Kotaro Hoshiba

High-Accuracy Measurement of Small Movement of an Object behind Cloth Using Airborne Ultrasound

The acoustic measurement of vital information such as breathing and heartbeat in the standing position whilst the subject is wearing clothes is a difficult problem. In this paper, we present the basic experimental results to measure small movement of an object behind cloth. We measured acoustic characteristics of various types of cloth to obtain the transmission loss through cloth. To observe the relationship between measurement error and target speed under a low signal-to-noise ratio (SNR), we tried to measure the movement of an object behind cloth. The target was placed apart from the cloth to separate the target reflection from the cloth reflection. We found that a small movement of less than 6 mm/s could be observed using the M-sequence, moving target indicator (MTI) filter, and tracking phase difference, when the SNR was less than 0 dB. We also present the results of theoretical error analysis in the MTI filter and phase tracking for high-accuracy measurement. Characteristics of the systematic error were clarified.

Non-contact measurement of propagation speed in tissue-mimicking phantom using pass-through airborne ultrasound

The elastic properties of human tissues can be quantitatively evaluated from the ultrasonic propagation speed in tissues. To effectively propagate ultrasound in human tissues, ultrasonic transducers are typically brought into contact with tissue surfaces. In this study, the non-contact evaluation of human tissues using pass-through airborne ultrasound has been proposed. When airborne ultrasound propagates and passes through tissues, the pass-through wave is extremely attenuated. To detect the attenuated pass-through wave in the received signal, the signal-to-noise ratio (SNR) of the received signal is improved by pulse compression using a higher-order M-sequence in the proposed method. In this paper, the estimation of ultrasonic propagation speeds in tissue-mimicking phantoms is described. The urethane-rubber phantom and solutions of ethanol in water are used as the phantoms. The time of flight (TOF) of the pass-through wave in the phantom is determined from the wave front. The propagation speed in the phantom is estimated using the determined TOF. Propagation speeds in the urethane-rubber phantom and ethanol solutions can be estimated within errors of 3 and 2% in experiments.

Study about the propagation of airborne ultrasonic wave through a heel for bone-density estimation

Bone density and elasticity can be measured from propagation parameters of acoustic waves. In typical bone-density estimation, a propagation path of the ultrasonic wave has to be filled with mediums, whose acoustic properties are similar to tissues, to reduce attenuation by boundary reflection. Therefore, transducers are brought into contact with examined regions. In this study, non-contact bone-density estimation for a calcaneus using airborne ultrasonic waves has been proposed. When airborne ultrasonic waves pass through a heel, the received signals are attenuated more than -70 dB, which is even estimated from ideal flat boundaries of air, soft tissue, solid bone and cancellous bone. Therefore, pulse compression using M-sequence is employed to improve the S/N of received signals. When the order of M-sequence is n-th order, S/N improvement of received signals by cross correlation of the received signal and the reference signal, which is corresponding to the transmitted signal is √(2n - 1) times. The pass-through waves in a heel can be detected by amplification of 60 dB and S/N improvement of more than 45 dB in the experiments. However, the TOF of pass-through waves can be estimated because first-arrival pass-through waves are not clarified. For measurement of the propagation velocity of pass-through waves, wideband transducers or S/N improvement is required to clarify the first-arrival pass-through waves.

Design of UAV-Embedded Microphone Array System for Sound Source Localization in Outdoor Environments

In search and rescue activities, unmanned aerial vehicles (UAV) should exploit sound information to compensate for poor visual information. This paper describes the design and implementation of a UAV-embedded microphone array system for sound source localization in outdoor environments. Four critical development problems included water-resistance of the microphone array, efficiency in assembling, reliability of wireless communication, and sufficiency of visualization tools for operators. To solve these problems, we developed a spherical microphone array system (SMAS) consisting of a microphone array, a stable wireless network communication system, and intuitive visualization tools. The performance of SMAS was evaluated with simulated data and a demonstration in the field. Results confirmed that the SMAS provides highly accurate localization, water resistance, prompt assembly, stable wireless communication, and intuitive information for observers and operators.

Bird Song Scene Analysis Using a Spatial-Cue-Based Probabilistic Model

∗ Graduate School of Information Science and Engineering, Tokyo Institute of Technology 2-12-1, O-okayama, Meguro-ku, Tokyo, 152-8552, JAPAN. kojima@cyb.mei.titech.ac.jp ∗∗Department of Systems and Control Engineering, School of Engineering, Tokyo Institute of Technology ∗∗∗ Honda Research Institute Japan Co., Ltd., 8-1 Honcho, Wako, Saitama,351-0114, JAPAN. ∗∗∗∗ Graduate School of Information Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan. ∗∗∗∗∗ Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA 90095, USA.

Non-contact measurement of propagation characteristics in human wrist using pass-through airborne ultrasound

The non-contact measurement of the propagation characteristics in the human body using pass-through airborne ultrasound has been proposed. Detection and evaluation of airborne ultrasound passed through the heel have been reported. However, estimation of the speed of sound (SOS) in the heel is difficult due to large attenuation of the pass-through ultrasound. In this paper, airborne ultrasound passed through the wrist is studied. The pass-through ultrasound can be detected by pulse compression using more than 16th-order M-sequence. Attenuation of the pass-through ultrasound or the estimated SOSs in the wrist are different by the transducer position. When the transducers are set at the center of the wrist, attenuation and the SOS are 86.2 dB and 1780 m/s, respectively.

Development of microphone-array-embedded UAV for search and rescue task

This paper addresses online outdoor sound source localization using a microphone array embedded in an unmanned aerial vehicle (UAV). In addition to sound source localization, sound source enhancement and robust communication method are also described. This system is one instance of deployment of our continuously developing open source software for robot audition called HARK (Honda Research Institute Japan Audition for Robots with Kyoto University). To improve the robustness against outdoor acoustic noise, we propose to combine two sound source localization methods based on MUSIC (multiple signal classification) to cope with trade-off between latency and noise robustness. The standard Eigenvalue decomposition based MUSIC (SEVD-MUSIC) has smaller latency but less noise robustness, whereas the incremental generalized singular value decomposition based MUSIC (iGSVD-MUSIC) has higher noise robustness but larger latency. A UAV operator can use an appropriate method according to the situation. A sound enhancement method called online robust principal component analysis (ORPCA) enables the operator to detect a target sound source more easily. To improve the stability of wireless communication, and robustness of the UAV system against weather changes, we developed data compression based on free lossless audio codec (FLAC) extended to support a 16 ch audio data stream via UDP, and developed a water-resistant microphone array. The resulting system successfully worked in an outdoor search and rescue task in ImPACT Tough Robotics Challenge in November 2016.

Noncontact measurement of body position and vital information using airborne ultrasound

Because of a growing need for unconstrained medical monitoring for unobtrusively observing individuals in a living space, we have been studied about non-contact measurement of vital information such as respiration and heartbeat using airborne ultrasound. In previous study, the measurement system of small displacement using the M-sequence-modulated signal and tracking phase difference of reflected signals from the target has been proposed. The measurement of respiration and heartbeat of the target in a standing position using a pair of the loudspeaker and the microphone has also been performed. However, body position cannot be measured using a pair of the loudspeaker and the microphone because the system can measure the distance to the body only. In this paper, we describe a basic study of the measurement of body position, respiration, and heartbeat. In the system, using microphone array, body position was estimated by synthetic aperture processing. In addition, small body-surface velocity by respiration a...