Stimulus presentation level and speech perception through a single-channel cochlear implant.

This study evaluated the effects of stimulus presentation level on 12 adult 3M/House single-channel cochlear implant users' speech perception performance. Dynamic ranges and loudness growth functions were measured for meaningful speech, and performance-intensity functions were plotted for VCV and CVC nonsense stimuli to determine the presentation level(s) that produced maximum speech perception performance for each subject. Considerable variability was found in the subjects' dynamic ranges. Generally, loudness growth functions were steep for subjects having restricted dynamic ranges and more gradual for those having wide dynamic ranges. No single optimal presentation level was determined; instead, a range of levels produced maximum performance for each subject. Mean levels producing peak scores in equivalent dB SPL were 80 for VCVs and 72 for CVCs. Presentation levels producing optimal performance varied with type of speech stimulus.

Performance of 3M/house cochlear implant users on tests of speech perception.

This report documents both closed- and open-set speech recognition performance for 18 adult experienced users of the 3M/House single-channel cochlear implant. The stimuli included tape-recorded, standard word and sentence recognition tests, an environmental-sound test, nonsense syllables, and sentences presented in auditory (implant-only), visual, and auditory-visual modes. All subjects were tested individually in a single session using their own cochlear implants, set to typical comfort use settings for running speech. Subjects' oral responses to the stimuli were transcribed by the experimenters and scored for percent correct. The results revealed considerable individual differences among the subjects and their performance on different tests. All subjects scored better than chance on the closed-set tests. Although they performed considerably poorer on the open-set tests, approximately half of these subjects demonstrated at least some open-set word recognition, a finding not previously reported in the literature for this device. All subjects performed better on the auditory-visual sentences than on either the auditory or visual conditions alone. These results contribute to the database on speech perception by cochlear implant users and show that open-set word recognition performance was somewhat better for these subjects using this implant than would have been predicted from the literature.

Hearing function in a hyperbaric environment.

Navy divers' hearing function was assessed as part of three saturation deep dives to 1,000 feet of sea water (fsw) to determine explanations for threshold shifts observed under hyperbaric conditions. Across the three deep dives, different aspects of the ear were evaluated, including air- and bone-conduction pure-tone thresholds, real ear probe microphone measurements, auditory evoked potentials, and central auditory processing assessments. Attempts to measure middle ear function and cochlear function (through otoacoustic emissions) were unsuccessful. Baseline measurements were obtained at 0 fsw in air before and after the saturation deep dives. Results showed that some aspects of hearing function remained unchanged with increases in depth. In general, audiometric thresholds at depth were similar to those measured on the surface at 500, 1,000, 2,000, 3,000, and 4,000 Hz. However, hearing sensitivity actually improved at depth at 6,000 and 8,000 Hz. The use of a specially designed sound booth for a pressurized heliox environment yielded significantly lower ambient noise levels and improved the accuracy of threshold measurement. Auditory evoked potential measurements and central auditory processing function were relatively unaffected by changes in depth. Significant changes at depth were seen in ear canal resonance which shifted up in frequency; this finding was attributed to the effect of helium on the hearing mechanism. Because objective measurement of middle ear and inner ear function were not methodologically possible, questions still remain regarding the interpretation of middle and inner ear function at depth. Nonetheless, our overall findings suggest that most aspects of hearing functioning are similar under high atmospheric pressures and in heliox as they are on the surface, with the exception of shifts in ear canal resonance and improvements in audiometric thresholds at high frequencies.

Counseling in audiology, or learning to listen: pre- and post-measures from an audiology counseling course.

Because of a "technology explosion," audiologists have more options than ever in providing for their patients' hearing needs. However, relatively few individuals with hearing loss seek out amplification, and those who do frequently report dissatisfaction with the quality of their interactions with audiologists. Most audiologists did not have coursework in counseling in their graduate programs, which may account for patient complaints. As part of a course development evaluation of an audiology counseling course, a preliminary study was conducted to examine two student learning objectives: to learn how to differentiate between content messages and affective messages and to learn how to respond to each type of message appropriately. Pre- and postcourse data collected from two cohorts of audiology graduate students indicated that (a) before taking the course, students were likely to provide informational responses to personal adjustment comments (a type of "communication mismatch"), and (b) at the end of the class, they were much more likely to match or mirror affective statements with affective responses.

Successful recruiting strategies.

Key aspects of a successful recruitment program to attract bright, talented students to this dynamic profession are (a) providing informative and attractive printed materials about the professions and the program, (b) establishing key personnel to provide personal contact with each student applicant, (c) specifying deadlines for application submission and decisions, (d) providing efficient feedback, (e) maintaining consistent contact with students prior to matriculation, and (f) offering several social and academic activities to orient new students. Although concepts important to retention are not included here, they are similarly important and should be considered carefully. Given the cyclical nature of student enrollment in the professions, a program's emphasis on recruitment may change. However, in order to keep student enrollment levels constant, consistent recruitment is necessary.

A sindscal analysis of perceptual features for consonants produced by esophageal and tracheoesophageal talkers.

This study was concerned with the perceptual responses of normal-hearing listeners to consonants produced by esophageal and tracheoesophageal (TE) talkers and a single talker who was proficient in both of these alaryngeal speech modes. The listeners' perceptual responses were analyzed using Symmetric Individual Differences Scaling (SINDSCAL) to determine whether distinctive feature differences existed between these two methods of alaryngeal speech. This a posteriori analysis revealed that primary features retrieved for both speech methods included sibilant, affricate, dental, nasal, and sonorant. Although greater perceptual weightings were observed for TE speech, these productive/perceptual features were weighted similarly for both speech methods. Some secondary group-specific feature differences were also observed, but these features did not contribute substantially to the total amount of variance accounted for in the analysis. Thus, the SINDSCAL results showed that the groups did not use different feature systems. These results are discussed in regard to the unique alaryngeal speech production methods employed by esophageal and TE talkers and the relative limitations of the alaryngeal (esophageal) voicing source they use. General clinical implications of the data are discussed.

Speech intelligibility assessment in a helium environment.

The purpose of this study was to compare the appropriateness and effectiveness of the speech perception in noise (SPIN) test and the Griffiths version of the modified rhyme test (GMRT) in assessing Navy divers' speech understanding using communication systems containing different helium speech unscramblers (HSUs), one of which produces, by subjective observations, more intelligible output than the other. Divers participating in a saturation deep dive and a group of nondivers using digital audio tape recordings of the stimuli used by the divers were tested. Mean percent correct scores on the SPIN and GMRT lists within two listening conditions (taped, topside-diver and live-voice, diver-diver) were almost identical. Listeners scored better on both tests in the topside-diver condition than in the diver-diver condition. The majority of the SPIN errors were on low-predictability items that are void of context. Context clearly played a role in measuring the performance of these subjects, at least for the SPIN test. No significant differences were measured between the two HSUs, although a trend was seen favoring one HSU over the other for the divers. These results have theoretical as well as practical value for measuring the quality and intelligibility of helium speech enhancement systems.

Speech intelligibility assessment in a helium environment. II. The speech intelligibility index.

The Speech Intelligibility Index (SII) was measured for Navy divers participating in two saturation deep dives and for a group of nondivers to test different communication systems and their components. These SIIs were validated using the Speech Perception in Noise (SPIN) test and the Griffiths version of the Modified Rhyme Test (GMRT). Our goal was to determine if either of these assessments was sensitive enough to provide an objective measure of speech intelligibility when speech was processed through different helmets and helium speech unscramblers (HSUs). Results indicated that SII values and percent intelligibility decreased incrementally as background noise level increased. SIIs were very reliable across the different groups of subjects indicating that the SII was a strong measurement for predicting speech intelligibility to compare linear system components such as helmets. The SII was not useful in measuring intelligibility through nonlinear devices such as HSUs. The speech intelligibility scores on the GMRT and SPIN tests were useful when the system component being compared had a large measurable difference, such as in helmet type. However, when the differences were more subtle, such as differences in HSUs, neither the SPIN nor the GMRT appeared sensitive enough to make such distinctions. These results have theoretical as well as practical value for measuring the quality and intelligibility of helium speech enhancement systems.