A brief history of audiology at Mayo Clinic.

Audiometric hearing tests were conducted at the Mayo Clinic in Rochester at the beginning of the 1930s. The list price for one of its audiometers at that time was 3,500 dollars, which translates into approximately 37,000 dollars in 2003 currency. Physicians and residents in training were responsible for conducting hearing tests in the 1930s and 1940s. In the early 1940s a registered nurse was trained as an audiometrist to assist for some of the audiometric testing. The first "consulting audiologist" at the Mayo Clinic in Rochester was hired in 1949, early in the development of audiology as a profession. Growth in demand for audiologic services for larger numbers of patients and in the variety of services provided to them led to marked increases in personnel, space, and specialization over the years.

Diagnostic implications of stimulus polarity effects on the auditory brainstem response.

The purpose of this study was to determine whether clicks presented in rarefaction or condensation modes produce more accurate diagnostic information. Subjects were 20 consecutive patients who were seen at the Mayo Clinic for unilateral acoustic neuromas. The nontumor ear served as a control to minimize intersubject variability in the latencies. A standard audiologic evaluation was followed by an auditory brainstem response (ABR) test for which the stimuli were rarefaction and condensation clicks. Responses were analyzed for the presence of waves I, III, and V; absolute latencies of waves I, III, and V; interpeak intervals I-III, III-V, and I-V; and interaural latency difference for wave V. The results indicated that measures from both polarities were similar in this set of patients and that neither click polarity provided diagnostic advantages over the other. Recommendations are to collect ABRs to both click polarities individually to obtain the full complement of waves on which to base the diagnostic impression.

Average Speech Levels and Spectra in Various Speaking/Listening Conditions: A Summary of the Pearson, Bennett, & Fidell (1977) Report.

The large study undertaken by Pearsons et al. (1977) for the Environmental Protection Agency nicely demonstrates "usual" speech levels in a variety of settings in classrooms, homes, hospitals, department stores, and commercial transportation. In most settings, speech levels were between 55 and 66 dBA at conversation distances in the school, home, hospital, and department store environments. S/N ratios on the order of 5 to 15 dB were maintained.Communication distance in the trains and airplanes was considerably less than the usual 1 m, and the speech levels were higher, 73 to 77 dBA, but still at a -1 or -2 dB S/N ratio in the train and airplanes, respectively. Their measurements in an anechoic chamber further reflected the levels of conversational speech in a quiet environment, as well as the levels and spectra for different vocal efforts by females, males, and children. Speech spectra were generally similar for the groups of talkers for casual conversation through raised vocal efforts. For loud speech, and particularly for shouted speech, male speech levels were greater than the speech levels of the females and children. The maximum one-third octave bands for loud and shouted speech shifted to higher frequencies for all three groups.