectric speakers, buzzers, haptics, and ultrasonic transducers. The improvement of the electromechanical conversion efficiency is the most important issue of piezoelectric actuator systems in mobile devices. The electrical power consumption of actuators must be suppressed as possible, due to mobile devices having small batteries. The frequency response around the mechanical resonance should be carefully designed for low power consumption driving. The resonant frequencies of the piezoelectric actuators consist of integrated components, for example, metal corns of ultrasonic speakers, are decided by the energy dispersion of the total system. Therefore, design factors such as sizes and physical properties of each component, are necessary to optimize the resonant frequencies for practical applications. The total energy of the piezoelectric system is described by Lagrange-Maxwell equation. Even though it is not easy to solve the differential equations written in the Lagrangian coordinate system by the exact calculation, useful information for design of the system can be derived by the approximate calculation. In this paper, we will indicate the design guideline to optimize resonant frequencies of the piezoelectric actuators with integrated components, based on the analysis in the Lagrangian coordinate system.

Railway noise is still one of the issues in the wayside environment despite of various countermeasures. For effective countermeasures, it is important to reveal characteristics of sound sources and sound propagation. Using parallel phase-shifting interferometry (PPSI) which measure the air density by interfering the reference light with object light, we tried to observe the sound field around a moving source. This system utilize laser and high-speed camera makes it possible to observe unstedy phenomena and visualize sound waves accurately. As a moving source, a speaker emitting 40kHz sinusoidal sound was mounted on a model, and the model was launched at 100 km/h. As A result, we succeed in observing the sound waves generated from the moving source clearly and visualizing the frequency modulation by Doppler effect. Furthermore, the result was averaged in sub-pixel to understand easily. These results clearly show the difference in frequency depending on the relative position to the sound source as it is in theory.