Thesis (M.S.)--Northern Michigan University, 2009. / Bibliography: leaves 24-26.

There is an estimated 10 million Americans that suffer from permanent, irreversible hearing loss from their workplace. Many soldiers come back from battle with this damage, mainly from the high sound levels of their weapons that they are exposed to. The U.S. government spends over $250 million a year in compensation to those whose hearing has been damaged. There are current medicines that have proven to help eliminate or lessen the affects from certain types of noise induced hearing loss, specifically from prolonged expose. A noise exposure system was needed to be built for impulse noise induced hearing loss testing. That would help lead to a medicine for impulse noise induced hearing loss. A system was designed and built to replicate the noise signal of an M-16 rifle. The system's digital noise signal produced was comparable to the recorded M-16 noise signal, which reached a 145 dB level. Testing showed that the relationship between the amplitude and the maximum levels measured were linear. Sound levels of the produced impulse waves had a maximum limit of approximately 160 dB. The system was designed with the idea of customization. There are multiple parameters that can be adjusted to best fit the testing needs. The noise exposure system will be used by researchers in the SIU school of medicine in research designed to test the effect. The results from Dr. the research will validate the effectiveness of the noise exposure system that was built.

The mechanism suggested for whistler triggered LHR noise is that of a whistler propagating from a region of the ionosphere where the unperturbed number densities are uniform into one where there is a small spatial irregularity in number density. To investigate at what frequencies the resulting induced electric field may be significant compared to the inducing field (a whistler), steady state solutions were obtained for the electric and magnetic fields that may exist in a fully ionized plasma that has a small spatial irregularity in number density. The plasma is taken to be in a constant and uniform background magnetic field and to have parameters consistent with the upper ionosphere. The irregularity is taken to be a spatially varying cosine function with wave number K. Assuming the governing equations to be Maxwell's equations and the zeroth and the first moment equations of the collisionless Boltzmann equation, we obtained solutions with a perturbation scheme. The equations were linearized and terms were only kept to second order. The first order terms formed a set of equations governing a plasma with unperturbed number densities that were constant in time and space. For first order variables that are plane waves with wave number k and frequency co, the postulated irregularity gives rise to a second order electric field with a frequency dependence of CJ. An investigation was made to determine at which frequencies the second order electric field was significant compared to first order fields. For k parallel to K and perpendicular to B^, it was found that the second order field had a peak value at the LHR (lower hybrid resonance) frequency. For K of the order of 10⁻³ cm⁻¹ , an additional peak occurred for a frequency less than the LHR frequency, when K = 2k. With K -4 -2 -1 increasing from 10 ⁻³ to 10 cm⁻¹ , this frequency increased from 36% to within .3% of the LHR frequency. Neglecting the second order magnetic field, solutions were obtained for k in the x-z plane, B[sup (0)] in the positive z-direction, and K in the positive x-direction. For 9, the angle formed by lc and B[sup (0]), not equal to 90°, the second order electric field had a peak that was greater than the LHR frequency. For 6 = 71.57°, the frequency of the peak changes from 1.005 to 31 times the LHR frequency as K varies from 10⁻² to 10⁻⁴ cm⁻¹ . For K = 10⁻³ cm⁻¹ , the frequency of the peak changes from 1 to approximately 3.5 times the LHR frequency as 8 varies from 90° to 0°. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Traffic noise is having an increasingly adverse impact on the quality of urban life. As a result it is necessary for community planners and engineers to develop better traffic management criteria and study techniques to keep the level of community traffic noise to socially desirable levels. In the recent past substantial research has been done to help understand the physical properties of traffic noise and indices of community noise perception. However, little is understood about the perception and annoyance levels of specific groups toward traffic noise. Complete knowledge of all dimensions of traffic noise annoyance is necessary for the further development of community traffic management criteria and neighborhood planning techniques. The purpose of this research is to investigate the dimensions of public annoyance to traffic noise in a large city. Specifically, the study objective is to investigate the relationship between noise annoyance in several urban neighborhoods and the socioeconomic and situational variables which have some impact on attitudes about traffic noise. Following a preliminary noise annoyance survey of 3500 households in Vancouver, British Columbia, a discriminant-classification statistical technique was used to analyze a follow-up, in depth, attitudinal survey of 331 households in several neighborhoods. Three categories of information were obtained in the survey: 1) a household survey of attitudes to noise using a semantic differential scaling technique; 2) measures of the socioeconomic and cultural profiles of each household surveyed, and 3) measures of the physical and situational neighborhood variables which would likely have some effect on the noise environment of the household. The statistical model was used to investigate the dimensions of socioeconomic, cultural, and physical variables on separating those social groupings which were highly sensitive to traffic noise from those who were less sensitive. Results show that the respondent's high socioeconomic status is the major factor in noise annoyance followed by the distance the respondent lives from major traffic arteries. Particularly, it appears that education levels are the dominant factor in traffic noise annoyance. The implication of the results of this research is that traffic management criteria must include consideration of the socioeconomic and cultural environment as well as accepted traffic planning criteria to meet publicly acceptable traffic noise levels. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

No description available.

No description available.

No description available.

Recent developments in digital communications at microwave frequencies have revealed that local oscillator phase noise is often a factor in the bit error rate (BER) analysis. Digital signals transported across microwave radio links acquire waveform jitter from local oscillator phase noise. As jitter increases so does BER. The main goals of the investigations described in this dissertation are to demonstrate the feasibility of determining rms jitter from measured phase noise and to develop mathematical models to describe how local oscillator phase noise is added to an information signal passing through a radio link. The first goal of estimating jitter from phase noise data has many applications. An obvious use is to specify the phase noise performance of a local oscillator for a given jitter specification which in turn may be specified for a desired BER level. A less obvious application is the ability to estimate the jitter of a microwave or millimeter wave signal based on measured phase noise. At these high frequencies it is often impractical or impossible to measure jitter directly due to performance limitations of time domain equipment such as the digital sampling oscilloscopes (DSO) which are typically limited to about 22 GHz. Conversely spectrum analysis techniques are well developed that allow accurate phase noise measurements to be performed well beyond 100 GHz. Experiments which validate the known relation between an oscillator's single sideband phase noise and associated mean square jitter [8, 28] are presented. Test equipment was developed to allow the addition of phase noise in a controlled manner to a clean reference signal which for practical purposes has no inherent jitter. By performing the experiments at the relatively low frequency of 33.333 MHz both the phase noise and jitter could be measured easily. Comparing the rms jitter predicted from phase noise data to direct measurement with a Digital Sampling Oscilloscope determined that the relation gave typically less than 14% error with a worst case disagreement of 24%. The experiment had an estimated uncertainty of �� 17%. This level of agreement is acceptable for many BER applications, which often specify jitter to an order of magnitude. The second goal of the research was to develop a model which describes how the phase noise of transmitter and receiver local oscillators add to an information signal carried over a communications link. It is shown that this added phase noise can in principle be eliminated in a double sideband communications system when the relative phase difference between the two local oscillators is synchronized to N��, where N is any integer. Experiments were performed which validated the predicted results. It was found that using real components allowed a 24 dB reduction added phase noise when compared to the case when no synchronization was used. A practical circuit is proposed to implement the technique in a practical manner for real radio systems. A final area of research presented phase noise measurements for a Gunn diode microwave integrated circuit (MIC) voltage controlled oscillator (VCO) in the 18 GHz region. The single sideband phase noise ratio of -96 dBc/Hz at 100 kHz offset frequency was significantly better than current published data for MESFET, HBT, and PHEMT VCOs at similar frequencies. These results are important in the area of digital radios, since improved phase noise allows higher data rates and reduces adjacent channel power. / Graduation date: 1999

Thesis PlanA (M.S.)--University of Wisconsin--Stout, 2009. / Includes bibliographical references.

Significant interior noise and vibrations in aircraft cabins are generated by the turbulent flow over the fuselage. The turbulent boundary layer (TBL) excitation is the most important noise source for jet powered aircraft during cruise flight. Reduced levels of interior noise are desirable both for comfort and health reasons. However, to efficiently design noise control systems, and to design new and optimized structures that are more efficient in the noise reduction, a clearer understanding of the sound radiation and transmission mechanisms is crucial. This task is far from being straightforward, mainly due to the complexity of the system consisted by the aircraft fuselage, and all the sound transmission mechanisms involved in a such complex environment. The present work aims to give a contribution for the understanding of these mechanisms. For that, a coupled aero-vibro-acoustic analytical model for the prediction of the TBL-induced noise and vibration in aircraft is developed. Closed form analytical expressions are obtained to predict the structural vibration levels, noise radiated from the structure and interior sound pressure levels. / Graduate