Suppression of the second harmonic distortion intrinsic to a thermoacoustic transducer was studied using a square root circuit. The thermoacoustic transducer used in this study is composed of aluminum film, polyimide, and graphite film in order for it to be thin and bendable. A theoretical model was developed to calculate the radiated sound pressure on the basis of a fundamental equation for the heat transfer between the transducer and surrounding air. A square root circuit was designed to enable real-time signal processing and the effectiveness of the circuit regarding the second harmonic distortion suppression was experimentally confirmed.
The alignment of transmitter coils for the three-dimensional electromagnetic articulograph (3D-EMA), an instrument used to measure articulatory movements, was studied. Receiver coils of the 3D-EMA are used as position markers and are placed in alternating magnetic field produced by multiple transmitter coils. The estimation of the state (the position and orientation) of each receiver coil is based on the minimization of the signal error between the measured and predicted receiver signals using a model of the magnetic field. Previous studies report a noticeable increase in the position estimation error irrespective of small signal error at a specific portion of the measurement region. The existence of the non-uniqueness problem in the position estimation is hypothesized to be the cause of this problem. To resolve the problem, we optimized the alignment of the transmitter coils by maximizing the difference between the receiver signals for any pair of states in the measurement region and evaluated the alignment by performing computer simulations and actual measurement. As a result, a measurement accuracy of approximately 0.4 mm was obtained.
This paper presents a finite-element analysis on the free vibration of Japanese drum wood barrels under insufficient material property data. Unlike isotropic material such as steel, wood behaves like an orthotropic composite material, whose elastodynamic characterization in a cylindrical shell needs Young’s modulus in the longitudinal (in-grain) and circumferential (cross-grain) directions, shear modulus, and Poisson ratios. Due to measurement difficulty encountered during the process of testing, only the longitudinal Young’s modulus and the specific gravity of the wood were measured. In the analysis, the finite-element models of the drum were constructed using conical shell elements. The required unknown elastic constants were estimated consecutively by a try-and-error approach, and the estimated values were reached when the computed resonance frequencies matched simultaneously with those of the seven lower modes measured in experiments. In order to accomplish this, both the estimated constants and the finite-element analysis must be within acceptable range of accuracy. It was found that the values of the circumferential (cross-grain) Young’s modulus, which was unknown at the beginning of the study, turns out to be crucial in determining the lower mode resonance frequencies. The usefulness of this analysis is that the estimated elastic constants can now be used for updating the finite-element model. The updated model can then be used calculating the higher order modes which cannot be practically obtained through measurements.
In this study, an influence of vehicle-exterior image on sound quality evaluation was investigated. Luxury- or sporty-vehicle image was presented to Japanese or German frequent drivers, while listening to an acceleration sound. Subsequently, loudness, luxury and sportiness for the sound were rated. As the result, significant influence was not observed in the loudness and luxury evaluation in both nationalities. However, sportiness rating to the presented sound was markedly increased when the sporty-vehicle image was presented with the sound. Consequently, it appeared that the influence of the vehicle-exterior image on the sound quality rating differs depending on the evaluation parameter and sportiness is markedly affected by the visual information.
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