Hiro Yamasaki

Envelope representations of pinna impulse responses relating to three‐dimensional localization of sound sources

Acoustical impulse responses of the external ear system are measured in order to investigate human three-dimensional auditory localization. A sound source of electric spark discharge is presented in nine directions for each of four vertical planes, 1.5 m from the center of the subjects head. The results show that a human pinna works as a compound sound reflector which produces major reflected components within 350 microseconds. The relationship between the direction of the sound source and the impulse response is clearly shown by the use of an envelope formation technique and radial ray displays.

Self-adapting multiple microphone system

Abstract An intelligent sound-sensing system is proposed. The system consists of a multiple microphone, a multiple-input linear filter, and a learning component for adapting the filter. This system can pick up a target sound signal out of other disturbing ambient noises with a better signal-to-noise ratio. A point of this system is a new self-learning algorithm for the adaptive filter. For self-learning, an internal learning signal is generated by multiplying a received signal by a cue signal. Any signal correlating with the power level of the target signal may be used as the cue signal. Since such cue signals are easy to obtain, many applications are available. In this paper, two types of intelligent microphone systems are described. The first type of system can pick up a non-stationary sound signal out of stationary disturbance sound signals. The second type of system has a photosensor to obtain a cue signal. The system distinguishes a target sound source from other disturbing sound sources by the visual cue. This new learning algorithm is theoretically analyzed, and the efficiency of the algorithm is demonstrated by experiments.

The future of sensor interface electronics

Abstract In the context of progress towards intelligent sensin systems, future technologies of sensor interface electronics are described. Functions of interface electronics are expanding in several directions and will contain new computing paradigms. One direction is the expansion to multidimensional sensing systems. One-dimensional signal processing is extending towards two-dimensional signal processing. Image processing is a typical example of two-dimensional signal processing. In the near future, sensed image processing will be carried out by electronics integrated with image-sensing devices in place of separate computers. Moving-image processing is done by parallel processing. Then we can get almost real-time results for feature extraction of the object or signal compression for communication. Moving-image compression is playing a key role in the present multimedia area. Another direction is the expansion towards multilayer signal processing. Advanced sensing systems have a hierarchical structure. Sensed signal processing is done in the lower layer, which entails a direct interface to the sensor device. More abstract information processing is carried out in the upper layer, where the processing is based on knowledge of the object and sensors. We can call it knowledge processing, and cite examples, such as target recognition and reasoning of the object state. Special information processing is carried out in the middle layer. The missions of the middle-layer processing are feature extraction from the sensor signal and multisensory signal integration and fusion. An important role of the future sensor interface electronics is multimodal sensor processing. In particular, fusion of the signals from various kinds of sensing devices will give us a higher order of information which we can never get without multimodal sensor signal processing. From the viewpoint of function, the future image of sensor interface electronics can be described as a major enlargement of present functions. However, the physical size of the future hardware will be much more compact and it will be integrated or embedded in the sensing devices.

Multi-dimensional intelligent sensing system using sensor array

Abstract In this paper two different kinds of multi-dimensional intelligent sensing systems are described. Both systems use a two-dimensional sensor array for sensing invisible objects. The intelligence of these systems gives us a visual moving image and the global structure of multi-dimensional dynamic phenomena by organizing local information from point-type multi-sensors based on a model of the phenomena. Overlapping with a video picture of the scene gives us the reality of the invisible state. These sensing systems may be useful for the understanding of a multi-dimensional dynamic state.

Real‐time visualization of acoustic wave fronts by using a two‐dimensional microphone array

This article describes a real‐time visualization system for sound fields. The system includes a two‐dimensional microphone array (8×8), which eliminates the need for mechanically scanning the microphone and enables real‐time processing. Three methods are tested for drawing interpolated images of sound fields from the sparse sampling points. A frequency‐detection circuit is introduced to show the direction of sound propagation stroboscopically. Superposition of visualized sound wave fronts on the video picture of the field helps one to understand the sound fields present.

A digital signal processing approach to data handling for ultrasound beam-forming

This report is presented on a new data handling technique for digital beam-former which utilizes ultrasound sensor array. Proposed method is a new approach to controlling and collecting of multi-channel ultrasound signals. The techniques are based on holographic beam-forming and multiplexing using switches. Multichannel RF signals are modulated by switching circuits for transmitting and multiplexing. Demultiplexing and beam-forming are performed numerically. This technique permits high speed data acquisition with simple hardware. We considered the utilization of Walsh-sequences and maximal-length binary sequences for the switching. Computer simulations and experimental results are presented to demonstrate the ability of the method.

Progress and promotion of the international interchange of information on sensing technologies

Fields of measurement can be divided into three categories such as scientific measurement, industrial measurement and legal metrology. At present, IMEKO(International Measurement Confederation) has more than twenty Technical Committees(TCs), and they cover almost all categories mentioned above. TCs of IMEKO have been founded from two kinds of view points. One is the specific quantities to be studied and the other is technologies or fields to be applied. In each view point, fundamental intellectual infrastructures including sensing technologies are effectively examined in order to obtain reliable information and measurement data.

A magnetic flowmeter with conducting pipe wall for expanded field of applications

Abstract The internal pipe wall of magnetic flowmeters should be non-conductive to prevent generated electromotive force from short-circuiting. Usually the inside of metallic pipe is lined with insulating material. The lining limits applicable temperature range of measured fluid and also its reliability. A new structure is proposed, in which the insulating liner is eliminated. A potential distribution is formed on the pipe wall by applying voltage proportional to fluid flowrate. The potential distribution is kept almost identical to the flow-induced potential in the fluid so that no current flows across the boundary between fluid and wall. Therefore the output signal is exactly the same as that of conventional magnetic flowmeters.

Global feature of wide‐band pinna frequency response relating to three‐dimensional localization

We studied the free‐field of external ear canal acoustic impulse responses. The fine structure of the frequency domain characteristics was correlated with the time domain profile of the pinna reflections previously [Hiranaka and Yamasaki, J. Acoust. Soc. Am. 73, 291–296 (1983)]. A recent measurement with wide band facilities (up to 50 kHz) revealed the fact that the global structure of the frequency response can be correlated with such effects as the head shadow and the pinna direction in a very simple form: the logarithmic amplitude declines almost linearly with linear frequency for all directions of a sound source, and the degree of the declination varies with the direction. In the experiment, impulsive sound source was positioned at nine elevation angles (30°/step) in each of six vertical planes, and 1.5 m from a subjects head. The directional map of the declination (ranging from − 1 dB/10 kHz to − 10 dB/10 kHz) indicated the opening pattern of the pinna. The patterns of such maps from several subject...

A Solid-state Electrometer and its Application to β Ray Thickness Gage

電離箱電流の10-10～10-12A程度の直流増幅器は半導体化がおくれていたが, 著者らは可変容量ダイオードによるリァクタンス変調を利用した発振増幅方式による完全に固体化された微小電流増幅器を開発した。少ない素子数の回路で大利得が得られ, ドリフトがなく安定である。これを応用して回路を固体化したβ線厚さ計はスイッチ・インと同時に指示が安定し, 振動に強く, 工業計器としてすぐれた特徴が付加された。さらに増幅器の高感度のために線源量も少なくてすみ安全性が向上した。この論文では, 新しい増幅器の原理, 特性を紹介し, β線厚さ計の諸特性について述べるが, 使用条件にマッチした検出部の構造にもふれる。