Sharon A. Hellman

The effect of compression ratio and release time on the categorical rating of sound quality

Two experiments were carried out to determine how manipulating the compression ratio and release time of a single-band wide dynamic range hearing aid affects sound quality. In experiment I, compression ratio was varied over the range from linear to 10:1 (low compression threshold, attack time = 5 ms, release time = 200 ms). In experiment II, compression ratios of 1.5, 2, and 3:1 were combined with release times of 60, 200, and 1000 ms (attack time = 5 ms). Twenty listeners with sensorineural hearing loss rated the clarity, pleasantness, background noise, loudness, and the overall impression of speech-in-noise (Ventilation, Apartment, Cafeteria) processed through a compression hearing aid. Results revealed that increasing compression ratio caused decreases in ratings on all scales. Increasing release time caused ratings of pleasantness to increase, and ratings of background noise and loudness to decrease. At the 3:1 compression ratio, increasing the release time caused increases in ratings of clarity, pleasantness, and overall impression, and a decrease in background noise. Significant correlations were found between scales. Regression analysis revealed that the contributions of the scales of clarity, pleasantness, background noise, and loudness to the prediction of overall impression differed as a function of the competing noise condition.

Effect of release time in compression hearing aids: Paired‐comparison judgments of quality

Paired-comparison judgments of quality were obtained from 20 hearing-impaired listeners for speech processed through simulated compression hearing aids varying in release time (60, 200, 1000 ms) at three different compression ratios (1.5, 2, 3:1) and for three different background noises (ventilation, apartment, cafeteria). Analysis revealed that the main effect of release time did not have a significant effect on perceived quality. The interaction between release time and noise type was found to be significant. While no significant difference in preference for release times was evident for the ventilation noise, the longer release times (200 and 1000 ms) were preferred for the higher level noises (apartment noise, cafeteria noise). Post hoc testing revealed that the mean preference scores for the 200- and 1000-ms release time were significantly greater than that of the 60-ms release time with the competing cafeteria noise (p < 0.05). Analysis of individual subject data revealed statistically significant preferences that differed from the group mean, suggesting that individualized fitting of this parameter of a compression hearing aid might be warranted.

Cochlear Implant Flap Complications

In a series of 52 patients who received cochlear implants, 4 patients suffered flap complications (7.7%). The problems encountered involved the postauricular flap and were usually minor in nature. None required explantation as a direct result of these complications. Flap ischemia in a patient with Cogans syndrome and vasculitis, two cases of suture extrusion with one having exposure of the implant, and a case of receiver unit magnet extrusion repaired with a vascularized pericranial flap based upon temporalis muscle are presented. Flap design in patients who have had postauricular incisions demands special consideration. Principles useful for avoiding complications as well as their management are discussed.

Speech changes following reimplantation from a single‐channel to a multichannel cochlear implant

The speech of a postlingually deafened preadolescent was recorded and analyzed while a single-electrode cochlear implant (3M/House) was in operation, on two occasions after it failed (1 day and 18 days) and on three occasions after stimulation of a multichannel cochlear implant (Nucleus 22) (1 day, 6 months, and 1 year). Listeners judged 3M/House tokens to be the most normal until the subject had one years experience with the Nucleus device. Spectrograms showed less aspiration, better formant definition and longer final frication and closure duration post-Nucleus stimulation (6 MO. NUCLEUS and 1 YEAR NUCLEUS) relative to the 3M/House and no auditory feedback conditions. Acoustic measurements after loss of auditory feedback (1 DAY FAIL and 18 DAYS FAIL) indicated a constriction of vowel space. Appropriately higher fundamental frequency for stressed than unstressed syllables, an expansion of vowel space and improvement in some aspects of production of voicing, manner and place of articulation were noted one year post-Nucleus stimulation. Loss of auditory feedback results are related to the literature on the effects of postlingual deafness on speech. Nucleus and 3M/House effects on speech are discussed in terms of speech production studies of single-electrode and multichannel patients.

Effect of compression ratio in a slow‐acting compression hearing aid: Paired‐comparison judgments of quality

Paired-comparison judgments of quality were obtained from 20 hearing-impaired listeners (half with a small dynamic range and half with a large dynamic range) for speech-in-noise (vent, apartment, and cafeteria) processed through a slow-acting compression hearing aid. Compression ratio was varied (1, 1.5, 2, 3, 5, and 10:1). Compression threshold, attack time, and release time were fixed. Sound quality judgments were significantly affected by compression ratio, noise, and dynamic range. Preference decreased with increasing compression ratio. The selection of compression ratio. The selection of compression ratios < or = 2:1 was significantly higher than of compression ratios > 3:1. Less compression (no compression or 1.5:1) was preferred with the highest level noise (cafeteria noise) than with the lower level noises (vent or apartment). In particular, the small dynamic range group preferred compression with the vent and apartment noises (noise below the compression threshold), but preferred a linear hearing aid with the cafeteria noise (above the compression threshold). The large dynamic range group showed a slightly greater preference for the linear hearing aid for all three noises.

The speech of a postlingually deafened teenager during the first year of use of a multichannel cochlear implant

The speech of a profoundly postlingually deafened teenager was recorded before, immediately after, 3 months after, and 1 year after electrical stimulation with a Nucleus multichannel cochlear implant. Listener tests of target words revealed significant improvement in overall quality over the year. Spectrograms showed less aspiration and better definition of the lower formants. Acoustic measurements indicated immediate change in F0 and gradual changes in syllable duration and some aspects of voicing and manner of articulation. Vowel space shrank steadily over the year, with both first- and second-formant frequencies dropping. Prestimulation results are discussed relative to the literature on the speech of the congenitally hearing impaired. Effects of multichannel electrical stimulation on speech are compared with studies of single-electrode stimulation.

Preferred listening levels for linear and slow-acting compression hearing aids

Objectiue The purpose of the present experiment was to determine the relationship between most comfortable listening level and preferred listening levels for linear and slow-acting compression hearing aids as a function of variations in speech and noise level. Design A digital hearing aid test system was used to simulate six hearing aids having compression ratios of 1, 1.5, 2, 3, 5, and 10:1. Speech was presented in three different noises (vent, apartment, and cafeteria), with speech input level being varied (55, 70, 85 dB SPL). Subjects were 20 listeners with sensori-neural hearing loss (half with a dynamic range 130 dB and half with a dynamic range > 30 dB). The boundaries of the most comfortable listening range were measured to estimate most comfortable listening level. Preferred listening level was measured by having subjects adjust the output of the hearing aid for satisfactory listening. Results On average, the deviation of preferred listening level from most comfortable loudness (MCL) was less than 5 dB. Dynamic range, noise type, and input level were all found to have small, but significant, effects on the deviation of preferred listening level from MCL. On average, subjects with a small dynamic range listened slightly below MCL, and subjects with a larger dynamic range listened slightly above MCL. For favorable signal-to-noise ratios, preferred listening levels were highest for high input levels and for conditions that resulted in high output levels before level adjustment. Although the pattern of average performance differed slightly at poorer signal-to-noise ratios, all preferred listening levels were close to MCL. Conclusions The gain of a slow-acting compression hearing aid should place the output within 5 dB of MCL. The output for low and medium inputs should approximate MCL and the output for high input levels should be slightly above MCL. This pattern of gain may be obtained with mild compression ratios and a gain rule that places a speech input of 70 dB at MCL.

A matched‐pairs comparison of single and multichannel cochlear implants in children

Auditory capabilities of Nucleus 22® multichannel cochlear implant users were compared to those of matched 3M/House® single‐channel users. Six children who received either the 3M/House or Nucleus 22 cochlear implants were separated into three matched pairs. Group 1 consisted of two postlinguistically deafened adolescents, group 2 consisted of two prelinguistically deafened school‐age children, and group 3 consisted of two perilinguistically deafened preschoolers.

Auditory perception changes after reimplantation in a child cochlear implant user.

The ability to remove cochlear implants from children and subsequently reimplant a more complex device in the same ear was the concern of this single case study. A postlinguistically deafened child, J.L., received a single-channel cochlear implant 1 yr after contracting meningitis and suffering a profound bilateral sensorineural hearing loss. After 3 yr of successful implant use, J.L. suffered an internal coil failure. She was then explanted and reimplanted with a multichannel cochlear implant in the same ear. This case report details her speech perception skills with her single-channel cochlear implant, a vibrotactile aid, and a multichannel cochlear implant. Results from auditory perceptual measures suggest that the explantation/reimplantation process was technically feasible with no adverse effects on J.L.s ability to utilize a more sophisticated device and to exceed her previous performance levels.

Speech changes in a postlingually deafened girl using a multichannel cochlear implant

The speech of a postlingually deafened girl previously implanted with a single electrode implant was spectrographically analyzed from recordings taken on six separate occasions; on three occasions after her single electrode implant failed (4 days post, 5 days post, 18 days post) and on three occasions after stimulation of the Nucleus multichannel implant (1 day post, 6 months post, 9 months post). Changes in acoustic measurements of vowel formants, vowel duration, voicing, manner of articulation, and place of articulation cues are discussed. Listener judgments of target words are presented. The present findings are related to previous case studies of speech changes with a multichannel cochlear implant [Tartter et al., J. Acoust. Soc. Am. 86, 2113–2121 (1989)] and single electrode stimulation [Leder et al., J. Acoust. Soc. Am. 79, 1967–1974 (1986)].