Federal regulations specify that an employee working for eight hours cannot legally be exposed to noise which has a time-weighted average greater than 90 decibels on the A scale. The industrial workforce is comprised of not only people with normal hearing acuity, but of individuals who suffer from hearing loss. While current noise regulation standards are deemed appropriate for those with normal hearing, it is difficult to apply these standards to persons wearing hearing aids on the job. The ambient, or unamplified, noise levels that fall below the maximum permitted by OSHA standards may very well be amplified to levels greater than 90 dBA, by the hearing aid. If this were the case, the company employing the hearing aid user would technically be in violation of the OSHA regulations. This study addressed the question of what noise exposure might be expected for hearing aid users on the job in different situations, as well as in non-vocational settings. The research involved two methods, conducted to determine the noise levels created by hearing aids with different amounts of gain and to determine whether the amplified noise levels exceed those requiring intervention under current regulations. For both methods, ambient and amplified noise levels for each condition were gathered in specified increments, and were compared with regard to current regulatory standards. The resultant data revealed that when ambient noise levels average between 80 and 84 dBA, amplification provided by even a mild gain hearing aid caused the eight hour time-weighted averages (TWA's) to increase to levels above the 90 dBA maximum permissible levels as delineated by OSHA. Moderate and high gain aids further increased these levels. The results of this study suggest that the hearing aid users in industrial and perhaps non-industrial settings may very well be exposed to intensity levels which exceed OSHA maximums, even when ambient levels do not. The extent to which these arc exceeded are based on the gain and output of the hearing aid in use.

No description available.

In order to examine the potential impact of military jet overflights and other disturbances on productivity of peregrine falcons (Falco peregrinus), we observed behavioral reactions of peregrines to disturbances at nests along the Tanana River, Alaska during the 1995-1997 breeding seasons. Military jets conducted low-altitude flights over a sample of nests under observation in each year (experimental nests), while other nests were not intentionally overflown (reference nests). Other disturbances occurred at random. Animal noise monitors (ANMs), which collect and store data on noise disturbance levels, were deployed at each observed nest. A total of 878 above-threshold (��� 85 dB) overflights were recorded by the ANMs during the course of the study. A total of 401 close (defined as ��� 1000 m slant distance from the nest) overflights by subsonic F-16, F-15, A-10, Harrier, Jaguar, or Tornado jet aircraft were recorded during observations. Close overflights by military jets accounted for 63% of all observed potential disturbances at experimental nests; they accounted for 2.6% of all observed potential disturbances at reference nests. Other potential disturbances at reference nests included civilian fixed-wing aircraft (41%), boats (33%), avian predators (17%), helicopters (5%), and mammalian predators (1%). Peregrine falcons responded differently to animate and inanimate sources of disturbance, and responded most intensely and most frequently to other raptors, particularly conspecifics. Flight reactions were common, but not in response to inanimate sources. Among inanimate potential disturbances, falcons responded most intensely to boats (6% of reactions involved flight), and least intensely to helicopters (3%) and fixed-wing aircraft (2%). Intensity of reactions to military jets was indistinguishable from that to either boats or other aircraft. Intense behavioral responses (including flight reactions) to military jet overflights were rarely observed in this study, even at slant distances <500 m, and no intense behavioral responses were observed at slant distances >550 m. Peregrine falcon productivity (number of fledglings produced per nesting attempt) in the study area was within the normal range for Interior Alaska and the Tanana River. Dose of jet aircraft disturbance was not correlated with productivity. Productivity was, however, negatively correlated with reactivity of both individual falcons and mated pairs. Those falcons that responded more intensely to overflights tended to have lower productivity. The sensitivity of breeding peregrine falcons to low-altitude jet overflights is a better indicator of subsequent productivity than actual dose of overflights. This is likely a reflection of lower parental quality/investment among breeding pairs with high reactivity (i.e., younger, less experienced parents are less likely to be productive). / Graduation date: 1999

No description available.

This investigation was concerned with measurements of middle ear muscle activity. Specifically, the investigation was designed: (a) to compare reflex thresholds for pure tone(PT), octave band noise(OBN), and one-third octave band noise(TQBN); (b) to study middle ear muscle activity during a five minute exposure to these stimuli at 114 dB SPL; and (c) to compare middle ear muscle activity for stimuli of different frequencies. Eighteen subjects were divided into two groups. Group I subjects were exposed to a 700 Hz PT, to OBN with center frequency 500 Hz, and TOBN with center frequency 630 Hz; Group II subjects were exposed to a 1400 Hz PT, to OBN with center frequency 1000 Hz, and TOBN with center frequency 1250 Hz. A Madsen Electroacoustic Impedance Bridge and graphic recorder were used to record impedance changes during stimulation with the above stimuli. These impedance changes were assumed to reflect muscle activity. Thresholds for the acoustic reflex were determined using standard procedures. Analysis of results indicated muscle activity decreased progressively during stimulation. Reflex decay was significantly greater for stimulation with PT than for stimulation with OBN(Groups I and II) and TOBN(Group II). It was noted that reflex decay was less during stimulation with a 700 Hz PT than during stimulation with a 1400 Hz PT. Finally, it was observed that reflex thresholds were higher for PT than for OBN and TOBN. Decrease in muscle activity during acoustic stimulation was discussed in terms of adaptation and possibly central mechanisms; the characteristics of the stimuli were compared and discussed, as a possible explanation for differences in results obtained for tones and noise. / Medicine, Faculty of / Audiology and Speech Sciences, School of / Graduate

No description available.

This investigation sought to identify sound levels potentially harmful to directors' hearing, and examine the effects of band size, instrumentation, bandroom and playing ability on sound levels. The subjects were 2 elementary, 2 middle, and 4 high school bands, in 7 rooms, 10 to 66 members, and 26 students, beginning and advanced. A sound level meter was used. Sounds were measured in flat and A-weighted decibels. Sounds measured were steady state (>.5 sec.) and impulse (<.5 sec.). Results were compared with safety limits of OSHA, EPA and Baughn's study of safety limits (1966). Results show exceedences of limits used for comparison. Small rehearsal areas and younger players seemed to cause high levels in the tests. Further testing may prove potential hazards.

Abstract not available

The purpose of the present study involved the investigation of the significance of wind noise as a contributing factor toward temporary threshold shifts among a select sample of motorcycle riders. Five ' normal-hearing, helmeted, female subjects were administered pure-tone air-conduction hearing tests immediately before and within 2 minutes after exposure to three noise-related aspects of motorcycle riding. The amount of ,hearing loss present at 3k, 4k and 6k Hz after each 20 minute exposure condition was recorded as the TTS for that subject. The three conditions consisted of motorcycle noise only, wind noise only and motorcycle and wind noise combined. A statistical analysis of the data revealed that motorcycle noise alone produced significantly less TTS than the wind only or the wind and motorcycle noise. These findings support the hypothesis that wind noise is a significant factor in the production of TTS and possible noise-induced hearing loss among motorcycle riders.

This dissertation examines associations among home noise exposure, language skills, and brain structure and function in children spanning multiple developmental stages. To measure home noise exposure, digital audio recordings of the home environment were obtained and used to calculate home noise levels. To examine brain structure in children, Study 1 leveraged magnetic resonance imaging (MRI). To examine brain function in response to speech sounds in toddlers, Study 3 leveraged electroencephalography (EEG) in order to elicit event-related potentials (ERPs) that have been related to language abilities. All studies also incorporated the use of standardized assessments of language to examine children’s developing language abilities and used either parent-report measures of language (Study 2) or direct assessments of children’s language abilities (Studies 1 & 3). Primary hypotheses included that higher home noise exposure would be associated with 1) reduced cortical thickness (Study 1), 2) lower scores on measures of language skills in infancy and childhood (Studies 1, 2, and 3), and reduced neural differentiation of speech sounds (Study 3). Together, these findings shed light on the potential impact of noise exposure on children’s brain and language development. By better understanding how factors in children’s everyday environments might influence neural and cognitive development, we can best inform efforts aimed at optimizing children’s developmental trajectories.