Dissertations / Theses: 'Acoustics data' – Grafiati (2024)

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

With the advent of commercial surround sound systems there is a growing demand for 11 system that can convert existing mono and stereo recor~ings into a surround sound recording. A part of this problem is to generate the reverberation for the additional audio channels from the reverberation in the mono or stereo recording. . , In thi~ thesis, it is investigated whether a room model can be constructed from one or two room impulse responses and in which a virtual surround sound recording can then be perfonned. The estimation of the room model parameters is based on the three well-mown room acoustic models; the geometrical acoustic model with specular reflections, the eigenmode model and the diffuse field model. It is shown that the scope with the geometrical acoustic and the eigenmode model is limited but it is possible to obtain useful and consistent results for the room volume and the source-to-receiver distance from the diffuse field model. Based on these findings, the problem of generating multiple room impulse responses from one or two input room impulse response(s) is approached slightly differently. The very early part of the room impulse responses (the early reflections) is generated by a geometrical model with specular and diffuse reflections. The remainder of the room impulse responses are copies of the input room impulses obtained by convolution with a set of filters that control the coherence between them. The values for the coherence are given by expressions for the coherence between microphones with first-order directivity in a diffuse field and these expressions are derived in the thesis. The results from objective and subjective tests indicate that this method works successfully.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Advances in ocean modeling (Barron et al., 2006) have improved such that ocean forecasts and even ensembles (e.g., Coelho et al., 2009) representing ocean uncertainty are becoming more widely available. This facilitates nowcasts (current time ocean fields / analyses) and forecasts (predicted ocean fields) of acoustic propagation conditions in the ocean which can greatly improve the planning of acoustic experiments. Modeling of acoustic transmission loss (TL) provides information about how the environment impacts acoustic performance for various systems and system configurations of interest. It is, however, very time consuming to compute acoustic propagation to and from many potential source and receiver locations for multiple locations on an area-wide grid for multiple analysis / forecast times, ensembles and scenarios of interest. Currently, to make such wide area predictions, an area is gridded and acoustic predictions for multiple directions (or radials) at each grid point for a single time period or ensemble, are computed to estimate performance on the grid. This grid generally does not consider the environment and can neglect important environmental acoustic features or can overcompute in areas of environmental acoustic isotropy. This effort develops two methods to pre-examine the area and time frame in terms of the environmental acoustics in order to prescribe an environmentally optimized computational grid that takes advantage of environmental-acoustic similarities and differences to characterize an area, time frame and ensemble with fewer acoustic model predictions and thus less computation time. Such improvement allows for a more thorough characterization of the time frame and area of interest. The first method is based on critical factors in the environment that typically indicate acoustic response, and the second method is based on a more robust full waveguide mode-based description of the environment. Results are shown for the critical factors method and show that this proves to be a viable solution for most cases studied. Limitations are at areas of high loss, which may not be of concern for exercise planning. The mode-based method is developed for range independent environments and shows significant promise for future development.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In June 2003, the Littoral Acoustic Demonstration Center conducted an acoustic characterization experiment for a standard seismic exploration array. Two moorings with Environmental Acoustic Recording Systems (EARS) were deployed in the northern part of the Gulf of Mexico to measure ambient noise and collect shot information. A 21-element seismic airgun array was towed along five parallel linear tracks with horizontal closest approach points to the EARS buoy position of 63, 500, 1000, 2000, and 5000 m. Calibrated acoustic pressure measurements collected during the experiment were analyzed to obtain zero-to-peak sound pressures, sound exposure levels, and pressure levels in 1/3-octave frequency bands. In addition, the experimental data were modeled by using a modified underwater acoustic propagation model to fill in missing data measurements. The resulting modeling procedure showed good agreement between measured and modeled data in absolute pressure amplitudes and frequency interference patterns for frequencies up to 1000 Hz. The analysis is important for investigating the potential impact on marine mammals and fish and predicting the exposure levels for newly planned seismic surveys in other geographic areas. Based on results of the experiment conducted and data analysis performed, a new experimental design was proposed to maximize the amount of collected data using the available equipment while minimizing the time needed for the source ship. The design used three patches, one with 3º angular spacing between the lines at a reference depth. Embedded is a smaller patch with 1º spacing and within that a still smaller patch with one half degree spacing. This arrangement gives a reasonably uniform distribution of shots versus solid angle with a large variety of emission and azimuthal angles for different ranges. Due to the uncertainty of positioning systems, the angular space is divided into solid angle bins. Simulations predicted more than 200 shots per bin for emission angles greater than 13 degrees. Statistical analysis of collected data will be performed on the proposed bin basis. An experiment based on the proposed design was conducted in Fall 2007. The data measurements collected during the experiment are currently being analyzed and will be reported in the near future.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Cette thèse s'inscrit dans le cadre de la statistique fonctionnelle appliquée à l'environnement.La statistique fonctionnelle constitue un domaine de la statistique qui se penche sur des données présentées sous forme fonctionnelle. Elle propose des techniques pour la réduction de dimension, l'apprentissage supervisé et non supervisé, tout en tenant compte des dépendances temporelles et/ou spatiales des données fonctionnelles. Ce type de données est de plus en plus disponible dans de nombreux domaines, notamment les sciences de l'environnement, grâce aux technologies modernes. C'est notamment le cas des techniques d'acoustique des pêches, qui permettent d'obtenir des échantillons spatiaux et temporels d'organismes marins à diverses profondeurs et échelles spatiales, sans intrusivité.Dans le cadre de cette thèse, nous avons analysé un ensemble de données acoustiques multifréquences extraites par des échosondeurs scientifiques afin d'étudier la structure spatiale des agrégations d'organismes marins, communément appelées "Sound Scattering Layers". Nous avons examiné les caractéristiques de ces objets biologiques complexes, telles que leur épaisseur, leur densité relative et leur profondeur, en relation avec leur environnement. Cet environnement a été représenté à une échelle fine grâce à un système multiparamétrique tracté. Pour ce faire, nous avons d'abord utilisé des méthodes standards de statistique multivariée, puis nous avons mobilisé des techniques de l'analyse de données fonctionnelles, avec ou sans la dimension spatiale.Dans notre première analyse exploratoire, l'Analyse en composantes Principales fonctionnelle multivariée a fourni des informations précises sur la variation des paramètres le long des profondeurs, contrairement à l'Analyse en composantes Principales classique. Dans le cadre des tâches de régression, nos analyses, qu'elles intègrent ou non la dimension spatiale, ont mis en évidence des interactions entre les caractéristiques des "Sound Scattering Layers" et les variables environnementales clés à l'échelle spatiale. Nous avons observé des différences significatives entre les "Sound Scattering Layers" du nord et du sud, ainsi qu'entre ceux des zones côtières et des zones hauturières. Il est à noter que la prise en compte de la dimension spatiale a amélioré la qualité de la modélisation. Ces résultats démontrent que l'analyse statistique spatiale-fonctionnelle revêt une importance cruciale dans les études écologiques portant sur des objets spatialement complexes.Au-delà de notre étude de cas spécifique, l'application de l'analyse de données fonctionnelles ouvre des perspectives prometteuses pour un large éventail d'études écologiques impliquant des données spatiales massives
This thesis falls within the framework of functional statistics applied to the environment.Functional data analysis is a field of statistics that studies data in functional forms. It provides techniques for dimension reduction, supervised and unsupervised learning, while considering temporal and/or spatial dependencies in functional data. Such data types are increasingly available in various fields, particularly in environmental sciences, thanks to modern technologies. One example is the use of fisheries acoustics, which allows for obtaining spatial and temporal samples of marine organisms at various depths and spatial scales, without intrusiveness.In this thesis, we analyzed a set of multifrequency acoustic data collected by scientific echosounders to study the spatial structure of marine organism aggregations, commonly known as "Sound Scattering Layers." We examined the characteristics of these complex biological entities, such as thickness, relative density, and depth, in relation to their environment, represented at a fine scale using a towed multiparametric system. To do so, we initially applied standard multivariate statistical methods and then incorporated functional data analysis techniques, with or without the spatial dimension.In our initial exploratory analysis, Multivariate Functional Principal Component Analysis provided precise information about parameter variation along depths, unlike traditional Principal Component Analysis. In regression tasks, our analyses, whether incorporating spatial dimension or not, revealed interactions between "Sound Scattering Layers" descriptors and key environmental variables on a spatial scale. We noted significant differences between the "Sound Scattering Layers" in the northern and southern regions, as well as between those in coastal and offshore zones. It is worth noting that considering the spatial dimension improved modeling quality. These results highlight spatial-functional statistical analysis as a key method in ecological studies involving spatially complex objects.Beyond our specific case study, the application of functional data analysis offers promising prospects for a wide range of ecological studies involving massive spatial data

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Airflow management is crucial for the performance of cooling systems in data centers.The amount of energy consumed by data centers is huge and a large amount is relatedto the cooling. In attempts to develop energy efficient data centers, numerical methodsare important for several reasons. Experimental procedures are more expensive and timeconsuming but when done carefully, experiments provide trustful results that can beused to validate simulations and give additional insights. Numerical methods in theirturn have the advantage that they can be applied to proposed designs of data centersbefore they are built and not only to already existing data centers. In this study, Computational Fluid Dynamics (CFD) is used to study the airflow indata centers. The aim is to use an experimentally validated CFD model to investigatethe effects of using different designs in data centers with respect to the performance ofthe cooling systems. Important parameters such as quality of the computational grid,boundary conditions and choice of turbulence model must be carefully considered in orderfor the results from simulations to be reliable. In Paper A, a hard floor configuration where the cold air is supplied directly into thedata center is compared to a raised floor configuration where the cold air is supplied intoan under-floor space instead and enters the data center through perforated tiles in thefloor. In Paper B, the performance of different turbulence models are investigated andvelocity measurements are used to validate the CFD model. In Paper C, the performanceof different cooling systems is further investigated by using an experimentally validatedCFD model. The effects of using partial aisle containment in the design of data centersare evaluated for both hard and raised floor configurations. Results show that the flow fields in data centers are very complex with large velocitygradients. The k − ε model fails to predict low velocity regions. Reynolds Stress Model(RSM) and Detached Eddy Simulation (DES) produce very similar results and based onsolution times, it is recommended to use RSM to model the turbulent airflow in datacenters. Based on a combination of performance metrics where both intake temperaturesfor the server racks and airflow patterns are considered, the airflow management is significantlyimproved in raised floor configurations. Using side covers to partially enclosethe aisles performs better than using top covers or open aisles.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, September 2003.
Thesis advisor(s): Kevin B. Smith, Daphne Kapolka. Includes bibliographical references (p. 69-71). Also available online.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

A challenge in Underwater Acoustics is identifying the independent variables associated with an environment’s ambient noise. A strict definition of ambient noise would focus on non-transient signatures and exclude transient impacts from marine mammals, pelagic fish species, man-made sources, or weather events such as precipitation or wind speeds. Recognizing transient signatures in acoustic spectra is an essential element for providing environmental intelligence to the U.S. Navy, specifically the acoustic signatures from meteorological events. While weather event detection in acoustic spectra has been shown in previous studies, leveraging these concepts via U.S. Navy assets is largely an unknown. Environmental intelligence collection can be improved by detecting precipitation events and establishing wind velocities with acoustic signatures. This will further improve meteorological models by enabling validation from both manned and unmanned sub-surface assets.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Data acquisition systems for rotordynamic analysis and machine vibration were explored for the purpose of replacing the obsolete Bently Nevada ADRE 208 and ADRE for Windows system. These included the development of Matlab based custom data acquisition systems and a user interface. A model of an anisotropic rotor response undergoing transient speed was developed for the rapid prototyping and testing of data acquisition systems. Several methods for the measurement of amplitudes and phase in both the time domain and frequency domain were developed and compared. An alternate data acquisition method which is more inline with industry practices was created for the purpose of spectral analysis. Additionally, an optimized data acquisition strategy was developed for implementation within the Matlab app which included batch processing, state-based acquisition, and differentiated vector and waveform acquisition rates. A Bently Nevada 2300/20 vibration monitor was configured for use in the lab but found unsuitable for replacing the ADRE 208. Ultimately a Bently Nevada ADAPT 3701/44 Vibration Monitor was configured and found to be an adequate replacement for the ADRE 208 system for use in the Cal Poly Vibrations Lab.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Binaural simulation is the recreation of a three-dimensional audio environment around a listener's head. The binaural simulation of structural acoustic data would open new opportunities in virtual prototyping and simulation. By modeling the structure as an array of vibrating monopoles and applying Head Related Transfer Functions (HRTFs) to each of the sources, a binaural simulation of this type can be created. Unfortunately, this simulation method requires an extensive amount of computer power and speed for real-time simulation, more so than is available with current technology.The objective of this research is to reduce the number of computations required in the binaural simulation of structural acoustic data. This thesis details two methods of reducing the number of real-time calculations required in this binaural analysis: singular value decomposition (SVD), and equivalent source reduction (ESR). The SVD method reduces the complexity of the HRTF computations by breaking the HRTFs into dominant singular values and vectors. The ESR method reduces the number of sources to be analyzed in real-time by replacing sources on the scale of a structural wavelength with sources on the scale of an acoustic wavelength. The ESR and SVD reduction methods can be combined to provide an estimated computation time reduction of 99.4%. In addition, preliminary tests show that there is a 97% correlation between the results of the combined reduction methods and the results found with current binaural simulation techniques.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis (Ph. D. in Mechanical Engineering)--Naval Postgraduate School, June 2003.
Dissertation supervisor: Anthony J. Healey. Includes bibliographical references (p. 169-173). Also available online.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In order to perform useful tasks for us, robots must have the ability to notice, recognize, and respond to objects and events in their environment. This requires the acquisition and synthesis of information from a variety of sensors. Here we investigate the performance of a number of sensor modalities in an unstructured outdoor environment, including the Microsoft Kinect, thermal infrared camera, and coffee can radar. Special attention is given to acoustic echolocation measurements of approaching vehicles, where an acoustic parametric array propagates an audible signal to the oncoming target and the Kinect microphone array records the reflected backscattered signal. Although useful information about the target is hidden inside the noisy time domain measurements, the Dynamic Wavelet Fingerprint process (DWFP) is used to create a time-frequency representation of the data. A small-dimensional feature vector is created for each measurement using an intelligent feature selection process for use in statistical pattern classification routines. Using our experimentally measured data from real vehicles at 50 m, this process is able to correctly classify vehicles into one of five classes with 94% accuracy. Fully three-dimensional simulations allow us to study the nonlinear beam propagation and interaction with real-world targets to improve classification results.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation BLDS-P devices. An expansion header is included in the core module to allow additional functionality to be added via daughter boards. An analog signal chain comprised of two-stage amplification and fourth-order active antialiasing filters was implemented as a daughter board to provide an AC-coupled end-to-end gain of 7,500 and a DC-coupled end-to-end gain of 50. This arrangement was tested in a wind tunnel to demonstrate that sensors with a full-scale range of 103 kPa can be used to reliably discriminate between laminar and turbulent flows based on pressure fluctuation differences on the order of tens of Pa. A combination of wind-off correction and band-filtering was used to reduce the effect of inherent and induced electrical noise, while two-sensor correlation was tested and shown to be effective at removing certain types of noise. Total power consumption for the FTDS-K in a representative mission is 208 mW, which translates to an operational endurance of 9 hours with 2 AAA LiFeS2 cells at -40°C.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

CubeSat designers are increasingly looking to incorporate delicate structures and optics into their payloads. These delicate payloads, however, may not survive the required absolute-worst-case launch vibration testing needed for flight certification. To help address this problem, and to better match testing conditions to real-world launch environments, this thesis introduces Sync, a compact 1/4U CubeSat payload designed to collect data on the vibrations and thermal environments CubeSats experience inside a deployer on the way to orbit. This data can be used to better understand the launch environment for different vehicles, and help develop new, more realistic testing guidelines that could enable more delicate payloads to be launched.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

During Mine Warfare (MIW) operations, MIW analysts perform change detection by visually comparing historical sidescan sonar imagery (SSI) collected by a sidescan sonar with recently collected SSI in an attempt to identify objects (which might be explosive mines) placed at sea since the last time the area was surveyed. This dissertation presents a data structure and three algorithms, developed by the author, that are part of an automated change detection and classification (ACDC) system. MIW analysts at the Naval Oceanographic Office, to reduce the amount of time to perform change detection, are currently using ACDC. The dissertation introductory chapter gives background information on change detection, ACDC, and describes how SSI is produced from raw sonar data. Chapter 2 presents the author's Geospatial Bitmap (GB) data structure, which is capable of storing information geographically and is utilized by the three algorithms. This chapter shows that a GB data structure used in a polygon-smoothing algorithm ran between 1.3 – 48.4x faster than a sparse matrix data structure. Chapter 3 describes the GB clustering algorithm, which is the author's repeatable, order-independent method for clustering. Results from tests performed in this chapter show that the time to cluster a set of points is not affected by the distribution or the order of the points. In Chapter 4, the author presents his real-time computer-aided detection (CAD) algorithm that automatically detects mine-like objects on the seafloor in SSI. The author ran his GB-based CAD algorithm on real SSI data, and results of these tests indicate that his real-time CAD algorithm performs comparably to or better than other non-real-time CAD algorithms. The author presents his computer-aided search (CAS) algorithm in Chapter 5. CAS helps MIW analysts locate mine-like features that are geospatially close to previously detected features. A comparison between the CAS and a great circle distance algorithm shows that the CAS performs geospatial searching 1.75x faster on large data sets. Finally, the concluding chapter of this dissertation gives important details on how the completed ACDC system will function, and discusses the author's future research to develop additional algorithms and data structures for ACDC.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Underwater sound is very important in the field of oceanography where it is used for remote sensing in much the same way that radar is used in atmospheric studies. One way to mathematically model sound propagation in the ocean is by using the parabolic-equation method, a technique that allows range dependent environmental parameters. More importantly, this method can model sound transmission where the source emits either a pure tone or a short pulse of sound. Based on the parabolic approximation method and using the split-step Fourier algorithm, a computer model for underwater sound propagation was designed and implemented. This computer model differs from previous models in its use of the interactive mode, structured programming, modular design, and state-of-the-art graphics displays. In addition, the model maximizes the efficiency of computer time through synchronization of loosely coupled dual processors and the design of a restart capability. Since the model is designed for adaptability and for users with limited computer skills, it is anticipated that it will have many applications in the scientific community.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Thesis (S.M. in Electrical Engineering)--Joint Program in Oceanography and Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2000.
Includes bibliographical references (leaves 64-65).
by James Willard Partan.
S.M.in Electrical Engineering

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The increased use of sonar surveys for both industrial and leisure activities has motivated the research for cost effective, automated processed for seabed classification. Seabed classification is essential for many fields including dredging, environmental studies, fisheries research, pipeline and cable route surveys, marine archaeology and automated underwater vehicles. The advancement in both sonar technology and sonar data storage has led to large quantities of sonar data being collected per survey. The challenge, however, is to derive relevant features that can summarise these large amounts of data and provide discrimination between several seabed types present in each survey. The main aim of this work is to classify sidescan bathymetric datasets. However, in most sidescan bathymetric surveys, only a few ground-truthed areas (if any) are available. Since sidescan ‘ground-truthed’ areas were also provided for this work, they were used to test feature extraction, selection and classification algorithms. Backscattering amplitude, after using bathymetric data to correct for variations, did not provide enough discrimination between sediment classes in this work which lead to the investigation of other features. The variation of backscattering amplitude at different scales corresponds to variations in both micro bathymetry and large scale bathymetry. A method that can derive multiscale features from signals was needed, and the wavelet method proved to be an efficient method of doing so. Wavelets are used for feature extraction in 1D sidescan bathymetry survey data and both the feature selection and classification stages are automated. The method is tested on areas of known types and in general, the features show good correlation with sediment types in both types of survey. The main disadvantage of this method, however, is that signal futures are calculated per swathe (or received signal). Thus, sediment boundaries within the same swathe are not detected. To solve this problem, information present in consecutive pings of data can be used, leading to 2-D feature extraction. Several textural classification methods are investigated for the segmentation of sidescan sonar images. The method includes 2D wavelets and Gabor filters. Effects of filter orientation filter scale and window size are observed in both cases, and validated on given sonar images. For sidescan bathymetric datasets, a novel method of classification using both sidescan images and depth maps is investigated. Backscattering amplitude and bathymetry images are both used for feature extraction. Features include amplitude-dependent features, textural features and bathymetric variation features. The method makes use of grab samples available in given areas of the survey for training the classifiers. Alternatively, clustering techniques are used to group the data. The results of applying the method on sidescan bathymetric surveys correlate with the grab samples available as well as the user-classified areas. An automatic method for sidescan bathymetric classification offers a cost effective approach to classify large areas of seabed with a fewer number of grab samples. This work sheds light on areas of feature extraction, selection and classification of sonar data.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Due to the recent advances in virtual and augmented reality, ambisonics has emerged asthe de facto standard for immersive audio. Ambisonic audio can be captured usingspherical microphone arrays, which are becoming increasingly popular. Yet, manymethods for acoustic and microphone array signal processing are not speci cally tailoredfor spherical geometries. Therefore, there is still room for improvement in the eldof automatic analysis and description of ambisonic recordings. In the present thesis,we tackle this problem using methods based on the parametric analysis of the sound eld. Speci cally, we present novel contributions in the scope of blind reverberationtime estimation, diffuseness estimation, and sound event localization and detection.Furthermore, several software tools developed for ambisonic dataset generation andmanagement are also presented.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

A data acquisition system (DAQ) was designed based on the use of a STM32 microcontroller. Its purpose is to provide a transparent and low-cost alternative to commercially available DAQs, providing educators a means to teach students about the process through which data are collected as well as the uses of collected data. The DAQ was designed to collect data from rotating machinery spinning at a speed up to 10,000 RPM and send this data to a computer through a USB 2.0 full-speed connection. Multitasking code was written for the DAQ to allow for data to be simultaneously collected and transferred over USB. Additionally, a console application was created to control the DAQ and read data, and MATLAB code written to analyze the data. The DAQ was compared against a custom assembled National Instruments CompactDAQ system. Using a Bentley-Nevada RK 4 Rotor Kit, data was simultaneously collected using both DAQs. Analysis of this data shows the capabilities and limitations of the low cost DAQ compared to the custom CompactDAQ.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This thesis presents a generic passive non-contact based acoustic health monitoring approach using ultrasonic acoustic emissions (UAE) to facilitate classification of bearing health via neural networks. This generic approach is applied to classifying the operating condition of conventional ball bearings. The acoustic emission signals used in this study are in the ultrasonic range (20-120 kHz), which is significantly higher than the majority of the research in this area thus far. A direct benefit of working in this frequency range is the inherent directionality of the microphones capable of measurement in this range, which becomes particularly useful when operating in environments with low signal-to-noise ratios. Using the UAE power spectrum signature, it is possible to pose the health monitoring problem as a multi-class classification problem, and make use of a multi-layer artificial neural network (ANN) to classify the UAE signature. One major problem limiting the usefulness of ANN's for failure classification is the need for large quantities of training data. Artificial training data, based on statistical properties of a significantly smaller experimental data set is created using the combination of a normal distribution and a coordinate transformation. The artificial training data provides a sufficient sized data set to train the neural network, as well as overcome the curse of dimensionality. The combination of the artificial training methods and ultrasonic frequency range being used results in an approach generic enough to suggest that this particular method is applicable to a variety of systems and components where persistent UAE exist.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Using MATLAB and a National Instruments data acquisition card, a signal processing program meant to monitor the behavior of rotordynamic systems in real-time was developed and tested. By using traditional analysis methods in this field of engineering, commonly desired data representations such as bode, polar, orbit, full spectrum plots were able to be produced to a very high accuracy. Additional capabilities offered by this application are slow roll compensation, synchronous and sub-synchronous filtering, and true three dimensional plotting. The verification of this program was done by comparing the results to the ones acquired with Bently Nevada’s “Automated Diagnostics for Rotating Equipment” (ADRE) system. In addition to a data acquisition program, theoretical models of the two-disk rotor were created to estimate the unknown physical parameters of the system. By simulating the rotor with and without gyroscopic effects included, estimates for the stiffness, damping, eccentricity, initial phase, and initial skew values present in the system were determined.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Vertical line arrays (VLAs) deployed below the critical depth in the deep ocean can exploit reliable acoustic path (RAP) propagation, which provides low transmission loss (TL) for targets at moderate ranges, and increased TL for distant interferers. However, sound from nearby surface interferers also undergoes RAP propagation, and without horizontal aperture, a VLA cannot separate these interferers from submerged targets. A recent publication by McCargar and Zurk (2013) addressed this issue, presenting a transform-based method for passive, depth-based separation of signals received on deep VLAs based on the depth-dependent modulation caused by the interference between the direct and surface-reflected acoustic arrivals. This thesis expands on that work by quantifying the transform-based depth estimation method performance in terms of the resolution and ambiguity in the depth estimate. Then, the depth discrimination performance is quantified in terms of the number of VLA elements.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

A method for tuning the spring rate and damping rate of a mountain bike suspension based on a data-driven procedure is presented. The design and development of a custom data acquisition system, known as the "MTB DAQ," capable of measuring acceleration data at the front and rear axles of a bike are discussed. These data are input into a model that is used to calculate the vertical acceleration and pitching angular acceleration response of the bike and rider. All geometric and dynamic properties of the bike and rider system are measured and built into the model. The model is tested and validated using image processing techniques. A genetic algorithm is implemented with the model and used to calculate the best spring rate and damping rate of the mountain bike suspension such that the vertical and pitching accelerations of the bike and rider are minimized for a given trail. Testing is done on a variety of different courses and the performance of the bike when tuned to the results of the genetic algorithm is discussed. While more fine tuning of the model is possible, the results show that the genetic algorithm and model accurately predict the best suspension settings for each course necessary to minimize the vertical and pitching accelerations of the bike and rider.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Parkinson's disease (PD) is a degenerative illness whose cardinal symptoms include rigidity, tremor, and slowness of movement. In addition to its widely recognized effects PD can have a profound effect on speech and voice.The speech symptoms most commonly demonstrated by patients with PD are reduced vocal loudness, monopitch, disruptions of voice quality, and abnormally fast rate of speech. This cluster of speech symptoms is often termed Hypokinetic Dysarthria.The disease can be difficult to diagnose accurately, especially in its early stages, due to this reason, automatic techniques based on Artificial Intelligence should increase the diagnosing accuracy and to help the doctors make better decisions. The aim of the thesis work is to predict the PD based on the audio files collected from various patients.Audio files are preprocessed in order to attain the features.The preprocessed data contains 23 attributes and 195 instances. On an average there are six voice recordings per person, By using data compression technique such as Discrete Cosine Transform (DCT) number of instances can be minimized, after data compression, attribute selection is done using several WEKA build in methods such as ChiSquared, GainRatio, Infogain after identifying the important attributes, we evaluate attributes one by one by using stepwise regression.Based on the selected attributes we process in WEKA by using cost sensitive classifier with various algorithms like MultiPass LVQ, Logistic Model Tree(LMT), K-Star.The classified results shows on an average 80%.By using this features 95% approximate classification of PD is acheived.This shows that using the audio dataset, PD could be predicted with a higher level of accuracy.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The sustained increase in computing performance over the last decades has brought enough computing power to perform significant audio processing in affordable personal computers. Following this revolution, we have witnessed a series of improvements in sound transformation techniques and the introduction of numerous digital audio effects to modify effectively the time, pitch, and loudness dimensions of audio signals. Due to the complex and multi-dimensional nature of timbre however, it is significantly more difficult to achieve meaningful and convincing qualitative transformations. The tools currently available for timbre modifications (e.g. equalizers) do not operate along perceptually meaningful axes of singing voice timbre (e.g. breathiness, roughness, etc.) resulting in a transformation control problem. One of the goals of this work is to examine more intuitive procedures to achieve high-fidelity qualitative transformations explicitly controlling certain dimensions of singing voice timbre. Quantitative measurements (i.e. voice timbre descriptors) are introduced and used as high-level controls in an adaptive processing system dependent on the characteristics observed in the input signal.
The transformation methods use a harmonic plus noise representation from which voice timbre descriptors are derived. This higher-level representation, closer to our perception of voice timbre, offers more intuitive controls over timbre transformations. The topics of parametric voice modeling and timbre descriptor computation are first introduced, followed by a study of the acoustical impacts of voice breathiness variations. A timbre transformation system operating specifically on the singing voice quality is then introduced with accompanying software implementations, including an example digital audio effect for the control and modification of the breathiness quality on normal voices.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Le zooplancton et le micronecton sont les deux premiers échelons animaux de la chaine trophique marine. Bien que de tailles très différentes (200μm à 2mm pour le zooplancton, 2 à 20cm pour le micronecton), ces deux groupes d'espèces variées partagent un comportement singulier : les migrations nycthémérales. Ces migrations journalières entre la profondeur de jour et la surface de nuit induisent des flux de matière organique très importants entre les différentes profondeurs de l'océan. L'étude des cycles biogéochimiques océaniques a une grande importance pour l'étude du changement climatique. Cette étude est notamment conduite à travers le développement de modèles globaux de circulation océanique et de biogéochimie. La suite logique de ces développements est donc la modélisation du zooplancton et du micronecton. La gamme de modèles SEAPODYM modélise avec parcimonie la chaine trophique depuis le zooplancton jusqu'aux prédateurs supérieurs à l'aide de trois modèles. Cette thèse présente le modèle de biomasse de zooplancton SEAPODYM-LTL (pour lower trophic level, niveau trophique bas), ainsi qu'une analyse de sa sensibilité aux forçages. En effet, la particularité de ces modèles est leur forçage offline par des champs de courants, température et production primaire produits par d'autres modèles. Le modèle SEAPODYM-LTL est également comparé au modèle PISCES (NPZD), et présente des performances similaires à ce dernier dans le cas testé. Afin d'améliorer les prédictions du modèle SEAPODYM-MTL (mid-trophic level, i.e. le modèle de biomasse de micronecton), une méthodologie d'assimilation de données a été mise en place pour affiner la paramétrisation utilisée. Des données d'acoustique active (38kHz) sont donc utilisées pour enrichir le modèle. Cette méthodologie a été conçue autour d'un cas test présenté dans cette thèse. L'extension du jeu de données acoustiques assimilées au modèle a permis de mettre en évidence le besoin de mieux modéliser les profondeurs des couches verticales de SEAPODYM. Cela a été réalisé à l'aide du jeu de données acoustiques évoqué précédemment. Cette étude est également présentée dans cette thèse
Zooplankton and micronecton are the first marine trophic levels. Different by their size (200μm to 2mm for zooplankton, 2 to 20cm for micronekton), this two groups undergo diel vertical migration from depth by day to the surface during the night. These migrations create major organic matter fluxes between the deep ocean and the surface. Biogeochemical cycles are of great importance for climate change studies. These studies are conducted with ocean global circulation model and biogeochemical model. The way to go is develop low and mid-trophic level modelling approaches. SEAPODYM ensemble of models are three parsimonious model of biomass at diverse level of the trophic chain, from zooplankton to top predators. This thesis introduce the zooplankton biomass model SEAPODYM-LTL (lower trophic level) and a forcing fields sensitivity analysis. Indeed, these model are forced off line by currents, temperature and primary production fields produced by other models. SEAPODYM-LTL has also been compared to PISCES (NPZD) and both have similar performance score in this study. In order to improve SEAPODYM-MTL (mid trophic level) predictions, a data assimilation framework has been developed to find a better parameterisation. 38kHz active acoustic data have been used to improve the model. This methodology has been develop thanks to a test case that we present in this thesis. The gathered acoustic dataset permitted to show the need of a better definition of vertical layer depths. It has been developed using the acoustic dataset. The related study is presented in this thesis

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Spectrum has been a scarce commodity in RF communication. Acoustic data communicationis an alternative to RF communication where data is transmitted through sound waves.In this thesis, several different aspects of acoustic data communication are investigated. Aphysical test setup is built where the data communication spectrum extends up to 40 kHz.Impulse response of the acoustic channel is considered in a laboratory environment. Acousticspectrum beyond the hearing limit between 25 kHz to 35 kHz is found as a suitable band forthe developed setup. Distance and multipath components are important factors, determiningthe communication accuracy. The physical layer for the communication system is built bytaking RF Pager system as a reference. This system is also modified to improve the performance.Dierent modulation techniques are used in order to evaluate their performancesfor acoustic channels. BFSK, BPSK, QPSK, GMSK, OFDM, DSSS and FHSS techniquesare implemented for comparison. Total and effective bit rate are considered for the overallperformance evaluation of differentt modulation techniques. Several experiments are done inlaboratory environment where there are several multipath components. As the distance betweenthe transmitter and receiver is increased, path loss and multipath increases. It is shownthat certain modulation techniques are more robust to multipath and are better candidates for acoustic communication. While acoustic environment is inefficient in terms of power, it isstill a good candidate for communication in short distances.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

L’étude porte sur les voyelles orales à double timbre dans le français parisien contemporain. La littérature rapporte une simplification du système phonologique dû à la perte progressive des oppositions dans les paires /a, ɑ/, /e, ɛ/, /ø, œ/ et /o, ɔ/ (Armstrong 2001). Une analyse en temps apparent de nouvelles données phonologiques provenant de 12 locuteurs de la haute bourgeoisie parisienne, permet de tester si la même tendance se manifeste dans les usages d’un milieu socialement favorisé et clos, et ainsi reconnu comme linguistiquement conservateur (Labov 1972, Milroy & Milroy 1992). Les données ont été produites dans différents contextes, allant du très formel à l’informel, et ont été soumises à des analyses acoustiques. L’analyse révèle que la perte des opposition phonologiques affecte moins les pratiques linguistiques des 12 locuteurs que les pratiques d’autres populations. Cependant, le degré de conservatisme linguistique varie selon la variable vocalique : par exemple, pour la paire /o, ɔ/ les usages des 12 locuteurs sont très conservateurs, mais pour la paire /a, ɑ/ ils se conforment aux résultats des travaux antérieurs, l’opposition /a/-/ɑ/ ayant disparu en faveur d’une seule variante antérieure.Une seconde enquête sur les attitudes linguistiques des locuteurs révèle un état de sécurité linguistique très forte au sein de l’échantillon ; quant aux variables vocaliques, une opposition instable va de pair avec un indice d’insécurité linguistique (IIL, Labov 1966) relativement élevé, mais ne rend pas compte des usages individuelles, ce qui met en question l’interprétation traditionnelle du lien entre les pratiques et les attitudes linguistiques
This dissertation is concerned with the vowels /A, E, Ø, O/ in contemporary Parisian French. Traditionally, the vowels each represent two phonemes, /a, ɑ/, /e, ɛ/, /ø, œ/ and /o, ɔ/, but literature on French phonology reports that the French vowel system is undergoing a simplification by neutralisation of these phonological contrasts (Armstrong 2001). By an apparent-time analysis of new phonological data produced by 12 informants from la haute bourgeoisie parisienne, the study seeks to determine whether this tendency also manifests itself in the behaviour of a socially privileged and close-knit, and as such presumably linguistically conservative, group (Labov 1972, Milroy & Milroy 1992). The data was produced in different contexts, ranging from very formal to informal, and acoustically analyzed.The analysis confirms that neutralisation of vowel contrasts is less common amongst the 12 informants than in other groups of speaker, although the degree of linguistic conservatism depends on the specific vowel. For instance, in the case of the pair /o, ɔ/, the 12 informants display a very conservative behaviour, whereas for the pair /a, ɑ/, the results differ very little from the results of other studies, the /a/-/ɑ/ contrast having practically disappeared.A survey of the informants’ linguistic attitudes reflects a very high level of linguistic security. For each vowel, ongoing change correlates with a relatively high Index of Linguistic Insecurity (ILI, Labov 1966). The ILI cannot, however, account for the individual behaviours; this raises questions about the traditional interpretation of the correlation between a speaker’s ILI and his/her linguistic behaviour

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The OFDM technology has been extensively used in many radio communicationtechnologies. For example, OFDM is the core technology applied in WiFi, WiMAXand LTE. Its main advantages include high bandwidth utilization, strong noise im-munity and the capability to resist frequency selective fading. However, OFDMtechnology is not only applied in the field of radio communication, but has alsobeen developed greatly in acoustic communication, namely the so called acousticOFDM. Thanks to the acoustic OFDM technology, the information can be em-bedded in audio and then transmitted so that the receiver can obtain the requiredinformation through certain demodulation mechanisms without severely affectingthe audio quality.This thesis mainly discusses how to embed and transmit information in audioby making use of acoustic OFDM. Based on the theoretical systematic structure, italso designs a simulation system and a measurement system respectively. In thesetwo systems, channel coding, manners of modulation and demodulation, timingsynchronization and parameters of the functional components are configured in themost reasonable way in order to achieve relatively strong stability and robustnessof the system. Moreover, power control and the compatibility between audio andOFDM signals are also explained and analyzed in this thesis.Based on the experimental results, the author analyzes the performance of thesystem and the factors that affect the performance of the system, such as the typeof audio, distance between transmitter and receiver, audio output level and so on.According to this analysis, it is proved that the simulation system can work steadilyin any audio of wav format and transmit information correctly. However, dueto the hardware limitations of the receiver and sender devices, the measurementsystem is unstable to a certain degree. Finally, this thesis draws conclusions of theresearch results and points out unsolved problems in the experiments. Eventually,some expectations for this research orientation are stated and relevant suggestionsare proposed.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This thesis deals with in situ estimates of fish target strength distribution which are important in acoustic stock assessment. The data were gathered on Newfoundland's Grand Banks in 1992 using a dual-beam sonar system. In situ measures of target strength distribution are biased unless a correction is made for nonignorable missing data because high target strength fish can be detected more readily than low target strength ones.
Two methods of correcting for the bias are described and implemented. Both methods use measured off-axis angle and rely on the accuracy of these angle measurements since they compare the distributions of measured and true off-axis angles. The first method involves varying the beam pattern threshold with the observed target strength of the fish. The second method uses a logistic model for the probability of detecting a fish given its target strength.
The analysis in this thesis found several previously undocumented results. Firstly, it was demonstrated that off-axis angles measured with a dual-beam system do not correspond well with true ones, which makes the results of both methods dubious; secondly, measured off-axis angles are shown to be dependent on target strength, which suggests that the process of measuring off-axis angles could be improved by taking this into account, and finally, target strength measurements below about -34 dB are observed to be strongly dependent on characteristics of the dual-beam system.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Ce travail de thèse traite de la propagation des ondes élastiques dans les milieux granulaires
denses sous contrainte. Elles permettent de sonder de manière non invasive la structure, les
propriétés viscoélastiques et les comportements non linéaires des réseaux de forces de contact dans
un tel milieu. Dans une première partie, nous rappelons quelques résultats concernant la propagation
linéaire d'ondes ultrasonores dans les matériaux granulaires (modes effectifs cohérents, diffusion
multiple des ondes élastiques). Nous montrons alors comment extraire les modules élastiques à l'aide
des ondes cohérentes et la dissipation interne à l'aide des ondes multiplement diffusées. En particulier,
l'étude de l'influence de la présence d'un fluide interstitiel en très faible quantité (< 0,1%)
et l'influence de l'état de surface des billes, sur les propriétés viscoélastiques de milieux granulaires
secs et mouillés, nous permet d'identifier deux mécanismes de dissipation : frictionnelle et visqueuse.
Enfin, nous nous intéressons au régime de propagation non linéaire des ondes élastiques dans les
milieux granulaires. Après avoir caractérisé expérimentalement l'élasticité non linéaire hertzienne
réversible du matériau granulaire par la génération d'harmoniques supérieures, nous discutons un
résultat original sur les processus d'interaction irréversibles onde-matière granulaire liés aux non
linéarités hystérétiques de type Mindlin entraînant une nette diminution du module élastique du
matériau granulaire et des micro-réarrangement à l'échelle des aspérités de grains.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This study examined the nature of deceptive vocal behavior in interactive situations. It compared those vocal features of deception that can be measured by acoustic equipment with those vocal features of deception that can be measured perceptually by human coders. As deception researchers traditionally measure vocal behavior with either acoustic or perceptual methods, it is uncertain what correspondence, if any, exists between these two methods. This study attempted to determine this correspondence. Deceptive interactions from an earlier study (Buller, Burgoon, Buslig & Roiger, 1993; Burgoon, Buller, Ebesu, White, and Rockwell, 1994) were used to conduct a detailed analysis of vocal features of deceptive speech. The vocal samples were analyzed perceptually and acoustically. Results indicated moderate correlations between some acoustic and perceptual variables, with neither measurement type proving conclusively superior to the other in discriminating between truth and deception. Of three categories examined (time, pitch, and intensity), the time variables of shorter message length, longer response latencies, slower tempo, and less fluency best discriminated between truthful and deceptive statements. Other variables that discriminated truth from deceit were increased intensity range, increased pitch level and variance, and less pleasant vocal quality. Analyses of deception type showed that fabricated deceptions were louder and lower pitched than equivocal deceptions. An analysis of deception planning, showed that planned deceptions exhibited more fluency, a lower pitch level, and less pitch variance than unplanned deceptions. An examination of correlations between deceiver/receiver evaluations of deceiver honesty and deceiver vocal behaviors showed moderate correlations occurred between these evaluations and length of response latencies, pitch level, pitch range, and pitch variance. In general, these findings provide further confirmation of Interpersonal Deception Theory.

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Grâce à leurs propriétés spécifiques (hom*ogénéité de l'épaisseur, de la densité bidimensionnelle et de la tension), les films de cristaux liquides smectiques forment des membranes bidimensionnelles idéales obéissant à l'équation d'onde de Helmholtz, avec les conditions de Dirichlet au bord. Dans cette thèse, une nouvelle expérience a été mise au point, qui permet, pour un film tendu sur un contour donné, de mesurer non seulement son spectre de fréquences propres, mais aussi la forme géométrique des modes. Le rôle de la forme de la membrane a ainsi pu être analysé. On a commencé par étudier une forme "préfractale", constituée par une courbe de Koch quadratique, dont la construction a été arrêtée à un ordre d'itération fini. L'accord entre les résultats expérimentaux et des résultats numériques obtenus par d'autres auteurs, tant sur le spectre que sur l'allure des modes propres, est excellent. Deux mécanismes de localisation des fonctions d'onde, d'origines physiques différentes, ont été mis en évidence. L'autre question étudiée est un problème mathématique que l'on peut résumer par : "Peut-on entendre la forme d'un tambour?" La réponse prévue par les mathématiciens est "non", c'est-à-dire qu'il existe des formes géométriques différentes, conduisant à des spectres de fréquences propres identiques ; ces formes sont appelées "isospectrales". On a ainsi vérifié expérimentalement l'isospectralité de deux contours avec une bonne précision. On a également montré en détail que seules les symétries de construction de ces deux contours, basées sur la théorie des groupes, importaient.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Infrasound is undetectable by the human ear and excessive exposure may be a substantial health risk. Low frequency sound propagates through walls with minimal attenuation, making it difficult to avoid. This study interprets the results from both analytical calculations and simulations of pressure waves propagating through a wall in one dimension. The wall is thin compared to the wavelength; the model implements properties of three materials commonly used in walls. The results indicate that the geometry of the wall, most importantly the small ratio between wall width and wavelength, is the prime reason for the low levels of attenuation observed in transmitted amplitudes of low frequency sounds, and that damping is negligible for infrasound. Furthermore, a one-dimensional hom*ogeneous wall model gives rise to periodicity in the transmitted amplitude, which is not observed in experiments. Future studies should prioritize the introduction of at least one more dimension to the model, to allow for variable angles of incidence.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This project is concerned with the development of software to invert seismic reflection data for acoustic impedance, with application to the YY-reservoir area in Gialo Field, Sirte Basin. The problem was that of inverting post-stack seismic reflection data from two seismic lines into impedance profiles. The main input to the inversion process is an initial guess, or initial earth model, of the impedance profile defined in terms of parameters. These parameters describe the impedance and the geometry of the number of layers that constitute the earth model. Additionally, an initial guess is needed for the seismic wavelet, defined in the frequency domain using nine parameters. The inversion is an optimisation problem subject to constraints. The optimisation problem is that of minimising the error energy function defined by the sum of squares of the residuals between the observed seismic trace and its prediction by the forward model for the given earth model parameters. To determine the solution we use the method of generalised linear inverses. The generalised inverse is possible only when the Hessian matrix, which describe the curvature of error energy surface, is positive definite. When the Hessian is not definite, it is necessary to modify it to obtain the nearest positive definite matrix. To modify the Hessian we used a method based on the Cholesky factorisation. Because the modified Hessian is positive definite, we need to find the generalised inverse only once. But we may need to restrict the step-length to obtain the minimum. Such a method is a step-length based method. A step-length based method was implemented using linear equality and inequality constraints into a computer program to invert the observed seismic data for impedance. The linear equality and inequality constraints were used so that solutions that are geologically feasible and numerically stable are obtained. The strategy for the real data inversion was to first estimate the seismic wavelet at the well, then optimise the wavelet parameters. Then use the optimum wavelet to invert for impedance and layer boundaries in the seismic traces. In the three real data examples studied, this inversion scheme proved that the delineation of the Chadra sands in Gialo Field is possible. Better results could be obtained by using initial earth models that properly parameterise the subsurface, and linear constraints that are based on well data. Defining the wavelet parameters in the time domain may prove to be more stable and could lead to better inversion results.

APA, Harvard, Vancouver, ISO, and other styles

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Acoustic Emission Analysis (AEA) is the study of the sonic (and ultrasonic) energy released by chemical systems in the form of transient waves, as the system attempts to (re)attain equilibrium. This area of chemistry, and chemical analysis, is ripe for fundamental studies since it has been little explored. The high potential of the technique as a non-invasive, non-destructive reaction monitoring scheme suggests that numerous applications will follow.In this work, an apparatus and software have been constructed to monitor acoustic emission (AE) and collect and process AE data. A broad-band piezoelectric transducer was used to convert the acoustic signals to electrical waveforms which could be captured by a digital storage oscilloscope. These waveforms were then stored on an IBM-compatible computer for further analysis.Analysis of the data was performed using pattern recognition techniques. The signals were characterized through the use of descriptors which can map each signal onto a multi-dimensional feature space. Visualization of the data structure in multidimensionalspace was accomplished using several methods. Hierarchical clustering was used to produce tree structures, known as dendrograms, which attempt to show clustering of the signals into various groups. Abstract factor analysis (AFA) - also called principal components analysis (PCA) - was used to project the data onto a two dimensional factor space to allow for direct viewing of structure in the multidimensionaldata.Sodium hydroxide dissolution, aluminum chloride hydration and heat activation of Intumescent Flame Retardants (IFR's) were used to test the assembled hardware and to provide data to submit to the pattern recognition algorithms coded as part of thiswork. The solid-solid phase transition of trimethylolethane (Trimet), and the liquid crystal phase transitions of two liquid crystals (α-ѡ-bis(4-n-decylaniline-benzilidene-4'-oxyhexane), and 4-n-pentyloxybenzylidene-4'-n-heptylaniline) were also monitored and the signals analyzed.The pattern recognition software was able to extract much information from the acoustically emitting samples - information which would not have been apparent by using standard (uni- and bi-variate) methods of analysis. Chemical acoustic emission, coupled with pattern recognition analysis, will be able to provide the chemist with knowledge (qualitative, quantitative, kinetic, etc.) about chemical systems which are often difficult or impossible to monitor and analyze by other means.
Science, Faculty of
Chemistry, Department of
Graduate