No abstract

In the 1980s, two studies found that children with unilateral hearing impairment were 10 times more likely to repeat a grade compared to the general school-age population. Since the publication of those reports, grade retention has been found to be an ineffective strategy for achieving long-term academic success, and is no longer widely recommended. This survey describeshow children with unilateral hearing loss are presently supported given this change in educational practices. Reports on 406 children indicated that 54% received individualized special education services, in addition to some level of audiologic support, and that 24% were functioning below average relative to their peers. Other information regarding demographics, use of amplification, and additional educational concerns are also reported.

The time course of the impedance changes caused by the contralateral acoustic reflex was investigated in five normal hearing, young adult subjects The acoustic reflex function was measured with equipment having a time constant of 15 milliseconds which permitted precise temporal measures. Temporal intervals from signal onset and termination to various portions of the acoustic reflex function were derived using an analysis procedure based on the slope function underlying the acoustic reflex response. These temporal intervals are related to physiological events underlying the acoustic reflex.There are three important applications for temporal measures of the acoustic reflex. First, precise temporal measurements may lead to a better understanding of the relationship between the physiology of the stapedius muscle and peripheral auditory input into the reflex mechanism, since impedance measurements of the acoustic reflex reflect stapedius muscle activity."'. ''7 13s4' Second, the acoustic reflex may provide a unique, nonbehavioral measure of initial temporal processing in the auditory system, because the acoustic reflex depends upon peripheral input for its function and involves brain stem central auditory mechanisms.2-Third, a potential diagnostic procedure may be developed for use in clinical audiology if valid and reliable differences in the time course of the acoustic reflex can be demonstrated between normal and hearing-impaired subjects. Previous research has indicated that such temporal measurements of the acoustic reflex may be affected by both cochlear and retrocochlear hear-Unfortunately, there are two major problems to overcome in order to make valid measures of the time course of the acoustic reflex. First, temporal measures must be made with instrumentation that has a short time constant. Second, the analysis of temporal intervals must be based upon a stable aspect of the acoustic reflex waveform.The time constant of many of the reflex measurement systems used in previous research is quite long. For example, an unmodified Madsen 20-70 impedance instrument, commonly used for temporal measures, has been shown to have a time constant on the order of 90 msec.29*30*35 The use of a measurement system with a time constant longer than the phenomenon to be measured casts doubt upon the validity of the temporal measures obtained. The present research used an acoustic impedance instrument with a time constant of 15 msec in order to circumvent this potential problem.A second difficulty is the determination of a stable aspect of the waveform of the acoustic reflex response upon which to base temporal measurements. The waveform of the reflex response is influenced by many factors and is not stable enough to be desirable for use as a foundation upon which to base temporal measures. The present research addressed this problem by using an analysis technique which concentrated upon the first derivative or slope function of the acoustic reflex response. By basing temporal measures upon the points of maximum and minimum slope...