Fifty-six subjects performed a decision and data-entry task (for 40 minutes) to determine the influence of realistic noises on task performance. Implementation of a mixed two-by-seven complete factorial design was used to investigate the influence of noise on a) objective performance measures (number of questions answered, and errors) and b) subjective perceptions of the noises. The task involved both high and low complexity levels. Seven noises with different characteristics and spectra were investigated: continuous high frequency industrial, intermittent high frequency industrial, continuous low frequency industrial, computer printer noise, office noise, music, and white noise. Analysis of covariance performed on the task performance data showed a significant main effect of complexity and noise-by-complexity interaction. As expected, for all noise conditions, the high complexity condition was more detrimental to performance than low complexity. Also, Newman-Keuls test of the noise-by-complexity interaction showed that subjects who performed the high complexity task while exposed to printer noise were hindered more than subjects performing any complexity level under any other noise condition. Analysis of variance on the subjective rating data showed both main effects of noise and complexity to be significant. Regardless of the noise, the high complexity condition was consistently perceived as more difficult than the low. Subjects perceived the music condition to be more enhancing than the low-frequency industrial noise. All other noises were perceived to be similar. Subject gender was not found to have any significant effect on objective task performance measures or subjective perception of noise. / M.S.

Most research on the urban sonic environment has been recent. One finding has been that physical noise exposure indices calibrate poorly with human noise response. The vagaries of human response to noise have given impetus to research to isolate the factors that differentiate human response to noise. The present thesis continues this research. The thesis specifies human noise response to occur on three levels: awareness, annoyance, and complaint. The factors that structure each level of noise response are identified in the published Iiterature. Noise awareness is a function of noise exposure. Noise annoyance is a function of noise exposure to a lesser degree. In addition annoyance is structured by attitudes toward the noise source, special interests in its economic benefits and personal susceptibility to noise irritation. Complaint concerning noise involves the previous factors plus an affluence or socio-economic component. The trend as one moves upward in the noise response hierarchy is for the structuring factors to become specific to individuals rather than location. Hence, noise awareness with respect to a stationary noise source will vary spatially, while complaint will be random in space. In testing these premises the author has made use of noise exposure indices for Portland International Airport and a social survey of response in the area surrounding the airport. The noise exposure indices were supplied by the consulting firm of Bolt, Beranek, and Newman Inc. and the social survey was conducted and tabulated by the Center for Population Research and Census at Portland State University. Multivariate methods were used for testing the premises concerning the hierarchical relationships between awareness, annoyance, and complaint.The variables representing awareness, annoyance, and complaint are quantified from the survey data through principle component and factor scores computer programs. The noise awareness measure is selected for greatest emphasis since it underlies to annoyance and complaint. The noise awareness measure is investigated and errors in its measurement are estimated through psychometric methods. Trend surface techniques are used to test the spatial regularity of awareness, annoyance, and complaint. As hypothesized, awareness is regular in space, annoyance less so, and complaint is random. Through multiple regression analysis noise awareness is tested against socio-economic measures, noise exposure measures, attitudes, and special interest. Noise exposure variables account for the largest part of the variation in noise awareness. A trend surface analysis is conducted on the values of awareness predicted by a large number of exposure, attitude, and other variables. The process is repeated for the residual values from the multiple regression. Predicted values are systematic in space but the residual values are largely random. The predicted values are mapped and compared with the actual smoothed awareness response surface. The two maps correspond well. It is concluded that noise exposure corrected for ambient noise levels adequately approximates the noise awareness response surface.

Thesis (MScMedSc (Interdisciplinary Health Sciences. Speech-Language and Hearing Therapy))--University of Stellenbosch, 2007. / Noise is a noxious stimulus with possible negative physiological effects on the infant, especially in the Neonatal Intensive Care Unit (NICU). The present study conducted a detailed noise assessment in a NICU of a state hospital in the Cape Metropole and documented 6 infants’ physiological responses to noise levels. Noise levels ranged from 62.3-66.7dBA (LAeq), which exceed all American and British standards (50dBA -60dBA) for a NICU. Continuous exposure to noise of these levels is potentially harmful to the infants’ auditory system and health stability. The general well-being of the staff working in the NICU may also be compromised. Analysis of the noise events revealed that staff conversations were the largest single contributor to the number of noise events, while the largest single non-human contributor was the alarm noise of the monitors. No significant correlations were found between the heart rates and noise levels and the respiratory rates and the noise levels for any of the participants in either room. The NICU was found to be an extremely reverberant environment, which suggested that the NICU noise levels were largely a result of reverberant noise reinforcements. NICU nursing staff’s most common suggestion for noise abatement strategies was reduction of staff conversation. Results of this study highlight the need for NICU noise abatement to optimise newborn patient care, reduce the risk of acoustic trauma and to improve the neonate’s quality of life, thus enhancing the infant’s physiologic stability, growth and health.