Wireless recording of the calls of Rousettus aegyptiacus and their reproduction using electrostatic transducers

Bats are capable of imaging their surroundings in great detail using echolocation. To apply similar methods to human engineering systems requires the capability to measure and recreate the signals used, and to understand the processing applied to returning echoes. In this work, the emitted and reflected echolocation signals of Rousettus aegyptiacus are recorded while the bat is in flight, using a wireless sensor mounted on the bat. The sensor is designed to replicate the acoustic gain control which bats are known to use, applying a gain to returning echoes that is dependent on the incurred time delay. Employing this technique allows emitted and reflected echolocation calls, which have a wide dynamic range, to be recorded. The recorded echoes demonstrate the complexity of environment reconstruction using echolocation. The sensor is also used to make accurate recordings of the emitted calls, and these calls are recreated in the laboratory using custom-built wideband electrostatic transducers, allied with a spectral equalization technique. This technique is further demonstrated by recreating multi-harmonic bioinspired FM chirps. The ability to record and accurately synthesize echolocation calls enables the exploitation of biological signals in human engineering systems for sonar, materials characterization and imaging

Coded Pulse Transmission and Correlation for Robust Ultrasound Ranging from a Long-Cane Platform

The objective of this research was to increase the independence and safety of the sight impaired by developing an enhanced travel aid in the form of a sensor embedded long-cane to reduce the risk of injury from walking into suspended or overhanging objects while providing the sight impaired community with a familiar and well accepted tool. Prior research at the Electromechanical Systems Laboratory had established a theoretical framework for ultrasound-based ranging and spatial obstacle localization from the moving reference frame of a long-cane. A prototype was implemented using analog threshold detection techniques. This research focused on a new approach. A coded pulse was transmitted and correlation techniques were used to identify echoes and determine time of flight. Compared to the prior effort this new approach was more sensitive, had greater noise immunity, and provide greater spatial resolution for obstacle detection. The first step in the coded pulse approach was to generate a transmit pulse with an embedded binary code that is highly distinguishable. A transmit pulse generated by phase modulating a 40 kHz carrier signal with a 13-bit Barker code word, with each bit consisting of 4 cycles of the 40 kHz carrier was used. Digitized representative echoes were used as reference vectors for correlation to account for the effect of the impulse responses of the transducers, the air, and the reflection, on the transmitted pulse. In a detection cycle, the coded pulse was transmitted, the A/D converters took 2600 samples at the 150 kHz sampling rate to capture any echoes from objects between 1 and 4 meters in front of the cane. The receiver data was cross-correlated with the stored echo image to find echoes in the received signal. The correlation peak positions from the upper receiver were then compared to the peak positions from the lower receiver and if they collaborated within the synthetic aperture, the range and height were calculated annunciation was made by a synthesized voice. The new obstacle detection system described above was designed and a prototype was constructed and embedded into the shaft of an 18 mm diameter body of a long cane

Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

Digital Signal Processing Research Program

Contains table of contents for Section 2, an introduction, reports on twenty-one research projects and a list of publications.U.S. Navy - Office of Naval Research Grant N00014-93-1-0686Lockheed Sanders, Inc. Contract P.O. BY5561U.S. Air Force - Office of Scientific Research Grant AFOSR 91-0034National Science Foundation Grant MIP 95-02885U.S. Navy - Office of Naval Research Grant N00014-95-1-0834MIT-WHOI Joint Graduate Program in Oceanographic EngineeringAT&T Laboratories Doctoral Support ProgramDefense Advanced Research Projects Agency/U.S. Navy - Office of Naval Research Grant N00014-89-J-1489Lockheed Sanders/U.S. Navy - Office of Naval Research Grant N00014-91-C-0125U.S. Navy - Office of Naval Research Grant N00014-89-J-1489National Science Foundation Grant MIP 95-02885Defense Advanced Research Projects Agency/U.S. Navy Contract DAAH04-95-1-0473U.S. Navy - Office of Naval Research Grant N00014-91-J-1628University of California/Scripps Institute of Oceanography Contract 1003-73-5

Acoustic modelling of bat pinnae utilising the TLM method

This thesis describes the numerical modelling of bioacoustic structures, the focus being the outer ear or pinnae of the Rufous Horseshoe bat (Rhinolophus rouxii). There have been several novel developments derived from this work including: • A method of calculating directionality based on the sphere with a distribution of measuring points such that each lies in an equal area segment. • Performance estimation of the pinna by considering the directionality of an equivalent radiating aperture. • A simple synthetic geometry that appears to give similar performance to a bat pinna. The outcome of applying the methods have yielded results that agree with measurements, indeed, this work is the first time TLM has been applied to a structure of this kind. It paves the way towards a greater understanding of bioacoustics and ultimately towards generating synthetic structures that can perform as well as those found in the natural world

Algorithm and Hardware Design for High Volume Rate 3-D Medical Ultrasound Imaging

abstract: Ultrasound B-mode imaging is an increasingly significant medical imaging modality for clinical applications. Compared to other imaging modalities like computed tomography (CT) or magnetic resonance imaging (MRI), ultrasound imaging has the advantage of being safe, inexpensive, and portable. While two dimensional (2-D) ultrasound imaging is very popular, three dimensional (3-D) ultrasound imaging provides distinct advantages over its 2-D counterpart by providing volumetric imaging, which leads to more accurate analysis of tumor and cysts. However, the amount of received data at the front-end of 3-D system is extremely large, making it impractical for power-constrained portable systems. In this thesis, algorithm and hardware design techniques to support a hand-held 3-D ultrasound imaging system are proposed. Synthetic aperture sequential beamforming (SASB) is chosen since its computations can be split into two stages, where the output generated of Stage 1 is significantly smaller in size compared to the input. This characteristic enables Stage 1 to be done in the front end while Stage 2 can be sent out to be processed elsewhere. The contributions of this thesis are as follows. First, 2-D SASB is extended to 3-D. Techniques to increase the volume rate of 3-D SASB through a new multi-line firing scheme and use of linear chirp as the excitation waveform, are presented. A new sparse array design that not only reduces the number of active transducers but also avoids the imaging degradation caused by grating lobes, is proposed. A combination of these techniques increases the volume rate of 3-D SASB by 4\texttimes{} without introducing extra computations at the front end. Next, algorithmic techniques to further reduce the Stage 1 computations in the front end are presented. These include reducing the number of distinct apodization coefficients and operating with narrow-bit-width fixed-point data. A 3-D die stacked architecture is designed for the front end. This highly parallel architecture enables the signals received by 961 active transducers to be digitalized, routed by a network-on-chip, and processed in parallel. The processed data are accumulated through a bus-based structure. This architecture is synthesized using TSMC 28 nm technology node and the estimated power consumption of the front end is less than 2 W. Finally, the Stage 2 computations are mapped onto a reconfigurable multi-core architecture, TRANSFORMER, which supports different types of on-chip memory banks and run-time reconfigurable connections between general processing elements and memory banks. The matched filtering step and the beamforming step in Stage 2 are mapped onto TRANSFORMER with different memory configurations. Gem5 simulations show that the private cache mode generates shorter execution time and higher computation efficiency compared to other cache modes. The overall execution time for Stage 2 is 14.73 ms. The average power consumption and the average Giga-operations-per-second/Watt in 14 nm technology node are 0.14 W and 103.84, respectively.Dissertation/ThesisDoctoral Dissertation Engineering 201

A multi-mode sonar transmitter

This project was initiated to evaluate appropriate microprocessor and digital logic techniques that could increase the flexibility and effectiveness of a sonar transmitter. The study led to a multi-channel signal synthesis concept designed to exploit 'phased array' steering techniques. Two versions of the equipment have now been built and evaluated. Mk.I is a relatively low power 15 channel system with 2 kilowatts total electrical power using a 40 kHz 15 λ x 1 line array. This system proved the practicability of the basic concept and its success led to the 16 kilowatt Mk2 high power version which drives a 16λ x 16 λ wideband transducer array. The study included: The design and construction of a multi-channel signal generator. The writing of control and signal synthesis software. The design, evaluation and commissioning of suitable linear power amplifiers . Investigations into suitable transducers and phased array design, leading to the manufacture of suitable matched wide band multi-channel 'staved' transducer arrays. Finally, a series of trials were made in a variety of open water conditions to evaluate the systems performance and investigate the multiple modes of operation that have been developed. The system has successfully demonstrated that transmitter beam steering is both practical and flexible. The techniques implemented permit sector interrogation by 'within-pulse' type sweeps, by 'Ripple-fire' and by transmitting steered 'Pings' sequentially on prededermined bearings. Each mode allows considerable flexibility in the generated waveform shape and frequency. The 'Multi-Mode' capability of this approach was conceived primarily as a research tool but many of the modes can be isolated and exploited in dedicated applications