Reissued 30 May 2017 with Second Reader’s non-NPS affiliation added to title page. / Approved for public release; distribution is unlimited / The purpose of this thesis is to characterize typical levels of vibrational noise on the ocean floor to ascertain the vibration's effect on possible future bottom mounted sensors. The data used for this thesis was obtained from publicly available recorded information from four ocean bottom seismometers (OBS). The OBSs were located in two geographical choke points: the Luzon Strait and west of the Strait of Juan de Fuca. These highly trafficked choke points were considered to be a good representation of where these experimental bottom mounted sensors might be located should they be built. Unix-based seismic processing software available from the Incorporated Research Institutions for Seismology (IRIS) proved essential to obtaining calibrated data, and the methodology used to get the calibrated data is discussed in detail. The results showed that one OBS out of the four was highly variable, with decibel levels varying widely from day to day. The other OBSs remained fairly consistent. In addition, there were no common discrete frequencies between sensors that were in the same geographic area. Recommended future research involves the study of environmental effects on the OBSs, additional research to correlate the results observed in the Luzon Strait, and a look into the electronic noise floors of the OBSs used. / Lieutenant Commander, United States Navy

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A dissertation in partial compliance with the requirements for a Master's Degree in Technology in the Department of Chiropractic at Technikon Natal / Cavitation sounds heard during chiropractic adjustments and manipulations to th extension spine are a common phenomena yet their significance is disputed, the mechanism of their production is a matter of speculation, and their origin has never been localized. (Lewit 1978: 4, Grieve 1989; 525) The purpose of this study was to locate the joints which cavitate during the performance of a L5 spinous hook adjustment and a lower sacroiliac adjustment. It was hypothesised that the cavitation sounds would arise from the L4-L5 and L5-S1facets on the side of contact during the L5 hook adjustment., and from the the sacroiliac joint on the side being adjusted during the lower sacroiliac adjustment. It was also hypothesised that the two adjustments would differ significantly in terms of the cavitation sounds produced. Volunteers were screened for agreement with the inclusion criteria. Of these 30 asymptomatic between the ages of 18 and 30 were selected. This was sample was then randomly divided into two groups of, one of which recieved the L5 hook adjustment and the other the lower sacroiliac adjustment. All of the subjects had eight microphones taped to the skin, over the relevant facets and the sacroiliac joints. Radiographic confirmation was used in order to ensure proper positioning of the microphones. The microphones were then connected to filters, amplifiers and a computer which recorded any sound signals registered during the adjustments. / M

A system comprising of a personal microcomputer and a Digital Signal Processor board has been assembled and programmed for real-time spectral analysis of Doppler ultrasound signals. Three spectrum analysis techniques were implemented to run in real-time on the system: The fast Fourier transform (FFT), the autoregressive (AR) model, and the moving average (MA) model. The FFT and the AR techniques were investigated in some depth. The advantages of using such a system are that it is entirely programmable, cheap, reliable, and that the processed information can be stored on diskettes. The inputs to the system are the forward and reverse components of the Doppler ultrasonic signal, and the outputs are the sonogram, the frequency envelope, and the intensity weighted mean frequency curve, which are presented on the screen and can be saved to diskette. Five frequency ranges can be selected by the operator, from 1.28 kHz to 20.48 kHz, corresponding to sampling frequencies from 2.56 kHz to 40.96 kHz. Most commercial systems for real-time spectral analysis of Doppler ultrasonic signals implement the modified FFT-periodogram technique for power spectral density estimation (PSDE), which is computationally very efficient but has some shortcomings, especially for the analysis of relatively short records. With the AR model approach the spectra can be estimated from short segments, no antileakage window is necessary and the spectral resolution is better than for the FFT. A study of some methods for order selection used with the autoregressive model for the spectrum analysis of Doppler signals is reported and the use of a fixed order of around 12 is suggested for the AR model. The implementation of the AR PSDE approach in real-time, in a reasonably priced system, is a step towards the practical use of the so called 'modern techniques' for spectral analysis of Doppler ultrasonic signals, but further work has to be done on the validation of the technique in clinical usage.

The frequency-shift (FRESH) filter is a structure which exploits the spectral correlation of cyclostationary signals for removing interference and noise from a wanted signal. As most digital communication signals are cyclostationary, FRESH filtering offers certain advantages for interference rejection in a communications receiver. This thesis explores the operation and application of FRESH filters in practical interference scenarios. The theoretical background to cyclostationarity is clarified with graphical interpretations of what cyclostationarity is, and how a FRESH filter exploits it to remove interference. The effects of implementation in a sampled system are investigated, in filters which use baud rate related cyclostationarity, leading to efficiency improvements. The effects of varying the wanted signal pulse shape to enhance the cyclostationarity available to the FRESH filter are also investigated. A consistent approach to the interpretation of the FRESH filter's operation is used throughout, while evaluating the performance in a wide range of realistic channel conditions. VLF radio communication is proposed as one area where interference conditions are particularly suitable for the use of FRESH filtering. In cases of severe adjacent channel interference it is found that a FRESH filter can almost completely remove the interferer. The effects of its use with an impulse rejection technique are also investigated. Finally, blind adaptation of FRESH filters through exploitation of carrier related cyclostationarity is investigated. It is found that one existing method loses the advantage of FRESH filtering over time invariant linear filtering. An improvement is proposed to the latter which restores its performance to that of a trained FRESH filter, and also reveals that carrier related cyclostationarity can be exploited, in some cases, by a simpler method. J.

Two questions can be posed for study: 1) Will the effect of auditory masking provided by a clinical noise significantly affect the performance of hearing children on the Knox Cube Test? 2) Are there significant differences among brain-injured, mentally, retarded, and "normal" children in ability to adjust to auditory masking in the performance of the Knox Cube Test?

This study was made to find the effects of noise on the human body, to measure sound levels that exist in school power laboratories, and to design and evaluate the effectiveness of two noise control devices. An accurately calibrated testing device was used to measure sound levels in an attempt to determine if excessive noise exists in school power laboratories and to find the extent to which such noise can be reduced by shielding or enclosing the engine test area. It was found that noise has undesirable physical and psychological effects on the human organism. Sixty-two and one-half per cent of the engines tested registered sound levels above 90 dBA; even so, simple, inexpensive noise control devices do control the noise levels generated in the school power laboratories.

Chapter 1, an introduction to the use of ultrasound in physiotherapy and in hyperthermia is given. Previous studies in ultrasound physiotherapy and hyperthermia are reviewed but the emphasis is given to those which investigated the mechanisms responsible for the beneficial effects of therapeutic ultrasound and for the efficacy of cell killing of ultrasound hyperthermia. A review of the studies of the non-thermal effects of ultrasound is the subject of Chapter 2. Some recent studies carried out in this field in our laboratory are included. Knowledge of acoustical power, spatial peak and spatial average intensities are central to useful studies of bioeffects and to patient safety in the cases of therapy and clinical hyperthermia. Some techniques for measurements of ultrasound dosimetry which have been employed (and studied) are outlined in Chapter 3. At present the total power output from a therapeutic transducer is often derived by measuring the radiation force of the ultrasonic beam exerting on either a total absorber or a total reflector suspended at 45 to vertical. In Chapter 4 and Chapter 5, I discuss some new problems of these techniques and the magnitude of errors which might be caused. Chapter 6 and Chapter 7 present the results of theoretical studies of the field distri-butions from a plane circular piston transducer under both progressive and standing wave conditions. The effect of wave diffraction on the field distribution, bulk streaming and mea-surement of radiation force using a plane reflector is discussed. The ratio of the spatial peak to spatial average intensity for plane circular transducers in a progressive field is theoretic-cally calculated and compared with experimental results. The question of how to define the standing wave ratio is considered by taking into account of the effect of wave diffraction. Chapter 8 and Chapter 9 concern the thermal distributions generated by ultrasound in tissues. An experimental study of the temperature distributions in tissue/bone phantoms induced by therapeutic ultrasound using infra-red technique is described in Chapter 8. In Chapter 9 the thermal patterns generated by a plane circular transducer in a 3-D tissue model were calculated and they were compared with the experimental results described in the previous chapter. The thermal distributions generated by an applicator consisting of five divergent transducers were simulated in the same tissue model. Possible advantages of using such an applicator for ultrasound therapy and for treating large superficial tumours are discussed.

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The basis of the thesis are based on the installation linked with real time manipulated audio, video and lights. Interactions between different parts of the installation is given by handling all its components. The aim is to comprehensively cover a darkened room space by creating a specific environment.