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Biomedical subjects

A J Klein

Publications and source records attributed to A J Klein.

17 recordsLinked to original sources
PubMed1992

Infant screening.

Explore the source record for details and available documents.

Acoustic Impedance Tests↗
PubMed1992

The effects of stimulus rate on detectability of the auditory brain stem response in infants.

This study was undertaken to determine the feasibility of using a fast stimulus rate for auditory brain stem response (ABR) hearing screening in infants. Eighty-four neonates and infants with postconceptional ages (PCA) from 30 to 78 weeks with clear ABRs to click rate of 40/sec at 30 dB HL were retested at 90/sec. Ninety-two percent of infants with PCA > 42 weeks had a clearly identifiable ABR at the 90/sec rate. In contrast, 71% of the infants with PCA between 37 and 42 weeks, and only 50% of the infants with PCA < 37 weeks, had clearly identifiable ABRs at 90/sec. Thus, a 90/sec stimulus rate was not practical on infants < 43 weeks PCA. Accordingly, ABR detectability was assessed to 40 dB clicks at 70/sec compared to the 40/sec rate on 20 infants between 33 and 42 weeks PCA. ABRs were detectable on 85% of this group, which suggests that these parameters may be more reasonable, but further data are needed. ABR measures for hearing screening on infants > 42 weeks and children can be satisfactorily performed at stimulus rates up to 90/sec; however, infants who fail the screening when using a fast stimulus rate should have a repeated measurement at a slower rate to rule out a false positive result.

Acoustic Stimulation↗
PubMed1991

Occupational hearing conservation.

Chronic exposure to high-intensity noise can produce permanent hearing loss, the amount of which depends on noise intensity, temporal and spectral characteristics, and the length of exposure. OSHA regulates workplace noise exposure in accordance with the Hearing Conservation Amendment of 1983. When noise levels equal or exceed an 85 dBA time-weighted average (TWA), the employer is required to provide annual audiometric screening. When noise levels exceed 90 dBA TWA, the worker's exposure must be reduced by engineering methods, administrative changes, or personal hearing protectors. If a worker demonstrates a standard (significant) threshold shift (10 dB or greater increased average hearing threshold at 2, 3, and 4 kHz in either ear) that is attributed to noise, the worker's exposure must be further reduced by one of the aforementioned methods.

Ear Protective Devices↗
PubMed1990

Hyperacusis and otitis media in individuals with Williams syndrome.

Williams syndrome is characterized by cardiac defects, varying degrees of physical and developmental delay, stellate eye pattern, possible elevated serum calcium level, and elfin/pixie facial features. A problem perhaps unique to these children is hyperacusis that can be severe enough to disrupt many routine daily activities. Parental questionnaires were used to determine the prevalence of hyperacusis and otitis media in individuals with Williams syndrome. Prevalences of 95% for hyperacusis and 61% for otitis media were found. This was significantly higher than in the general population. Despite the prevalence of hyperacusis, parents of these children were not counseled about management of the problem. The audiologist may become involved with Williams syndrome patients through hearing assessment and management, parental counseling, and research.

Adolescent↗
PubMed1990

Upward spread of masking, hearing loss, and speech recognition in young and elderly listeners.

Upward spreading of masking, measured in terms of absolute masked threshold, is greater in hearing-impaired listeners than in listeners with normal hearing. The purpose of this study was to make further observations on upward-masked thresholds and speech recognition in noise in elderly listeners. Two age groups were used: One group consisted of listeners who were more than 60 years old, and the second group consisted of listeners who were less than 36 years old. Both groups had listeners with normal hearing as well as listeners with mild to moderate sensorineural loss. The masking paradigm consisted of a continuous low-pass-filtered (1000-Hz) noise, which was mixed with the output of a self-tracking, sweep-frequency Bekesy audiometer. Thresholds were measured in quiet and with maskers at 70 and 90 dB SPL. The upward-masked thresholds were similar for young and elderly hearing-impaired listeners. A few elderly listeners had lower upward-masked thresholds compared with the young control group; however, their on-frequency masked thresholds were nearly identical to the control group. A significant correlation was found between upward-masked thresholds and the Speech Perception in Noise (SPIN) test in elderly listeners.

Adolescent↗
PubMed1989

Assessing speech recognition in noise for listeners with a signal processor hearing aid.

Hearing aids with signal processors use advanced circuitry to enhance speech recognition in noise. The effectiveness of these processors has not been well established. The purpose of this study was to evaluate performance on a speech recognition in noise task for listeners wearing a Zeta signal processor aid with the processor turned on and with the processor turned off. In addition, comparisons were made to performance while unaided and aided with a conventional hearing aid. A simple adaptive procedure and a psychometric function were the procedures used. Results for normal-hearing subjects indicate performance was usually better without a hearing aid. Performance when aided was similar for the processor on and the conventional aid. Performance in both of these conditions was clearly better than with the signal processor off. Although results for the hearing-impaired subjects varied widely, there was a trend for better performance with the conventional aid and with the signal processor on than for the signal processor off condition.

Adaptation, Physiological↗
PubMed1987

Effect of signal temporal shaping on the frequency specificity of the action potential in gerbils.

We examined the effects of temporal shaping of a tone burst on the frequency specificity of evoked responses in gerbils. Frequency specificity was assessed by means of whole-nerve action potential (AP) tuning curves (APTCs). The envelopes of the onset and offset portions of the AP-eliciting tone burst (or probe) were either a linear or nonlinear (1/4 sine) function of time. At probe frequencies of 1, 4 and 8 kHz, APTCs in the two envelope conditions were similar in shape and had equally narrow tips. This was true at both low (40-50 dB SPL) and high (70-75 dB SPL) probe levels. It suggests that tone bursts in the two envelope conditions evoke AP responses that are equally frequency specific. Despite these similarities, a notable difference in the two conditions was found at high probe levels. Specifically, raising the level of an 8-kHz probe from 40 to 70 dB SPL resulted in a downward shift of the APTC tip frequency, and this shift was greater for probes with linear on-off envelopes than for those with nonlinear on-off envelopes. This result suggests that of the two waveform shapes, the nonlinear envelope is likely to produce responses at frequencies closer to the nominal signal frequency. Reducing the rise-fall time of the probe from 2.0 to 0.75 ms caused the tip of the 8-kHz APTC to undergo an even greater displacement in frequency, indicating a greater 'off-frequency' response for briefer rise times.

Action Potentials↗
PubMed1986

Masking effects on ABR waves I and V in infants and adults.

The effects of high- and low-pass masking on waves I and V of the auditory brain stem response (ABR) were measured in normal infants who were 2-4 weeks old, and in adults. The signal was a 4-kHz tone pip presented at 86 dB peak equivalent sound-pressure level (p.e.SPL). The masking patterns were different for latency and amplitude criteria, and were also different for infants and adults. The largest difference between infants and adults was seen in the wave I data. Low-pass maskers were very disruptive of the infant wave I, while little or no effect was noted on the adult wave I. High-pass maskers were very disruptive of the adult wave I, while less of an effect was measured on the infant wave I. The wave V data were similar between groups. Cochlear regions which contribute most importantly to wave I extend up to one octave above the frequency of the signal in adults, and to one-half octave above the signal frequency in infants. The reasons for the differences found between infants and adults are uncertain. Two possible mechanisms which can explain these data are differences in peripheral auditory sensitivity, and differences in tuning characteristics of the auditory system.

Adult↗
PubMed1979

A technique for separating endogenous from exogenous human cortical potentials.

In a temporal discrimination paradigm, if signal duration is the stimulus dimension to be discriminated, the moment of subject's decision can be manipulated by varying the duration of the target stimulus. As stimulus duration is lengthened, task-contingent potentials related to the decision process can be separated from those evoked by stimulus onset. Analysis of individual evoked responses indicates that 3 task-contingent components, occurring at 220, 300 and 340 msec are precisely time-locked to the moment of decision.

Acoustic Stimulation↗
PubMed1978

Acoustically dependent latency shifts of BSER (wave V) in man.

The latencies of wave V in Brain Stem Evoked Responses (BSER) elicited by a set of acoustic transients were measured. The stimuli were produced by delivering pulses to two filters, arranged in series. The filters were set so that the maximum acoustic energy in the transients, i.e., filtered clicks, occurred at 0.5, 1, 2, 4, or 8 kHz. The filtered clicks were presented via earphones at a rate of 30/s at 20, 40, or 60 dB HL to ten subjects with normal hearing. The latencies of wave V varied systematically with center frequency of the filtered clicks when they were each at the same HL. Stimuli presented at 40 dB HL produced the greatest opportunity for relating stimulus frequency to latency. The latencies for a smaller set of responses to stimuli presented at 10/s were the same as those for the principal data taken at 30/s. The changes in latency of wave V due to frequency are similar to those observed by other investigators in whole-nerve responses recorded in man.

Acoustic Stimulation↗
PubMed1978

Payments arrangements.

No matter what financial arrangements are made with patients, there is no foolproof method of ensuring payment. As stated earlier, the financial arrangement does not indicate mistrust of the patient, but is a means of communication. If we accept the fact that nearly all patients have full intentions of meeting their financial obligations, the guiding rule should be flexibility. Inflexibility when making financial arrangements may limit the growth of your practice. Sensitivity is an important ingredient in helping to understand and to meet your patient's needs. Many more patients will accept necessary dentistry if they are given the opportunity to select a method of payment with which they are comfortable.

Dental Offices↗
PubMedDate not supplied

Thresholds of filtered transients.

Absolute and masked thresholds were obtained for sinusoids, one-third-octave filtered noise, one-third-octave filtered clicks, and for broadband noise and clicks as a function of repetition rate of the filtered clicks. The results indicate that if signal energy is computed for each stimulus, then similar absolute and masked thresholds can be obtained. Thresholds for repetition rate and number of clicks were similar to published results on temporal integration of tones. These results provide a direct and objective means for measuring the level of brief narrow-band stimuli and support the use of these signals as a means of probing auditory sensitivity.

Acoustic Stimulation↗