Biomedical subjects

B C Moore

Publications and source records attributed to B C Moore.

At least 109 records · Page 6Linked to original sources

PubMed1993

Audibility of partials in inharmonic complex tones.

These experiments examined the ability of musically trained subjects to hear out individual partials in complex tones with partials uniformly spaced on a scale related to the equivalent rectangular bandwidth (ERB) of the auditory filter. ERB spacings of 0.75, 1.0, 1.25, 1.5, and 2 were used, and the central component always had a frequency of 1000 Hz. All components had a level of 65 dB SPL. On each trial, subjects heard a pure tone (the "probe") followed by a complex tone. The probe was close in frequency to one of the partials in the complex, but was mistuned downward by 4.5% on half the trials (at random) and mistuned upward by 4.5% on the other half. The task of the subject was to indicate whether the probe was higher or lower in frequency than the nearest partial in the complex. The partial that was "probed" varied randomly from trial to trial. Scores for the highest and lowest components in the complexes were generally high (> 90%) for component spacings greater than 1 ERB, but worsened somewhat for ERB spacings of 0.75 and 1.0. Scores for the inner components were close to chance level at 0.75-ERB spacing, and improved progressively as the ERB spacing was increased from 1 to 2 ERBs. For ERB spacings of 1.25 or less, the scores did not change smoothly with component frequency; marked irregularities were observed, as well as systematic errors. An explanation for these is suggested in terms of irregularities in the middle ear transfer function. Performance for the inner components tended to be worse for component frequencies above 1000 Hz than below 1000 Hz. It is suggested that this happens because the pitches of partials are partly coded in the time patterns of neural impulses (phase locking), and the precision of phase locking deteriorates progressively with increasing frequency above 1000 Hz. The auditory filter shapes of the subjects were measured for a center frequency of 1000 Hz, using the notched noise method. One subject had a broader auditory filter than the other three subjects, and this same subject generally had more difficulty in hearing out partials from complex tones than the other subjects.

Acoustic Stimulation↗

PubMed1993

Modulation detection interference: some spectral effects.

Several experiments are described in which the threshold for detecting 10-Hz amplitude modulation (AM) of a 2000-Hz signal carrier was measured in the presence of a masker that consisted of one to ten carrier frequencies. The masker was either unmodulated or amplitude modulated at a depth of 0.5 and a frequency of 10 Hz. In experiment 1, threshold was measured as a function of the frequency of a single masker carrier. The patterns of the interference effect were similar whether the masker was modulated or not, suggesting that some of the interference was due to a within-channel effect (spread of excitation). In experiment 2, it was shown that a masker consisting of two carrier frequencies could produce more interference than either carrier alone. However, there was generally no additional interference when more than two carriers were presented, at least up to the ten tested here (experiments 3 and 4). In experiment 5, the masker carrier frequencies were either harmonically or nonharmonically related to the signal carrier frequency. There was little difference in the size of the interference effect between the two maskers, suggesting that harmonicity may not play an important role in modulation detection interference.

Acoustic Stimulation↗

PubMed1993

Dichotic interference effects in gap detection.

Thresholds for detecting a temporal gap in a 20-Hz-wide band of noise (the target) were measured for the target alone, and in the presence of multiple 20-Hz-wide flanking bands presented to the opposite ear. The flanking bands caused gap thresholds to increase, and this effect was greater at higher levels of the flanking bands. The impairment to gap detection was greater when the flanking bands were comodulated with the target (i.e., had the same envelope) than when they were not comodulated, except at very low and high levels of the flanking bands. A series of supplementary experiments was conducted to investigate why the difference between comodulated and noncomodulated bands was reduced at high levels. The results suggest that this was not due to inter-aural crosstalk. It may have been partly caused by: (1) a central masking effect that reduced the effective sensation level of the target band at high levels of the contralateral flanking bands; (2) reduced independence of the flanking bands owing to broadening of the auditory filters at high levels. The results are discussed in terms of perceptual grouping processes.

Acoustic Stimulation↗

PubMed1993

Comodulation masking release as a function of type of signal, gated or continuous masking, monaural or dichotic presentation of flanking bands, and center frequency.

Thresholds were measured for detecting a signal centered in a narrow-band noise (NBN) masker (on-frequency band, OFB), for the OFB alone, and with two flanking bands (FBs) added to the OFB, one centered above and one below the OFB. The FBs were either correlated with the OFB or were independent and were presented either to the same ear as the signal plus OFB (monaural condition) or to the opposite ear (dichotic condition). The OFB and FBs were either gated with the signal, or were presented continuously. Three signal types were used: a pure tone; an NBN uncorrelated with the OFB; and an NBN correlated with the OFB. The signal was centered at 0.5, 2, or 6 kHz. Comodulation masking release was estimated either as the difference between threshold with the OFB alone and with the OFB plus correlated FBs [CMR(R-C)], or as the difference between thresholds using correlated and uncorrelated FBs [CMR(U-C)]. Although there were marked individual differences, positive CMR(R-C) values were found in all conditions for all three signal types. CMR(U-C) values were often larger than those for CMR(R-C), reflecting the fact that the uncorrelated FBs tended to produce interference effects, especially for the gated maskers, and at 6 kHz. Values of CMR were larger and more consistent across subjects for continuous than for gated maskers. For continuous maskers, the values of CMR tended to be smallest for the correlated-NBN signal. Results are discussed in terms of available cues and in terms of perceptual grouping mechanisms.

Acoustic Stimulation↗

PubMed1993

Detection of temporal gaps in sinusoids: effects of frequency and level.

Thresholds for the detection of gaps in sinusoidal signals were measured as a function of frequency (100-2000 Hz) and level (25-85 dB SPL) in 11 normally hearing subjects. The sinusoids were presented in a background noise intended to mask spectral splatter associated with the gap. In a separate experiment, auditory filter shapes and detection efficiency were estimated for the same 11 subjects using the notched-noise method, at center frequencies of 100, 200, 400, and 800 Hz. Gap thresholds varied only slightly with frequency over the range 400-2000 Hz, but increased markedly at 200 and 100 Hz. At all center frequencies, gap thresholds were almost invariant with level for levels above 55 dB SPL. Gap thresholds increased at low levels, reaching values about 50% greater than their asymptotic values at a sensation level of about 20 dB. The decrease in auditory filter bandwidth with decreasing center frequency does not seem sufficient to account for the increase in gap thresholds. Also, individual gap thresholds at a given center frequency were not significantly correlated with the bandwidth of the auditory filter at that center frequency, as would be expected if the auditory filter played a role in limiting gap detection. Detection efficiency decreased with decreasing center frequency. Individual differences in detection efficiency were significantly correlated with gap thresholds. However, changes in detection efficiency with frequency do not seem to be of the right form to account for the increase in gap thresholds at low frequencies. It seems likely that there is a central sliding temporal integrator which integrates over longer times at lower center frequencies.

Acoustic Stimulation↗

PubMed1993

Simulation of the effects of loudness recruitment and threshold elevation on the intelligibility of speech in quiet and in a background of speech.

These experiments simulated the threshold elevation and loudness recruitment associated with three different types of cochlear hearing loss: Moderate flat (condition R2), severe flat (condition R3), and moderate-to-severe sloping (condition RX). This was done to allow an examination of the effects of these factors on the intelligibility of speech, in isolation from other factors that are normally associated with cochlear hearing loss, such as reduced frequency selectivity. The simulation was performed by splitting the input signal into 13 frequency bands, and processing the envelope in each band so as to create loudness sensations in a normal ear that would resemble those produced in an impaired ear with recruitment. The bands were then recombined. All tests were performed using subjects with normal hearing. For speech in quiet, simulation of hearing loss produced a reduction in the ability to understand low-level speech. However, speech at sufficiently high levels was highly intelligible in all conditions. Linear amplification according to the National Acoustic Laboratory (NAL) prescription gave high intelligibility for speech at normal conversational levels. For speech presented at a fixed input level of 65 dB SPL, against a background of a single competing talker, simulation of hearing loss produced substantial decrements in performance. The speech-to-background ratios in conditions R2 and RX had to be 11-13 dB higher than in the control condition (unprocessed stimuli) to achieve similar levels of performance. Linear amplification according to the NAL prescription improved performance markedly for the conditions simulating flat losses, but was less effective for the condition simulating a sloping loss. This indicates that threshold elevation combined with recruitment produces a loss of intelligibility for speech in the presence of a single competing talker that is only partly compensated by linear amplification of the type typically used in hearing aids.

Acoustic Stimulation↗

PubMed1993

Detection and identification of a single modulated carrier in a complex sound.

Hall and Grose [J. Acoust. Soc. Am. 90, 3028-3035 (1991)] reported that subjects had difficulty in deciding which carrier in a two-carrier complex sound was modulated. The present experiments examined how the ability to identify a single modulated carrier was affected by the number of carriers in the complex and by harmonicity. Initially, thresholds were measured for detecting amplitude modulation of a single carrier in a complex sound. Thresholds were higher when that carrier was one of the inner carriers in a six-carrier harmonic or inharmonic complex than when it formed part of a two-carrier complex. Thresholds were only slightly, if at all, higher when the modulated carrier was varied randomly from trial to trial than when its frequency was fixed within a block of trials. Next, subjects were required to decide whether the frequency of a single modulated carrier (with a suprathreshold modulation depth) in a complex sound was the same as or different from the frequency of a probe composed of a single modulated carrier. They generally performed well above chance. Performance was not greatly affected by whether the probe was presented before or after the complex, but was generally slightly better for a modulation depth of 100% than for a depth of 50%. Randomly varying the level of each carrier in the complexes from one stimulus to the next produced only a slight impairment of performance, indicating that short-term across-frequency differences in level were not used to identify the modulated carrier in experiment 2. Overall, performance was best for the six-carrier harmonic complex, less good for the six-carrier inharmonic complex, and worst for the two-carrier complex. The results are interpreted in terms of perceptual grouping.

Auditory Perception↗

PubMed1993

Effect on the speech reception threshold in noise of the recovery time of the compressor in the high-frequency channel of a two-channel aid.

This paper describes two experiments in a series evaluating and optimising a hearing aid incorporating two forms of automatic gain control (AGC). The first form is a front-end AGC which is normally slow acting and which compensates for variations in the overall level of speech from one situation to another. The second form of AGC follows the front-end AGC. The signal is split into two frequency bands, and fast-acting AGC is applied in the upper band only. The bands are then recombined. The two experiments described here were aimed at determining the optimum value of the recovery time of the AGC in the high-frequency channel. Speech reception thresholds (SRTs) were measured in the presence of speech-shaped noise as a function of the recovery time, for subjects with mild-to-moderate sensorineural loss. In the first experiment the recovery time was varied over the range 10-80 ms. SRTs tended to be lowest (best) at the shorter recovery times but the effects were small. In the second experiment, the recovery time was varied over the range 5-320 ms. In this case, there was a clear trend for SRTs to increase with increasing recovery time. A recovery time of about 20 ms appears to be optimal.

Aged↗

PubMed1993

Spectral contrast enhancement of speech in noise for listeners with sensorineural hearing impairment: effects on intelligibility, quality, and response times.

This paper describes a series of experiments evaluating the effects of digital processing of speech in noise so as to enhance spectral contrast, using subjects with cochlear hearing loss. The enhancement was carried out on a frequency scale related to the equivalent rectangular bandwidths (ERBs) of auditory filters in normally hearing subjects. The aim was to enhance major spectral prominences without enhancing fine-grain spectral features that would not be resolved by a normal ear. In experiment 1, the amount of enhancement and the bandwidth (in ERBs) of the enhancement processing were systematically varied. Large amounts of enhancement produced decreases in the intelligibility of speech in noise. Performance for moderate degrees of enhancement was generally similar to that for the control conditions, possibly because subjects did not have sufficient experience with the processed speech. In experiment 2, subjects judged the relative quality and intelligibility of speech in noise processed using a subset of the conditions of experiment 1. Generally, processing with a moderate degree of enhancement was preferred over the control condition, for both quality and intelligibility. Subjects varied in their preferences for high degrees of enhancement. Experiment 3 used a modified processing algorithm, with a moderate degree of spectral enhancement, and examined the effects of combining the enhancement with dynamic range compression. The intelligibility of speech in noise improved with practice, and, after a small amount of practice, scores for the condition combining enhancement with a moderate degree of compression were found to be significantly higher than for the control condition. Experiment 4 used a subset of conditions from experiment 3, but performance was assessed using a sentence verification test that measured both intelligibility and response times. Scores on both measures were improved by spectral enhancement, and improved still more by enhancement combined with compression. The effects were statistically more robust for the response times. When expressed as equivalent changes in speech-to-noise ratio, the improvements were about twice as large for the response times as for the intelligibility scores. The overall effect of spectral enhancement combined with compression was equivalent to an improvement of speech-to-noise ratio by 4.2 dB.

Adult↗

PubMed1992

Modulation discrimination interference and auditory grouping.

The detection of a change in the modulation pattern of a (target) carrier frequency, fc (for example a change in the depth of amplitude or frequency modulation, AM or FM) can be adversely affected by the presence of other modulated sounds (maskers) at frequencies remote from fc, an effect called modulation discrimination interference (MDI). MDI cannot be explained in terms of interaction of the sounds in the peripheral auditory system. It may result partly from a tendency for sounds which are modulated in a similar way to be perceptually 'grouped', i.e. heard as a single sound. To test this idea, MDI for the detection of a change in AM depth was measured as a function of stimulus variables known to affect perceptual grouping, namely overall duration and onset and offset asynchrony between the masking and target sounds. In parallel experiments, subjects were presented with a series of pairs of sounds, the target alone and the target with maskers, and were asked to rate how clearly the modulation of the target could be heard in the complex mixture. The results suggest that two factors contribute to MDI. One factor is difficulty in hearing a pitch corresponding to the target frequency. This factor appears to be strongly affected by perceptual grouping. Its effects can be reduced or abolished by asynchronous gating of the target and masker. The second factor is a specific difficulty in hearing the modulation of the target, or in distinguishing that modulation from the modulation of other sounds that are present. This factor has effects even under conditions promoting perceptual segregation of the target and masker.

Acoustic Stimulation↗

PubMed1992

Effects of envelope fluctuations on gap detection.

The inherent fluctuations present in narrowbands of noise may limit the ability to detect gaps in the noise; 'dips' in the noise may be confused with the gap to be detected. For subjects with cochlear hearing loss, loudness recruitment may effectively magnify the fluctuations and this could partly account for the reduced ability to detect gaps in noise bands that is usually found in subjects with cochlear hearing loss. In the present experiments we tested these ideas by processing noise bands to alter the amount of envelope fluctuation. The envelopes of the noise bands were raised to a power, N. Powers greater than 1 result in expansion of the envelope (magnified fluctuations, simulating loudness recruitment), while powers less than 1 result in compression of the envelope (decreased fluctuations). Thresholds for detecting gaps in processed noise bands centered at 1 kHz were measured as a function of noise bandwidth and of N. To prevent the detection of spectral changes introduced by the gap or by the processing, stimuli were either presented in background noise, or at a low sensation level (20 dB). Three normally hearing subjects, two subjects with unilateral cochlear hearing loss and two subjects with bilateral cochlear hearing loss were tested. Gap thresholds generally increased with increasing N. This effect was large for small noise bandwidths (50 Hz or less) and smaller for larger noise bandwidths (200 Hz or more). For both the normal and impaired ears, gap thresholds at narrow bandwidths were improved relative to those for unprocessed noise bands (N = 1) by compressing the envelope fluctuations (N < 1). The results support the idea that fluctuations in narrowband noises affect gap detection, and that loudness recruitment may adversely affect the ability to detect gaps in noise bands. They also show that compression of the fluctuations in the noise can improve gap detection.

Acoustic Stimulation↗

PubMed1992

Evaluation of a dual-channel full dynamic range compression system for people with sensorineural hearing loss.

This article describes an evaluation of an in the ear hearing aid, which applies fast-acting full dynamic range compression independently in two frequency bands. This can compensate for the loudness recruitment typically associated with sensorineural hearing loss. The crossover frequency between the two bands and the gain and compression ratio in each band are programmable to suit the individual patient. Twenty subjects with moderate sensorineural hearing loss were tested in a counterbalanced order using the aid programmed as a linear amplifier (condition L) and as a two-band compressor (condition C). All subjects were fitted binaurally. Subjects were also tested without hearing aids (condition U) and using the hearing aids that they normally wore (condition Own). Speech intelligibility was measured in quiet at three sound levels (50, 65, and 80 dB SPL), and speech reception thresholds (SRTs) in 12-talker babble were measured under monaurally and binaurally aided conditions, with the speech and babble both coincident and spatially separated. In condition C, speech intelligibility in quiet was high at all sound levels. Speech intelligibility at the two lower levels decreased in condition L, and decreased still further in conditions Own and U. Condition C gave, on average, better speech intelligibility in babble (lower SRTs) than conditions L, Own, or U. The advantage of condition C over condition L varied across subjects and was correlated with the dynamic range for tones at high frequencies; small dynamic ranges were associated with greater benefit from compression. A significant advantage for binaural aiding was found both when the speech and noise were spatially separated and when they were coincident. The binaural advantage was similar for the C and L conditions, indicating that the independent compression at the two ears did not adversely affect the use of binaural cues. Questionnaires on the subjects' experiences with the aids in everyday life indicated that they generally preferred condition C over condition L.

Adult↗

PubMed1992

Auditory filter shapes at low center frequencies in young and elderly hearing-impaired subjects.

Auditory filter shapes were measured for two groups of hearing-impaired subjects, young and elderly, matched for audiometric loss, for center frequencies (fc) of 100, 200, 400, and 800 Hz using a modified notched-noise method [B. R. Glasberg and B. C. J. Moore, Hear. Res. 47, 103-138 (1990)]. Two noise bands, each 0.4fc wide, were used; they were placed both symmetrically and asymmetrically about the signal frequency to allow the measurement of filter asymmetry. The overall noise level was either 77 or 87 dB SPL. Stimuli were delivered monaurally using Sennheiser HD424 earphones. Although auditory filters for the hearing-impaired subjects were generally broader than for normally hearing subjects [Moore et al., J. Acoust. Soc. Am. 87, 132-140 (1990)], some hearing-impaired subjects with mild losses had normal filters. The filters tended to broaden with increasing hearing loss. There were not any clear differences in filter characteristics between young and elderly hearing-impaired subjects. The signal-to-noise ratios at the outputs of the auditory filters required for threshold (K) tended to be lower than normal for the young hearing-impaired subjects, but were not significantly different from normal for the elderly hearing-impaired subjects. The lower K values for the young hearing-impaired subjects may occur because broadened auditory filters reduce the deleterious effects on signal detection of fluctuations in the noise.

Adult↗

PubMed1992

Evaluation of a method of simulating reduced frequency selectivity.

The accuracy of a method of simulating reduced frequency selectivity by the spectral smearing of complex stimuli has been evaluated. First an excitation pattern that would be evoked by a given nonsmeared stimulus in an impaired ear with broad auditory filters was estimated. Then the spectral smearing of the stimulus that would be necessary to create the same excitation pattern in a normal ear was calculated. The smearing was based on the shapes of simulated broad auditory filters; both symmetric and asymmetric broad filters were simulated. The method was used to process notched noise, and tones in notched noise, and the processed stimuli were used in a series of experiments with normally hearing subjects measuring the threshold for the tone in notched noise. The resulting data were used to derive auditory filter shapes. The derived filter shapes were generally similar to the expected shapes (based on the type of spectral smearing used), but there were some systematic discrepancies and some individual differences. The discrepancies do not seem to be due to the use of information derived from phase locking, since they were observed both at 1 kHz (where phase locking occurs) and at 6 kHz (where phase locking probably does not occurs). The discrepancies also do not seem to be due to the transmission characteristics of the outer/middle ear, since they occurred both when these characteristics were taken into account in the fitting procedure, and when the stimuli were preshaped to compensate for these characteristics. The influence of the subjects' own auditory filters probably can explain some of the discrepancies; the excitation pattern evoked by the spectrally smeared stimuli can be significantly influenced by the subjects' own filters when those filters are not much sharper than the simulated filters used to produce the smeared stimuli. Finally, some of the discrepancies can probably be explained by subjects combining information across auditory filters, rather than just using the single 'best' filter in each condition; this represents a limitation of the fitting procedure rather than of the simulation itself. Overall, the simulation worked reasonably well, especially when the smearing was based on symmetric filters.

Attention↗

PubMed1992

Accuracy of pitch matching for pure tones and for complex tones with overlapping or nonoverlapping harmonics.

The discrimination of the fundamental frequency (fo) of pairs of complex tones with no common harmonics is worse than the discrimination of fo for tones with all harmonics in common. These experiments were conducted to assess whether this effect is a result of pitch shifts between pairs of tones without common harmonics or whether it reflects influences of spectral differences (timbre) on the accuracy of pitch perception. In experiment 1, pitch matches were obtained between sounds drawn from the following types: (1) pure tones (P) with frequencies 100, 200, or 400 Hz; (2) a multiple-component complex tone, designated A, with harmonics 3, 4, 8, 9, 10, 14, 15, and fo = 100, 200, or 400 Hz; (3) A multiple-component complex tone, designated B, with harmonics 5, 6, 7, 11, 12, 13, 16, and with fo = 100, 200 or 400 Hz. The following matches were made; A vs A, B vs B, A vs P, B vs P and P vs P. Pitch shifts were found between the pure tones and the complex tones (A vs P and B vs P), but not between the A and B tones (A vs B). However, the variability of the A vs B matches was significantly greater than that of the A vs A or B vs B matches. Also, the variability of the A vs P and B vs P matches was greater than that for the A vs B matches. In a second experiment, frequency difference limens (DLCs) were measured for the A vs A, B vs B, and A vs B pairs of sounds. The DLCs were larger for the A vs B pair than for A vs A or B vs B. The results suggest that the poor frequency discrimination of tones with no common harmonics does not result from pitch shifts between the tones. Rather, it seems that spectral differences between tones interfere with judgements of their relative pitch.

Adult↗

PubMed1992

Pitch discrimination and phase sensitivity in young and elderly subjects and its relationship to frequency selectivity.

Frequency difference limens for pure tones (DLFs) and for complex tones (DLCs) were measured for four groups of subjects: young normal hearing, young hearing impaired, elderly with near-normal hearing, and elderly hearing impaired. The auditory filters of the subjects had been measured in earlier experiments using the notched-noise method, for center frequencies (fc) of 100, 200, 400, and 800 Hz. The DLFs for both impaired groups were higher than for the young normal group at all fc's (50-4000 Hz). The DLFs at a given fc were generally only weakly correlated with the sharpness of the auditory filter at that fc, and some subjects with broad filters had near-normal DLFs at low frequencies. Some subjects in the elderly normal group had very large DLFs at low frequencies in spite of near-normal auditory filters. These results suggest a partial dissociation of frequency selectivity and frequency discrimination of pure tones. The DLCs for the two impaired groups were higher than those for the young normal group at all fundamental frequencies (fo) tested (50, 100, 200, and 400 Hz); the DLCs for the elderly normal group were intermediate. At fo = 50 Hz, DLCs for a complex tone containing only low harmonics (1-5) were markedly higher than for complex tones containing higher harmonics, for all subject groups, suggesting that pitch was conveyed largely by the higher, unresolved harmonics. For the elderly impaired group, and some subjects in the elderly normal group, DLCs were larger for a complex tone with lower harmonics (1-12) than for tones without lower harmonics (4-12 and 6-12) for fo's up to 200 Hz. Some elderly normal subjects had markedly larger-than-normal DLCs in spite of near-normal auditory filters. The DLCs tended to be larger for complexes with components added in alternating sine/cosine phase than for complexes with components added in cosine phase. Phase effects were significant for all groups, but were small for the young normal group. The results are not consistent with place-based models of the pitch perception of complex tones; rather, they suggest that pitch is at least partly determined by temporal mechanisms.

Adult↗

PubMed1992

Speech pattern hearing aids for the profoundly hearing impaired: speech perception and auditory abilities.

A family of prototype speech pattern hearing aids for the profoundly hearing impaired has been compared to amplification. These aids are designed to extract acoustic speech patterns that convey essential phonetic contrasts, and to match this information to residual receptive abilities. In the first study, the presentation of voice fundamental frequency information from a wearable SiVo (sinusoidal voice) aid was compared to amplification in 11 profoundly deafened adults. Intonation reception was often better, and never worse, with fundamental frequency information. Four subjects scored more highly in audio-visual consonant identification with fundamental frequency information, five performed better with amplified speech, and two performed similarly under these two conditions. Five of the 11 subjects continued use of the SiVo aid after the tests were complete. A second study examined a laboratory prototype compound speech pattern aid, which encoded voice fundamental frequency, amplitude envelope, and the presence of voiceless excitation. In five profoundly deafened adults, performance was better in consonant identification when additional speech patterns were present than with fundamental frequency alone; the main advantage was derived from amplitude information. In both consonant identification and connected discourse tracking, performance with appropriately matched compound speech pattern signals was better than with amplified speech in three subjects, and similar to performance with amplified speech in the other two. In nine subjects, frequency discrimination, gap detection, and frequency selectivity were measured, and were compared to speech receptive abilities with both amplification and fundamental frequency presentation. The subjects who showed the greatest advantage from fundamental frequency presentation showed the greatest average hearing losses, and the least degree of frequency selectivity. Compound speech pattern aids appear to be more effective for some profoundly hearing-impaired listeners than conventional amplifying aids, and may be a valuable alternative to cochlear implants.

Adult↗

PubMed1992

Consonant recognition by some of the better cochlear-implant patients.

Fifty-four of the better cochlear-implant patients from Europe and the United States were tested on two consonant recognition tests using nonsense syllables. One was produced in an accent appropriate for their own language by a male and a female talker. Recorded tokens of /ibi, idi, igi, ipi, iti, iki, ifi, ivi, ifi, isi, izi, imi, ini/ were presented. With the French syllables, six patients with the Chorimac device averaged 18% correct (6%-29%). With the German syllables, nine patients with the 3M/Vienna device averaged 34% correct (17%-44%), ten patients with the Nucleus device (tested in Hannover) averaged 31% correct (19%-42%), and ten patients with the Duren/Cologne device averaged 27% correct (10%-56%). With the English syllables, ten patients with the Nucleus device (tested in the United States) averaged 42% correct (29%-62%), and nine patients with the Symbion device averaged 46% correct (31%-69%). An information-transmission analysis and sequential information-transfer analysis of the confusions suggested that different implants provided differing amounts of feature information. The place of articulation feature was typically the most difficult to code for all implants. In the second test a male and a female talker recorded the stimuli /ibi, idi, igi, imi, ini, ifi, isi, izi/ in a single manner that was appropriate for all three languages. Six patients with the Chorimac device averaged 27% (13%-48%), ten patients with the Duren/Cologne implant averaged 29% (15%-75%), ten patients with the Nucleus device (tested in Hannover) averaged 40% (25%-58%), ten patients with the Nucleus device (tested in the United States) averaged 49% (40%-60%), nine patients with the Symbion device averaged 61% (40%-75%), and nine patients with the 3M/Vienna device averaged 41% (29%-52%) correct.

Cochlear Implants↗