In an increasingly data-driven society, sensors and actuators are the bridge between the physical world and the world of "data." Electroacoustic transducers convert acoustic energy into electrical energy (or vice versa), so it can be interpreted as data. Piezoelectric materials are often used for transducer manufacturing, and recent advancements in additive manufacturing have enabled this material to take on complex geometric forms with micro-scale features. This work advances the additive manufacturing of piezoelectric materials by developing a model for predictive success of complex 3D printed geometries in Mask Image Projection-Stereolithography (MIP-SL) by accounting for mechanical wear on Polydimethylsiloxane (PDMS). This work proposes a framework for the rapid manufacture of 3D printed transducers, adaptable to a multitude of transducer element forms. Using the print model and transducer framework, latticed hydrophone elements are designed and tested, showing evidence of selectively tunable sensitivity, resonance, and directivity pattern. These technology advancements are extended to enable a workflow for users to input polar coordinates and receive an acoustic element of a continuously tuned directivity pattern. Investigation into customer problem spaces via tech-push methods are adapted from the NSF's Lean Launchpad to reveal insight to the problems faced in hydrophone applications and other neighboring problem spaces. / Master of Science / In an increasingly data-driven world, sensors are the bridge between the physical world and the world of "data." The better the sensor; the better the data. Electroacoustic transducers are sensors that convert acoustic sound energy into electrical energy or vice versa. These are observed in the world around us as microphones, speakers, ultrasound devices, and more. In the early 1900's, piezoelectric materials became one of the dominant methods for transducer creation, and recent advancements in additive manufacturing have enabled this material to take on highly complex geometric forms with micro-scale feature sizes. Further advancements to additive manufacturing of piezoelectric materials are contributed through development of a model for predicting the success of complex 3D printed geometries in an Mask Image Projection-Stereolithography (MIP-SL) by accounting for mechanical wear on the Polydimethylsiloxane (PDMS) print window. This work proposes a framework for the rapid manufacture of 3D printed transducers, adaptable to a multitude of element forms. Using the developed print model and transducer framework, latticed hydrophone elements are designed and tested, showing evidence of selectively tunable sensitivity, resonance and beampattern. The advancements in technology are extended to enable a workflow for users to input polar coordinates and receive an acoustic element of continuously tuned beampattern. Investigation into customer problem spaces via tech-push methods are adapted from NSF's Lean Launchpad and reveals great insight to the problems faced in hydrophone applications and other neighboring industry spaces.

Orientador: Ricardo Tokio Higuti / Resumo: O ultrassom pode ser utilizado para gerar imagens aplicadas aos ensaios não destrutivos (END) e diagnóstico médico, em que arrays são utilizados para obter imagens com melhor resolução lateral e contraste em relação a um único transdutor. No entanto, os arrays precisam ter o centro do seus elementos espaçados por uma distância (pitch) menor que λ/2, em que λ é o comprimento de onda gerado pelo transdutor, para que as imagens geradas por estes não apresente artefatos causados pelos lóbulos de espaçamento. Porém, para evitar circunstâncias como o aumento na complexidade eletrônica e tempo elevado para geração de imagens ultrassônicas, os arrays esparsos podem ser utilizados, os quais possuem os elementos espaçados por uma distância maior que λ/2 e as imagens geradas apresentam artefatos causados por lóbulos de espaçamento. Contudo, quando os arrays esparsos são utilizados, existem diversas combinações entre os pitches dos elementos para produzir imagens com diferentes qualidades, inviabilizando o teste de todas as combinações possíveis. Assim, neste trabalho, foi utilizado o algoritmo de busca genética para encontrar configurações de arrays esparsos que gerem imagens com boa qualidade, sendo proposto duas novas funções aptidão para avaliar os arrays esparsos. A primeiraé baseada no diagrama de radiação, e a segunda, na comparação entre PSFs (Point Spread Function). As configurações de arrays esparsos encontrados pelo algoritmo genético foram comparadas aos arrays esparsos dispo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Ultrasound can be used to generate images for nondestructive testing and medical diagnostic, in which arrays are used to generate images with better lateral resolution and contrast in comparison to a single transducer. In order to avoid artifacts in ultrasonic images caused by grating lobes, arrays need to have the center of their elements spaced by a distance (pitch) less than λ/2, where λ is the wavelength generated by the transducer. However, in order to avoid electronic complexity and high time to create an ultrasonic image, sparse arrays can be used, which their elements have a pitch greater than λ/2 that generates images with artifacts caused by grating lobes. Although, sparse arrays have their elements with different pitches that produce images with different qualities which it makes impossible to test all combinations. Thus, in this work, the genetic search algorithm was used to find sparse arrays that generate images with good quality. In addition, two new fitness functions were proposed. The first one based on the beam pattern and the second one in the comparison of two PSFs (Point Spread Function). The quality of the sparse arrays found by the genetic algorithm was then compared to the sparse arrays proposed by different authors using the beam pattern, PSF, and images generated from experimental data provided by CSIC (Consejo Superior de Investigaciones Científicas). In general, the images generated by the arrays obtained by the methodology developed in this work p... (Complete abstract click electronic access below) / Mestre

Odontocetes use echolocation to detect, track, and discriminate their prey, as well as negotiate their environment. Their hearing abilities match the frequency of greatest sensitivity to the higher frequencies used for foraging and navigation. Hearing and echolocation together provide odontocetes with a highly developed biosonar system. This dissertation examines the hearing ability of several odontocete species to understand what signals they can perceive during echolocation. The variability in hearing ranges between species is examined in the context of phylogenetic and ecological differences among taxa. An autonomous hydrophone array is also developed that could be used in an expanded form in field deployments to study echolocation signals in a wider range of species. Methods for measuring hearing sensitivity include both psychophysical and electrophysiological procedures. Behavioral methods require a large time commitment, for both training and data collection, and can only be performed on captive dolphins. Auditory evoked potential (AEP) methods are non-invasive, rapid measurements of the brain's response to sound stimuli and allow for audiograms to be collected on stranded, high risk dolphins. By determining the hearing abilities of odontocetes either in captivity or during stranding, data can be collected about inter- and intraspecies variability, and the occurrence of hearing impairment. It can also be used as another diagnostic tool to determine the releasability of a stranded animal. A juvenile male short-finned pilot whale (Globicephala macrorhynchus) that stranded in Curacao had severe hearing impairment at all frequencies tested. Four female short-finned pilot whales tested had the best sensitivity at 40 kHz. The juveniles had greater high frequency sensitivity than the adult pilot whales. Cutoff frequencies were between 80 and 120 kHz. Hearing sensitivity was determined for the two mother/calf pairs of Risso's dolphins (Grampus griseus) before and after antibiotic treatment in order to measure any potential effects of antibiotic treatment. Greatest sensitivity occurred at 40 kHz and cutoff frequencies were around 120 kHz for all dolphins tested. Changes in hearing sensitivity after antibiotic dosage were 12 dB or less in all cases except one. The adult female Betty showed a threshold shift at 120 kHz of 54 dB from May to June, which partially demonstrates the presence of an ototoxic effect at one frequency. Dosages of antibiotics during drug treatment detailed in this study should be considered safe dosages of antibiotics for Risso's dolphins. AEP and behavioral methods were used to collect audiograms for three Stenella spp. dolphins. The frequency of best hearing for the Atlantic spotted dolphin and the spinner dolphin was 40 kHz, and their upper cutoff frequencies were above 120 kHz. The pantropical spotted dolphin had the greatest sensitivity at 10 kHz, and had severe high frequency hearing loss with a cutoff frequency between 14 and 20 kHz. Comparisons of high frequency hearing sensitivities among the species tested show two distinct groups. Short-finned pilot whales and Risso's dolphins have a cutoff frequency below 120 kHz, whereas Stenella spp. dolphins have cutoff frequencies above 120 kHz. Expanding the comparison to include other species, killer whales, pygmy killer whales, false killer whales, and long-finned pilot whales also have cutoff frequencies below 120 kHz. Common bottlenose dolphins, white-beaked dolphins, Indo-Pacific humpback dolphins, rough-toothed dolphins, and common dolphins have cutoff frequencies above 120 kHz. Genetic evidence exists for two subfamilies within Delphinidae (Vilstrup et al., 2011) and those species with cutoff frequencies below 120 kHz belong to the subfamily Globicephalinae and those species with cutoff frequencies above 120 kHz belong to the subfamily Delphininae. An autonomous, field-deployable hydrophone array was developed to measure free-swimming echolocation. The array contained 25 hydrophones, two cameras, and a synchronization unit on a PVC frame. The distinct click train was used to time-align all 25 channels, and the light was used to synchronize the video and acoustic recordings. Echolocation beam patterns were calculated and preliminary evidence shows a free-swimming dolphin utilizes head movement, beam steering and beam focusing. Among all areas of cetacean biology more research is necessary to gain a clearer picture of how odontocetes have adapted to function in their acoustic environment. The array system developed can be used to study how dolphins use echolocation in the wild, the impacts of anthropogenic sound on echolocation production, and the potential consequences of high frequency hearing loss.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23206号 / 工博第4850号 / 新制||工||1757(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 和田 修己, 教授 山本 衛 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Master’s thesis deals with description of issues of reading spatial audio signals using microphone array. Basic method of beamforming (Delay and Sum) is characterized on basis of chosen conception of the microphone array. Specific issues of audio detection and digital signal processing of converted audio signals are characterized and some ways how to solve the issues are adumbrated. Features and limitations of chosen ARM processor in the digital processing of multiple audio signals are described. Especially features and limitations of an internal A/D converter from the perspective of the beamforming are described.

The goal of this master’s thesis is to explore the possibilities of multichannel localization of acoustic signal sources and their following application on a real signal localization and separation, using Beamforming methods. During this thesis two beamforming methods were selected, namely Delay and Sum a Constant Directivity Beamforming - Circular Arrays, and were applicated on real environment signals using two microphone arrays’ geometries ULA (Uniform linear array) and UCA (Uniform Circular array).

Among the research topics needing to be addressed to further the development of phased array feeds (PAFs) for radio astronomical use are challenges associated with calibration, beamforming, and imaging for single dish observations. This dissertation addresses these concerns by providing analysis and solutions that provide a clearer understanding of the effort required to implement PAFs for complex scientific research. It is shown that calibration data are relatively stable over a period of five days and may still be adequate after 70 days. A calibration update system is presented with the potential to refresh old calibrators. Direction-dependent variations have a much greater affect on calibration stability than temporal variations. There is an inherent trade-off in beamformer design between achieving high sensitivity and maintaining beam pattern stability. A hybrid beamformer design is introduced which uses a numerical optimizer to balance the trade-off between these two conflicting goals to provide the greatest sensitivity for a desired amount of pattern control. Relative beam variations that occur when electronically steering beams in the field of view must be reduced in order for a PAF to be useful for source detection and imaging. A dual constraint beamformer is presented that has the ability to simultaneously achieve a uniform main beam gain and specified noise response across all beams. This alone does not reduce the beam variations but it eliminates one aspect of the problem. Incorporating spillover noise control through the use of rim calibrators is shown to reduce the variations between beams. Combining the dual constraint and rim constraint beamformers offers a beamforming option that provides both of these benefits.