In this paper, we have proposed a low-cost self-localization method which uses 4 elements of microphones, wheel rotation and sound sources as beacons, whose absolute location and frequency bands are known. The proposed method consists of following 4 steps. The proposed method (i) execute self-localization using wheel-based odometry, (ii) estimate direction-of-arrival (DOA) of the sound sources using sounds recorded by the elements of the microphone array, (iii) predict the DOA of the sound sources from estimated location and pose, and (iv) conduct self-localization by integrating all of the information. To evaluate the proposed method, experiments were conducted. The proposed method was compared to the conventional methods, which were wheel-based odometry and self-localization using only DOA. In the experiments, we have supposed the house-cleaning robot and its trajectory. As results, without any obstacles or walls, the mean of the estimation errors by wheel-based odometry were 670 mm and 0.08 rad, and those of self-localization using only DOA were 2870 m and 0.07 rad in the worst case. In contrast with these methods, proposed method results in 69 mm, 0.02 rad as the worst estimation error of self location and pose. From the result with occlusion of a sound source, the mean of the localization error increased 60 mm, as the proposed method detects the incorrect DOA and prevents it from estimation. From the result with reflective wave from wall, there was a place where the localization error was large. The cause of this error was considered as directivity of sound source. These results indicate that the proposed method is feasible under indoor environment.

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Underwater acoustic (UWA) communication is an essential technology that supports underwater surveys by transmitting images and movies wirelessly. However, UWA communication is still challenging due to the large delay and Doppler spreads in UWA channels. Doppler-resilient orthogonal signal division multiplexing (D-OSDM) under water has been found effective in such channels, but Doppler modeling errors prevent further improvement in communication quality. In this paper, we clarify the effect of Doppler modeling errors on the communication quality of D-OSDM and propose the use of a window function in D-OSDM to address the issues that such errors raise. We also evaluate the communication quality of D-OSDM using the window function through simulations and experiments. The experimental results show a 56% increase in the number of error-free data blocks, indicating that windowing can improve communication quality.

In this study, we evaluated a method of estimating the contact force of a bone-conducted sound transducer using human subjects. The method was previously proposed and evaluated only with a human model. First, the relationship between the contact force and the electrical impedance was validated for 12 human subjects from 10 Hz to 60 kHz. The results showed that the electrical impedance shows four peaks and that the peaks change with contact force for all subjects in the same manner. A method of estimating the contact force was implemented with a three-layered neural network and evaluated with the data from 12 human subjects. The estimation results showed that 90% of the estimation error was within ±0.43 N, which shows that the estimation of contact force is possible. This result enables the estimation of contact force only from the electrical impedance and may support reproducible fitting of the bone-conducted sound transducer.

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Compassing the spatial shape is sometimes performed to develop a surround speaker system or enhance a signal. Although the spatial shape is reconstituted from the boundary position, conventional methods offer arrays consisting of a large number of elements (microphones and loudspeakers). In this research, we developed a method of localizing the acoustic reflective boundary based on the direction-of-arrival (DOA) of direct and reflected sounds using a pair of microphones. This method offers the DOA values of direct and reflected arbitrary sound sources. Although the estimation involves some estimation errors caused by approximations in the calculation, the correction function was obtained from several conditions numerically. Results indicate that it is possible to localize the reflective boundary almost accurately (the average error ratio from the true value is below 10%) through the presented method.

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High resolution far ultraviolet (12W2000,4) spectra of 17 cool giant and supergiant stars have been obtained using the IUE satellite of ESA, NASA and UK. We have measured the line intensities, wavelengths and widths of approximately 200 EUV emission lines in these spectra, using a least squares gaussian fitting technique. Line identification has been obtained in about one third of the cases. The measured values are organized in a database in order to facilitate updating and investigation of interrelations with stellar atmospheric parameters.The observations include lines from C I. C 11, C IV, S I, 0 I, 0 IV, Si 11, Si IV, N V, A1 111. Fe I1 and Mg 11. These lines are mostly formed by radiative processes in the extremely rarefied plasma in the outer stellar atmospheres, and occasionally involve highly excited energy levels of the atoms and ions. The temperature of formation ranges from about 5 x lo' to IO5 K, corresponding to different depth levels in the atmosphere, and the lines serve as a valuable tool for probing the physical conditions in these regions. We may also get new information on atomic processes that take place under conditions that are never duplicated in the laboratory. The present data may therefore give important contributions both to astrophysics and to atomic physics.