Speech Intelligibility Index Values Research Articles

An objective comparison of speech intelligibility and quality of hearing aid of different companies

Abstract Purpose: This study aimed to verify the intelligibility and quality of hearing aid-processed speech across companies through objective measures. The output of hearing aids programmed to different prescriptive formulae (Company fit, NAL NL 1, NAL NL 2, and DSLv5) across companies (Company I, Company II, Company III, Company IV, and Company V) were recorded and stored in the sound level meter connected to the manikin. Materials and Methods: Offline analysis of speech quality of the recorded speech was done using the Hearing Aid Speech Quality Index (HASQI), the intelligibilty was measured using the Hearing Aid Speech Perception Index (HASPI) and Speech Intelligibility Index (SII), and Long-Term Average Speech Spectrum (LTASS) was used to measure the spectral composition of speech. Results: When the companies are compared, the hearing aid of Company V showed significantly higher SII values for all prescriptive formulae indicative of better speech intelligibility provided by Company V hearing aids. In terms of speech quality, all the hearing aids showed similar HASQI values. Conclusions: The reasons for each of these findings are highlighted and recommendations for best practices on the use of objective measures for verifying the hearing aid output in clinical setups are suggested.

Fit-to-Targets and Aided Speech Intelligibility Index Values for Hearing Aids Fitted to the DSL v5-Adult Prescription.

Matching hearing aid output levels to prescribed targets is a component of preferred practice, yet recent normative data on appropriateness of fittings are lacking. Verification measures that assess closeness of fit-to-target include raw deviations from target, root-mean-squared-error (RMSE) deviations from target, and aided Speech Intelligibility Index (SII) values. Establishing normative ranges for these measures may help hearing professionals determine whether a patient's fit-to-targets and/or aided speech audibility is typical for his or her degree of hearing loss. This article aims to characterize the range of fit-to-target and the range of aided SII associated with hearing aid fittings using the Desired Sensation Level version 5.0 (DSL v5-adult) prescription with adults, considering also hearing aid style, venting, and audiometric characteristics. A descriptive and correlational study of data collected from a retrospective chart review. Hearing aid fittings to 281 ears were compiled. The four-frequency average deviation from target (RMSE) was within ± 5 dB of target in 77% of fittings for mid-level speech. Deviation from targets increased with hearing loss, particularly when the loss is greater than 85 dB hearing level or if the loss was steeply sloping. Venting increased the deviation from targets in the low frequencies. Aided SII values strongly correlated with the participants' hearing thresholds. Clinical ranges for RMSE and aided SII were developed for characterization of fitting outcomes. Fitting to DSL v5-adult targets was observed within ± 5 dB absolute deviation, or within 5 dB RMSE, on average for typical adult hearing aid fittings. Confidence intervals for deviation from target and aided SII are proposed.

Aided Hearing Moderates the Academic Outcomes of Children With Mild to Severe Hearing Loss.

There are very limited data regarding the spoken language and academic outcomes of children with mild to severe hearing loss (HL) during the elementary school years, and the findings of these studies are inconsistent. None of these studies have examined the possible role of aided hearing in these outcomes. This study used a large cohort of children to examine these outcomes and in particular to examine whether aided hearing moderates the effect of HL with regard to these outcomes. The spoken language, reading, writing, and calculation abilities were measured after second and fourth grades in children with mild to severe HL (children who are hard of hearing; CHH, n = 183) and a group of children with normal hearing (CNH, n = 91) after the completion of second and fourth grades. Also, among the CHH who wore hearing aids, aided better-ear speech intelligibility index values at the age of school entry were obtained. Oral language abilities of the CHH with mild and moderate HL were similar to the CNH at each grade. Children with moderately-severe HL (better-ear pure tone threshold >59 but <76 dB HL) had significantly poorer oral language and reading skills than the CNH at each grade. The children with mild and moderate HL did not differ from the CNH in oral language or reading. No differences were found between the CHH regardless of severity and CNH with regard to spelling, passage writing, or calculation. The degree to which hearing aids provided audible speech information played a moderating role in the oral language outcomes of CHH and this moderation of language mediated the relationship between the unaided hearing ability of the CHH and their academic outcomes. As a group, children with mild and moderate HL have good outcomes with regard to language and academic performance. Children with moderately-severe losses were less skilled in language and reading than the CNH and CHH children with mild and moderate losses. Audibility provided by hearing aids was found to moderate the effects of HL with respect to these outcomes. These findings emphasize the importance of including the effects of clinical interventions such as aided hearing when examining outcomes of CHH.

Evaluation of Hearing Aid Manufacturers' Software-Derived Fittings to DSL v5.0 Pediatric Targets.

Hearing aid prescriptive methods are a commonly recommended component of evidence-based preferred practice guidelines and are often implemented in the hearing aid programming software. Previous studies evaluating hearing aid manufacturers' software-derived fittings to prescriptions have shown significant deviations from targets. However, few such studies examined the accuracy of software-derived fittings for the Desired Sensation Level (DSL) v5.0 prescription. The purpose of this study was to evaluate the accuracy of software-derived fittings to the DSL v5.0 prescription, across a range of hearing aid brands, audiograms, and test levels. This study is a prospective chart review with simulated cases. A set of software-derived fittings were created for a six-month-old test case, across audiograms ranging from mild to profound. The aided output from each fitting was verified in the test box at 55-, 65-, 75-, and 90-dB SPL, and compared with DSL v5.0 child targets. The deviations from target across frequencies 250-6000 Hz were calculated, together with the root-mean-square error (RMSE) from target. The aided Speech Intelligibility Index (SII) values generated for the speech passages at 55- and 65-dB SPL were compared with published norms. Thirteen behind-the-ear style hearing aids from eight manufacturers were tested. The amount of deviation per frequency was dependent on the test level and degree of hearing loss. Most software-derived fittings for mild-to-moderately severe hearing losses fell within ± 5 dB of the target for most frequencies. RMSE results revealed more than 84% of those hearing aid fittings for the mild-to-moderate hearing losses were within 5 dB at all test levels. Fittings for severe to profound hearing losses had the greatest deviation from target and RMSE. Aided SII values for the mild-to-moderate audiograms fell within the normative range for DSL pediatric fittings, although they fell within the lower portion of the distribution. For more severe losses, SII values for some hearing aids fell below the normative range. In this study, use of the software-derived manufacturers' fittings based on the DSL v5.0 pediatric targets set most hearing aids within a clinically acceptable range around the prescribed target, particularly for mild-to-moderate hearing losses. However, it is likely that clinician adjustment based on verification of hearing aid output would be required to optimize the fit to target, maximize aided SII, and ensure appropriate audibility across all degrees of hearing loss.

Efficacy of a Smartphone Hearing Aid Simulator

Almost all smartphone-based personal sound amplification applications (PSAPs) do not provide amplification specifications as well as medical hearing aid (HA) products. Therefore, the main purpose of this study is to develop an HA-simulator and investigate the possible fitting range of this smartphone-based PSAP app equipped with a commercial headset, and to evaluate whether the aided outcome provides reasonable benefits for individuals with hearing loss by analyzing the Speechmap and speech intelligibility index (SII). An HA-simulator with a four-channel compression structure was developed and evaluated using a smartphone equipped with Apple EarPods. Measurement methods specified by the ANSI S3.22 were used to evaluate the electroacoustic performance of the proposed system. The Speechmap method and SII were used to check if the amplified speech for five different hearing loss configurations. These ANSI S3.22 and Speechmap measurement results were then compared with a digital HA under the same test conditions. The results demonstrated that the proposed HA-simulator system provided an adequate output sound level for patients with mild-to-moderate hearing loss and a tolerable group delay for the user while providing an electroacoustic performance comparable to that of a digital HA based on ANSI S3.22 test criteria. The amplified speech signals presented by Speechmap and the corresponding SII values indicated that the proposed HA-simulator provided benefits comparable to those of medical HA. These results indicate that a smartphone-based HA simulator could provide suitable performance to that of a medical HA, and it potentially aid individuals with hearing loss.

Audibility-Based Hearing Aid Fitting Criteria for Children With Mild Bilateral Hearing Loss.

Purpose Because of uncertainty about the level of hearing where hearing aids should be provided to children, the goal of the current study was to develop audibility-based hearing aid candidacy criteria based on the relationship between unaided hearing and language outcomes in a group of children with hearing loss who did not wear hearing aids. Method Unaided hearing and language outcomes were examined for 52 children with mild-to-severe hearing losses. A group of 52 children with typical hearing matched for age, nonverbal intelligence, and socioeconomic status was included as a comparison group representing the range of optimal language outcomes. Two audibility-based criteria were considered: (a) the level of unaided hearing where unaided children with hearing loss fell below the median for children with typical hearing and (b) the level of unaided hearing where the slope of language outcomes changed significantly based on an iterative, piecewise regression modeling approach. Results The level of unaided audibility for children with hearing loss that was associated with differences in language development from children with typical hearing or based on the modeling approach varied across outcomes and criteria but converged at an unaided speech intelligibility index of 80. Conclusions Children with hearing loss who have unaided speech intelligibility index values less than 80 may be at risk for delays in language development without hearing aids. The unaided speech intelligibility index potentially could be used as a clinical criterion for hearing aid fitting candidacy for children with hearing loss.

Speech Perception in Noise With Formant Enhancement for Older Listeners

Purpose Degraded speech intelligibility in background noise is a common complaint of listeners with hearing loss. The purpose of the current study is to explore whether 2nd formant (F2) enhancement improves speech perception in noise for older listeners with hearing impairment (HI) and normal hearing (NH). Method Target words (e.g., color and digit) were selected and presented based on the paradigm of the coordinate response measure corpus. Speech recognition thresholds with original and F2-enhanced speech in 2- and 6-talker babble were examined for older listeners with NH and HI. Results The thresholds for both the NH and HI groups improved for enhanced speech signals primarily in 2-talker babble, but not in 6-talker babble. The F2 enhancement benefits did not correlate significantly with listeners' age and their average hearing thresholds in most listening conditions. However, speech intelligibility index values increased significantly with F2 enhancement in babble for listeners with HI, but not for NH listeners. Conclusions Speech sounds with F2 enhancement may improve listeners' speech perception in 2-talker babble, possibly due to a greater amount of speech information available in temporally modulated noise or a better capacity to separate speech signals from background babble.

Evaluation of Hearing Aid Manufacturers’ Software- Derived Fittings to DSL v5.0 Pediatric Targets

Background: Hearing aid prescriptive methods are a commonly recommended component of evidencebasedpreferred practice guidelines and are often implemented in the hearing aid programming software.Previous studies evaluating hearing aid manufacturers’ software-derived fittings to prescriptionshave shown significant deviations from targets. However, few such studies examined the accuracy ofsoftware-derived fittings for the Desired Sensation Level (DSL) v5.0 prescription.&lt;br /&gt;Purpose: The purpose of this study was to evaluate the accuracy of software-derived fittings to the DSLv5.0 prescription, across a range of hearing aid brands, audiograms, and test levels.&lt;br /&gt;Research Design: This study is a prospective chart review with simulated cases.&lt;br /&gt;Data Collection and Analysis: A set of software-derived fittings were created for a six-month-old testcase, across audiograms ranging from mild to profound. The aided output from each fitting was verified inthe test box at 55-, 65-, 75-, and 90-dB SPL, and compared with DSL v5.0 child targets. The deviationsfrom target across frequencies 250–6000 Hz were calculated, together with the root-mean-square error(RMSE) from target. The aided Speech Intelligibility Index (SII) values generated for the speech passagesat 55- and 65-dB SPL were compared with published norms.&lt;br /&gt;Study Sample: Thirteen behind-the-ear style hearing aids from eight manufacturers were tested.&lt;br /&gt;Results: The amount of deviation per frequency was dependent on the test level and degree of hearingloss. Most software-derived fittings for mild-to-moderately severe hearing losses fell within ±5 dB of thetarget for most frequencies. RMSE results revealed more than 84 percent of those hearing aid fittings for themild-to-moderate hearing losses were within 5 dB at all test levels. Fittings for severe to profound hearinglosses had the greatest deviation from target and RMSE. Aided SII values for the mild-to-moderate audiogramsfell within the normative range for DSL pediatric fittings, although they fell within the lower portionof the distribution. For more severe losses, SII values for some hearing aids fell below the normative range.&lt;br /&gt;Conclusions: In this study, use of the software-derived manufacturers’ fittings based on the DSL v5.0pediatric targets set most hearing aids within a clinically acceptable range around the prescribed target,particularly for mild-to-moderate hearing losses. However, it is likely that clinician adjustment based onverification of hearing aid output would be required to optimize the fit to target, maximize aided SII, andensure appropriate audibility across all degrees of hearing loss.&lt;br /&gt;

Fit-to-Targets for the Desired Sensation Level Version 5.0a Hearing Aid Prescription Method for Children.

The purpose of this study was to measure the range of fit to Desired Sensation Level version 5.0 (DSL v5.0) targets in pediatric practice environments. Results will be used in the future to develop clinical-aided speech intelligibility index typical performance data. Clinical partners collected data from 161 final hearing aid settings for children aged ≤ 10 years. Measured data were obtained by performing 2-cm3 coupler-simulated real-ear measurements using the DSL v5.0 implementation on the Audioscan VF-1 (Etymonic Design Inc., Dorchester, ON, Canada) for soft, average, and loud speech inputs and maximum hearing aid output levels. Fittings were within ± 5-dB root-mean-square (RMS) error of target for 77%, 80%, and 82% of fittings for the soft, medium, and loud speech test levels, respectively. Aided maximum power output measures were within ± 5-dB RMS error in 72% of cases. Degree of hearing loss, test frequency, and frequency by test level were significant factors in deviation from target. The range of aided speech intelligibility index values exhibited a strong correlation with the hearing levels of the children tested. This study provides evidence that typical hearing aid fittings for children can be achieved within ± 5-dB RMS error of the DSL v5.0 target. Greater target deviations were observed at extreme frequencies and as the severity of hearing loss increased.

Hearing loss classification by degree, configuration and relationship with amplified Speech Intelligibility Index (SII).

To establish the relationship between speech intelligibility index (SII) values generated at the verification of hearing aids programmed according to DSLm [i/o] v5 prescription rule and a proposed individual classification that considers the combination of hearing loss degree and configuration. Forty-one children aged between 4 and 80 months were selected, totaling 78 ears for analysis. We considered hearing thresholds at the frequencies of 250, 500, 1000, 2000 and 4000 Hz; and analyzed values of the Speech Intelligibility Index (SII) for the input signal of 65 dB SPL obtained during the verification of hearing aids using the equipment Verifit®Audioscan. Hearing losses were classified into five homogeneous groups regarding audiometric degree and configuration. The groups were heterogeneous when compared to each other. From the groups, three ranges of SII values were determined. Equations were developed for classification of hearing loss according to groups and for determination of the adjusted SII values. The SII value is a useful indicator of audibility for speech sounds in different characteristics of hearing losses, and can guide observations of auditory skills. The SII has stronger relationship with the association of the audiometric degree and configuration when compared with degree of hearing loss alone.

Speech recognition for multiple bands: Implications for the Speech Intelligibility Index.

The Speech Intelligibility Index (SII) assumes additivity of the importance of acoustically independent bands of speech. To further evaluate this assumption, open-set speech recognition was measured for words and sentences, in quiet and in noise, when the speech stimuli were presented to the listener in selected frequency bands. The filter passbands were constructed from various combinations of 20 bands having equivalent (0.05) importance in the SII framework. This permitted the construction of a variety of equal-SII band patterns that were then evaluated by nine different groups of young adults with normal hearing. For monosyllabic words, a similar dependence on band pattern was observed for SII values of 0.4, 0.5, and 0.6 in both quiet and noise conditions. Specifically, band patterns concentrated toward the lower and upper frequency range tended to yield significantly lower scores than those more evenly sampling a broader frequency range. For all stimuli and test conditions, equal SII values did not yield equal performance. Because the spectral distortions of speech evaluated here may not commonly occur in everyday listening conditions, this finding does not necessarily represent a serious deficit for the application of the SII. These findings, however, challenge the band-independence assumption of the theory underlying the SII.

Acoustical Evaluation of High-School Technology-Education Shops

This study investigated the acoustical conditions in high-school Technology-Education Shops (TES) and the conflict that may exist due to their use at the same time as classrooms for learning and as industrial workshops for fabrication. This was done by measuring relevant acoustical characteristics in twenty TES in British Columbia when unoccupied with building services operating, and in ten of them when occupied and in normal operation with shop equipment running. The results were compared to existing acceptability/design criteria for classrooms and industrial workshops, related to background-noise level, teacher noise exposure, reverberation time, speech-intelligibility index (SII) and sound-level reduction with distance doubling (DL2), and pass/fail ratings were assigned. Noise levels and reverberation times in most unoccupied TES were higher than the acceptability/design criteria for core learning spaces. Teacher daily noise exposures in occupied TES were high and often exceeded regulatory limits. SII values often indicated ‘poor’ speech intelligibility for ‘normal’ and ‘raised’ vocal outputs, and ‘good’ speech intelligibility only for ‘loud’ and ‘shout’ vocal outputs. DL2 values were unacceptable in most of the TES. Most TES received a failing grade with respect to most evaluation criteria. The results confirm the existence of an acoustical conflict; the acoustical conditions in the TES as industrial rooms are generally unsatisfactory for their use as classrooms. In general, the results suggest that TES provide poor acoustical conditions, overexposing teachers and students to noise, and are in need of effective sound-design and noise-control measures.

A novel method for in-vehicle speech intelligibility evaluation and statistical variability analysis

A novel method for evaluating in-vehicle speech intelligibility is proposed using the speech intelligibility index (SII) based on measured speech signal, evaluated at the sentence speech reception threshold (sSRT) in a simulated driving environment. The statistical variability was quantified by considering the hearing ability of normal hearing individuals and the influence of multi-sensory perception on the in-vehicle speech intelligibility. The sSRT values were obtained from the hearing in noise test (HINT) using a jury of 30 participants in a driving simulation created by Samardzic et al. (2012). Different configurations of the talker and the listener and vehicle operating conditions were also considered. The SII values evaluated at the sSRT and the associated statistical variability presented in this study provide a benchmark for future evaluation of in-vehicle speech intelligibility.

Acoustical characteristics of Technology Educational Shops in British Columbia

Technology Educational Shops (TES) are designed to develop high school students’ technological literacy. Their acoustical conditions play a dominant role in the quality of these environments. TES are, at the same time, classrooms for learning and industrial workshops for making things. Each use has its own standards governing its acoustical characteristics: ANSI S12.60-2002 for classrooms and the Ondet & Sueur DL2 criteria for workshops. A major conflict could exist by using the same room for two different purposes. This study investigated this conflict by evaluating the acoustical characteristics of 20 unoccupied wood, metal and automotive shops. It conducted measurements of background noise level (BNL), reverberation time (RT), speech intelligibility index (SII), and DL2. Results showed that BNLs and RTs in most TES were higher than the acceptability criteria for unoccupied core learning spaces. SII values indicated bad/poor speech intelligibility for normal and raised voice levels and reasonable/good speech intelligibility for loud and shout voice levels. DL2 values were found acceptable in TES larger than 100 m2 in floor area. In general, these results indicate the poor acoustical conditions of TES as classrooms, and the need for special sound control measures.

Modeling speech intelligibility in quiet and noise in listeners with normal and impaired hearing

The speech intelligibility index (SII) is an often used calculation method for estimating the proportion of audible speech in noise. For speech reception thresholds (SRTs), measured in normally hearing listeners using various types of stationary noise, this model predicts a fairly constant speech proportion of about 0.33, necessary for Dutch sentence intelligibility. However, when the SII model is applied for SRTs in quiet, the estimated speech proportions are often higher, and show a larger inter-subject variability, than found for speech in noise near normal speech levels [65 dB sound pressure level (SPL)]. The present model attempts to alleviate this problem by including cochlear compression. It is based on a loudness model for normally hearing and hearing-impaired listeners of Moore and Glasberg [(2004). Hear. Res. 188, 70-88]. It estimates internal excitation levels for speech and noise and then calculates the proportion of speech above noise and threshold using similar spectral weighting as used in the SII. The present model and the standard SII were used to predict SII values in quiet and in stationary noise for normally hearing and hearing-impaired listeners. The present model predicted SIIs for three listener types (normal hearing, noise-induced, and age-induced hearing loss) with markedly less variability than the standard SII.

Noise-management algorithm may improve speech intelligibility in noise

A likely consequence of sensorineural hearing loss is a diminished ability to understand speech in noisy backgrounds. Indeed, the inability to hear in noise is one of the main reasons for dissatisfaction with hearing aid use.1 Although hearing aids with a directional microphone provide substantial improvement in the ability of wearers to understand speech in noisy environments,2 space requirements and the uncertainty of directional characteristics when a directional hearing aid is inserted deeply into the ear canal prevent the implementation of such technology in the smallest completely-in-the-canal (CIC) hearing aids. A patient who insists on wearing CIC hearing aids will have to rely solely on the efficacy of single-mic noise-management strategies. Currently, most commercial “noise reduction” schemes use the modulation rates of the input signal as a basis for estimating the “speech” and “noise” nature of the input. “Speech” sounds are amplified with input-dependent gain, while “noise” sounds are typically amplified at a reduced gain level beyond input-dependent levels (see Chung, 20043). The exact amount of gain reduction and its time course vary greatly among manufacturers. Despite such differences, most studies have reported only an improvement in listening comfort by use of such a scheme.4 The improvement in listening comfort is noteworthy. It suggests that hearing-impaired persons whose hearing aids have noise reduction may be less affected by high-output sound pressure levels, less stressed, and less distracted in noisy situations, and may be more likely to attend to the sound sources and wear their hearing aids longer than if they lacked this feature. Wearers may also improve their participation in daily activities and their quality of life. It is possible that the reduction in stress level (or distractions) may improve the user’s speech understanding in some noisy environments.

Prevalence of Hearing Impairment in a Rural Midwestern Cohort: Estimates from the Keokuk County Rural Health Study, 1994 to 1998

The current paper estimates the prevalence of hearing problems in a rural population, analyzes the prevalence of hearing problems across age groups, and compares the prevalence of hearing problems in this population with results obtained in other populations. Data were obtained from a random sample of the residents of a rural county, stratified by farm, rural non-farm, and town residence. Hearing test results were obtained from participants between the ages of 8 and 92 years (N = 1972; 47% male). Pure-tone thresholds were classified as normal or impaired using a number of metrics, including speech intelligibility index values. Selected comparisons of crude rates were made with previous population-based studies of hearing loss prevalence. Nearly all (99%) of the participants in this study had significant hearing impairment. Atypical hearing impairment is most prevalent at 6 kHz. In males, this excess impairment shifts to lower frequencies with age but monotonically decreases in females. Notched configurations were most common among those between 30 and 59 years old. In females, the prevalence of hearing impairments sufficient to interfere with speech understanding begins to rapidly increase in the 6th decade (4th decade in males). Comparisons with prior population-based studies in the United States and Great Britain identified few significant differences. Significant hearing impairment is common in rural populations. The high prevalence in this population is similar to that found in other population-based studies. Future studies are needed to examine (1) the risk factors for hearing impairment, (2) the natural course of hearing problems across the life span, and (3) the effect of programs for the prevention of hearing impairment and rehabilitation for persons with existing hearing impairments.

Coherence and the speech intelligibility index

The speech intelligibility index (SII) (ANSI S3.5-1997) provides a means for estimating speech intelligibility under conditions of additive stationary noise or bandwidth reduction. The SII concept for estimating intelligibility is extended in this paper to include broadband peak-clipping and center-clipping distortion, with the coherence between the input and output signals used to estimate the noise and distortion effects. The speech intelligibility predictions using the new procedure are compared with intelligibility scores obtained from normal-hearing and hearing-impaired subjects for conditions of additive noise and peak-clipping and center-clipping distortion. The most effective procedure divides the speech signal into low-, mid-, and high-level regions, computes the coherence SII separately for the signal segments in each region, and then estimates intelligibility from a weighted combination of the three coherence SII values.

An SII-based approach to predict the speech intelligibility in fluctuating noise for normal-hearing listeners

The speech intelligibility index (SII) is frequently used to predict the speech intelligibility for speech in a given interfering noise. However, the SII model only has been validated for speech in stationary noise. Since the SII departs from speech and noise spectra, it does not take into account any fluctuations in the masking noise. Hence, the model will yield similar SII values, regardless of the degree of fluctuation. In contrast, from the literature it is clear that normal-hearing listeners can benefit from the fluctuations in the noise. The present paper describes an SII-based approach to model speech reception thresholds (SRTs) for speech in both stationary and fluctuating noise. The basic principle of this approach is that both speech and noise signals are partitioned into small time frames. Within each time frame, the conventional SII is determined, yielding the speech information available to the listener at that time frame. Next, the SII values of these time frames are averaged, resulting in the SII for that particular condition. With the aid of SRT data from the literature, it will be shown that this approach can give a good account for most existing data.

Speech production in noise with and without hearing protection.

People working in noisy environments often complain of difficulty communicating when they wear hearing protection. It was hypothesized that part of the workers' communication difficulties stem from changes in speech production that occur when hearing protectors are worn. To address this possibility, overall and one-third-octave-band SPL measurements were obtained for 16 men and 16 women as they produced connected speech while wearing foam, flange, or no earplugs (open ears) in quiet and in pink noise at 60, 70, 80, 90, and 100 dB SPL. The attenuation and the occlusion effect produced by the earplugs were measured. The Speech Intelligibility Index (SII) was also calculated for each condition. The talkers produced lower overall speech levels, speech-to-noise ratios, and SII values, and less high-frequency speech energy, when they wore earplugs compared with the open-ear condition. Small differences in the speech measures between the talkers wearing foam and flange earplugs were observed. Overall, the results of the study indicate that talkers wearing earplugs (and consequently their listeners) are at a disadvantage when communicating in noise.