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PubMedDate not supplied

Effect of time scale modification of speech on the speech recognition threshold in noise for elderly listeners.

The effect of time scale modification of speech on the speech recognition threshold in noise (SRTN) was investigated for a group of 44 elderly subjects, varying in age from 56 to 88 years with sloping mild-to-moderate sensorineural hearing losses. Subjects' pure-tone average thresholds at 500, 1,000 and 2,000 Hz (PTA1) ranged from 3 to 58 dB. The study confirms the well-known fact that speech recognition in noise deteriorates with increasing age. Furthermore, time-compressing speech results in an even greater influence of age on the SRTN. The apparent age effect on SRTN values referenced to SRTN in the control condition is mostly caused indirectly by the significant correlation between age and PTA1, although there was a slight tendency for age to have a greater independent effect on relative SRTN values when the amount of time compression increased. The percentage of explained variance in relative SRTN values by the subject variables in this study was limited, indicating that there are other factors not investigated in this study (e.g. cochlear mechanisms, short-term memory, feature extractors) that significantly influence the effect of time compression on SRTN.

Age Factors↗
PubMedDate not supplied

Objective evaluation of vowel identification with the Digisonic cochlear implant.

Perceptual assessment of speech recognition performance with cochlear implants is confronted with problems raised by patients' availability and specificity. These problems can be avoided by using objective evaluation methods based on automatic classification of speech sounds. In the present report, different tuning strategies for the Digisonic cochlear implant were evaluated by discriminant analysis. The results presented here concern the correct classification of vowels. A set of 600 vocalic items, corresponding to 10 vowel categories and produced by 20 French speakers, were processed by the Digisonic DX10 with two different strategies. In the linear strategy, center frequencies of the 15 Digisonic channels were almost equally spaced in acoustic units (Hz). In the mel strategy, center frequencies were almost equally spaced in psychoacoustic units. For each strategy, energy levels of the frequency channels were quantified for each vocalic item and processed by statistical discriminant analysis for classification into 10 vowel categories. Results mainly show that the percent correct classification (PCC) is larger for the mel strategy and that the improvement is due to a higher concentration of frequency channels below 4 kHz. Implications of these results for the tuning of cochlear implants are discussed.

Adult↗
PubMedDate not supplied

Audiovisual speech reception in noise and self-perceived hearing disability in sensorineural hearing loss.

Multiple regression analyses were performed on a corpus of data from 56 sensorineurally hearing-impaired subjects. In addition to tonal thresholds, the corpus included simple, quantitative self-ratings for disability and results from speech reception tasks in auditory-only, audiovisual, quiet and noisy conditions. The aim was to evaluate to what extent the predictive power of disability formulas based on the audiogram can be enhanced, when measures derived from speech reception tasks are added to tonal thresholds as supplementary predictors. The better-ear speech reception threshold proved to be a strong exclusive predictor: if speech reception thresholds were introduced into the prediction, the contribution of better-ear pure-tone averages became redundant. Speechreading ability always significantly enhanced the prediction's accuracy. Tonal thresholds or speech reception data combined with lipreading ability scores can explain considerable amounts (42 per cent and 54 per cent, respectively) of the variance in disability ratings. The conclusion is that auditory-only, audiogram-based prediction schemes must not be abandoned, but can be tailored to individuals on the basis of realistic audiovisual speech reception performance.

Adult↗
PubMedDate not supplied

Assessing aspects of auditory handicap by means of pupil dilatation.

The demand on extra effort and concentration during listening are notorious handicapping effects of hearing impairment as is shown by self-assessment studies. In an attempt to explore new ways of assessing hearing handicap, the present study focuses on an objective measure of mental effort during listening. Pupil dilatation is used as the index of mental effort. Results for 14 hearing-impaired and 14 normal hearing listeners show a relation between pupil dilatation and difficulty in speech reception in noise, as manipulated by the speech-to-noise ratio. In addition the study shows that, with regard to effort and concentration, hearing-impaired subjects benefit less than normals from easier listening situations (e.g. at 5 dB above the individual speech-reception threshold). The results show a significant correlation between self-rated handicap and pupil dilatation.

Adult↗
PubMedDate not supplied

Audio-visual perception of compressed speech by profoundly hearing-impaired subjects.

For many people with profound hearing loss conventional hearing aids give only little support in speechreading. This study aims at optimizing the presentation of speech signals in the severely reduced dynamic range of the profoundly hearing impaired by means of multichannel compression and multichannel amplification. The speech signal in each of six 1-octave channels (125-4000 Hz) was compressed instantaneously, using compression ratios of 1, 2, 3, or 5, and a compression threshold of 35 dB below peak level. A total of eight conditions were composed in which the compression ratio varied per channel. Sentences were presented audio-visually to 16 profoundly hearing-impaired subjects and syllable intelligibility was measured. Results show that all auditory signals are valuable supplements to speechreading. No clear overall preference is found for any of the compression conditions, but relatively high compression ratios (> 3-5) have a significantly detrimental effect. Inspection of the individual results reveals that compression may be beneficial for one subject.

Adolescent↗
PubMedDate not supplied

Speech audiometry in noise-exposed workers: the SRT-PTA relationship revisited.

The speech recognition threshold (SRT) is believed to be related primarily to the pure-tone average (PTA) and the steepness of the hearing loss. However, there are indications that it may also be influenced by perceptual or cognitive-linguistic factors, or both, such as meaningfulness of the speech stimuli. The purpose of the present study was to ascertain the correspondence between SRT and PTA in noise-exposed workers with various degrees of speech recognition threshold shift in noise. To this end, a total of 807 SRTs and PTAs collected from fluent speakers of Quebec French noise-exposed workers were compared. Measurements of context effects on speech recognition were taken based on a general hypothesis that they should be facilitating phoneme or word restoration in conditions of high stimulus uncertainty as present in SRT assessment, thus acting to confound the SRT PTA relationship. Using principal components analysis, we found a significant effect not only of low-frequency hearing sensitivity but language context effects on SRT. After a correction was introduced to partial out these linguistic context effects, correlations between SRT and PTA increased but they were lower than predicted. In a related treatment analysis, we found a large number of observations (230 out of 807) where SRTs were more sensitive than PTAs by a factor of 8 to 16 dB. This was the case even though correlations between the two measurements were within the range commonly advocated in the field of clinical audiology (0.85-0.95). This was interpreted as a sign of phonological and lexical context effects on the speech recognition task actually used by individual subjects to facilitate speech understanding, to the point perhaps of making it as simple as the detection of pure tones.

Adult↗
PubMed1984

Signal-to-noise threshold with and without hearing aid.

We determined the necessary signal-to-noise threshold for 50% sentence discrimination in 130 patients with sensorineural hearing disorders with and without a hearing aid, as well as the minimum monosyllable discrimination loss without hearing aid. A significant correlation coefficient was found to exist of the signal-to-noise threshold with vs. that without hearing aid (r = 0.61), and between the minimum discrimination loss and the signal-to-noise threshold with hearing aid (r = 0.38). These differences in the correlation coefficient indicate that the impairment of speech perception in noise when using a hearing aid is obviously due to the deterioration of the signal-to-noise threshold induced by the hearing loss rather than to the discrimination loss per se.

Adult↗
PubMed1986

The benefit of hearing aids: influence of hearing loss and age.

The relation between accessible benefit and hearing loss in combination with age of the patient is analysed. The degree of hearing loss and improvement derived by hearing aid use as found in this work is based on the individually determined speech reception threshold (SRT) for the condition with and without hearing aid in a noiseless environment. It was found that a significant correlation exists between hearing loss and SRT gain by the hearing aid (difference between unaided and aided speech reception threshold) for a pure-tone hearing loss of less than 40 dB at 500 Hz, irrespective of age, whereas for a hearing impairment of 40-60 dB, the gain by using the hearing aid is dependent on the age of the patient. A multiple regression analysis was performed to study the relation between benefit and hearing loss for the two groups of hearing impairment and different age groups.

Age Factors↗
PubMed1987

Speech understanding and directional hearing for hearing-impaired subjects with in-the-ear and behind-the-ear hearing aids.

With respect to acoustical properties, in-the-ear (ITE) aids should give better understanding and directional hearing than behind-the-ear (BTE) aids. Also hearing-impaired subjects often prefer ITEs. A study was performed to assess objectively the improvement in speech understanding and directional hearing afforded by ITE aids versus BTEs. In 28 hearing-impaired subjects, who visited our Centre for a check-up of their ITEs, the following parameters were measured: (a) thresholds for third-octave bandpass noises between 0.25 and 4 kHz, (b) speech reception thresholds for short Dutch sentences in quiet and with background noise, (c) directional hearing. All three experiments were done binaurally with the subjects wearing their ITEs, BTEs, and no hearing aid. With the 2-cc coupler, the gain used by the subject was measured. The SRT values for the ITE were significantly lower than those for BTE. More gain at 2 and 4 kHz in the ITE proved to be a responsible factor for this improvement. Directional hearing was not improved by wearing an ITE. Large interindividual differences were found between functional gain and the 2-cc coupler measurements. The mean functional gain at 4 kHz for an ITE is higher than the gain measured in a 2-cc coupler. For a BTE, the functional gain at 2 and 4 kHz is lower than the 2-cc coupler gain.

Adult↗
PubMed1990

Harmonic distortion measurements in clinical hearing and fitting. Preliminary report.

Measurement of the distortion from hearing aids and its influence on their fitting has become practicable with the implementation of real ear measurement in the audiological clinic. Thus the harmonic distortion measured in the ear fitted with the hearing aid can be measured by means of a probe in the ear canal. The objective of the present investigation was to examine the value of harmonic distortion measurements in the fitting of hearing aids within a clinical setting. The material comprised 101 consecutive patients who had been prescribed different types of hearing aids based on the POGO formula, using insertion gain measurements. 160 hearing aids were fitted and with the fitting strategy used, a distortion less than 10% was indicated in 122 fittings (76%), a distortion between 10 and 20% in 30 fittings (19%) and finally a distortion greater than 20% in 8 fittings (5%). In the cases with the distortion greater than 10%, the hearing aid setting was maintained and the magnitude of the harmonic distortion was controlled with a 2-cc coupler. At the hearing aid fitting, the audiology technician can listen to the signal at the patient's drum and thus may hear distortion products. The relationship between the 'distortion' heard by the audiology technician and the 'distortion' heard by the patient was fairly good. Based on these preliminary findings it is concluded that harmonic distortion measurements may prove useful in the hearing aid fitting procedure.

Adolescent↗
PubMed1996

Transient-evoked otoacoustic emissions. Helpful tool in the detection of pseudohypacusis.

The object of the present study was to demonstrate the use of TEOAEs for diagnosing pseudohypacusis. Thirty-four patients were investigated for suspected pseudohypacusis based on the case history and clinical and audiological findings. TEOAEs confirmed the diagnosis in all cases except four patients with a pre-existing organic hearing loss exceeding 25-30 dB HL. All the remaining 30 patients showed normal TEOAE responses except four of the ears in which final assessment revealed hearing threshold lower than 30 dB in the middle frequency region. The method can be time-saving when performed at the first consultation. With its element of surprise, the patient can be confronted with the existence of a functional hearing loss. This frequently results in marked threshold improvement on repeat pure-tone audiometry.

Acoustic Stimulation↗
PubMed2000

Comparison of the NAL(R) and Cambridge formulae for the fitting of linear hearing aids.

This paper describes a laboratory-based comparison of the effectiveness of two formulae for fitting linear hearing aids, the NAL(R) formula and the Cambridge formula. The formulae prescribe the desired insertion gain as a function of frequency, based on the audiometric threshold. The two formulae have a similar rationale; both are based on the goal that, for speech with a moderate level, all frequency bands should be equally loud (equal loudness per critical band) over the frequency range important for speech (400-5000 Hz), and the overall loudness should be comfortable. However, the formulae differ; generally the Cambridge formula leads to slightly more high-frequency gain (above 2 kHz) and slightly less mid-frequency gain (between 500 Hz and 2000 Hz) than the NAL(R) formula. The two formulae were implemented using an experimental digital hearing aid whose frequency-gain characteristic could be controlled very precisely. A loudness model (Moore and Glasberg, 1997) was used to adjust the overall gains for each subject and each formula so that a speech-shaped noise with an overall level of 65 dB SPL would give the same loudness as for a normally hearing person (according to the model). The adjustments were, on average, smaller for the Cambridge than for the NAL(R) formula. A condition was also used with all insertion gains set to zero, simulating unaided listening. Evaluation was based on: (1) subjective ratings of the loudness, intelligibility and quality of continuous discourse presented in quiet at levels of 45, 55, 65 and 75 dB SPL and in babble at an 0-dB speech-to-babble ratio, using speech levels of 55, 65 and 75 dB SPL; (2) measures of the speech reception threshold (SRT) in background noise for two noise levels (65 and 75 dB SPL) and four types of background noise. Neither the subjective ratings nor the measures of the SRTs revealed any consistent difference between the results obtained using the two formulae, although both formulae led to lower (better) SRTs than for simulated unaided listening. It is concluded that the differences between the NAL(R) formula and the Cambridge formula are too small to have measurable effects, at least in a laboratory setting.

Aged↗
PubMed1981

Some effects of training and experience for children using one and two hearing aids.

In order to determine whether increased binaural advantages accompany experience with binaural inputs, this study: (a) compared the pattern of performance in selective listening between normally-hearing and monaurally-issued hearing-impaired subjects; (b) examined the effects of training with one and two hearing aids on the speech intelligibility of hearing-impaired children, and (c) examined the effects of children's past experience with two hearing aids on selective listening performance. Results showed (i) differences in patterns of selective listening between normal and hearing-impaired subjects; (ii) training in the binaural mode to offer more scope for improvement than training in the monaural mode; (iii) no clear indication that past experience with two hearing aids automatically leads to marked binaural gains. The implications of these results are discussed with reference to fitting binaural hearing aids.

Adolescent↗
PubMed1981

Pure tone audiograms from hearing-impaired children. II. Predicting speech-hearing from the audiogram.

Pure tone audiograms and speech audiograms using sentence lists were obtained from 150 8-16-year-old children with pure tone hearing losses ranging from mild to severe. Most of the hearing impairments were cochlear in origin. Three 'speech-hearing' measures were selected from the speech audiograms, and it was shown that the correlation coefficients between two of these and the pure tone hearing thresholds were roughly in agreement with figures from previous studies of adults = 0.882 for Speech Reception Threshold and 0.533 for Discrimination Score. In addition, a correlation of 0.329 was found between the slope of the speech audiogram and pure tone thresholds. The strength of different summaries of the pure tone audiogram for predicting the various speech-hearing measures were compared. It was found that although the traditional summaries did quite well, their relative strengths varied according to the speech-hearing measure under consideration. The best summary predictors for all the speech-hearing measures were, either alone or in combination, two indices which have been proposed recently by the present authors, and which measure both the degree of pure tone hearing loss and the slope of the pure tone audiogram. However, the gains in predictive strength achieved with these indices were small.

Adolescent↗
PubMed1988

A comparison of four methods of implementing automatic gain control (AGC) in hearing aids.

Hearing impairment of cochlear origin is usually associated with loudness recruitment. As a consequence, the dynamic range between threshold and the highest comfortable level is smaller than normal. To ensure that low-level sounds can be heard, while avoiding discomfort at high levels, a hearing aid with automatic gain control (AGC) is required. This paper compares four different systems for implementing AGC, and compares each of them with unaided listening and with linear amplification. The systems were evaluated by measuring thresholds for understanding speech in quiet and in five types of background sound: speech-shaped noise, 12-talker babble, cafeteria noise, traffic noise and a single competing speaker. The first system used a new dual-action AGC (called dual front-end AGC) operating on the whole speech signal. A slow-acting control voltage (recovery time 5 s) held the average level of speech at the output constant, regardless of the input level. In response to sudden intense transients, a fast-acting control voltage (recovery time 150 ms) reduced the gain rapidly and then returned the gain to the value set by the slow-acting component. In the second system, referred to as the mark II aid, the output of the dual front-end AGC was split into two frequency bands, and fast-acting (syllabic) compression was applied in the high-frequency band only. The bands were then recombined. The third system resembled the mark II aid except that fast-acting compression was applied in both bands. The fourth system resembled the 2-channel aid evaluated in previous trials (Moore, 1987). It was similar to the third system, but had only single-action front-end AGC with a recovery time of 400 ms. Six subjects with moderate sensorineural hearing loss accompanied by recruitment were used. Best results overall were obtained using the mark II aid. Speech reception thresholds (SRTs) in noise were, on average, 4 dB better than for linear amplification and 2.4 dB lower than for the previous 2-channel aid. There was a significant advantage of having fast-acting AGC in the high-frequency band, but no advantage of having AGC in the low-frequency band.

Acoustics↗
PubMed1997

Effects of fast-acting high-frequency compression on the intelligibility of speech in steady and fluctuating background sounds.

This study examines whether speech intelligibility in background sounds can be improved for persons with loudness recruitment by the use of fast-acting compression applied at high frequencies, when the overall level of the sounds is held constant by means of a slow-acting automatic gain control (AGC) system and when appropriate frequency-response shaping is applied. Two types of fast-acting compression were used in the high-frequency channel of a two-channel system: a compression limiter with a 10:1 compression ratio and with a compression threshold about 9 dB below the peak level of the signal in the high-frequency channel; and a wide dynamic range compressor with a 2:1 compression ratio and with the compression threshold about 24 dB below the peak level of the signal in the high-frequency channel. A condition with linear processing in the high-frequency channel was also used. Speech reception thresholds (SRTs) were measured for two background sounds: a steady speech-shaped noise and a single male talker. All subjects had moderate-to-severe sensorineural hearing loss. Three different types of speech material were used: the adaptive sentence lists (ASL), the Bamford-Kowal-Bench (BKB) sentence lists and the Boothroyd word lists. For the steady background noise, the compression generally led to poorer performance than for the linear condition, although the deleterious effect was only significant for the 10:1 compression ratio. For the background of a single talker, the compression had no significant effect except for the ASL sentences, where the 10:1 compression gave significantly better performance than the linear condition. Overall, the results did not show any clear benefits of the fast-acting compression, possibly because the slow-acting AGC allowed the use of gains in the linear condition that were markedly higher than would normally be used with linear hearing aids.

Adult↗