Existing weapon detection systems such as metal detectors and X-ray baggage scanners have many drawbacks. While metal detectors can only detect metallic objects, X-ray scanners are unsafe for use on passengers. Also, these systems can only scan people within a short range. These limitations of detecting potentially harmful objects have led to tragic events such as the 9/11 attack on the world trade centre and the 2008 terrorist attack in Mumbai. Development of more advanced security systems would help in curbing such terrorist attacks. These systems could also be used to help security officials in tackling knife and gun related crimes in the streets. The aim of this research is to develop a concealed weapon detection system using acoustic waves. Ideally, the system would have large standoff distance, should be cost-effective and easy to manufacture and would be able to detect both metal and non-metallic weapons. Different techniques such as acoustic signature, resonance acoustic spectroscopy and acoustic imaging were analysed. Acoustic signature techniques identify the target by comparing the acoustic waves reflected by the target to a database of previously recorded acoustic reflections. Resonance acoustic spectroscopy was used on the data acquired using both experimental measurements and Finite Element simulations. A series of resonant frequencies from the acoustic waves reflected by the concealed target were extracted using this technique. This series of resonant frequencies that are unique to the target were used to identify the target. Acoustic camera was used to experimentally record the acoustic reflection from different targets. This was then used to develop images of concealed targets. These tests were performed using commercially available array speaker systems. The probability of improving these results using a better designed ultrasonic or acoustic array speaker system was analysed. This was done by changing different array design parameters and obtaining a highly focused acoustic beam. The results from the experimental tests and Finite Element simulations proved the possibility of using acoustic waves for concealed weapon detection. In the acoustic signature measurements, the frequency spectra of the reflected acoustic waves were shown to be different for different targets. The results from resonance acoustic spectroscopy showed structural resonant frequencies in the frequency spectra that corresponded to the natural frequency of the target. Using acoustic camera kit the image of the concealed target was identified. The array results showed the formation of focused beams for different array configurations. The results showed the formation of grating lobes and side lobes when the inter-element gap became larger than the wavelength of sound waves at the excitation frequency. Finally, a program using neural network was developed to demonstrate how the natural frequencies from the target could be used to identify them. This research work provides a proof of concept of different acoustic wave-based detection and imaging techniques. It has shown the possibility of detecting concealed targets at standoff distances. Using parametric arrays highly focused acoustic or ultrasonic beams could be generated which could be focused on a person suspected of carrying a weapon in a crowded environment. The sound waves reflected back could be analysed using the resonance acoustic spectroscopic technique or one could use the acoustic camera to generate images of targets in real-time. The use of acoustic waves would also help in keeping the cost and complexity of the equipment to a minimum. It also ensures that the public is not exposed to any harmful radiation. The techniques described in this thesis would significantly support the development of a commercially viable, robust acoustic waves based concealed weapon detection system.

No description available.

Today’s production industry is faced with the challenge of maximising its resources and productivity. Tool condition monitoring (TCM) is an important diagnostic tool and if integrated in manufacturing, machining efficiency will increase as a result of reducing downtime resulting from tool failures by intensive wear. The research work presented in the study highlights the principles in tool condition monitoring and identifies acoustic emission (AE) as a reliable sensing technique for the detection of wear conditions. It reviews the importance of acoustic emission as an efficient technique and proposes a TCM model for the prediction of tool wear. The study presents a TCM framework to monitor an end-milling operation of H13 tool steel at different cutting speeds and feed rates. For this, three industrial acoustic sensors were positioned on the workpiece. The framework identifies a feature selection, extraction and conditioning process and classifies AE signals using an artificial neural network algorithm to create an autonomous system. It concludes by recognizing the mean and rms features as viable features in the identification of tool state and observes that chip coloration provides direct correlation to the temperature of machining as well as tool condition. This proposed model is aimed at creating a timing schedule for tool change in industries. This model ultimately links the rate of wear formation to characteristic AE features.

Sudden rock failure in the form of rockbursting has long been a problem in underground mines. The basic mechanism of this phenomenon is still unresolved. This thesis describes the research work on this problem conducted by the doctoral candidate Daihua Zou in the Department of Mining and Mineral Process Engineering at The University of British Columbia, under the supervision of Professor Hamish D.S. Miller. This research project was undertaken in order to investigate the process of violent rock failure and was achieved by examining various aspects of the rock failure mechanism. The assumption that acoustic emission can be used as a reliable means of predicting rock failure was investigated, as well as the possibility that violent rock failure could occur in any mine rock. As part of the research, a rock failure mechanism was postulated. A process analogous to shearing is postulated to be important at the post-failure stage. The stick-slip phenomenon has been analyzed using a numerical model under a variety of conditions. The conditions which could give rise to possible violent rock failure were determined. At the same time, acoustic emissions were tested from rock specimens under different loading conditions. The experimental results obtained show a correlation with field measurements made in a mine. In order to verify the testing results from limited experiments, a numerical acoustic model was developed, which is unique in that it is entirely based on the stick-slip process not on any acoustic theory. This model allows rock tests and their associated acoustic emission to be realistically simulated. With this model, acoustic emissions were simulated under various loading conditions for different kinds of rocks. The case of a hard or a soft intercalation was also modelled. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

This thesis is concerned with the problem of estimating broadband acoustic impedance from normal incidence reflection seismograms. This topic is covered by following the linear inverse formalisms described by Parker (1977) and Oldenburg (1980). The measured seismogram is modelled as a convolution of subsurface reflectivity with a source wavelet. Then an appraisal of the seismogram is performed to obtain unique bandlimited reflectivity information. This bandlimited reflecitivity information is then utilized in two different construction algorithms which provide a broadband estimate of reflectivity; from which a broadband impedance function may be computed. The first construction method is a maximum entropy method which uses an autoregressive representation of a small portion of the reflectivity spectrum to predict spectral values outside that small portion. The second and most versatile construction method is the linear programming approach of Levy and Fullagar (1981) which utilizes the unique bandlimited spectral information obtained from an appraisal and provides a broadband reflectivity function which has a minimum 1( norm. Both methods have been tested on synthetic and real seismic data and have shown good success at recovering interpretable broadband impedance models. Errors in the data and the uniqueness of constructed reflectivity models play important roles in estimating the impedance function and in assessing its uniqueness. The Karhunen-Loeve transformation is discussed and applied on real data to stabilize the construction results in the presence of noise. The generally accepted idea that low frequency impedance information must be supplied from well log or velocity analyses because of the bandlimited nature of seismic data has been challenged. When accurate, bandlimited reflectivity information can be recovered from the seismic trace, then an interpretable, broadband impedance model may be recovered using the two construction algorithms presented in this thesis. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Feedback procedures are an important class of operant behavior change methods used in a wide variety of settings. One innovative method of providing immediate feedback adapted from the animal literature is through the use of an acoustical stimulus, such as a clicker. Methods utilizing this response contingent delivery of acoustic feedback in humans is commercially referred to as TAGteaching. Several studies have documented the effectiveness of this teaching procedure with various human populations. Despite the successes, very little is known of the environmental manipulations necessary to produce desirable effects; and if these effects sustain when this procedure is implemented in clinical settings. Moreover, several authors have asserted that the acoustic stimulus functions like a conditioned reinforcer, however no explicit pairing procedures are traditionally implemented with humans, to establish the functions of contingent deliveries of the acoustic stimulus. The purpose of the current study was twofold; first this study sought to evaluate the role of textual instructions in establishing the functions of response contingent acoustic feedback using a laboratory task. Secondly, this study sought to evaluate the extent to which instructions and acoustic feedback, produce changes in staff and client behaviors in a clinical setting. Study one was conducted across 40 college students and evaluated the role of instructions in establishing the functions of contingent acoustic feedback in the context of a Multistep Experimental Task (MSET). The MSET was adopted from a previous laboratory evaluation of TAGteach (Smith & Lambert, 2014). Participants were assigned to four different experimental groups for both a within-subject and a between-group analysis of performance. Results indicated improved performance for all participants who received both instructions and contingent acoustic feedback, whereas three participants who received acoustic feedback only showed similar improvements. Study two was conducted across three staff participants and sought to evaluate an intervention comprised of in-situ instructions and response contingent acoustic feedback to teach staff to use Behavior Specific Praise procedures (BSP) with clients. Results from a multiple-baseline-across staff design revealed that the intervention increased staff’s rates of BSP in this clinical setting. Additionally, intervention effects were maintained during one to three-week probes. The intervention also maintained client correct responding across different targeted behavior chains. Staff members also rated the acoustic feedback procedure as more worthwhile, helpful, relevant, pleasant, and less disruptive than their typical feedback methods. Both findings provide useful data to support the design and implementation of acoustic feedback procedures in clinical settings. They also provide preliminary data to clarify the antecedent conditions necessary to establish the functions of contingent acoustic feedback.

No description available.

No description available.

This research introduces a new application of the three microphones method, which was originally developed to analyse standing waves, to measure the aeroacoustic power of a duct housing a shallow cavity coupled with a longitudinal acoustic mode. In addition, this work provides, for the first time, the spatial distribution of the aeroacoustic sound sources over the cavity region for this type of flow-sound-structure interaction pattern. Furthermore, this research includes a comprehensive study of the effect of cavity geometrical parameters on the characteristics of the cavity aeroacoustic source. An experimental investigation of the aeroacoustic source of an axisymetric cavity in a pipeline is presented. This aeroacoustic source is generated due to the interaction of the cavity shear layer oscillation with the resonant acoustic field in the pipe. The source is determined under high Reynolds number, fully developed turbulent pipe flow. The experimental technique (Sound Wave Method, SWM) employs six microphones distributed upstream and downstream of the cavity to evaluate the fluctuating pressure difference generated by the oscillating cavity shear layer in the presence of externally imposed sound waves. The results of the dimensionless aeroacoustic sources are in good agreement with the concepts of free shear layer instability and the fluid resonant oscillation behavior. A validation study is performed in order to validate the measurement technique and the measured source term from the SWM. The validation methodology consisted of comparing the self-excited resonance response obtained from self-excitation measurements with that estimated from an acoustic model supplemented with the measured source term using the SWM. The comparison depicts a very good agreement for the resonance frequency, lock-in ranges, and the resonance amplitude. Extensive PIV flow measurements are performed to clarify the non-linear behavior of the aeroacoustic source at high levels of the acoustic particle velocity, and to understand the dependence of the flow-sound interaction patterns on the main system parameters such as the Strouhal number and excitation level. The results of a finite element analysis of the resonant sound field are combined with those of the PIV flow measurements into Howe’s aeroacoustic integrand to compute the spatial and temporal distributions of the aeroacoustic sources. The results are also compared with the measured aeroacoustic source strength obtained by means of the SWM. This comparison highlights the superior efficiency of the SWM technique. Identification of the aeroacoustic source distributions as function of the acoustic excitation level showed that the non-linear behaviour of the source strength, which occurs at moderate sound levels, is caused by a gradual transition in the vorticity field oscillation pattern; from a distributed vorticity cloud over the whole cavity length at small excitation amplitudes to a pattern involving rapid formation of (discrete) vortices at the leading edge which becomes dominant at large excitation levels. The spatial distribution of the acoustic power over the cavity length at resonance condition shows sources of sound generation at the first and last thirds of the cavity mouth and an absorption sink in the middle third. This distribution is different from that observed for deep cavities and trapped modes of shallow cavities. Due to these differences in the aeroacoustic source distributions, the effects of cavity geometrical parameters for the present shallow cavity are not necessarily similar to those reported in the literature for deep cavities and trapped mode resonance cases. A comprehensive study of the effect of cavity geometrical parameters (including rounding-off the cavity edges) on the aeroacoustic sound sources is also included. Nine cavity sizes are studied in three different groups of length to depth ratios (L/H) with three different cavity volumes for each group of L/H. The aeroacoustic source strength and the Strouhal number corresponding to its maximum value are found to increase in a systematic manner as the cavity volume is increased for the same L/H ratio. These results indicate that the aeroacoustic sources of shallow cavities are affected not only by the ratio L/H, but also by the cavity volume. The effect of cavity edge curvatures on the resonance response is experimentally investigated by testing different sizes of curvatures at different locations (upstream, downstream or both edges). The results show that rounding-off the cavity edges causes a reduction in the vertical component of the acoustic particle velocity but also an increase in the cavity length. These two consequences have opposite effects on acoustic power generation and therefore, rounding-off the edges has no significant effect on the resonance amplitude in the present case, except for relatively large radius. / Thesis / Doctor of Philosophy (PhD)

Hidden Markov models (HMM) with Gaussian mixture observation densities are the dominant approach in speech recognition. These systems typically use a representational model for acoustic modeling which can often be prone to overfitting and does not translate to improved discrimination. We propose a new paradigm centered on principles of structural risk minimization using a discriminative framework for speech recognition based on support vector machines (SVMs). SVMs have the ability to simultaneously optimize the representational and discriminative ability of the acoustic classifiers. We have developed the first SVM-based large vocabulary speech recognition system that improves performance over traditional HMM-based systems. This hybrid system achieves a state-of-the-art word error rate of 10.6% on a continuous alphadigit task ? a 10% improvement relative to an HMM system. On SWITCHBOARD, a large vocabulary task, the system improves performance over a traditional HMM system from 41.6% word error rate to 40.6%. This dissertation discusses several practical issues that arise when SVMs are incorporated into the hybrid system.