Though miniaturization and mass production via integrated circuit fabrication techniques have transformed our society, the methods have yet to be successfully applied to the generation of motion, and as a consequence the many potential benefits of microrobotics has yet to be realized. The characteristics of electrostatic, electromagnetic and piezoelectric transduction for generating motion at the micro scale is considered, employing scaling laws and a reasoned consideration of the difficulties in motor fabrication and design using each method. The scaling analyses show that electrostatic, electromagnetic and piezoelectric actuators all have comparable force scaling characteristics of F∝L2; if one employs permanent magnets, electromagnetic forces do not scale as F∝L4. Though the torque, τ, of piezoelectric ultrasonic motors scale rather poorly with τ∝L4, they have the clear advantage of possessing torque amplitudes some two orders of magnitude larger than motors employing the other transduction schemes at the micro scale.
In this paper, a new method for obtaining the array manifold in sensor array beampattern design and optimization is proposed. The basic idea behind the proposed method is replacing the theoretical obtained or experimentally measured array manifold by the calculated one, which is obtained by calculating the sound field at each element positions in the array. The acoustical boundary element method is used to calculate the sound field and the array manifold is obtained by accumulating the values at all sensor in all interested directions. By doing so, the effects of the array supporting structure or baffle can be included so as to yield a result which is more approaching the practical situation, and at the same time, avoids the tedious work of practical measurements. A conformal array with 27 sensors was designed and built and analyzed by the proposed method. The calculated sensor directivity by the proposed method has a similar tendency with that measured in an anechoic water-tank, and the design requirements of beampatterns which use the optimized weighting coefficient obtained from the array manifold calculated by the proposed method are well met in practical system. The simulation results have verified the effectiveness and feasibility of the proposed method.
The ability by which the blind can recognize objects around them solely by hearing is called “obstacle sense.” By analyzing and modeling the mechanism of this sense, the resultant model could be utilized in new concepts for blind mobility aids as well as training methods. In this paper, we first conducted a comparative experiment regarding coloration perception between the blind and the sighted. In the experiment, subjects are asked to answer whether two successive sounds with a different dip-to-dip interval are perceived to be same by means of two alternative forced choices. The results show no significant difference in discrimination between the two groups; the blind and the sighted. Next, “impressions” elicited by the sounds with various dip-to-dip intervals are analyzed on the two groups using the Semantic Differential Method (SDM). The results indicate that the sighted tend to focus mainly on the quantitatively represented changes such as pitch and loudness of the sounds, while the blind are inclined to focus not only on the quantitative sound change, but also on qualitative impressions in the sound changes. Since it is assumed that the qualitative impressions are related to distances of the obstacles from the blind, third, we carry out a comparative experiment regarding the obstacle-distance perception. The result indicates that the blind can more exactly answer the obstacle-distance than the sighted. From the results of the three experiments and past studies, we discuss whether the obstacle sense is formed in the peripheral process or in the central process of the auditory nervous system, and then we propose new concepts for blind mobility aids as well as the obstacle sense training method.
In this paper, we numerically simulate speech production on the basis of vocal fold (VF) models with geometrical (effective VF vibrational depth, glottal half gap and VF thickness) or mechanical (Young’s modulus, density and viscosity) asymmetries as a pathological VF model, and consider the effects of the asymmetries on the speech production process. The simulation shows asymmetric vibrations with a phase difference between the left and right VFs and fluctuations in the pressure wave within the larynx. To investigate the relationship between the fluctuations and VF asymmetry, we quantitatively estimate the fundamental frequency, amplitude and waveform fluctuations in the pressure wave by varying the asymmetry. For most cases, increasing the VF asymmetry increases the fluctuations. The fluctuations obtained from the simulation for symmetric models are in rough agreement with those of actual speech signals. However, with increasing asymmetry, the fluctuations exceed the range for actual speech data. This result suggests that the degree of VF asymmetry can be evaluated by estimating fluctuations in speech waves.
Speech sounds convey information about the size of the speaker. Several studies have demonstrated that human vowel recognition is possible even for an unnatural size range, and have revealed that size factor normalization can be achieved automatically in the auditory system. In this study, we further investigated the characteristics of the size normalization process, using vowel sequences with temporal changes in the speaker size. In the current experiments, listeners were presented with six-vowel sequences in which the vocal-tract length was alternated vowel by vowel. The experimental results for the identification of the vowel sequence showed that it was increasingly difficult for listeners to identify vowels in the correct order as size alternation was applied with a higher speed and to a larger degree. However, they showed the high performance of vowel recognition when serial order judgment between vowels was not required, and in this case the performance deterioration caused by size alternation became small. The observed deterioration of sequence identification is likely to have been caused not by a failure in size normalization in the auditory system but because of a difficulty in judging the serial order between vowels in the sequence with rapid size changes. The results suggest that the auditory system has a fast process for normalizing speaker-size information and that it operates appropriately even when a sequence contains the temporal alternation of vocal-tract length.
In this work, head movements for three human subjects were measured simultaneously during head-related transfer function (HRTF) measurement for a period of 95 min each. The subjects’ heads moved in all directions during measurements. Excessive head movements were observed in the pitch and yaw directions. Head movements in the roll direction were small for all subjects. Specifically, the head position at the beginning and end of HRTF measurement differed by less than 1° in roll but by as much as 10° in pitch and yaw. Consequently, HRTFs for the front position measured at the beginning and the end of the measurement session differed by 4–6 dB in spectral distortion. These results reveal that when no head-support aids are used, HRTFs might contain large errors attributable to head movement.
A method of sampling jitter measurement based on time-domain analytic signals is proposed. Computer simulations and actual measurements were performed to compare the proposed method with the conventional method, in which jitter is evaluated from the amplitudes of sideband spectra for observed signals in the frequency domain. The results show that the proposed method is effective in that it 1) provides high temporal resolution as a result of the direct derivation of the jitter waveform, 2) achieves higher accuracy in the measurement of jitter amplitude, and 3) can separate phase modulation that originate in sampling jitter from amplitude modulation that originate in digital-to-analog and analog-to-digital conversion processes. Suitable measurement conditions and measurements to separate the effects of jitter in a digital-to-analog converter and an analog-to-digital converter are described.
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