Speech Intelligibility In Quiet Research Articles

Adaptation of the HINT (hearing in noise test) for adult Canadian Francophone populations

The HINT provides an efficient and reliable method of assessing speech intelligibility in quiet and in noise by using an adaptive strategy to measure speech reception thresholds for sentences, thus avoiding ceiling and floor effects that plague traditional measures performed at fixed presentation levels. A strong need for such a test within the Canadian Francophone population, led us to develop a French version of the HINT. Here we describe the development of this test. The Canadian French version is composed of 240-recorded sentences, equated for intelligibility, and cast into 12 phonemically balanced 20-sentence lists. Average headphone SRTs, measured with 36 adult Canadian Francophone native speakers with normal hearing, were 16.4 dBA in quiet, −3.0 dBA SNR in a 65 dBA noise front condition and −11.4 dBA SNR in a 65 dBA noise side condition. Reliability was established by means of within-subjects standard deviation of repeated SRT measurements over different lists and yielded values of 2.2 and 1.1 dB for the quiet and noise conditions, respectively.

Bilateral cochlear implants in children

This study investigated the extent to which 9 months of listening with bilateral cochlear implants (CIs) improves the ability of children to hear speech in noise and to localize sounds. Three children ages 8–12 who received sequential bilateral CIs, 3–8 years apart, participated in a series of binaural tasks at 3 and 9 months after activation of the second CI. Each child participated in a battery of tests under unilateral and bilateral conditions. Results suggest that speech intelligibility in noise improves with added bilateral experience, but that speech intelligibility in quiet does not. In addition, the improvement was seen primarily for the two younger children, who had received the second CI at the age of 8, but not for the older child whose second CI was received at the age of 12. None of the children were able to localize sounds well at 3 or 9 months after receiving the second CI. Further research is necessary to establish the importance of age of implantation and duration of bilateral experience necessary in order for maximal performance to be achieved.

Effects of reverberation on perceptual segregation of competing voices.

Two experiments investigated the effect of reverberation on listeners' ability to perceptually segregate two competing voices. Culling et al. [Speech Commun. 14, 71-96 (1994)] found that for competing synthetic vowels, masked identification thresholds were increased by reverberation only when combined with modulation of fundamental frequency (F0). The present investigation extended this finding to running speech. Speech reception thresholds (SRTs) were measured for a male voice against a single interfering female voice within a virtual room with controlled reverberation. The two voices were either (1) co-located in virtual space at 0 degrees azimuth or (2) separately located at +/-60 degrees azimuth. In experiment 1, target and interfering voices were either normally intonated or resynthesized with a fixed F0. In anechoic conditions, SRTs were lower for normally intonated and for spatially separated sources, while, in reverberant conditions, the SRTs were all the same. In experiment 2, additional conditions employed inverted F0 contours. Inverted F0 contours yielded higher SRTs in all conditions, regardless of reverberation. The results suggest that reverberation can seriously impair listeners' ability to exploit differences in F0 and spatial location between competing voices. The levels of reverberation employed had no effect on speech intelligibility in quiet.

Cochlear-implant simulations of speech in complex acoustic backgrounds

Cochlear-implant simulations have shown that good speech intelligibility in quiet can be obtained with very poor spectral resolution and no temporal fine-structure information. It is not known how robust speech is to such processing in the presence of complex interfering sounds. This study examined speech reception for sentences in the presence of four types of interference (broadband noise, broadband noise modulated with a speech envelope, a single male talker, and a single female talker) and three processing schemes (24- and 8-channel cochlear-implant simulations and unprocessed). The spectral resolution in the 24-channel condition was designed to be comparable to that of normal hearing, but the original temporal fine structure was replaced by noise in both the 24- and 8-channel processing conditions. Performance with 24-channel processing was substantially poorer than in unprocessed conditions, despite the relatively good frequency resolution. Eight-channel processing produced the poorest performance. Stimulus processing was generally more detrimental to speech reception in the fluctuating interferers than in the unmodulated noise. The detrimental effects of eliminating fine-structure information may be due to the reduction in pitch cues, which listeners may use to help segregate the sources. [Work supported by NIDCD Grant R01DC05216.]

Should children who use cochlear implants wear hearing aids in the opposite ear?

The aim of this study was to investigate 1) whether a hearing aid needs to be adjusted differently depending on whether a child wears a cochlear implant or another hearing aid in the contralateral ear; 2) whether the use of a hearing aid and a cochlear implant in opposite ears leads to binaural interference; and 3) whether the use of a hearing aid and a cochlear implant in opposite ears leads to binaural benefits in speech perception, localization, and communicative functioning in real life. Sixteen children participated in this study. All children used a Nucleus 22 or Nucleus 24 cochlear implant system programmed with the SPEAK strategy in one ear. The hearing aid amplification requirements in the nonimplanted ear of these children were determined using two procedures. A paired comparison technique was used to identify the frequency response that was best for speech intelligibility in quiet, and a loudness balancing technique was used to match the loudness of speech in the ear with a hearing aid to that with a cochlear implant. Eleven of the 16 children participated in the investigation of binaural effects. Performance in speech perception, localization, and communicative functioning was assessed under four aided conditions: cochlear implant with hearing aid as worn, cochlear implant alone, hearing aid alone, and cochlear implant with hearing aid adjusted according to individual requirements. Fifteen of the 16 children whose amplification requirements were determined preferred a hearing aid frequency response that was within +/-6 dB/octave of the NAL-RP prescription. On average, the children required 6 dB more gain than prescribed to balance the loudness of the implanted ear for a speech signal presented at 65 dB SPL. For all 11 children whose performance was evaluated for investigating binaural effects, there was no indication of significantly poorer performance under bilaterally aided conditions compared with unilaterally aided conditions. On average, there were significant benefits in speech perception, localization, and aural/oral function when the children used cochlear implants with adjusted hearing aids than when they used cochlear implants alone. All individuals showed benefits in at least one of the measures. Hearing aids for children who also use cochlear implants can be selected using the NAL-RP prescription. Adjustment of hearing aid gain to match loudness in the implanted ear can facilitate integration of signals from both ears, leading to better speech perception. Given that there are binaural advantages from using cochlear implants with hearing aids in opposite ears, clinicians should advise parents and other professionals about these potential advantages, and facilitate bilateral amplification by adjusting hearing aids after stable cochlear implant MAPs are established.

Effects of low-pass filtering on the intelligibility of speech in quiet for people with and without dead regions at high frequencies.

A dead region is a region of the cochlea where there are no functioning inner hair cells (IHCs) and/or neurons; it can be characterized in terms of the characteristic frequencies of the IHCs bordering that region. We examined the effect of high-frequency amplification on speech perception for subjects with high-frequency hearing loss with and without dead regions. The limits of any dead regions were defined by measuring psychophysical tuning curves and were confirmed using the TEN test described in Moore et al. [Br. J. Audiol. 34, 205-224 (2000)]. The speech stimuli were vowel-consonant-vowel (VCV) nonsense syllables, using one of three vowels (/i/, /a/, and /u/) and 21 different consonants. In a baseline condition, subjects were tested using broadband stimuli with a nominal input level of 65 dB SPL. Prior to presentation via Sennheiser HD580 earphones, the stimuli were subjected to the frequency-gain characteristic prescribed by the "Cambridge" formula, which is intended to give speech at 65 dB SPL the same overall loudness as for a normal listener, and to make the average loudness of the speech the same for each critical band over the frequency range important for speech intelligibility (in a listener without a dead region). The stimuli for all other conditions were initially subjected to this same frequency-gain characteristic. Then, the speech was low-pass filtered with various cutoff frequencies. For subjects without dead regions, performance generally improved progressively with increasing cutoff frequency. This indicates that they benefited from high-frequency information. For subjects with dead regions, two patterns of performance were observed. For most subjects, performance improved with increasing cutoff frequency until the cutoff frequency was somewhat above the estimated edge frequency of the dead region, but hardly changed with further increases. For a few subjects, performance initially improved with increasing cutoff frequency and then worsened with further increases, although the worsening was significant only for one subject. The results have important implications for the fitting of hearing aids.

Comparison of Performance with Wide Dynamic Range Compression and Linear Amplification

AbstractThis study compared subject performance and preference using a compression-limiting hearing aid set to linear amplification (program 1) and wide dynamic range compression (WDRC, program 2). The frequency responses of the hearing aid were matched to a 65 dB SPL signal and maximum output to a 90 dB SPL signal. Twenty subjects with moderate to moderately severe sensorineural hearing loss were tested. Speech recognition scores and speech reception thresholds were obtained both in quiet and in noise. Subjective preference for WDRC or linear amplification was measured via a paired-comparison procedure on "loudness appropriateness,” “clarity," and "pleasantness" to continuous discourse presented in quiet and in noise. Results suggested that WDRC yielded better speech intelligibility in quiet for low-level signals and no difference in speech intelligibility in noise compared to linear amplification. Subjects preferred WDRC for loudness to both high- and low-level signals and for pleasantness to high-level signals. Abbreviations: ANOVA = analysis of variance, AVC = automatic volume control, CL = compression limiting, CVR = consontant-vowel-ratio, HINT = Hearing In Noise Test, Ρ = program, REIG = real-ear insertion gain, REIR = real-ear insertion response, SNR = signal-to-noise ratio, SRS = speech recognition score, SRT = speech reception threshold, WDRC = wide dynamic range compression

Speech intelligibility prediction in hearing-impaired listeners based on a psychoacoustically motivated perception model.

Sensorneural hearing-impaired listeners suffer severely from deterioration in the processing and internal representation of acoustic signals. In order to understand this deterioration in detail, a numerical perception model was developed which is based on current functional models of the signal processing in the auditory system. To test this model, the individual's speech intelligibility in quiet and in noise was predicted. The primary input parameter of the model is the precisely measured audiogram of each listener. In a refined version of the model, additional input parameters are derived from predicting the individual's temporal forward masking and notched-noise measurements with the same model assumptions. The predictions of the perception model were compared with those of the articulation index (AI) and the speech transmission index (STI). The accuracy of prediction with the perception model is in the same range as with the AI and the STI. The model does not require a calibration function and has the advantage of a greater flexibility in including different processing deficits associated with hearing impairment. However, it requires more time for computation. For the hearing-impaired listeners examined so far the individually measured psychoacoustical parameters have only a secondary effect on the prediction as compared to the audiogram. Nevertheless, the underlying model is a first step toward a quantitative understanding of speech intelligibility and helps to distinguish between the influence of the "attenuation" and the "distortion" component of the hearing loss.

The handbook of hearing and the effects of noise: physiology, psychology, and public health

Definitions and Measurement of Noise and Sound. Structures and Functions of the Ear. Auditory Sensations and Perceptions. Normal Hearing, Sociocusis, Nosocusis, and Hearing Loss from Industrial Noise. Derivation of a General Theory and Procedure for Predicting Hearing Loss from Exposure to Sound. Speech Intelligibility in Quiet and in Noise. The Assessment of Hearing Handicap and Damage Risk from Noise. Mental and Psychomotor Task Performance in Noise. Nonauditory System Responses to Sound and Noise and Relations to Health. Community Reactions to Environmental Noise. References. Index.

Effects of spectral smearing on the intelligibility of sentences in the presence of interfering speech

In a previous study [T. Baer and B. C. J. Moore, J. Acoust. Soc. Am. 94, 1229–1241 (1993)], a spectral smearing technique was used to simulate some of the effects of impaired frequency selectivity so as to assess its influence on speech intelligibility. Results showed that spectral smearing to simulate broadening of the auditory filters by a factor of 3 or 6 had little effect on the intelligibility of speech in quiet but had a large effect on the intelligibility of speech in noise. The present study examines the effect of spectral smearing on the intelligibility of speech in the presence of a single interfering talker. The results were generally consistent with those of the previous study, suggesting that impaired frequency selectivity contributes significantly to the problems experienced by people with cochlear hearing loss when they listen to speech in the presence of interfering sounds.

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.

Effects of spectral smearing on the intelligibility of sentences in noise

Cochlear hearing loss is generally associated with a variety of deficits in the ability to analyze sounds, including reduced frequency selectivity. The complex interrelationships between the different deficits have made it difficult to assess the contribution of reduced frequency selectivity to the difficulties experienced by hearing-impaired people in understanding speech. To address this question, the effects of reduced frequency selectivity on the place representation of speech stimuli in the auditory system were simulated by ‘‘smearing’’ the spectra of the stimuli, using the overlap–add method. The smearing was designed to evoke excitation patterns in a normal ear that would resemble those evoked in an impaired ear using unsmeared stimuli. Several different types of smearing were used, simulating specific degrees of broadening and asymmetry of the auditory filter. Sentences in quiet and in speech-shaped noise were smeared and presented to normally hearing listeners in intelligibility tests. The results showed that the intelligibility of speech in quiet was hardly affected by spectral smearing, even for smearing that simulated auditory filters six times broader than normal. However, the intelligibility of speech in noise was adversely affected by the smearing, especially for large degrees of smearing and at a low speech-to-noise ratio (−3 dB). Simulation of asymmetrical broadening of the lower side of the auditory filter had a greater effect than simulation of asymmetrical broadening of the upper side, suggesting that upward spread of masking may be particularly important.

Estimated hearing handicap (using the AMA method and a self-evaluation questionnaire) versus reduction in speech intelligibility in quiet and noise

Three methods of estimating hearing handicap were compared in subjects with bilateral sensorineural losses. Sentence speech-reception thresholds (sSRT) measured in quiet and 65 dB(A) noise were compared to the American Medical Association (AMA) method, based on pure-tone thresholds above 25 dB HL, and to a self-evaluation of handicap (Hearing Handicap Inventory for Adults, HHIA). The AMA correlated highest with sSRTs in quiet (r=0.92), followed by sSRTs in noise (r=0.81), and directional hearing in noise (r=0.84). The HHIA was confounded by age effects, and increasing age decreasing perceived handicap. Thresholds were also measured with noise at a sensation level (SL) 25 dB above sSRTs to partially compensate for audibility differences among subjects. In this noise condition, the AMA correlated with sSRTs in noise (r=0.76) and directional hearing in noise (r=0.58), though the directional hearing is better predicted by pure-tone thresholds at 3 kHz (r=0.64). Stepwise regression analysis suggests handicap continues below 0% AMA handicap in the quiet and 25-dB SL noise conditions.

Speech intelligibility, localization, and binaural detection with monaural and binaural amplification

As part of a continuing study of monaural and binaural amplification, performance on binaural detection, speech intelligibility, and localization was measured for four listeners with bilateral, sensorineural hearing losses, and one listener with a unilateral sensorineural loss. Masking-level differences (MLDs) were measured using speech-spectrum noise maskers and octave-band speech-spectrum noise targets. Localization was measured in anechoic and reverberant environments using three-word phrases at nine locations in the horizontal plane. Intelligibility of monosyllabic words was assessed in quiet and in three signal and noise configurations (0/0, 0/+90, 0/−90) in anechoic and reverberant environments. Performance on all three tests varies among hearing-impaired listeners, even those with similar hearing losses, and is generally poorer than normal-hearing listeners. In most cases, subjects with bilateral losses have better speech intelligibility and localization and larger MLDs with binaural amplification than monaural amplification. Listening environment does not appear to affect localization or speech intelligibility in quiet, but speech intelligibility in noise is usually better in the anechoic environment. Combined data for all the subjects shows a tendency for the S/N ratios for 50% speech intelligibility and the rms localization errors to decrease as MLDs increase. [Work supported by NIH Grant No. DC00428.]

Effects of the fitting parameters of a two-channel compression system on the intelligibility of speech in quiet and in noise.

These experiments were carried out to assess how accurately the gains and compression ratios in a two-channel compression system needed to be set. We used as a research tool a laboratory version of a two-channel full-dynamic-range compression system. The system was initially adjusted to suit each hearing-impaired subject according to the manufacturer's recommendations. Then, further adjustments were made to ensure that speech stimuli were both audible and comfortable over a wide range of sound levels. Finally, the settings of the gains and compression ratios were systematically varied from the adjusted values and the effects of this on the intelligibility of speech in quiet and in noise (12-talker babble, levels of 65 and 75 dB SPL) were measured. The results indicated that speech reception thresholds (SRTs) in quiet were significantly adversely affected by decreases in low-level gain. However, SRTs in noise were relatively unaffected by changes in low-level gain. An exception occurred at the higher noise level used, where increases in the low-level gains (with corresponding increases in compression ratios) had a significant adverse effect on the SRTs. It is concluded that, provided excessive low-level gains (associated with high compression ratios) are avoided, the main criteria for fitting such a system should be listening comfort (i.e. achieving an acceptable tonal balance, and avoiding uncomfortably loud sounds) and an appropriate value of the threshold for detecting speech in quiet (which should be a little below 50 dB SPL).

On prediction of hearing disability.

The present investigation was performed in order to evaluate the pure-tone frequency and/or averages of frequencies best correlated with speech intelligibility measured by the discrimination score (DS) in quiet and in background noise, and, in addition, indicate a valid low fence of the DS when correlated to a self-assessment procedure. The material comprises 158 male subjects with a median age of 60 years, range 52-72 years, drawn from an ongoing longitudinal epidemiological investigation. By self-assessment 36% indicated hearing disability in noisy backgrounds, while 64% had no hearing problems. The pure-tone frequency that correlated best with the speech intelligibility in quiet was the 2-kHz pure-tone frequency. In background noise the best correlation was found with the 3-kHz pure-tone frequency. In the group of subjects with complaints of hearing problems, the median discrimination score in background noise was 84% (IQR 72-92), while in the group of subjects with no complaints the median discrimination score in noise was 92% (IQR 88-96). Based on the results it is concluded that DS in background noise is a valuable measure in the assessment of hearing disability, but no low fence value can be indicated on the basis of the present results.

A Comparison of Two-Channel and Single-Channel Compression Hearing Aids: Comparaison de prothèses acoustiques avec compression à un et deux canaux

Eight subjects with bilateral sensorineural hearing losses took part in a trial comparing listening unaided with listening binaurally through two types of hearing aid, aid A and aid B. Both aids incorporated slow-acting automatic gain control (AGC) operating on the whole speech signal. However, aid A also incorporated two-channel syllabic compression. The two aids were chosen to be as similar as possible in other respects, and both were worn behind the ear. Subjects were tested in a counter-balanced order, and had at least 2 weeks of everyday experience with each aid before testing took place. Performance was evaluated in three ways: by measuring speech intelligibility in quiet for sentences at three peak sound levels, 55, 70 and 85 dB SPL; by measuring the level of speech required for 50% intelligibility (called the SRT) of sentences in two levels of speech-shaped noise, 60 and 75 dB SPL; and by administering questionnaires about experience with the aids in everyday life. Both aid A and aid B improved th...

The effect of noise-induced hearing loss on speech intelligibility in quiet and in noise

Following a pilot study (Smoorenburg et al., Scand. Audiol., Suppl. 16, 123–133) based on 44 ears (22 subjects) with noise-induced hearing loss (NIHL) we conducted a study based on 400 ears with different degrees of NIHL. The study included speech reception thresholds for sentences presented in quiet and in noise, tone audiograms measured in quiet and against a low-frequency background noise, and self-rating of the hearing handicap according to the Social Hearing Handicap Index. The results show virtually no correlation between the hearing loss for speech presented in quiet and the loss for speech presented in background noise. Speech thresholds found in quiet show the highest correlation with losses in the tone audiogram at 0.5 and 1 kHz, whereas speech thresholds in noise show the highest correlation with the losses at 2–4 kHz. The speech thresholds will be compared with predictions from the audiogram using the Articulation Index procedure and with the audiograms measured against a low-frequency background noise. Only those questions in the Social Hearing Handicap questionnaire that refer directly to practical situations show a correlation with the speech thresholds. The results for speech perception in noise show that the AAOO fence of 25-dB average hearing loss across 1/2, 1, and 2 kHz implies a severe auditory handicap. The fence should be set at a lower level and it should include audiometric frequencies.

Improvements in speech intelligibility in quiet and in noise produced by two-channel compression hearing aids.

Eight subjects suffering from bilateral sensorineural hearing losses with recruitment were fitted binaurally with two-channel compression hearing aids, worn behind the ear. After they had worn the aids for some time, measures of speech intelligibility were compared for two conditions: listening unaided, and listening aided. the dynamic range for speech, defined as the difference in level between the speech reception threshold in quiet and the highest comfortable level for speech, was substantially increased in the aided condition for seven of the eight subjects (the exception was a subject with almost normal low-frequency hearing). Speech reception thresholds were also measured in two levels of background noise ('babble'), 60 and 75 dB SPL. Seven of the eight subjects showed a reduced speech reception threshold (i.e. an improvement) in the aided condition for at least one of the two noise levels, although the size of the improvement differed considerably from one subject to another. The subjects were also given a battery of psycho-acoustical tests in an attempt to better characterise their hearing loss, and to gain more insight into individual differences. Results of measurements of frequency selectivity, frequency discrimination, temporal acuity and temporal masking are described and related to the measures of speech intelligibility.

Hearing aid evaluation based on measures of benefit, use, and satisfaction.

A comprehensive follow-up protocol was designed and utilized to assess benefit, use, and satisfaction from hearing aids. The benefit assessments included functional gain measures, and speech intelligibility in quiet and in noise. Hearing aid use was evaluated based on a questionnaire which asked for an estimate of daily use in hours and also an accounting of times when the aid was not in use during the day. Two use values were derived, an absolute daily use value and an adjusted percentage of use value. Satisfaction also was assessed using a questionnaire. The subjects were asked to indicate their general satisfaction with the aid on a seven-point scale. Two communication assessment questionnaires were used to assess communication handicap. Data are provided on 45 subject. The subjects were categorized into groups according to both low- and high-frequency hearing. These preliminary mean scores by group can be used as target goals for benefit, use, and satisfaction on persons fit with hearing aids. The protocol as used can provide considerable evaluative clinical information in a reasonable amount of time.