Higher Speech Intelligibility Research Articles

Influence of Test Room Acoustics on Non-Native Listeners’ Standardized Test Performance

Understanding the impact of room acoustics on non-native listeners is crucial, particularly in standardized English as a foreign language (EFL) proficiency testing environments. This study aims to elucidate how acoustics influence test scores, considering variables overlooked in prior research such as seat position and baseline language proficiency. In this experiment, 42 Japanese university students’ performance on standardized EFL listening tests was assessed in two rooms with distinct acoustic qualities, as determined by the speech transmission index (STI) and reverberation time (RT). The rooms differed significantly in their STI values and RT measurements, with one exhibiting high speech intelligibility qualities of ≥0.66 STI and RT0.5–2kHz < 0.7 s and the other falling below these benchmarks. The findings revealed that listening test scores were consistently higher in the acoustically favorable room across all participants. Notably, the negative effect of poor acoustics was more pronounced for students with lower baseline language proficiency. No significant score differences were observed between front- and rear-seat positions, suggesting that overall room acoustics may be more influential than individual seating locations. The study concludes that acoustics play a significant role in the standardized EFL test performance, particularly for lower-proficiency learners. This highlights the necessity of standardized testing environments to be more carefully selected in order to ensure the fair and reliable assessment of language proficiency.

Case study of HVAC noise in a conference room under varying operating conditions

Conference rooms are acoustically sensitive environments due to the need for high speech intelligibility both in-person and over teleconferencing systems. Room noise from building systems is a key contributing factor to speech intelligibility. Mechanical design, and in turn noise control design, focuses on peak heating and cooling demand; however, operating conditions vary based on the demand at any given time. This case study presents sound pressure level measurements from a conference room on the top floor of an office building, which was below a mechanical penthouse. The measurements were guided by ANSI/ASA S12.2, "Criteria for Evaluating Room Noise." Commissioning and developer agents varied the operating conditions of the entire building heating and cooling system to identify the primary contributors to room noise levels in the conference room, which varied as much as 13 dBA over background. Particular attention is given to the correlation between room noise levels and airflow from the air terminal unit serving the space. Comparisons between measured noise levels and noise modeling predictions are also provided.

A prediction model of speech transmission index based on reverberation time in non-native linguistic context

High speech intelligibility is an essential requirement for classrooms, especially in relation to non-native students. Speech transmission index (STI) was proved as the most relevant acoustic parameter to assess speech intelligibility. In this paper, twenty-seven classrooms for non-native teaching purposes were selected for investigation. Physical acoustic measurements were conducted in these classrooms and numerical simulation verification was determined by ODEON version 16. The relationships between STI values and RT values were fitted based on non-linear curve fitting regression models. In this paper, three primary forms of non-linear curve fitting regression models were employed for predicting curves. A logarithmic function was selected as the basic regression equation to describe the effects of RT values on STI values. The results showed that STI values increase with the decrease of RT values for all age groups. From the verified results, it was possible to propose the predictive equation that presents the best accuracy in predicting the experimental data for non-native teaching purposes. The impact of different age groups and linguistic environment on STI were discussed. The prediction model is expected to estimate STI values by using RT values during the early design stage in a non-native linguistic context.

To Study the Effect of Anterior Palatal Surface Modifications of Complete Denture on Speech Intelligibility Oral Perception and Cortical Brain Function Activity: An In Vivo Study.

The classic maxillary full denture covers the whole palate,preventing the tongue from touching the denture base tissues itself.Thus, it has deleterious effects on cortical brain function and the ability to understand spoken language. This study aimed to determinethe effect of anterior palatal surface modifications of the complete denture on speech intelligibility oral perception and cortical brain function activity. This study compared the speech clarity, oral discernment, and cortical mind capability activity of complete denture wearers in three study groups: a)complete denture wearers with a small opening (SO) in the maxillary front palatal base; b) complete denture patients who wear regular complete denture; c) complete denture patients who did not wear complete denture; and d) complete denture patients who wear a functionally contoured modified palate(FCMP). Patients with no teeth at all underwent four phases of testing to assess their cognitive abilities and speech quality (pitch and volume). In the first phase, partial dentures were used. During phase 2, a conventional full denture was inserted.In the third phase, a palatal base denture was functionally altered. In phase 4, dentures with a little aperture at the front of the palatal base were used. Results:The values of pitch and intensity of sound in category A with FCMP modification I were 180.76 ± 24.12 and 73.27 ± 9.74,respectively. On the other hand, the values of pitch and intensity of sound in category B with FCMP modification I were 185.41 ± 27.29and 73.91 ± 8.31, respectively. The values of pitch and intensity of sound in category A with SO modification II were 188.52 ± 21.11 and 76.13 ± 5.21, respectively. On the other hand, the values of pitch and intensity of sound in category B with SO modification II were 194.59 ± 24.02and 75.21 ± 6.12, respectively. The findings for values of pitch and intensity were statistically significant among the four phases (p < 0.001). The highest speech intelligibility and cortical brain function were observed in phase 4 in both categories A and B, with the highest scores by experts of 3.21 and 3.42, respectively. Conclusion:Based on the findings of this in vivo investigation, it can be concluded that using modified dentures (modification types I and II) following denture installation improves speech intelligibility, oral perception, and cortical brain function activity.

Assessment of speech transmission index and reverberation time in standardized English as a foreign language test rooms

Today, millions of standardized English as a foreign language proficiency tests are administered globally each year. A large portion of this is conducted as a paper-based test in which the listening section is commonly delivered through loudspeakers to groups of test takers, a method in which the audio signals are exposed to the acoustic tendencies of each particular venue. As it is well-established in the literature that non-native listeners are more susceptible to adverse listening conditions compared to their native counterparts, there is a need for an objective examination of the acoustic quality of such environments. This study examined the speech transmission index for public address systems (STIPA) for three types of sound sources (wall-mounted speakers, radio cassette player, and amplified speaker) and reverberation time (RT) in 10 unoccupied classrooms commonly used as test rooms at a university in Japan. The results revealed that STI was found to be statistically significantly different for the amplified speaker compared to both or one other sound source in eight out of 10 rooms. The amplified speaker also recorded the highest STI among the three sound sources in eight out of 10 rooms and the most rooms with STI entirely above 0.66, a minimum target value prescribed in IEC 60268–16:2020 as exhibiting high speech intelligibility. Additionally, ≥ 0.66 STI was consistently observed in rooms with RT0.5-2kHz≤ 0.7 s. Further observations are discussed to better understand the current conditions under which these tests are administered

Use of Automated Kinematic Diadochokinesis Analysis to Identify Potential Indicators of Speech Motor Involvement in Children With Cerebral Palsy.

This study examined multiple variables obtained from an automated measure of lip movement during a diadochokinesis (DDK) task to identify those with potential to detect mild speech motor involvement in school-age children diagnosed with cerebral palsy (CP). Eight children with CP and high speech intelligibility and a matched group of eight children with typical development (TD) completed a DDK task while their lip and jaw movements were recorded. A custom MATLAB algorithm was used to automatically extract 23 kinematic measures of children's lip movements during production of the DDK sequences. Mann-Whitney U tests were used to compare groups on the kinematic measures, and receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic accuracy of measures that significantly differed between groups. Five of the 23 kinematic variables differed significantly between the CP and TD groups. These were two measures of overall DDK performance (i.e., duration of the DDK sequence and number of cycles) and three spatial and temporal measures of lip movement. Duration of the DDK sequence and the mean displacement of the lips across cycles had the highest diagnostic accuracy, differentiating CP and TD groups with 88% sensitivity and 88% specificity. Automatically derived kinematic measures of DDK sequences differentiated children with CP and high intelligibility from typically developing children. Future research is needed to determine the clinical utility of these measures for detecting speech motor impairment.

Using active noise-cancelling headphones in open-plan offices: No influence on cognitive performance but improvement of perceived privacy and acoustic environment

High speech intelligibility in open-plan offices and thus a high changing-state character of the acoustic environment have been found to negatively influence cognitive performance. This is often attributed to the so-called irrelevant speech effect. Office workers lately use active noise-cancelling (ANC) headphones to improve the acoustic situation by blocking unwanted sound. However, it is currently unknown if using ANC headphones in a noisy setting improves cognitive performance. Two studies were conducted to examine if ANC headphones improve cognitive performance and the subjective well-being of employees in an open-plan office. Cognitive performance was measured using a serial recall test. Subjective assessments were measured using a questionnaire. The participants were tested in silence, speech without headphones, speech with ANC headphones switched off and speech with ANC headphones switched on. No statistically significant differences were found between the conditions with ANC headphones switched on and off as well as without headphones for cognitive performance. However, ANC headphones statistically significantly improved subjective assessments such as perceived privacy and the assessment of the acoustic environment. The results provide a scientific basis for evaluating and planning the appropriate use of ANC headphones for concentration-intensive activities such as office work.

Employer ratings of cochlear implant users from speech samples

This study continues a project on speech-based perceptual “first impressions” of early-implanted cochlear implant (CI) users. Hiring managers with typical hearing (TH, N = 72) from various industries heard speech samples from CI users and TH young adults and rated their personalities and attractiveness as applicants for various types of jobs. As with college-student peer listeners in prior studies, employers rated TH speakers most positively, CI users with high speech intelligibility (CI-Hi) as intermediate, and CI users with lower intelligibility (CI-Lo) most negatively. Within this pattern, CI-Hi were rated somewhat lower by managers hiring for white-collar jobs (versus blue-collar) and by those who placed high importance on communication skills, who also rated CI-Lo lower on communication skills and “hirability” but higher on extroversion. These patterns underline the practical importance of CI users’ speech intelligibility on their employment opportunities, particularly when entering white-collar and highly communicative jobs, where biases may exist against deaf speech and other unfamiliar patterns. However, managers with more knowledge of and experience with deafness rated CI-Hi communication skills more positively, supporting the value of increasing opportunities for interaction at school and work, as well as education about deafness, its effects on speech, and communication-repair strategies within the workplace.

Factors Associated With Hearing Aid Wear Time in a Subset of U.S. Military Veterans: Tinnitus, the Presence of One or More Neurologic Conditions, and Unaided Speech Intelligibility Index.

A retrospective analysis was conducted to explore how tinnitus, one or more neurologic conditions, unaided speech intelligibility index, and other comorbidities impact the average number of hours hearing aids are worn each day by U.S. Military Veterans. Medical records and a hearing aid database were queried to obtain information regarding active medical problems and average daily hearing aid wear time. Multiple linear regression was used to explore these relationships for 215 male Veterans whose records were available from 2009 to 2020. To be analyzed, Veterans must have possessed their hearing aid(s) for at least 3 consecutive months. An active problem of subjective tinnitus was associated with increased hearing aid wear time (positive association) and one or more active neurologic conditions were associated with decreased hearing aid wear time (negative association). A high unaided speech intelligibility index (greater access to speech sounds without hearing aids) was also associated with decreased hearing aid wear time (negative association). There are many complex audiologic and medical concerns that may affect hearing aid wear time in U.S. Military Veterans. Therefore, the information from this study should be expanded on prospectively by further exploring these associations, and their severity, on hearing aid wear time. The information from this and future studies may lead to clinical recommendations with the goal of increasing daily hearing aid use in this and other populations.

Assessment of speech intelligibility in university lecture rooms of different sizes using objective and subjective methods

The scores of speech intelligibility, obtained using objective and subjective methods for three university lecture rooms of the small, medium, and large sizes with different degrees of filling, were presented. The problem of achieving high speech intelligibility is relevant for both students and university administration, and for architects designing or reconstructing lecture rooms. Speech intelligibility was assessed using binaural room impulse responses which applied an artificial head and non-professional quality audio equipment for measuring. The Speech Transmission Index was an objective measure of speech intelligibility, while the subjective evaluation of speech intelligibility was carried out using the articulation method. Comparative analysis of the effectiveness of parameters of impulse response as a measure of speech intelligibility showed that Early Decay Time exceeded the score of the T30 reverberation time but was ineffective in a small lecture room. The C50 clarity index for all the considered lecture rooms was the most informative. Several patterns determined by the influence of early sound reflections on speech intelligibility were detected. Specifically, it was shown that an increase in the ratio of the energy of early reflections to the energy of direct sound leads to a decrease in speech intelligibility. The exceptions are small, up to 30‒40 cm, distances from the back wall of the room, where speech intelligibility is usually slightly higher than in the middle of the room. At a distance of 0.7–1.7 m from the side walls of the room, speech intelligibility is usually worse for the ear, which is closer to the wall. The usefulness of the obtained results lies in refining the quantitative characteristics of the influence of early reflections of sound on speech intelligibility at different points of lecture rooms.

Development of an Australian behavioural method for assessing listening task difficulty at high speech intelligibility levels

Objective To develop and validate an Australian version of a behavioural test for assessing listening task difficulty at high speech intelligibility levels. Design In the SWIR-Aus test, listeners perform two tasks: identify the last word of each of seven sentences in a list and recall the identified words after each list. First, the test material was developed by creating seven-sentence lists with similar final-word features. Then, for the validation, participant’s performance on the SWIR-Aus test was compared when a binary mask noise reduction algorithm was on and off. Study sample All participants in this study had normal hearing thresholds. Nine participants (23.8–56.0 years) participated in the characterisation of the speech material. Another thirteen participants (18.4–59.1 years) participated in a pilot test to determine the SNR to use at the validation stage. Finally, twenty-four new participants (20.0–56.9 years) participated in the validation of the test. Results The results of the validation of the test showed that recall and identification scores were significantly better when the binary mask noise reduction algorithm was on compared to off. Conclusions The SWIR-Aus test was developed using Australian speech material and can be used for assessing task difficulty at high speech intelligibility levels.

Effect of Auditory Distraction on Working Memory, Attention Switching, and Listening Comprehension.

The effect of non-informational speech spectrum noise as a distractor on cognitive and listening comprehension ability was examined in fifty-three young, normal hearing adults. Time-controlled tasks were used to measure auditory working memory (WM) capacity and attention switching (AS) ability. Listening comprehension was measured using a lecture, interview, and spoken narratives test. Noise level was individually set to achieve at least 90% or higher speech intelligibility. Participants’ listening comprehension in the presence of distracting noise was better on inference questions compared to listening in quiet. Their speed of information processing was also significantly faster in WM and AS tasks in noise. These results were consistent with the view that noise may enhance arousal levels leading to faster information processing during cognitive tasks. Whereas the speed of AS was faster in noise, this rapid switching of attention resulted in more errors in updating items. Participants who processed information faster in noise and did so accurately, more effectively switched their attention to refresh/rehearse recall items within WM. More efficient processing deployed in the presence of noise appeared to have led to improvements in WM performance and making inferences in a listening comprehension task. Additional research is required to examine these findings using background noise that can cause informational masking.

Speech Perception with Noise Vocoding and Background Noise: An EEG and Behavioral Study.

This study explored the physiological response of the human brain to degraded speech syllables. The degradation was introduced using noise vocoding and/or background noise. The goal was to identify physiological features of auditory-evoked potentials (AEPs) that may explain speech intelligibility. Ten human subjects with normal hearing participated in syllable-detection tasks, while their AEPs were recorded with 32-channel electroencephalography. Subjects were presented with six syllables in the form of consonant-vowel-consonant or vowel-consonant-vowel. Noise vocoding with 22 or 4 frequency channels was applied to the syllables. When examining the peak heights in the AEPs (P1, N1, and P2), vocoding alone showed no consistent effect. P1 was not consistently reduced by background noise, N1 was sometimes reduced by noise, and P2 was almost always highly reduced. Two other physiological metrics were examined: (1) classification accuracy of the syllables based on AEPs, which indicated whether AEPs were distinguishable for different syllables, and (2) cross-condition correlation of AEPs (rcc) between the clean and degraded speech, which indicated the brain's ability to extract speech-related features and suppress response to noise. Both metrics decreased with degraded speech quality. We further tested if the two metrics can explain cross-subject variations in their behavioral performance. A significant correlation existed for rcc, as well as classification based on early AEPs, in the fronto-central areas. Because rcc indicates similarities between clean and degraded speech, our finding suggests that high speech intelligibility may be a result of the brain's ability to ignore noise in the sound carrier and/or background.

An Archaeoacoustics Analysis of Cistercian Architecture: The Case of the Beaulieu Abbey

The Cistercian order is of acoustic interest because previous research has hypothesized that Cistercian architectural structures were designed for longer reverberation times in order to reinforce Gregorian chants. The presented study focused on an archaeoacacoustics analysis of the Cistercian Beaulieu Abbey (Hampshire, England, UK), using Geometrical Acoustics (GA) to recreate and investigate the acoustical properties of the original structure. To construct an acoustic model of the Abbey, the building’s dimensions and layout were retrieved from published archaeology research and comparison with equivalent structures. Absorption and scattering coefficients were assigned to emulate the original room surface materials’ acoustics properties. CATT-Acoustics was then used to perform the acoustics analysis of the simplified building structure. Shorter reverberation time (RTs) was generally observed at higher frequencies for all the simulated scenarios. Low speech intelligibility index (STI) and speech clarity (C50) values were observed across Abbey’s nave section. Despite limitations given by the impossibility to calibrate the model according to in situ measurements conducted in the original structure, the simulated acoustics performance suggested how the Abbey could have been designed to promote sacral music and chants, rather than preserve high speech intelligibility.

Speech and language characteristics in Smith–Magenis syndrome: Case report

Smith–Magenis syndrome (SMS) is a rare neurodevelopmental disorder with mild-to-moderate intellectual disability. Speech and language impairments have not been well described as part of the SMS phenotype. This study reports the speech and language characteristics presented by a classical SMS case, a 20-year-old woman with positive deletion in the region 17p11.2. The case presented a borderline IQ on verbal and performance Wechsler scales. Language standardized tests (i.e., Peabody, Token test, CEG test and Boehm test) and naturalistic language sample (i.e. conversation and story generation) were used to assess speech and language performance. Speech characteristics included imprecise speech, with a high speech rate, hoarse voice, hypernasality and intelligibility deficits. The performance in all standardized tests was poor. Socio-communicative deficits included repetitive and persistent verbal behavior, difficulties in the use of linguistic strategies to repair communication breakdowns, limited vocabulary production and short overall length utterances with reduced grammatical components. The results contribute to expanding knowledge about the SMS phenotype, also to highlight the need to include speech and language evaluation as part of the clinical assessment of SMS and, at the same time, to draw attention to the need to include early communications skills in language intervention programs.

Combined Brain-Perfusion SPECT and EEG Measurements Suggest Distinct Strategies for Speech Comprehension in CI Users With Higher and Lower Performance.

Cochlear implantation constitutes a successful therapy of inner ear deafness, with the majority of patients showing good outcomes. There is, however, still some unexplained variability in outcomes with a number of cochlear-implant (CI) users, showing major limitations in speech comprehension. The current study used a multimodal diagnostic approach combining single-photon emission computed tomography (SPECT) and electroencephalography (EEG) to examine the mechanisms underlying speech processing in postlingually deafened CI users (N = 21). In one session, the participants performed a speech discrimination task, during which a 96-channel EEG was recorded and the perfusions marker 99mTc-HMPAO was injected intravenously. The SPECT scan was acquired 1.5 h after injection to measure the cortical activity during the speech task. The second session included a SPECT scan after injection without stimulation at rest. Analysis of EEG and SPECT data showed N400 and P600 event-related potentials (ERPs) particularly evoked by semantic violations in the sentences, and enhanced perfusion in a temporo-frontal network during task compared to rest, involving the auditory cortex bilaterally and Broca’s area. Moreover, higher performance in testing for word recognition and verbal intelligence strongly correlated to the activation in this network during the speech task. However, comparing CI users with lower and higher speech intelligibility [median split with cutoff + 7.6 dB signal-to-noise ratio (SNR) in the Göttinger sentence test] revealed for CI users with higher performance additional activations of parietal and occipital regions and for those with lower performance stronger activation of superior frontal areas. Furthermore, SPECT activity was tightly coupled with EEG and cognitive abilities, as indicated by correlations between (1) cortical activation and the amplitudes in EEG, N400 (temporal and occipital areas)/P600 (parietal and occipital areas) and (2) between cortical activation in left-sided temporal and bilateral occipital/parietal areas and working memory capacity. These results suggest the recruitment of a temporo-frontal network in CI users during speech processing and a close connection between ERP effects and cortical activation in CI users. The observed differences in speech-evoked cortical activation patterns for CI users with higher and lower speech intelligibility suggest distinct processing strategies during speech rehabilitation with CI.

An exploratory study of student, speech–language pathologist and emergency worker impressions of speakers with dysarthria

Purpose To explore the influence of listener profession on impressions of speakers with dysarthria with varying intelligibility using semantic differential scales. M ethod: Three listener groups (undergraduate students, emergency workers, speech–language pathologists (SLPs); n = 38) rated non-speech attributes of six adults with dysarthria that ranged from low to high speech intelligibility. Participants rated 22 bipolar adjective pairs and listening effort on visual analogue scales. Following factor analysis of the semantic differential scales, listener impression and effort ratings were compared across listening groups and speaker intelligibility. Result Repeated measures ANOVA revealed that neither impressions nor effort ratings differed across listener groups. However, impressions significantly decreased and listening effort significantly increased with reduced intelligibility. Analysis of the semantic differential scale items revealed two factors (Capability, Personality) that predicted 52% of the variance. Listener impressions were significantly higher for Personality than Capability. C onclusion: Preliminary findings suggest that speakers with dysarthria with reduced intelligibility are at risk to be negatively judged, particularly on their physical and mental capability. This study demonstrates the promise of employing semantic differential scales to investigate listener impressions and therefore the daily communication experiences of speakers with dysarthria. SLPs should consider patient experience of negative impressions when designing treatment.

Effects of Reverberation on the Relation Between Compression Speed and Working Memory for Speech-in-Noise Perception.

Previous study has suggested that when listening in modulated noise, individuals benefit from different wide dynamic range compression (WDRC) speeds depending on their working memory ability. Reverberation reduces the modulation depth of signals and may impact the relation between WDRC speed and working memory. The purpose of this study was to examine this relation across a range of reverberant conditions. Twenty-eight older listeners with mild-to-moderate sensorineural hearing impairment were recruited in the present study. Individual working memory was measured using a Reading Span test. Sentences were combined with noise at two signal to noise ratios (2 and 5 dB SNR), and reverberation was simulated at a range of reverberation times (0.00, 0.75, 1.50, and 3.00 sec). Speech intelligibility was measured in listeners when listening to the sentences processed with simulated fast-acting and slow-acting WDRC conditions. There was a significant relation between WDRC speed and working memory with minimal or no reverberation. Consistent with previous research, this relation was such that individuals with high working memory had higher speech intelligibility with fast-acting WDRC, and individuals with low working memory performed better with slow-acting WDRC. However, at longer reverberation times, there was no relation between WDRC speed and working memory. Consistent with previous studies, results suggest that there is an advantage of tailoring WDRC speed based on an individual's working memory under anechoic conditions. However, the present results further suggest that there may not be such a benefit in reverberant listening environments due to reduction in signal modulation.

A dissociation between speech understanding and perceived reverberation

As direct-to-reverberant energy ratio (DRR) decreases or decay time increases, speech intelligibility tends to decrease for both normal-hearing and hearing-impaired listeners. Given this relationship, it is easy to assume that perceived reverberation (reverberance) would act as an intermediary—as physical reverberation increases, so does reverberance, and speech intelligibility decreases as a result. This assumption has not been tested explicitly. Two experiments were conducted to test this hypothesis. In Experiment 1, listeners performed a magnitude estimation task, reporting reverberance for speech stimuli that were convolved with impulse responses whose reverberant properties were manipulated. Listeners reported a decrease in reverberance when the DRR was increased at both ears (Natural Room condition), but not when it was increased at only the ear nearest the source (Hybrid condition). In Experiment 2, listeners performed a speech intelligibility task wherein noise-masked speech was convolved with a subset of the impulse responses from Experiment 1. As predicted by the speech transmission index (STI), speech intelligibility was good in cases where at least one ear received non-reverberant speech, including the Hybrid listening condition in Experiment 1. Thus, the Hybrid listening condition resulted simultaneously in high reverberance (Exp. 1) and high speech intelligibility (Exp. 2), demonstrating that reverberance and speech intelligibility can be dissociated.

Effect of Noise Reduction Gain Errors on Simulated Cochlear Implant Speech Intelligibility.

It has been suggested that the most important factor for obtaining high speech intelligibility in noise with cochlear implant (CI) recipients is to preserve the low-frequency amplitude modulations of speech across time and frequency by, for example, minimizing the amount of noise in the gaps between speech segments. In contrast, it has also been argued that the transient parts of the speech signal, such as speech onsets, provide the most important information for speech intelligibility. The present study investigated the relative impact of these two factors on the potential benefit of noise reduction for CI recipients by systematically introducing noise estimation errors within speech segments, speech gaps, and the transitions between them. The introduction of these noise estimation errors directly induces errors in the noise reduction gains within each of these regions. Speech intelligibility in both stationary and modulated noise was then measured using a CI simulation tested on normal-hearing listeners. The results suggest that minimizing noise in the speech gaps can improve intelligibility, at least in modulated noise. However, significantly larger improvements were obtained when both the noise in the gaps was minimized and the speech transients were preserved. These results imply that the ability to identify the boundaries between speech segments and speech gaps may be one of the most important factors for a noise reduction algorithm because knowing the boundaries makes it possible to minimize the noise in the gaps as well as enhance the low-frequency amplitude modulations of the speech.