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PubMed2004

Using the Speech Transmission Index for predicting non-native speech intelligibility.

While the Speech Transmission Index (STI) is widely applied for prediction of speech intelligibility in room acoustics and telecommunication engineering, it is unclear how to interpret STI values when non-native talkers or listeners are involved. Based on subjectively measured psychometric functions for sentence intelligibility in noise, for populations of native and non-native communicators, a correction function for the interpretation of the STI is derived. This function is applied to determine the appropriate STI ranges with qualification labels ("bad"-"excellent"), for specific populations of non-natives. The correction function is derived by relating the non-native psychometric function to the native psychometric function by a single parameter (nu). For listeners, the nu parameter is found to be highly correlated with linguistic entropy. It is shown that the proposed correction function is also valid for conditions featuring bandwidth limiting and reverberation.

Humans↗

PubMed1995

Speech intelligibility of implanted children.

The speech intelligibility of 61 prelingually deaf children was measured prior to their receiving a multichannel cochlear implant (CI) and at subsequent intervals. The speech intelligibility of the implanted subjects was compared to that of three groups of subjects with profound hearing loss who used conventional hearing aids (HAs), grouped on the basis of unaided thresholds: "gold" (pure tone average [PTA] = 93 dB hearing level [HL]), "silver" (PTA = 103 dB HL), and "bronze" (PTA > or = 110 dB HL). Intelligibility was measured in terms of the percentage of words from a set of 10 sentences that were correctly understood by a panel of listeners. The speech intelligibility of the implanted subjects increased gradually over time, remaining relatively low throughout the first 2 years of implant use. After that time, the average speech intelligibility of the CI subjects surpassed that of the silver HA users. The gold HA subjects demonstrated speech intelligibility that was markedly better than that of the CI subjects, even after 3 1/2 or more years of implant use.

Child, Preschool↗

PubMed1998

Respirator performance ratings for speech intelligibility.

A respirator degrades speech intelligibility and thus interferes with the ability of the wearer to communicate. The magnitude of this degradation is not well-studied and can vary as a function of numerous parameters. This study investigated the performance degradation of speech intelligibility in low-level noise for different speaker-listener distances and message sets (single words or predictable sentences) that occurred while wearing a respirator compared with not wearing a respirator. Thirteen speaker-listener pairs with normal hearing and speech were used. Speaker-listener separation distances were 0.61, 1.22, 1.83, 2.44, 3.05, and 3.66 m (2, 4, 6, 8, 10, and 12 ft) for the respirator condition and 1.22, 2.44, 3.05, 6.1, 9.15, and 12.2 m (4, 8, 10, 20, 30, and 40 ft) for the no-respirator condition. The means of the scores were used to determine the speech performance rating for both the single-word and sentence comprehension tests. The performance rating expresses the percentage of performance that can be expected while wearing a respirator compared with not wearing a respirator. Scores were interpolated linearly at distances at which no data were obtained. As expected, the speech performance rating was higher for the sentence comprehension test than for the single-word comprehension test at each distance. At a distance of 12.2 m, the speech performance rating for the sentence comprehension was 70%. For the single-word comprehension test, the speech performance rating was zero for distances greater than 9.1 m.

Adolescent↗

PubMed1986

Speech intelligibility studies in classrooms.

Speech intelligibility tests and acoustical measurements were made in ten occupied classrooms. Octave-band measurements of background noise levels, early decay times, and reverberation times, as well as various early/late sound ratios, and the center time were obtained. Various octave-band useful/detrimental ratios were calculated along with the speech transmission index. The interrelationships of these measures were considered to evaluate which were most appropriate in classrooms, and the best predictors of speech intelligibility scores were identified. From these results ideal design goals for acoustical conditions for classrooms were determined either in terms of the 50-ms useful/detrimental ratios or from combinations of the reverberation time and background noise level.

Adolescent↗

PubMed1996

Speech intelligibility index transfer functions and speech spectra for two Swedish speech recognition tests.

Speech spectra and Speech Intelligibility Index (SII) transfer functions are presented for the Swedish PB word material (SPB) and for a Swedish sentence material known as Hagerman's Sentences (HS). The transfer function were derived from the normative recognition scores in noise previously obtained from normal-hearing subjects. The transfer function for HS is very similar to a transfer function for familiar English sentences. The function for SPB is more like functions of other monosyllabic word test materials. The slope of the HS transfer function is twice as steep as the slope of the SPB function. The long-term rms spectra of the speech materials and their associated noise signals are presented and recommended to facilitate accurate SII calculations with these speech tests.

Hearing↗

PubMed2005

Minimum audible angle, just noticeable interaural differences and speech intelligibility with bilateral cochlear implants using clinical speech processors.

Sound localization and speech intelligibility were assessed in 5 patients implanted bilaterally with Medel C40+ or Medel C40 cochlear implant (CI) systems. The minimum audible angle (MAA) around the head in the horizontal plane was assessed in patients with bilateral CI using white noise bursts of 1000 ms duration presented from a loudspeaker mounted on a rotating boom and compared with the MAA of age-matched normal hearing controls. Spatial discrimination was found to be good in front and in the back of the head with near-normal MAA values (patients: 3-8 degrees , controls: 1-4 degrees ). In contrast, poor performance on the sides was found (patients: 30 to over 45 degrees , controls 7-10 degrees ). Bilateral CI significantly improved spatial discrimination in front for all patients, when compared with the use of either CI alone. Just noticeable differences (JNDs) in interaural intensity and time were assessed using white noise bursts (1000 ms duration; 50 ms linear ramp). In addition, interaural time JNDs were assessed using click trains (800 ms duration, 40 mus clicks, 50 Hz) and noise bursts in which either only the envelope or only the fine structure was shifted in time. In comparison with normal hearing controls, patients with bilateral CI showed near-normal interaural intensity JNDs but substantially poorer interaural time JNDs depending on the type of stimulus. In contrast to envelope onset/offset cues, interaural fine structure time differences were not perceived by the patients using CI systems employing the continuous interleaved sampling strategy without synchronization between their pulse stimulation times. Speech intelligibility in quiet and CCITT noise from the side (+/-90 degrees ) was assessed using the German HSM sentence test and was significantly better when using bilateral CI in comparison with either unilateral CI, mainly due to a head shadow effect. These favorable results are in agreement with the patients' subjective experiences assessed with a questionnaire and support the use of bilateral CI.

Adolescent↗

PubMed2004

Visual prosody and speech intelligibility: head movement improves auditory speech perception.

People naturally move their heads when they speak, and our study shows that this rhythmic head motion conveys linguistic information. Three-dimensional head and face motion and the acoustics of a talker producing Japanese sentences were recorded and analyzed. The head movement correlated strongly with the pitch (fundamental frequency) and amplitude of the talker's voice. In a perception study, Japanese subjects viewed realistic talking-head animations based on these movement recordings in a speech-in-noise task. The animations allowed the head motion to be manipulated without changing other characteristics of the visual or acoustic speech. Subjects correctly identified more syllables when natural head motion was present in the animation than when it was eliminated or distorted. These results suggest that nonverbal gestures such as head movements play a more direct role in the perception of speech than previously known.

Adult↗

PubMed1994

[Communication and noise. Speech intelligibility of airplane pilots with and without active noise compensation].

Noise exposure measurements were performed with pilots of the German Federal Navy during flight situations. The ambient noise levels during regular flight were maintained at levels above a 90 dB A-weighted level. This noise intensity requires wearing ear protection to avoid sound-induced hearing loss. To be able to understand radio communication (ATC) in spite of a noisy environment, headphone volume must be raised above the noise of the engines. The use of ear plugs in addition to the headsets and flight helmets is only of limited value because personal ear protection affects the intelligibility of ATC. Whereas speech intelligibility of pilots with normal hearing is affected to only a smaller degree, pilots with pre-existing high-frequency hearing losses show substantial impairments of speech intelligibility that vary in proportion to the hearing deficit present. Communication abilities can be reduced drastically, which in turn can affect air traffic security. The development of active noise compensation devices (ANC) that make use of the "anti-noise" principle may be a solution to this dilemma. To evaluate the effectiveness of an ANC-system and its influence on speech intelligibility, speech audiometry was performed with a German standardized test during simulated flight conditions with helicopter pilots. Results demonstrate the helpful effect on speech understanding especially for pilots with noise-induced hearing losses. This may help to avoid pre-retirement professional disability.

Adult↗

PubMed1996

Predicting the speech recognition performance of elderly individuals with sensorineural hearing impairment. A procedure based on the Speech Intelligibility Index.

The Speech Intelligibility Index (SII) was used as a basis for predicting the performance of elderly hearing-impaired subjects on a speech-in-noise test. The standard SII calculation scheme was compared with modified schemes, and correlations were obtained between measured and predicted scores. The results suggested that a modified calculation scheme, which includes corrections for sensorineural hearing impairment and age, is appropriate for evaluating individual speech recognition scores. Based on the results, a computer program has been developed for clinical prediction and evaluation of speech recognition scores.

Age Factors↗

PubMed2003

The interlanguage speech intelligibility benefit.

This study investigated how native language background influences the intelligibility of speech by non-native talkers for non-native listeners from either the same or a different native language background as the talker. Native talkers of Chinese (n = 2), Korean (n = 2), and English (n = 1) were recorded reading simple English sentences. Native listeners of English (n = 21), Chinese (n = 21), Korean (n = 10), and a mixed group from various native language backgrounds (n = 12) then performed a sentence recognition task with the recordings from the five talkers. Results showed that for native English listeners, the native English talker was most intelligible. However, for non-native listeners, speech from a relatively high proficiency non-native talker from the same native language background was as intelligible as speech from a native talker, giving rise to the "matched interlanguage speech intelligibility benefit." Furthermore, this interlanguage intelligibility benefit extended to the situation where the non-native talker and listeners came from different language backgrounds, giving rise to the "mismatched interlanguage speech intelligibility benefit." These findings shed light on the nature of the talker-listener interaction during speech communication.

Adolescent↗

PubMedDate not supplied

Speech intelligibility during respirator wear: influences of respirator speech diaphragm size and background noise.

This study assessed the effect of respirator speech device size on speech intelligibility and the impact of background noise on respirator communications effectiveness. Thirty-five subjects completed modified rhyme test (MRT) speech intelligibility testing procedures with and without a respirator under background noises of 40, 60, and 80 dBA. Respirator wear conditions included the use of one unmodified and three mechanical speech diaphragms modified to reduce the surface area of the vibrating inner membrane available for sound transmission. Average MRT scores decreased linearly as background noise levels increased for all conditions. Lower MRT scores were observed for all respirator speech diaphragm conditions compared to the nonrespirator condition within each noise category. Average MRT scores differed significantly between the unmodified speech diaphragm and one with a 70% reduced surface area with a 40-dBA background noise. However, MRT scores were similar between the modified and unmodified diaphragms at both the 60- and 80-dBA noise levels. These findings provide evidence that alternate designs of mechanical-type respirator speech devices can be achieved without further degradation of speech sound transmission.

Adult↗

PubMed2001

Reliability of a rating scale for measuring speech intelligibility after pediatric cochlear implantation.

OBJECTIVE: To evaluate the reliability of the Speech Intelligibility Rating scale to monitor the speech intelligibility of deaf children who have received cochlear implants. STUDY DESIGN: A prospective study assessing the speech intelligibility of deaf children with cochlear implants by local and cochlear implant program speech and language therapists. SETTING: Pediatric tertiary referral center for cochlear implantation. PATIENTS AND METHODS: Fifty-four children were each rated by two speech and language therapists, one working with the child locally and the other working with the child at the cochlear implant program. All children were between 1.2 and 10.9 years of age at the time of implantation (median, 4.0 years). The follow-up intervals ranged from before implantation to 9 years after implantation. MAIN OUTCOME MEASURE: Correlation coefficient, intraclass correlation coefficient, and kappa statistics were used to assess the interobserver reliability of the Speech Intelligibility Rating scale. RESULTS: Spearman rank correlation coefficient and intraclass correlation coefficient were 0.82 with high statistical significance (p < 0.00001). Kappa statistical analysis revealed a moderate to substantial agreement between the ratings. This agreement also reached a high statistical significance (overall kappa = 0.53, p < 0.000001). The Speech Intelligibility Rating scale was found to be able to discriminate speech intelligibility among subjects, and the ratings covaried with high consistency. CONCLUSION: The study found a high rate of agreement between observers when they used the Speech Intelligibility Rating scale to assess the speech intelligibility of deaf children after cochlear implantation. Because the scale presents information in a format that is understood by parents, local professionals, and health care purchasers, it will be useful to provide them with accessible information on speech intelligibility outcomes of deaf children who have received cochlear implants.

Child↗

PubMed2006

Extended speech intelligibility index for the prediction of the speech reception threshold in fluctuating noise.

The extension to the speech intelligibility index (SII; ANSI S3.5-1997 (1997)) proposed by Rhebergen and Versfeld [Rhebergen, K.S., and Versfeld, N.J. (2005). J. Acoust. Soc. Am. 117(4), 2181-2192] is able to predict for normal-hearing listeners the speech intelligibility in both stationary and fluctuating noise maskers with reasonable accuracy. The extended SII model was validated with speech reception threshold (SRT) data from the literature. However, further validation is required and the present paper describes SRT experiments with nonstationary noise conditions that are critical to the extended model. From these data, it can be concluded that the extended SII model is able to predict the SRTs for the majority of conditions, but that predictions are better when the extended SII model includes a function to account for forward masking.

Adolescent↗

PubMed1982

Frequency selectivity and speech intelligibility in noise.

Poor speech intelligibility in noise is a major problem for persons afflicted by a sensorineural hearing loss, and this problem is generally not alleviated by a hearing aid. For a typical hearing loss the effective signal-to-noise ratio is degraded by 10 - 15 dB, predominantly due to impoverished frequency selectivity. The critical ratio averaged over speech frequencies is a convenient measure of this component of the auditory handicap. An attempt to improve speech intelligibility in noise through dichotic combfiltering was not successful.

Audiometry, Pure-Tone↗

PubMed2004

Using statistical decision theory to predict speech intelligibility. III. Effect of audibility on speech recognition sensitivity.

The speech recognition sensitivity (SRS) model [H. Müsch and S. Buus, J. Acoust. Soc. Am. 109, 2896-2909 (2001)] is a macroscopic model for predicting speech intelligibility. The present study proposes a modification to the relation between the SRS model's audibility-noise variance and the signal-excitation to noise-excitation ratio (SNRE) in the auditory periphery. The modified relation is derived from data obtained in nine studies that measured normal-hearing listeners' consonant-recognition performance at several levels of speech-spectrum shaped noise. When the audibility-noise variance is directly proportional to the relative power of the noise excitation in the auditory periphery, the SRS model yields good predictions of the data. Four of the nine studies also reported consonant-recognition performance in various filtering conditions. Good predictions of these data were achieved with SRS model parameters that were consistent with the model parameters fitting the speech-in-noise data and with the model parameters used in the original SRS papers.

Auditory Cortex↗

PubMed2005

Speech intelligibility of Mandarin-speaking deaf children with cochlear implants.

OBJECTIVE: Speech intelligibility, the extent to which the speakers can be understood verbally by their listeners, is an evaluator for the effectiveness of cochlear implantation. Thus, our goals were to evaluate the result of a tonal language through comparing the speech intelligibility between normal-hearing and implanted children who speak Mandarin, and to evaluate the relationship between speech intelligibility and duration of implants use. The effects of the age at implantation were also evaluated. METHODS: Twenty-six children (mean age of 5.9 years), who were congenitally deaf and implanted age at 3.5 years, were compared with 26 normal-hearing children (mean age of 5.84 years). The average post-implanted time was more than 6 months. Speech intelligibility was represented with the speech intelligibility ratings (SIR) and the correct percentage of dictation. The relationships between speech intelligibility, age at implantation and duration of implant were evaluated by linear regression analysis. RESULTS: Speech intelligibility of most subjects ranked from SIR category 3-5. The average correct perception rate (CI group/normal group) of words, consonants, vowels, and tones were 42.5%, 64.9%, 73.5%, and 72.3%, respectively. These differences were statistically significant (p<0.001). Speech intelligibility was positively correlated with age only in the normal-hearing group. Speech intelligibility in the implanted group was negatively correlated with age at implantation but positively correlated with the duration of implant. CONCLUSIONS: Speech intelligibility of tonal language was poorer in implanted children than normal-hearing children, but their communication outcomes were satisfactory when measured with SIR. Speech intelligibility is better if the age at implantation is younger or duration of implants use is longer.

Age Factors↗

PubMed1993

Intelligibility of selected passages from the Speech Intelligibility Rating (SIR) test.

Two experiments were conducted to examine the intelligibility of 12 of the 72 passages of connected discourse prepared by Cox and McDaniel (1984, 1989) in the development of the Speech Intelligibility Rating (SIR) test. Intelligibility was assessed with a method-of-adjustment procedure in the presence of two maskers. One was a multi-talker babble with a variable S/N ratio environment that yields intelligibility scores that are potentially level-dependent because of the almost inevitable difference in speech intensity from passage to passage. The second was a signal-correlated noise with a constant S/N ratio environment that provides scores that are essentially level-independent. Two homogeneous subsets of nine passages each were identified that yield equivalent intelligibility scores. The outcome underscores the value of incorporating a signal-correlated noise masker that yields scores that are relatively unaffected by small differences in signal level among passages.

Adult↗

PubMed1996

The effect of a headset leakage on speech intelligibility in helicopter noise.

INTRODUCTION: Speech intelligibility tests in recorded helicopter noise were performed on 10 subjects with normal hearing, using a Peltor aviation headset. The subjects acted as their own controls, a pair of sunglasses being the only variable factor. METHODS: Noise levels were also measured at the tympanic membrane in one of the test subjects for 7 consecutive fittings of the headset, with and without glasses. RESULTS: Results showed a substantial decrease in speech intelligibility when wearing glasses, being most marked for critical signal-to-noise ratios and the most difficult speech material. Changes were statistically highly significant. Average speech intelligibility scores decreased from 68% to 29% for one-syllable words when wearing glasses at critical signal-to-noise ratios. Noise measurements at the tympanic membrane in one subject showed a low-frequency leakage varying between consecutive fittings. CONCLUSION: Our findings show that even small leakages due to fitting of the headset or helmet should be avoided, particularly in noisy aircraft with communication-demanding mission profiles.

Adult↗