Young Normal-hearing Listeners Research Articles

Subjective Speech Intelligibility Drives Noise-Tolerance Domain Use During the Tracking of Noise-Tolerance Test.

Recently, the Noise-Tolerance Domains Test (NTDT) was applied to study the noise-tolerance domains used by young normal-hearing (NH) listeners during noise acceptance decisions. In this study, we examined how subjective speech intelligibility may drive noise acceptance decisions by applying the NTDT on NH and hearing-impaired (HI) listeners at the signal to noise ratios (SNRs) around the Tracking of Noise-Tolerance (TNT) thresholds. A single-blind, within-subjects design with 22 NH and 17 HI older adults was followed. Listeners completed the TNT to determine the average noise acceptance threshold (TNTAve). Then, listeners completed the NTDT at the SNRs of 0, ±3 dB (re: TNTAve) to estimate the weighted noise-tolerance domain ratings (WNTDRs) for each domain criterion. Listeners also completed the Objective and Subjective Intelligibility Difference (OSID) Test to establish the individual intelligibility performance-intensity (P-I) functions of the TNT materials. All test measures were conducted at 75 and 82 dB SPL speech input levels. NH and HI listeners were tested in the unaided mode. The HI listeners were also tested using a study hearing aid. The WNTDRs were plotted against subjective speech intelligibilities extrapolated from individual P-I of the OSID at the SNRs corresponding to NTDT test conditions. Listeners were grouped according to their most heavily weighed domain and a regression analysis was performed against listener demographics as well as TNT and OSID performances to determine which variable(s) affected listener grouping. Three linear mixed effects (LMEs) models were used to examine whether WNTDRs changed with subjective speech intelligibility. All three LMEs found significant fixed effects of domain criteria, subjective intelligibility, and speech input level on WNTDRs. In general, heavier weights were assigned to speech interference and loudness domains at poorer intelligibility levels (<50%) with reversals to distraction and annoyance at higher intelligibility levels (>80%). The comparison between NH and HI-unaided showed that NH listeners assigned greater weights to loudness than the HI-unaided listeners. The comparison between NH and HI-aided groups showed similar weights between groups. The comparison between HI-unaided and HI-aided found that HI listeners assigned lower weights to speech interference and greater weights to loudness when tested in aided compared with unaided modes. In all comparisons, loudness was weighed heavier at the 82 dB SPL input level than at the 75 dB SPL input level with greater weights to annoyance in the NH versus HI-unaided comparison and lower weights to distraction in the HI-aided versus HI-unaided comparison. A generalized linear model determined that listener grouping was best accounted for by subjective speech intelligibility estimated at TNTAve. The domain criteria used by listeners were driven by their subjective speech intelligibility regardless of their hearing status (i.e., NH versus HI). In general, when subjective intelligibility was poor, the domains of speech interference and loudness were weighed the heaviest. As subjective intelligibility improved, the weightings on annoyance and distraction increased. Furthermore, a listener's criterion for >90% subjective speech understanding at the TNTAve may allow one to profile the listener.

Comparison of Psychometric Functions Measured Using Remote Testing and Laboratory Testing.

The use of remote testing to collect behavioral data has been on the rise, especially after the COVID-19 pandemic. Here we present psychometric functions for a commonly used speech corpus obtained in remote testing and laboratory testing conditions on young normal hearing listeners in the presence of different types of maskers. Headphone use for the remote testing group was checked by supplementing procedures from prior literature using a Huggins pitch task. Results revealed no significant differences in the measured thresholds using the remote testing and laboratory testing conditions for all the three masker types. Also, the thresholds measured obtained in these two conditions were strongly correlated for a different group of young normal hearing listeners. Based on the results, excellent outcomes on auditory threshold measurements where the stimuli are presented both at levels lower than and above an individual's speech-recognition threshold can be obtained by remotely testing the listeners.

Sound-localization-related activation and functional connectivity of dorsal auditory pathway in relation to demographic, cognitive, and behavioral characteristics in age-related hearing loss.

Patients with age-related hearing loss (ARHL) often struggle with tracking and locating sound sources, but the neural signature associated with these impairments remains unclear. Using a passive listening task with stimuli from five different horizontal directions in functional magnetic resonance imaging, we defined functional regions of interest (ROIs) of the auditory "where" pathway based on the data of previous literatures and young normal hearing listeners (n = 20). Then, we investigated associations of the demographic, cognitive, and behavioral features of sound localization with task-based activation and connectivity of the ROIs in ARHL patients (n = 22). We found that the increased high-level region activation, such as the premotor cortex and inferior parietal lobule, was associated with increased localization accuracy and cognitive function. Moreover, increased connectivity between the left planum temporale and left superior frontal gyrus was associated with increased localization accuracy in ARHL. Increased connectivity between right primary auditory cortex and right middle temporal gyrus, right premotor cortex and left anterior cingulate cortex, and right planum temporale and left lingual gyrus in ARHL was associated with decreased localization accuracy. Among the ARHL patients, the task-dependent brain activation and connectivity of certain ROIs were associated with education, hearing loss duration, and cognitive function. Consistent with the sensory deprivation hypothesis, in ARHL, sound source identification, which requires advanced processing in the high-level cortex, is impaired, whereas the right-left discrimination, which relies on the primary sensory cortex, is compensated with a tendency to recruit more resources concerning cognition and attention to the auditory sensory cortex. Overall, this study expanded our understanding of the neural mechanisms contributing to sound localization deficits associated with ARHL and may serve as a potential imaging biomarker for investigating and predicting anomalous sound localization.

The contributions of acoustic and non-acoustic factors to spatial release from masking

The ability to identify speech at worse signal-to-noise ratios when the maskers are spatially separated compared to when they are colocated is called spatial release from masking (SRM) and is thought to be a combination of monaural and binaural advantages arising from spatially separating the target from the maskers. Also, a host of other cognitive skills including attention, working memory, and executive function that support listeners’ ability to segregate, track and attend to a “target” signal while tuning out other unwanted signals contributes to understanding speech better in complex environments. Previous research with young normal hearing listeners from our lab indicated that SRM was predicted by an individual’s ability to use binaural cues (ITD thresholds), switch attention between two streams of information (trail making test) and ability to suppress irrelevant information (flanker task). Here, we present data from older listeners with varying hearing abilities on acoustic (envITD sensitivity) and non-acoustic tasks measuring attention (auditory and visual single and dual task), processing (trail making task), executive control (flanker task) and speech in noise tests (spatial release from masking using coordinate Response Measure sentences). The relationship between these acoustic and non-acoustic factors to speech understanding in complex listening environments will be discussed.

Portable automated rapid testing: Validation of automated testing on older listeners from India

Portable automated rapid testing (PART) is an iPad application (https://braingamecenter.ucr.edu/games/p-a-r-t/) capable of measuring various psychoacoustic thresholds in an automated and rapid format using commercially available headphones. The app has been validated previously in native speakers of English and an adapted version of the app has been validated in young normal hearing listeners from Mexico. Previous research from our labs indicated that the thresholds obtained using non-speech tasks did not differ significantly between the native and the non-native speakers of English while the native speakers of English had significantly better thresholds in the speech task. However, there was no significant difference in the amount of spatial release from masking between the groups. Here, we present psychoacoustic threshold data for a large cohort of older listeners from India with various English proficiencies. The thresholds obtained from this group will be compared against previously published thresholds based on native speakers of English. It is hypothesized that the results would be similar to what was found earlier with younger listeners from India. These results will give us the evidence to start using this app to measure thresholds of various central auditory processing measures in non-native speakers of English.

Estimating the high-frequency extent of binaural sensitivity to temporal fine structure across listeners

Füllgrabe et al. [2017, Int. J. Audiol. 56:926-35] developed a novel procedure to estimate the frequency dependence of listeners’ sensitivity to temporal fine structure in the form of interaural phase differences (IPD). Whereas traditional approaches fixed tone frequency and varied IPD, the new “TFS-AF” test fixed the IPD and varied frequencies adaptively so as to estimate the upper frequency limit (UFL) of IPD sensitivity, even in listeners who struggle with traditional tests. UFL estimates for young normal hearing listeners were consistently 1200–1400 Hz, with notable exceptions of lower UFL (e.g. 800–1000 Hz) in a small subset. The consistency of UFL and abrupt loss of IPD sensitivity above it remain among the most puzzling aspects of binaural hearing, unexplained by the (rather shallow) frequency dependence of audibility, neuronal phase locking, or internal noise in this region. Recently, our group adapted a version of the TFS-AF test to measure UFL as a function of sound level, comparing the resulting slope to predictions of candidate mechanisms. The limitation closely matches the upper edge of an auditory filter centered at ∼700 Hz, suggesting that IPD sensitivity is mediated exclusively by neurons tuned to that frequency or below. [Work supported by NIH R01DC014948, R01DC016643, and R01DC017924.]

Benefits of Harmonicity for Hearing in Noise Are Limited to Detection and Pitch-Related Discrimination Tasks.

Harmonic complex tones are easier to detect in noise than inharmonic complex tones, providing a potential perceptual advantage in complex auditory environments. Here, we explored whether the harmonic advantage extends to other auditory tasks that are important for navigating a noisy auditory environment, such as amplitude- and frequency-modulation detection. Sixty young normal-hearing listeners were tested, divided into two equal groups with and without musical training. Consistent with earlier studies, harmonic tones were easier to detect in noise than inharmonic tones, with a signal-to-noise ratio (SNR) advantage of about 2.5 dB, and the pitch discrimination of the harmonic tones was more accurate than that of inharmonic tones, even after differences in audibility were accounted for. In contrast, neither amplitude- nor frequency-modulation detection was superior with harmonic tones once differences in audibility were accounted for. Musical training was associated with better performance only in pitch-discrimination and frequency-modulation-detection tasks. The results confirm a detection and pitch-perception advantage for harmonic tones but reveal that the harmonic benefits do not extend to suprathreshold tasks that do not rely on extracting the fundamental frequency. A general theory is proposed that may account for the effects of both noise and memory on pitch-discrimination differences between harmonic and inharmonic tones.

Auditory enhancement in younger and older listeners with normal and impaired hearinga).

Auditory enhancement is a spectral contrast aftereffect that can facilitate the detection of novel events in an ongoing background. A single-interval paradigm combined with roved frequency content between trials can yield as much as 20 dB enhancement in young normal-hearing listeners. This study compared such enhancement in 15 listeners with sensorineural hearing loss with that in 15 age-matched adults and 15 young adults with normal audiograms. All groups were presented with stimulus levels of 70 dB sound pressure level (SPL) per component. The two groups with normal hearing were also tested at 45 dB SPL per component. The hearing-impaired listeners showed very little enhancement overall. However, when tested at the same high (70-dB) level, both young and age-matched normal-hearing listeners also showed substantially reduced enhancement, relative to that found at 45 dB SPL. Some differences in enhancement emerged between young and older normal-hearing listeners at the lower sound level. The results suggest that enhancement is highly level-dependent and may also decrease somewhat with age or slight hearing loss. Implications for hearing-impaired listeners may include a poorer ability to adapt to real-world acoustic variability, due in part to the higher levels at which sound must be presented to be audible.

Effect of energetic and informational masking on speech reception performance in middle-aged adults

Speech reception in the presence of competing sounds declines in middle age. Experiments on young normal-hearing listeners have revealed that speech reception performance in the presence of competing sounds is determined by the cumulative effects of two different types of masking: energetic masking and information masking. Here we examined how energetic and informational masking degrades speech reception in middle-aged adults. Fifteen young (seven males, eight females, 20–26 years) and seventeen middle-aged (four males, thirteen females, 47–57 years) listeners with normal hearing participated in the experiment. Speech reception in the presence of competing sounds was assessed by the Coordinated Response Measure. Participants were required to listen to a target phrase spoken by a female in the presence of noise or a single interfering phrase spoken by the same talker, same-sex talker, or different-sex talker. Speech reception performance was lower in middle-aged adults than young adults, regardless of the type of disturbing sounds. The performance differences between the same-talker and different-sex talker conditions, which reflects the effects of informational masking, was larger in middle-aged adults. These results suggest that both energetic and informational masking contributes to the degradation of speech reception in middle-aged adults.

Visual speech benefit provided by realistic sentences in noise

Understanding speech in background noise presents a significant challenge to listeners with hearing loss. Even though hearing aids are very successful in restoring listening in quieter conditions, current devices provide only limited benefit in noise. While seeing a talker can improve intelligibility, visual benefit has typically been quantified using rather unrealistic audio-visual speech materials. Here, we investigated visual benefit using realistic effortful speech from the ECO-SiN corpus. Audio-only, audio-visual, and visual-only sentences were presented in three simulated real-world environments at their realistic sound levels in a 3-D loudspeaker array equipped with integrated high-resolution video projectors. Ten young normal-hearing (NH) listeners as well as 18 older listeners with sensorineural hearing loss participated in the experiment with and without their own hearing aids. While the NH listeners rapidly hit ceiling, listeners with hearing loss struggled to understand the audio-only sentences in the louder background noise—even when aided. There was, however, demonstrable visual benefit of up to 16% in the audio-visual condition for both groups, which is significantly less than commonly reported. Future research will explore if the individual outcomes of the audio-visual ECO-SIN test better reflects real-world hearing experience and how far this is maintained when using virtual reality glasses.

Lack of a clear head movement benefit in a spatial release form masking task

The study of spatial benefit in complex listening environments often requires listeners to maintain a fixed head position so that controls are in place for understanding binaural function. In natural listening environments, however, listeners may use head movements (e.g., turns and tilts) to achieve their maximum speech reception. In a previous study, we developed a spatial release from masking task that adapts the location of the maskers to determine the angular threshold for a predetermined masking release (in dB), and in the present study, we modified this task to allow for the listeners to move their heads as they wished to maximize performance on the task. Twenty young normal hearing listeners were tested on the head-fixed and head-free conditions. Head tracking was collected for posthoc analyses. Overall, there was no significant difference in behavioral thresholds between conditions despite wide ranges of head movements in the head-free condition. Interestingly, large individual differences in head movement translated to a narrowing of the variance in behavioral thresholds relative to the head-fixed condition, suggesting that listeners were indeed optimizing their speech reception. Further analyses will dissect the types of head movements and strategic differences among the participants, with implications for listeners with hearing loss.

Speech perception in noise: no interaction between working memory and degree of speech degradation

ABSTRACT Speech recognition in noise (SiN) requires explicit cognitive resources such as working memory capacity (WMC). However, existing evidence on the role of WMC in SiN, especially for young adults with normal hearing, is mixed. This study aimed to systematically evaluate the role of WMC when the degree of speech recognition varied as a consequence of adding background noise of varying intensity levels. Specifically, the objective was to determine whether or not there was an effect of noise level on the recruitment of WMC during speech recognition tasks. Fifty-three young adults (18–37 years) with normal hearing were recruited and their ability to recognize speech in the presence of background noise was measured using sentences and words. Speech-to-noise ratios (SNRs) were varied from +10 to −10 dB SNR in 5 dB steps to manipulate the degree of speech recognition. Listeners’ WMC was also measured using two working memory tasks. A significant positive association between WMC and SiN was found for sentence recognition in noise. However, no significant interaction between WMC and SNR was found for isolated word and sentence recognition tasks. WMC was not found to be a significant predictor of word recognition in noise. These results suggests that for young normal hearing listeners, the recruitment of WMC during sentence recognition, especially in non-informational fluctuating noise, is not modulated by the SNR .

Lateralization of binaural envelope cues measured with a mobile cochlear-implant research processora).

Bilateral cochlear implant (BICI) listeners do not have full access to the binaural cues that normal hearing (NH) listeners use for spatial hearing tasks such as localization. When using their unsynchronized everyday processors, BICI listeners demonstrate sensitivity to interaural level differences (ILDs) in the envelopes of sounds, but interaural time differences (ITDs) are less reliably available. It is unclear how BICI listeners use combinations of ILDs and envelope ITDs, and how much each cue contributes to perceived sound location. The CCi-MOBILE is a bilaterally synchronized research processor with the untested potential to provide spatial cues to BICI listeners. In the present study, the CCi-MOBILE was used to measure the ability of BICI listeners to perceive lateralized sound sources when single pairs of electrodes were presented amplitude-modulated stimuli with combinations of ILDs and envelope ITDs. Young NH listeners were also tested using amplitude-modulated high-frequency tones. A cue weighting analysis with six BICI and ten NH listeners revealed that ILDs contributed more than envelope ITDs to lateralization for both groups. Moreover, envelope ITDs contributed to lateralization for NH listeners but had negligible contribution for BICI listeners. These results suggest that the CCi-MOBILE is suitable for binaural testing and developing bilateral processing strategies.

Portable automated rapid testing: Validation of automated testing on listeners from India

Portable Automated Rapid Testing (PART) is an iPad application (https://braingamecenter.ucr.edu/games/p-a-r-t/) capable of measuring various psychoacoustic thresholds (speech on speech masking, temporal, spectral, and spectrotemporal modulation detection, temporal gap detection, frequency modulation tasks, and pure tone detection in noise) in an automated and rapid format using commercially available headphones. The app has been validated previously in native speakers of English and an adapted version of the app has been validated in young normal hearing listeners from Mexico. Here, we present psychoacoustic threshold data for a large cohort of younger college going listeners from India whose native language is not English but are proficient in English. The thresholds obtained from this group will be compared against previously published thresholds based on native speakers of English. It is hypothesized that there will not be any significant differences in thresholds between listeners from India and the thresholds published in the literature. These results will give us the required evidence to start using this freely available app to measure reliable thresholds of various central auditory processing measures in non-native speakers of English who are proficient in the language as well.

Relating monaural and binaural envelope processing abilities to spatial release from masking

The difference in speech identification thresholds between colocated condition (when the target and the maskers are placed at the same location) and spatially separated condition (when target and the maskers are symmetrically separated) is quantified as Spatial Release from Masking (SRM). SRM is thought to be a combination of monaural and binaural advantages arising from spatially separating the target from the maskers. Monaural contributions are from the head shadow effect whereas the binaural contributions are from processing the interaural differences between the two ears. However, the exact contributions of the monaural and binaural advantage to SRM is unknown. Here, we present data on monaural and binaural envelope processing abilities and their relationship to SRM on a large cohort of young normal hearing listeners. Monaural envelope processing ability was measured using the envelope regularity discrimination task (Moore et al., 2019). Sensitivity to ITD-envelopes was used to quantify binaural envelope processing ability. SRM was measured using coordinate response measure sentences. The relationship between SRM, envelope regularity index, and ITD thresholds along with the monaural and binaural envelope processing abilities to SRM will be discussed.

Defining functional spatial boundaries using a spatial release from masking task.

The classic spatial release from masking (SRM) task measures speech recognition thresholds for discrete separation angles between a target and masker. Alternatively, this study used a modified SRM task that adaptively measured the spatial-separation angle needed between a continuous male target stream (speech with digits) and two female masker streams to achieve a specific SRM. On average, 20 young normal-hearing listeners needed less spatial separation for 6 dB release than 9 dB release, and the presence of background babble reduced across-listener variability on the paradigm. Future work is needed to better understand the psychometric properties of this adaptive procedure.

Correlation between Mandarin acceptable noise level and cortical auditory evoked potential in young normal-hearing listeners

Objective:To investigate the correlation between Mandarin acceptable noise level （M-ANL） and cortical auditory evoked potential （CAEP）, and to explore the possible mechanism leading to individual differences in M-ANL values. Methods:Thirty listeners aged 22-33 years with normal hearing were selected as the study subjects, and the M-ANL test and CAEP test were performed respectively. The most comfortable level （MCL）, maximum background noise level （BNL）, M-ANL and CAEP values of each subject were recorded. The latency of each wave of P1, N1, P2, N2, P300 and the amplitude of P1-N1, P2-N2, P300 in CAEP were recorded for each subject. SPSS 25.0 was used for statistical analysis to explore the correlation between the MCL value, BNL value and M-ANL values and the latency of P1, N1, P2, N2, P300 and P1-N1, P2-N2, P300 amplitudes of CAEP. Results:①The MCL value and M-ANL value were positively correlated with the P2 latency of CAEP, and the correlation coefficients were 0.404 and 0.400, respectively, and the differences were statistically significant （P<0.05）. There was no correlation with P1, N1, N2, and P300 latencies of CAEP （P>0.05）. ②The MCL value, BNL value and M-ANL value had no significant difference with the CAEP wave amplitudes of P1-N1, P2-N2, and P300 （P>0.05）. Conclusion:There was a certain correlation between M-ANL and CAEP in young adults with normal hearing, suggesting that the central auditory cortex might play a potential regulatory role in the background noise tolerance. Individuals with a greater background noise acceptance might have stronger central efferent mechanisms and/or less active central afferent mechanisms.

The Thomas More Lists: A Phonemically Balanced Dutch Monosyllabic Speech Audiometry Test.

Speech audiometry tests are a crucial tool in clinical care and research. In Dutch, the common practice is to use lists of monosyllabic words with a consonant-vowel-consonant (CVC) structure. However, there are relatively few lists, and they are short. Here, the goal is to develop an adult speech audiometry test for Dutch (Flemish) consisting of phonemically balanced lists of 25 CVC words. The ISO 8253-3:2012 norm was followed. From a pool of 689 well-known words, an initial set of 26 lists was recorded by a female speaker. The lists were optimized for perceptual balance by means of two studies with young normal hearing listeners (N1 = 24, N2 = 32). The final corpus contains 16 phonetically and perceptually balanced lists. In a last study (N3 = 25), the reference speech recognition curves in quiet and in speech-shaped noise were determined. Reference speech recognition threshold and slope values for phoneme scoring are respectively 20.3 dBSPL in quiet (slope 5.2%/dB) and −7.7 dBSNR (7.5%/dB) in noise, similar to existing materials. The lists may be a useful addition to the existing audiometric tests.

Effect of wearing personal protective equipment on acoustic characteristics and speech perception during COVID-19

With the COVID-19 pandemic, the usage of personal protective equipment (PPE) has become ‘the new normal’. Both surgical masks and N95 masks with a face shield are widely used in healthcare settings to reduce virus transmission, but the use of these masks has a negative impact on speech perception. Therefore, transparent masks are recommended to solve this dilemma. However, there is a lack of quantitative studies regarding the effect of PPE on speech perception. This study aims to compare the effect on speech perception of different types of PPE (surgical masks, N95 masks with face shield and transparent masks) in healthcare settings, for listeners with normal hearing in the audiovisual or auditory-only modality. The Bamford–Kowal–Bench (BKB)-like Mandarin speech stimuli were digitally recorded by a G.R.A.S KEMAR manikin without and with masks (surgical masks, N95 masks with face shield and transparent masks). Two variants of video display were created (with or without visual cues) and tagged to the corresponding audio recordings. The speech recording and video were presented to listeners simultaneously in each of four conditions: unattenuated speech with visual cues (no mask); surgical mask attenuated speech without visual cues; N95 mask with face shield attenuated speech without visual cues; and transparent mask attenuated speech with visual cues. The signal-to-noise ratio for 50 % correct scores (SNR50) threshold in noise was measured for each condition in the presence of four-talker babble. Twenty-four subjects completed the experiment. Acoustic spectra obtained from all types of masks were primarily attenuated at high frequencies, beyond 3 kHz, but to different extents. The mean SNR50 thresholds of the two auditory-only conditions (surgical mask and N95 mask with face shield) were higher than those of the audiovisual conditions (no mask and transparent mask). SNR50 thresholds in the surgical-mask conditions were significantly lower than those for the N95 masks with face shield. No significant difference was observed between the two audiovisual conditions. The results confirm that wearing a surgical mask or an N95 mask with face shield has a negative impact on speech perception. However, wearing a transparent mask improved speech perception to a similar level as unmasked condition for young normal-hearing listeners.

The Intelligibility of Time-Compressed Speech Is Correlated with the Ability to Listen in Modulated Noise.

Speech perception in difficult listening conditions depends highly on the temporal processing ability of the auditory pathway. In the present study, we investigate the inter-subject variability of young normal-hearing listeners in the identification of time-compressed speech and how the ability to identify time-compressed speech, as assessed by the speech reception threshold (SRTrate: the speech rate at which 50% of the speech is perceived correctly) is associated with the ability to identify speech in unmodulated (SRTunmod) and modulated noise (SRTmod). These tasks are highly dependent on the temporal processing abilities of the auditory pathway. We observed a large inter-subject variability in the SRTrate and found that it is significantly correlated with the SRT when listening to unmodulated and modulated noise. Furthermore, we found that listeners who are better at perceiving speech at high rates are better in listening to speech in modulated noise. This effect persisted even when controlling for their ability to perceive speech in unmodulated noise. In addition, we also found that an increase in speech rate from 2.7 to 6.6 syllables per second resulted in a reduction in glimpsing of 5.3dB when listening to speech in a 4-Hz amplitude-modulated masker, even though speech in quiet was 100% intelligible at both rates. These results indicate that the ability of young normal-hearing individuals to efficiently process temporal features of speech is an imperative factor when listening to speech in difficult listening situations.