Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvi, 195 p.; also includes graphics. Includes bibliographical references (p. 183-195). Available online via OhioLINK's ETD Center

The thesis had two main objectives: namely to provide information on the sound attenuating abilities of tree species of the lower mainland region of British Columbia and to ascertain what stand characteristics cause trees to attenuate sound. After an extensive literature review an experiment was designed to investigate sound attenuation in eighteen tree stands, comprised of four species, at three distances, for eight different sound frequencies. The exerimental work was done during the winter of 1969 and the summer of 1970. Prior to this the tree stands were enumerated and various tree parameters measured. No patterns could be found which significantly correlated the measured stand characteristics with the amount of sound attenuated. Little significant difference was found between the summer and winter attenuations and it was found that stands reacted independently of the season. Tables are presented in the Appendix showing the attenuations for each stand, at each distance and for each frequency. Mean values together with their standard deviations are given for all stands within a species. Suggestions are given for future work on this topic and the implications of the results on various design fields are discussed. / Forestry, Faculty of / Graduate

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Vita. / Includes bibliographical references. / Ph.D.

A field research study was conducted to determine the actual noise attenuation and perceived comfort achieved by 40 noise-exposed industrial workers in 5 industrial workplaces wearing 4 different industrial hearing protection devices (HPDs) while on the job. Over 2 consecutive 3-week periods of HPD use, the study investigated the effects of 2 different HPD fitting procedures (subject-fit versus trained-fit) on the spectral field attenuation and user-rated comfort achieved with a user-molded foam earplug, a premolded, triple-flanged polymer earplug, a popular foam cushion earmuff, and an ear canal cap with compliant rubber earpods. Workers were pulled from their workplaces without prior knowledge of when they were to be tested and without re-adjusting the fit of their HPDs. Attenuation data were collected using psychophysical real-ear-attenuation-at-threshold measurement procedures as per the ANSI S12.6-1984 standard. Subjective comfort data were also obtained based on multi-dimensional bipolar rating scales. The results of statistical analyses indicated that when training for proper fitting was used, the earplugs significantly improved in noise protection (from 7.2 to 14.6 dB, depending on the frequency and the earplug) at frequencies of 125 - 1000, 6300, and 8000 Hz, whereas the earmuff and the ear canal cap were relatively resistant to the fitting effect. The training was most effective for the slow-recovery foam earplug over the 3-week period. For the comfort rating data, the foam earplug was again sensitive to the fitting effect, but the other HPDs were not. Among the 4 HPDs evaluated in the study, the canal cap protector was judged as the least comfortable HPD, while the other 3 HPDs yielded about the same perceived comfort. This research also showed that the overall field HPD protection afforded can be accurately predicted from single test band (i.e., centered at 500 or 1000 Hz) attenuation measurements. In addition, the field study demonstrated that laboratory simulation protocols designed to simulate field influences on HPD performance (used in the precursor laboratory study) may not be relied upon to yield accurate estimates of field performance of all HPDs. However, the estimates of field attenuation performance were more accurate for the earmuff than for the earplugs tested. Finally, this study demonstrated that the labeled manufacturers' single-number noise reduction ratings (NRRs) and frequency-specific data substantially overestimate the actual HPD attenuation performance achieved in the field. Consequently, on the basis of the results of this study, it appears that an appropriate, device-specific derating scheme to correct unrealistic labeled attenuation data is needed. / Ph. D.

Healing and clinical work requires a complex choreography of architectural acoustic design in healthcare settings. In most healthcare settings, medical staff members conduct vital tasks that may have life-and-death implications. Patients visit the hospitals to heal. Their expectations include fast recovery, restful sleep, and privacy (i.e., speech privacy). However, sound environment qualities of the care settings often fall far from supporting the mission of hospitals. There is strong and growing evidence showing that effective soundscapes in healthcare settings potentially impact errors, healing and stress for patients, families and staff but it is still not clear what measures of the sound environment best predict key healthcare outcomes and what design strategies best impact those measures. By using a multi-method approach (i.e., objective and subjective noise level measurements, in-situ impulse response measurements, heuristic design analysis, theoretical studies, acoustic simulations and statistical analysis), this study aims to develop evidence based design strategies by statistically defining the relationships between three types of variables: (1) architectural floor-plate design metrics, (2) acoustic metrics, and (3) occupant response. The research is conducted in three phases. The first phase of the study compared the objective and subjective qualities of the hospital sound environments with different architectural designs, assessed the effectiveness of a newer acoustic metrics in capturing caregiver perceptions, and evaluated the impact of particular noise sources on caregiver outcomes. The second phase of the study tested the validity of an acoustic simulation tool in estimating the acoustic qualities of the healthcare soundscapes. The third phase of the study systematically explored the relationship between floor-plate design and acoustics of complex inter-connected nursing unit corridors. Even though the relationship between design and acoustics of proportional spaces (a.k.a. rooms with more traditional dimensions) has been well documented, the number of studies linking design and acoustics of complex non-proportional spaces such as inter-connected corridors still remains limited. The findings of the first phase show that critical care sound environments with different designs can vary drastically and impact caregivers` perceived wellbeing and task performance (e.g., patient auditory monitoring). Despite their extensive use, traditional noise metrics sometimes may not be effective in capturing unique characteristics of healthcare sound environments. This study validated the effectiveness of a new more detailed noise metric, "occurrence rate", in capturing the differences between acoustic characteristics of healthcare sound environments. Moreover, particular noise sources such as impulsive noises are likely to dominate the ICU sound environments and interfere with perceived caregiver health and performance. The findings of the second phase suggest the potential effectiveness of acoustic simulation tools (with hybrid prediction programs) in estimating the acoustic qualities of complex inter-connected hospital corridors. The findings of the third phase suggest the potential significant impact of design features of particular hallways (e.g., number of turns, corridor length, and number of branches) and overall floor-shape characteristics of inter-connected corridors (i.e., relative grid distance, and visual fragmentation) on reverberation time. Overall, in the units with shorter, more compact, fragmented corridors with multiple number of branching hallways, reverberation times are likely to be less. Moreover receivers located at the corridors with less number of turns from the sound source also potentially experience lower reverberation times. According to previous research, the human auditory system`s ability to monitor auditory cues is likely to be higher in the less reverberant sound environments.

In the global framework of improving vibro-acoustic numerical prediction quality together with the need to decrease the number of prototyping stages, this manuscript focuses on achieving greater accuracy for acoustic numerical simulations by making use of a parametric updating technique, which enables tuning the model parameters inside physically meaningful boundaries. The improved model is used for the next prototyping stages, allowing more accurate results within reduced simulation times. The updating technique is based on recent works dealing with the constitutive relation error method (CRE) applied to acoustics. The updating process focuses on improving the acoustic damping matrix related to the absorbing properties of the materials covering the borders of the acoustic domain. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished