Faculty Bibliography

Digital hearing aids offer many advantages over conventional hearing aids. These include signal-processing capabilities that are superior to those of a conventional analog hearing aid, methods of signal-processing and control that are unique to digital systems and which cannot be implemented in conventional analog hearing aids, and innovative new techniques that are changing our way of thinking about hearing aids. An example of the first of these advantages is the extremely high precision with which the frequency-gain characteristic can be specified and the use of this capability to study the effects of frequency response irregularities commonly encountered with hearing aids. An example of the second advantage is the use of memory and logical operations in the implementation of multivariate adaptive paired-comparison techniques for more effective hearing-aid prescription. Another example is the use of powerful new signal processing techniques for noise reduction. The third advantage is the most important. The digital hearing aid can be viewed as a generalized hearing instrument which can be used for simulation, testing and prescription, as well as amplification. The use of the digital hearing aid as a simulator of other hearing aids is discussed and an illustrative example provided in which a new form of amplitude compression, orthogonal-polynomial compression, has been simulated using a digital master hearing aid

A recent increase of interest in spectral analysis has been prompted by the suggestion that spectral components of the ABR may contribute to differential diagnosis. Knowledge of the effects of stimulus parameters on the spectral content of the ABR is essential. The present study examined the effect of intensity, rate, and polarity on the spectral content of ABRs of 15 normal-hearing subjects. The effects of intensity were significant at all spectral frequencies examined while the effects of rate and polarity were frequency specific. These results indicate that the effects of stimulus parameters must be considered in examining the ABR spectral analysis.

Complete medical interviews and physical exams were performed on two stimulated patients by a class of medicine interns. These interviews and examinations were videotaped and were then scored using a rating scale developed by the authors. This system of videotaping and rating complete interviews and physical examinations is called the The Northwestern Evaluation & Training System (NETS). Selected findings are presented and discussed. It is shown how the NETS can be used for educational feedback to the individual student and for quality assurance feedback to training programs regarding the effectiveness of their instruction in interview and physical examination skills

This is a report comprised of 78 cases of melanoma of the mucous membrane of the head and neck and is part of a larger study of 995 cases of head and neck melanoma. These cases represent a review of patients over a 55-year period from the Pack Medical Foundation. Melanoma of the mucous membrane is a rare condition and the most serious of all head and neck melanomas. Its highest incidence is in the oral cavity, followed by the nasal and pharyngeal cavities. It usually occurs during the fifth decade of life. In its early stages it is asymptomatic and often located in areas difficult to see upon visual examination and technically inaccessible. These facts lead to a delay in diagnosis, which reduces curability to 8%. In spite of these negative factors, there has been a significant improvement in the extension and quality of life for patients with melanoma of the mucous membrane. The biological characteristics of this disease are analyzed and a philosophy of management is offered.

The auditory brain stem responses (ABRs) to 500- and 2,000-Hz bone-conducted (BC) tones were recorded from 48 infants with ears exhibiting various external and middle ear states (normal, otitis media, auditory meatal atresia). Amplitudes were greater, wave V latencies longer, and detectability better for responses to 500-Hz BC tones compared to 2,000-Hz BC tones. Overall, most (94% to 100%) infants with normal cochlear sensitivity demonstrate ABRs to 20-dB normal hearing level (nHL) 500-Hz BC tones and 30-dB nHL 2,000-Hz BC tones. In cases in which masking is difficult (eg, bilateral atresia), infant ipsilateral/contralateral ABR asymmetries may help determine from which cochlea a response to the BC tones originates. In conclusion, two-channel ABR recordings to BC tones appear to be feasible for demonstrating normal cochlear sensitivity in infants.

Twelve children with laboratory evidence of human immunodeficiency virus (HIV) infection underwent diagnostic flexible bronchoscopy with washings or bronchoalveolar lavage at Bellevue Hospital Center from October 1987 to April 1989. The patients included 7 boys and 5 girls ranging from age 3.5 months to 10 years 5 months. Indications for bronchoscopy included respiratory distress with or without focal changes on chest radiograph in 11 patients, and persistent but asymptomatic right middle lobe collapse in one child. The etiology of pneumonia was diagnosed in 7 children and included Pneumocystis carinii, (PCP) (17%), Streptococcus viridans (17%), mechanical obstruction (17%) and cytomegalovirus (CMV) (8%). Bronchoscopy was non-diagnostic in 5 cases. Techniques for maximal yield of information using flexible bronchoscopy in HIV-positive children are discussed

The acoustic-reflex thresholds (ART) for multicomponent tonal complexes of varying bandwidth and spectral density were obtained from 20 normal-hearing (air-conduction thresholds less than or equal to 20 dB HL at 250-8000 Hz) young adults ranging in age from 20-30 years and 20 normal-hearing, old subjects ranging in age from 60-71 years. The results revealed that the ART decreased with spectral density, plateauing after seven components in the young group and after five components in the old group; the decrease in the acoustic-reflex threshold as a result of the increase in spectral density was less in the old than in the young group. The bandwidth effect (when bandwidth was plotted in hertz or octaves) on the acoustic-reflex threshold was present in the young adults, but substantially reduced in the elderly, as evidenced by the statistically significant interaction between subject group and signal bandwidth. The spectral density results are discussed in terms of their theoretic implications for the energy summation capacity and frequency resolution of the auditory system. The bandwidth results are discussed in terms of their theoretic implications for the frequency-resolving power of the auditory system.