A theoretical and experimental investigation into the penetration of parametric acoustic beams into sediment is conducted. The theory is based on the assumption that the interface completely truncates the array. With this assumption, the asymtotic farfield of the secondary radiation in sediment is developed and discussed. When the primary field is truncated in its nearfield, the secondary farfield is found to be due to two apertures, one coincident with the transducer and one with the truncation. At subcritical angles of incidence the field is similar to that produced by a conventional beam. At post-critical angles of beam incidence the presence of the truncation aperture results in a steeper and deeper penetration of the beam than in the conventional case. As the trucation moves into the farfield of the primaries, the effect of the truncation aperture is reduced until the parametric beam behaves qualitatively similar to a conventional beam. Experimental measurements of the secondary field throughout two vertical planes in the sediment are made, and are in good agreement with the theoretical predictions. The wide bandwidth of the parametric array is exploited to distinguish in time Snell's law and evanescent arrivals in the sediment. These latter are seen to be important close to the interface. It is concluded that the postcritical penetration of parametric sound beams into sediment is due to virtual secondary sources close to the interface and suitably phased.

Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

It is widely acknowledged that elevated levels of noise are commonplace in the healthcare environment, particularly in high acuity areas such as the operating room (OR). Excessive ambient noise may pose a threat to patient safety by adversely impacting provider performance and interfering with communication among perioperative care team members. With respect to the certified registered nurse anesthetist (CRNA), increased ambient OR noise may engender distractibility, diminish situation awareness and cause untoward health effects, thereby increasing the possibility for the occurrence of error and patient injury. This research project analytically examines the perceived impact of ambient noise in the operating room by CRNAs. Findings from this study reveal that CRNAs perceive elevated noise to be regularly present in the OR, specifically during the critical emergence phase of the anesthetic. However, CRNAs feel that increased noise only occasionally limits their ability to perform procedures, concentrate and communicate with the perioperative team. OR noise rarely interferes with memory retrieval. CRNAs perceive that noise is sometimes a threat to patient safety but infrequently engenders adverse patient outcomes. CRNAs do not perceive noise in the OR to be detrimental to their health but strongly agree that excessive noise can and should be controlled. Increased ambient OR noise is a veritable reality that may pose a potential threat to patient safety. Further research to identify elevations in noise during critical phases of the anesthetic and delineation of significant contributors to its genesis is warranted.

The oil and gas industry is of major economic importance to Australia. Offshore seismic surveys are an essential component of exploration for fossil fuel reserves. Offshore seismic surveys involve the use of arrays of air-guns that produce repetitive high energy, low frequency sound. There is increasing concern about the effect that the noise generated by a seismic survey has on the surrounding marine life. Various species of captive marine fish and one species of squid were exposed to the noise from a single Bolt PAR 600 B air-gun with a 20 cui firing chamber and a source level at 1 m of 203.6 dB re 1 μPa mean squared pressure. Ten trials were conducted in Jervoise Bay and two were carried out off the coast of Exmouth. A different noise regime was used in each trial, however most involved the use of approach-depart scenarios to simulate an actual seismic survey and a 10 second duty cycle. Noise levels received by the animals ranged between 128 - 192 dB re 1 μPa mean squared pressure. Behavioural observations of the fish and squid were made before, during and after air-gun noise exposure. The physiological stress response of the fish was monitored by measuring plasma cortisol and glucose levels before and after noise exposure. The sensory epithelium was removed from the ears of the fish prior to, immediately after and up to 86 days after air-gun noise exposure and examined using a scanning electron microscope. No statistically significant physiological stress response in fish was detected as a result of the air-gun noise exposure regimes used. Significant damage to the ciliary bundles of the sensory epithelium of the sacculus was observed in pink snapper (Pugrus auratus) that had been exposed to air-gun noise between 144 - 191 dB re 1 μPa for 1.71 hours. No regeneration of the hair bundles was observed 58 days after exposure to air-gun noise. / However, evidence of regeneration was observed between 58 and 86 days after noise exposure. Behavioural observations suggested that as air-gun noise levels increase, fish respond by swimming faster, in tighter groups and towards the bottom of the water column. Significant increases in alarm responses were observed in fish and squid to air-gun noise exceeding 158 - 163 dB re 1μPa. An increasing proportion of alarm responses were also observed as the noise level increased. A decrease in the frequency of alarm responses for repeated exposures was observed in squid and some fish. The implications of these findings are discussed with comparisons of noise levels measured from an actual 2678 cui seismic survey air-gun array.

The purpose of the study was to examine the existence of an association between child blood pressure (BP) and exposure to domestic jet aircraft noise in the context of the construction of a new parallel north-south runway at Sydney (Kingsford-Smith) Airport. The baseline study was commissioned and funded by the Federal Airports Corporation (FAC), with measurements conducted in 1994 and 1995. A follow-up longitudinal component to the study was subsequently commissioned and funded by the FAC in 1997, and measurements conducted in the same year. As the same individuals were measured and re-measured over changing conditions of exposure to aircraft noise, the quasiexperimental nature of the study allowed inferences to be made regarding exposure to aircraft noise and child BP. The main hypotheses for testing were that BP, and within-subject longitudinal changes in BP, are positively related to domestic jet aircraft noise exposure and longitudinal changes in domestic jet aircraft noise exposure respectively. Subsidiary hypotheses tested for evidence of short- and long-term BP adaptation effects where BPs were related to prior changes to aircraft noise exposures. A sample of 75 primary schools within a 20 km radius of Sydney Airport under various noise exposure conditions, both existing and those projected with the advent of the new runway, participated in the study. The baseline cohort comprised 1,230 Year 3/4 children attending the schools in 1994 and 1995, and the follow-up participants comprised 628 of the original baseline sample re-measured in 1997. Study participants were enrolled by active parental consent. The baseline response rate was approximately 40% of children in the participating schools. Systolic (SBP) and diastolic (DBP) blood pressure readings of the children were taken using automated BP measuring equipment along with anthropometric measurements (heights, weights, skinfold thicknesses and waist measurements). Parental surveys captured items pertaining to the child�s ethnic background as measured by the country of birth of the child and parent(s), residential address and housing structure, child eating habits and activity levels, along with family and child history of high blood pressure. Aircraft noise exposure data were collected by the National Acoustic Laboratories and processed into the energy-averaged noise metric used in Australia for aircraft noise exposure assessment called the Australian Noise Exposure Index (ANEI). Mean exposures for a given calendar month were used in the analysis. ANEI values were geocoded to exact geographic locations using digitised street maps from which values for each house and school address, also geocoded, were interpolated. A child BP measured in a given month was matched to a aircraft noise exposure value both at their school and residential address for that month for analysis. After adjusting for confounding and other factors, the cross-sectional relationship between BP and aircraft noise exposure was found to be inconsistent. SBP was nonsignificantly negatively associated with school aircraft noise exposure at baseline (0.05 mmHg/ANEI, cluster-sampling-adjusted p&gt0.05), but positively and non-significantly associated with school aircraft noise exposure at follow-up (0.05 mmHg/ANEI, p&gt0.05). As for SBP, baseline DBP was significantly negatively related to school aircraft noise exposure at (0.09 mmHg/ANEI, p&lt0.001) and non-significantly positively associated with school aircraft noise exposure at follow-up (0.05 mmHg/ANEI, p&gt0.05). Within-subject BP changes, occurring from baseline to follow-up, regressed on corresponding longitudinal changes in aircraft noise exposures produced inconsistent results. SBP change was positively and non-significantly (0.027 mmHg/ANEI, p&gt0.05) associated with corresponding school aircraft noise exposure change, while SBP change was negatively associated total aircraft noise exposure change (statistically nonsignificant, 0.06 mmHg/ANEI, p&gt0.05). DBP changes were similarly and nonsignificantly related to corresponding aircraft noise exposure changes. Some evidence for short-term BP adaptation to recent changes in aircraft noise exposure was found. Consistent negative associations between systolic and diastolic BP and recent changes in school aircraft noise exposure were found. This association was statistically significant at study baseline (SBP: 0.19 mmHg/ANEI, p&lt0.001; DBP: 0.12 mmHg/ANEI, p&lt0.001), and of similar magnitude although not statistically significant at follow-up (SBP: 0.14 mmHg/ANEI; DBP: 0.10 mmHg/ANEI, p&gt0.05). In the presence of inconsistent cross-sectional BP-aircraft noise exposure associations, this finding is consistent with evidence of a homoeostatic BP response to recent changes in aircraft noise exposure, where resting BP returns to pre-existing levels unrelated to aircraft noise exposure. The public health implication of this finding appears to be benign.

Bibliography: p. 283-311. / xxii, 311 p. : ill. (some col.), photos (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Mechanical Engineering, 2004

Thesis (M.S. in electrical engineering)--Washington State University, December 2007. / Includes bibliographical references (p. 55-56).

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This thesis presents distinctly different methods of accurately predicting phase noise and absolute jitter in ring oscillators. The phase noise prediction methods are the commercially available SpectreRF and isf_tool, a simulator developed in this work from the Hajimiri and Lee theory of phase noise. Absolute jitter due to deterministic supply and substrate noise is predicted by Spectre time domain simulations and equations developed that can predict the absolute jitter due to a sinusoidal noise source at any frequency. These jitter prediction methods show that ring oscillator circuits respond differently to deterministic noise that is injected symmetrically versus noise that is injected asymmetrically, and a new jitter metric, peak jitter, is developed in this work to characterize absolute jitter caused by deterministic noise sources. These prediction methods are validated with measurements from two test chips with a combined 18 oscillators and 5 distinct architectures, and both are fabricated in the TSMC 0.35μm process. Each prediction method is shown to be consistent with over 2500 phase noise measurements taken from 10 oscillators and 5 architectures and over 1200 absolute jitter measurements due to sinusoidal supply and substrate noise taken from 11 oscillators and 3 architectures. / Graduation date: 2002