The physical nature of weak body-conducted vocal-tract resonance signals called non-audible murmur (NAM) were investigated using numerical simulation and acoustic analysis of the NAM signals. Computational fluid dynamics simulation reveals that a weak vortex flow occurs in the supraglottal region when uttering NAM; a source of NAM is a turbulent noise source produced due to a vortex flow. Furthermore, computational acoustics simulation reveals that NAM signals attenuate 50 dB at 1 kHz consisting of 30-dB full-range attenuation due to air-to-body transmission loss and –10dB/octave spectral decay due to a sound propagation loss within the body, which roughly equals to the measurement results.

A number of works have been reported on robot control using EMG signals. Control of robots, wheelchairs, and rehabilitation aids using the arms, hands or legs by EMG signals has been quite popular and effective. However, few works have dealt with head-movement control using neck EMG signals. We have built a model that estimates continuous human head movement from neck EMG signals. Our proposed model, which considered not only static but also dynamic effects, effectively suppressed the over/undershoot, and predicted head-rotation movements well. This result indicates that the proposed model has the potential to reconstruct the observed data from neck EMG signals properly.

A multi-degree-of-freedom (DOF) ultrasonic motor can rotate in three DOFs and does not generate noise. In addition, with an appropriate preloading mechanism, it can generate high torque for its size. The multi-DOF ultrasonic motor is, therefore, anticipated for use as a servomotor in the next generation of robots. However, for several reasons, there have been few applications of multi-DOF ultrasonic motors. One reason is the difficulty in designing a proper preloading mechanism for the motor and the limitation of the size of the stators. Another is the difficulty in developing a control algorithm, due to the motor's complex and changing dynamical characteristics, and the serious jaggy motion caused by its very quick response. This paper proposes a preloading mechanism and control algorithm for a multi-DOF ultrasonic motor, considering the motor's application to an actual auditory tele-existence robot, TeleHead. TeleHead is an elaborate dummy head robot that has a 3-DOF neck mechanism. The proposed methods achieve smooth and fast multi-DOF rotating motion of the dummy head with little time delay. In the preloading method, tensioned springs generate high preloading force and make up for the lack of torque by compensating for the resistance torque generated by the inclining motion of the dummy head. In the control algorithm, high-DOF motion is managed by high-frequency switching of the rotating axis, and smooth and quick trajectory tracking motion is achieved by introducing feed-forward control using an inverse model, with multiresolution acquired by feedback-error learning. Experimental results verify the high performance of these methods.

A multi degree of freedom (DOF) ultrasonic motor can rotate in three degrees of freedom and does not generate noise. In addition, it generates high torque with an appropriate pre-loading mechanism. This motor is therefore anticipated for use as a servomotor in robots in the next generation. This paper proposes a pre-loading mechanism and control algorithm for the multi-DOF ultrasonic motor for its application to an actual auditory tele-existence robot, TeleHead. The proposed methods realize fast multi-DOF rotating motion with little time delay. The pre-loading method generates pre-loading force by using tensioned springs, and compensates for the torque generated by the weight load on the motor by using these springs and a counter weight. The control algorithm uses feed forward control based on online feedback error learning. Experimental results show the high performance of these proposed methods.

An acoustical tele-presence robot that transfers the sound environment at a remote place should have a human-like head whose movement is synchronized with the listener's head movement. To realize the concept, we built TeleHead I and II. TeleHead I, the prototype, has a molded dummy head and follows the user's head movement. Recently, we built TeleHead II, which is an advanced version of TeleHead I. TeleHead II can synchronize at 120 Hz with only 40 dB SPL drive noise. The size difference between the dummy head and its model is 4 mm in head breadth, which is smaller than 3%. Motion is followed with a 120-ms delay. The total performance of TeleHead II was measured in sound localization experiments. The results show that the listener who is the model for the TeleHead II's dummy head can localize when TeleHead II is stationary or synchronized, but that the localization is more precise in the synchronized situation. They also show that a listener who is not a model can localize in the horizontal plane in the synchronized situation. These results indicate that a human-like dummy head and synchronization with the listener's head movement are effective for realizing an acoustical tele-presence robot.

A multi degree of freedom (multi-DOF) ultrasonic motor is anticipated as an actuator in the next generation, because it can drive three-DOF motion with high torque and low noise that can not be perceived by the human auditory system. Using a multi-DOF ultrasonic motor as an actuator that constitutes the mechanism of the neck of the auditory tele-existence robot "TeleHead" is a good example of its applicability. However getting enough torque requires a suitable pre-loading method, and properly controlling three-DOF motion requires a suitable measurement method of the three-DOF angular position of the rotor and a control algorithm that takes into account the high-DOF motion and complex physical characteristics of the motor. This paper proposes both a hardware system for pre-loading and measuring 3-DOF angular position and a software system for controlling 3-DOF motion of the motor from the view point of application to TeleHead (see video). The proposed pre-loading method can generate enough pre-loading force and reduce resistance torque when the dummy head of "TeleHead" is in the inclined state. The proposed measuring method for three-DOF motion achieves a wide range of angular position of the motion of the dummy head in each rotating direction, especially in the yaw direction. The proposed control algorithm adopts a serial switching method with a very high frequency, and does not need any dynamics model of the physical characteristics of the motor for control signal calculation. Experimental results show the high performance of the proposed system when a 1-kg load is attached to the rotor of the multi-DOF ultrasonic motor.

Recurrent neural networks with arbitrary feedback connections are highly nonlinear dynamical systems exhibiting variegated complex dynamical behavior. The applications of this temporal behavior hold possibilities for information processing. Supervised learning for recurrent networks is studied with emphasis on learning aperiodic motions. APOLONN (adaptive nonlinear pair oscillators with local connections) is used for speech synthesis. The naturalness of a human's voice seems to come from fluctuations in voice source waveforms. The authors trained APOLONN to learn the voice source waveforms, including fluctuations of amplitudes and periodicities. After the learning, APOLONN was able to generate the waveforms with fluctuations. APOLONN can also generate waveforms with modulated amplitudes and frequencies by a simple scaling of the parameters. The results encourage further applications of recurrent networks

A computational nonlinear cochlear filter model with adaptive Q circuits is described. The model is built by introducing adaptive Q circuits into the linear cascade/parallel cochlear filter bank. The adaptive Q circuit is composed of two parts: a second-order low-pass function (LPF) and a Q decision circuit which calculates the LPF's Q in every time frame according to the input spectrum level. This model functionally simulates three level-dependent characteristics observed in the basilar membrane motion: level-dependent selectivity, level-dependent sensitivity, and level-dependent resonance frequency shift. The model output gives better internal speech spectrum representation than those of a linear cochlear filter bank. Weak consonant and higher formants are enhanced, both the temporal and the harmonic structure are consistent at the same time frame, and the spectra are spread and enhanced where the spectrum changes abruptly. These advantages, which are the phenomena observed in the real auditory frequency analysis, support the effectiveness of the model.>

A Japanese text-to-speech conversion technology has been developed, where a new text analysis method and a new speech synthesis method have been employed to improve pronunciation of Kanji characters and phoneme articulation. Morpheme analysis is first performed for an input text, and pronunciation and grammatical information are extracted. For word identification in Kanji character strings, an efficient method based on Japanese word statistics is introduced, and the text is converted into Kana strings, Kana strings are represented with a string of Dyad-type units(CV,VC,VV). Speech parameters for the Dyad-type units are concatenated to produce continuous speech. Residual signal is used as an excitation source for LSP synthesis in unvoiced consonant periods. An articulation test has shown that the residual signal is more effective than a noise signal and significantly improves explosive consonant synthesis.