A super-resolution algorithm is proposed to solve the problem of measuring the thin thickness of oil slick using compressed sensing theory. First, a mathematical model of a single pulse underwater ultrasonic echo is established. Then, the estimation model of the transmit time of flight (TOF) of ultrasonic echo within oil slick is given based on the sparsity of echo signals. At last, the super-resolution TOF value can be obtained by solving the sparse convex optimization problem. Simulations and experiments are conducted to validate the performance of the proposed method.

Some non-acoustic modalities have the ability to reveal certain speech attributes that can be used for synthesizing speech signals without acoustic signals. This study validated the use of ultrasonic Doppler frequency shifts caused by facial movements to implement a silent speech interface system. A 40kHz ultrasonic beam is incident to a speaker's mouth region. The features derived from the demodulated received signals were used to estimate the speech parameters. A nonlinear regression approach was employed in this estimation where the relationship between ultrasonic features and corresponding speech is represented by deep neural networks (DNN). In this study, we investigated the discrepancies between the ultrasonic signals of audible and silent speech to validate the possibility for totally silent communication. Since reference speech signals are not available in silently mouthed ultrasonic signals, a nearest-neighbor search and alignment method was proposed, wherein alignment was achieved by determining the optimal pair of ultrasonic and audible features in the sense of a minimum mean square error criterion. The experimental results showed that the performance of the ultrasonic Doppler-based method was superior to that of EMG-based speech estimation, and was comparable to an image-based method.

In non-destructive testing (NDT), ultrasonic echo is often an overlapping multi-echo signals with noise. However, the accurate estimation of ultrasonic time-of-flight (TOF) is essential in NDT. In this letter, a novel method for TOF estimation through envelope is proposed. Firstly, the wavelet denoising technique is applied to the noisy echo to improve the estimation accuracy. Then, the Hilbert transform (HT) is used in ultrasonic signal processing in order to extract the envelope of the echo. Finally, the TOF of each component of multi-echo signals is estimated by the local maximum point of signal envelope. Furthermore, the time resolution of time-overlapping ultrasonic echoes is discussed. Numerical simulation has been carried out to show the performances of the proposed method in estimating TOF of ultrasonic signal.

Earlier attempts to deploy two units of parametric loudspeakers have shown encouraging results in improving the accuracy of spatial audio reproductions. As compared to a pair of conventional loudspeakers, this improvement is mainly a result of being free of crosstalk due to the sharp directivity of the parametric loudspeaker. By replacing the normal parametric loudspeaker with the steerable parametric loudspeaker, a flexible sweet spot can be created that tolerates head movements of the listener. However, spatial aliasing effects of the primary frequency waves are always observed in the steerable parametric loudspeaker. We are motivated to make use of the spatial aliasing effects to create two sound beams from one unit of the steerable parametric loudspeaker. Hence, a reduction of power consumption and physical size can be achieved by cutting down the number of loudspeakers used in an audio system. By introducing a new parameter, namely the relative steering angle, we propose a stereophonic beamsteering method that can control the amplitude difference corresponding to the interaural level difference (ILD) between two sound beams. Currently, this proposed method does not support the reproduction of interaural time differences (ITD).

This paper describes an ultrasonic system that estimates the cell quantity of an artificial culture bone, which is effective for appropriate treat with a composite of this material and Bone Marrow Stromal Cells. For this system, we examine two approaches for analyzing the ultrasound waves transmitted through the cultured bone, including stem cells to estimate cell quantity: multiple regression and fuzzy inference. We employ two characteristics from the obtained wave for applying each method. These features are the amplitude and the frequency; the amplitude is measured from the obtained wave, and the frequency is calculated by the cross-spectrum method. The results confirmed that the fuzzy inference method yields the accurate estimates of cell quantity in artificial culture bone. Using this ultrasonic estimation system, the orthopaedic surgeons can choose the composites that contain favorable number of cells before the implantation.

The separation time-overlapping ultrasound signals is necessary to obtain accurate estimate of transit time and material properties. In this letter, a method to determine the optimal transform order of fractional Fourier transform (FRFT) for decomposition of overlapping ultrasonic signals is proposed. The optimal transform order is obtained by minimizing the mean square error (MSE) between the output and the reference signal. Furthermore, windowing in FRFT domain is discussed. Numerical simulation results show the performances of the proposed method in separating signals overlapping in time.

This paper proposes a sensing system for a behavior detection system using an ultrasonic oscillosensor and an air pressure sensor. The ultrasonic oscillosensor sensor has a cylindrical tank filled with water. It detects the vibration of the target object from the signal reflected from the water surface. This sensor can detect a biological vibration by setting to the bottom bed frame. The air pressure sensor consists of a polypropylene sheet and an air pressure sensor, and detects the pressure information by setting under the bed's mattress. An increase (decrease) in the load placed on the bed is detected by the increase (decrease) in the pressure of the air held in the tube attached to the sheet. We propose a behavior detection system using both sensors, complementally. The system recognizes three states (nobody in bed, keeping quiet in bed, moving in bed) using both sensors, and we detect the behavior before getting out of bed by recognized these states. Fuzzy logic plays a primary role in the system. As the fundamental experiment, we applied the system to five healthy volunteers, the system successfully recognized three states, and detected the behavior before getting out of bed. As the clinical experiment, we applied the system to four elderly patients with dementia, the system exactly detected the behavior before getting out of the bed with enough time for medical care support.

We report the growth of carbon nanofibers (CNFs) from carbon particles by chemical vapor deposition (CVD) with ultrasonic neblizer using ethanol as carbon source. Dense CNFs having diameters of several tens of nanometers have been successfully synthesized by the CVD without using any metal catalysts. The carbon particles formed from decompostion of fullerene were found to be suitable for the synthesis of CNFs. Details of the optimum conditions for producing CNFs and the expected growth mechanism are also described.

This paper proposes the design of a driver to deal with a thin-disc central supporting structure ultrasonic actuator based on the vibration modes and the equivalent circuit. In order to gain the electromechanical match at resonant frequency, a spectrum analyzer should measure admittance for driving piezoelectric ceramics. The virtual analyzer also investigated the characteristics of a MODEL-E equivalent circuit based upon the admittance-frequency response. The inherent capacitance from an ultrasonic actuator became the partial component in the design of a resonant circuit. IsSpice software is introduced to simulate as well as the experimental results has demonstrated a high agreement related to the conceptual design and practical implementation for the driving circuit.

A new in vitro experimental tool was developed to study the mechanism of the ultrasonic closing clicks' genesis of mechanical heart valves. Since the newly developed tester adopted compressed air flow directly instead of the blood analog fluid to drive the mechanical heart valve, it is not possibe to generate any cavitation. Closing clicks were measured with a small accelerometer at the surface of the valve holder made of silicone rubber. Ultrasonic closing clicks as well as audible closing clicks, similar to those measured clinically, could be observed using this setup. Thus, it was confirmed that the ultrasonic closing clicks can be generated without the existence of cavitation. Simultaneous measurements of the valve motion were made with a high-speed video camera, and the analysis of the video frames and clicks showed that higher frequency signal components of more than 50 kHz could be generated only at the instant of the closure, which means the collision of the occluder with the housing. Eighteen miniature accelerometers with an area of one square millimeter were developed and stuck on the housing to monitor the distribution of the housing vibrations in detail, and it was found that the vibrations correspond to the ultrasonic closing clicks propagated from the valve stop: the collision point of the occluder with the housing. This fact indicated that the generation of ultrasonic closing clicks are limited to the small area of the collision. From those results, it was concluded that the major origin of the ultrasonic closing clicks' genesis should be the collision of the occluder with the housing.

Ultrasonic distance measurement using the pulse-echo method is based on the determination of the time of flight of ultrasonic waves. The pulse-compression technique, in which the cross-correlation function of a detected ultrasonic wave and a transmitted ultrasonic wave is obtained, is the conventional method used for improving the resolution of distance measurement. However, the calculation of a cross-correlation operation requires high-cost digital signal processing. This paper presents a new method of sensor signal processing within the pulse-compression technique using a delta-sigma modulated single-bit digital signal. The proposed sensor signal processing method consists of a cross-correlation operation employing single-bit signal processing and a smoothing operation involving a moving average filter. The proposed method reduces the calculation cost of the digital signal processing of the pulse-compression technique.

In this paper, we describe a new ultrasonic oscillosensor and its application in a biological information measurement system. This ultrasonic sensor has a cylindrical tank of 26 mm (diameter)20 mm (height) filled with water and an ultrasonic probe. It detects the vibration of the target object by obtaining echo signals reflected from the water surface. This sensor can noninvasively detect the vibration of a patient by placing it under a bed frame. We propose a recognition system for humans in bed. Using this sensor, we could determine whether or not a patient is in the bed. Moreover, we propose a heart rate monitoring system using this sensor. When our system was tested on four volunteers, we successfully detected a heart rate comparable to that in the case of using an electrocardiograph. Fuzzy logic plays a primary role in the recognition. Consequently, this system can noninvasively determine whether a patient is in the bed as well as their heart rate using a constraint-free and compact device.

A new hybrid model to calculate echoes and ultrasonic fields scattered by flaws is presented. In this model, transmitted fields by a transducer and fields scattered by flaws are calculated using the Rayleigh integral and the FDTD method, respectively. Received echo signals by the transducer are obtained by the inner product of the transmitted fields and the scattered ones at each grid for the FDTD method, and integrating those in a calculation area. Since the calculation area for the FDTD method can be limited around flaws, the calculation time is short and computer memory usage can be reduced. Experiments are done for two types of test object to confirm the validity of the hybrid model. As a result, experimental results are in good agreement with calculated ones.

A novel sensing system for glucose in aqueous solution based on cataluminescence(CTL) is proposed. CTL is a kind of chemiluminescence emitted in a course of catalytic oxidation of combustible substances. A sensing system consisting of a CTL-based chemical-sensor made of the γ-Al2O3 catalyst activated with Tb and an ultrasonic nebulizer is developed. CTL is emitted by injection of air containing mist of a glucose solution prepared by the nebulizer on the catalyst. The CTL intensity measured by a photomultiplier is reproducible for the repeated injection of the mist, and the system can measure glucose concentration in a range of 1-200 mg/dl.

In our previous research, we proposed a nonlinear digital filter to Estimate the Smoothed and Differential values of the sensor inputs by using Sliding mode system (ESDS). This estimator is able to eliminate impulsive noise efficiently from time series data. We applied this filter to processing outputs of robot sensors, and it became possible to perform robust environment recognition. ESDS is designed using a theory of variable structure system (VSS) with sliding mode. In short, ESDS is a nonlinear filter. Therefore, it is very difficult to clarify the behavior of the system analytically. Consequentially, we deal with the step function with impulsive noise as an example, and we attempt to eliminate this impulsive noise by keeping the sudden shift of signals. In this case, there is a trade-off between the noise elimination ability and the tracking performance for an input signal. Although ESDS is a nonlinear filter, it has the same trade-off as linear filters such as a low-pass filter. In order to satisfy these two conditions simultaneously, we use two filters whose parameters are independent of each other. Furthermore, in order to repress the adverse affect of impulsive noise in the steady-state, we introduced the boundary layer. Generally, a boundary layer is used so as to inhibit the harmful effect of chattering. Chattering is caused in the sliding mode system when the state of the system vibrates on the switching line of a sliding mode system. By introducing the boundary layer to ESDS, we can repress the adverse effect of impulsive noise in the steady-state. According to these considerations, we clarify the relationship between these characteristics of ESDS and the arbitrary parameters.

This paper focuses on a global ultrasonic system for self-localization of a mobile robot. The global ultrasonic system consists of some ultrasonic generators fixed at some arbitrary position in the global coordinates and two receivers in the moving coordinates of the mobile robot. This system is used to obtain the state vector of the mobile robot in the global coordinates from the distance measurement between the ultrasonic generator and the receiver. In order to avoid the cross-talk and to synchronize the ultrasonic sensors, the sequential cuing technique using small-sized radio frequency module is adopted. An extended Kalman filter algorithm is used to process the noisy ultrasonic signal and to estimate the state vector. Computer simulations and experiments are conducted to verify the effectiveness of the proposed global ultrasonic system.

We describe a new automated method for detecting embedded objects in the ultrasonic non-destructive testing (NDT) system. A-scan waves collected by our developed system are converted into a B-scan image. The sensor system has the noise signals independent from targets to be detected. In the ultrasonic NDT system, the signals are due to disturbing of echoes produced by the transducers and multiple reflections. These signals are called inherent wave. This paper first proposes the estimation method of the inherent wave from the B-scan image. After this method subtracts the inherent wave, the resultant image (suppression image) is considered as the image consisting of only echoes from the embedded objects. Second, analysis of the intensity histogram of the suppression image leads the candidate points of embedded objects. Finally, fuzzy if-then rules can represent information on distribution of the intensity histogram and the homogeneous intensity levels of the objects. Evaluated degrees from the inference results can demonstrate the embedded objects. The method was applied to concrete members with reinforcing bars, resin tubes and steel pipes. The experimental results showed that this method was able to automatically detect the embedded objects with high accuracy and to display the location of embedded objects.

Technique of Measuring 3-D velocity vector components is important for the correct diagnosis of the blood flow pattern and quantitative assessment of intratumor perfusion. However, present equipment based on ultrasonic Doppler can not provide us true 3-D velocity. To overcome the problem, we previously proposed a new method of 3-D velocity vector measurement. The method uses 2-D array probe and enable us to obtain three components of velocity vector with real time by integrating the Doppler phase shift on the each element with the relative small single aperture compared with conventional method. Basic performance of the method has been evaluated by computer simulation. In this paper, to evaluate the feasibility of the proposed method, experimental investigation using a simple ring array probe and a phantom were carried out. Three components of velocity vector for different velocity magnitude and flow direction were measured. Experimental results validated its ability of measuring 3-D velocity and its feasibility.

The ultrasonic wave is widely used for acquiring perceptual information necessary for indoor/outdoor navigation of mobile robots, where the system is implemented as a sound navigation and ranging system (sonar). A robot equipped with multiple ultrasonic sonars is likely to exhibit undesirable operation due to erroneous measurements resulting from cross-talk among the sonars. Each sonar transmits and receives a pulse-modulated ultrasonic wave for measuring the range and identifying its own signal. We propose a technique for generating pulse patterns for multiple concurrently operated ultrasonic sonars. The approach considers pulse-pattern generation as a combinatorial optimization problem which can be solved by a genetic algorithm (GA). The aim is to acquire a pulse pattern satisfying certain conditions in order to avoid cross-talk or keep the probability of erroneous measurement caused by cross-talk low. We provide a method of genotype coding for the generation of the pulse pattern. Furthermore, in order to avoid a futile search encountered when the conventional technique is used, we propose an improved genotype coding technique that yields considerably different results from those of the conventional technique.

To develop a smoothing method for speckle reduction is a significant problem, because of the complex ultrasonic characteristics and the obscurity of the tissue image. This paper presents a new method for speckle reduction from medical ultrasonic image by using fuzzy morphological speckle reduction algorithm (FMSR) that preserves resolvable details while removing speckle in order to cope with the ambiguous and obscure ultrasonic images. FMSR creates a cleaned image by recombining the processed residual images with a smoothed version of an original image. Performance of the proposed method has been tested on the phantom and tissue images. The results show that the method effectively reduces the speckle while preserving the resolvable details.