Speech Understanding In Noise Research Articles

Improving speech perception in noise with current focusing in cochlear implant users

Cochlear implant (CI) users typically have excellent speech recognition in quiet but struggle with understanding speech in noise. It is thought that broad current spread from stimulating electrodes causes adjacent electrodes to activate overlapping populations of neurons which results in interactions across adjacent channels. Current focusing has been studied as a way to reduce spread of excitation, and therefore, reduce channel interactions. In particular, partial tripolar stimulation has been shown to reduce spread of excitation relative to monopolar stimulation. However, the crucial question is whether this benefit translates to improvements in speech perception. In this study, we compared speech perception in noise with experimental monopolar and partial tripolar speech processing strategies. The two strategies were matched in terms of number of active electrodes, microphone, filterbanks, stimulation rate and loudness (although both strategies used a lower stimulation rate than typical clinical strategies). The results of this study showed a significant improvement in speech perception in noise with partial tripolar stimulation. All subjects benefited from the current focused speech processing strategy. There was a mean improvement in speech recognition threshold of 2.7 dB in a digits in noise task and a mean improvement of 3 dB in a sentences in noise task with partial tripolar stimulation relative to monopolar stimulation. Although the experimental monopolar strategy was worse than the clinical, presumably due to different microphones, frequency allocations and stimulation rates, the experimental partial-tripolar strategy, which had the same changes, showed no acute deficit relative to the clinical.

The addition of a contralateral routing of signals microphone to a unilateral cochlear implant system—A prospective study in speech outcomes

The purpose of the study was to investigate the potential clinical advantages of incorporating a contralateral routing of signals (CROS) microphone in unilateral cochlear implant (CI) users. A prospective study was undertaken on a group of 21 postlingually deafened adults who were all implanted with the same multichannel CI system. Performance with a unilateral CI was compared with performance using both a unilateral implant and a CROS microphone system worn on the opposite site (CI-CROS). Speech understanding using the AzBio sentence was evaluated in quiet, with speech presented at 0° and 270° azimuth in the horizontal plane. Speech understanding in noise was performed with speech at 0°, and noise at 0°, 90°, and 270°. A significant gain in speech understanding using CI-CROS compared to the unilateral CI alone was found in quiet when speech was presented at 270° (average improvement of 8.8%, P < .01). Participants also demonstrated statistically significant improvement using CI-CROS compared with the unilateral CI alone when noise was presented at 90° and speech at 0° (average improvement of 6.7%, P < .01). Adding a contralateral microphone to a unilateral CI resulted in a significant improvement in speech understanding in different conditions. This method could provide a greater cost/benefit ratio than bilateral CIs and be a potential improvement for those who are not candidates for bilateral CIs.

Unilateral Deafness in Children

Recently, several studies have shown that a cochlear implant is a suitable treatment for hearing rehabilitation of adults with unilateral sensorineural hearing loss (UHL), and benefits for speech comprehension in noise and localization have been demonstrated. The aim of this clinical study was to evaluate the benefit of cochlear implantation in children with UHL in comparison to their unaided listening situation. Prospective repeated measures single subject design. Tertiary referral center; cochlear implant (CI) program Three children (4, 10, and 11 yr) with noncongenital UHL resulting from different causes were enrolled in the study. After extensive consultation with each family and confirming CI-candidacy, each child received a cochlear implant. Open set speech recognition measures in competing background noise and tests of sound localization were performed for unaided preoperative and CI-aided postimplant intervals after 6 and 12 months. The parent and child versions of the Speech, Spatial and Qualities scale (SSQ) were used for subjective evaluation of hearing at preimplant and 12-month postimplant intervals. All children consistently use their CI 1 year postimplant. Our preliminary results suggest binaural hearing benefits for speech understanding in noise, localization ability and subjectively perceived hearing ability for school-aged children with UHL. Trends for CI-benefits in younger preschoolaged children are confirmed through subjective assessment reported by the parents. The benefits in hearing performance suggest binaural integration and processing of electric and acoustic stimulation arriving at 2 different ears is possible for children with UHL.

New cochlear implant research coding strategy based on the MP3000™ strategy to reintroduce the virtual channel effect

Conclusion: Results for speech recognition in noise tests when using a new research coding strategy designed to introduce the virtual channel effect provided no advantage over MP3000™. Although statistically significant smaller just noticeable differences (JNDs) were obtained, the findings for pitch ranking proved to have little clinical impact. Objectives: The aim of this study was to explore whether modifications to MP3000 by including sequential virtual channel stimulation would lead to further improvements in hearing, particularly for speech recognition in background noise and in competing-talker conditions, and to compare results for pitch perception and melody recognition, as well as informally collect subjective impressions on strategy preference. Methods: Nine experienced cochlear implant subjects were recruited for the prospective study. Two variants of the experimental strategy were compared to MP3000. The study design was a single-blinded ABCCBA cross-over trial paradigm with 3 weeks of take-home experience for each user condition. Results: Comparing results of pitch-ranking, a significantly reduced JND was identified. No significant effect of coding strategy on speech understanding in noise or competing-talker materials was found. Melody recognition skills were the same under all user conditions.

Seeing facial motion affects auditory processing in noise

Speech perception, especially in noise, may be maximized if the perceiver observes the naturally occurring visual-plus-auditory cues inherent in the production of spoken language. Evidence is conflicting, however, about which aspects of visual information mediate enhanced speech perception in noise. For this reason, we investigated the relative contributions of audibility and the type of visual cue in three experiments in young adults with normal hearing and vision. Relative to static visual cues, access to the talker's phonetic gestures in speech production, especially in noise, was associated with (a) faster response times and sensitivity for speech understanding in noise, and (b) shorter latencies and reduced amplitudes of auditory N1 event-related potentials. Dynamic chewing facial motion also decreased the N1 latency, but only meaningful linguistic motions reduced the N1 amplitude. The hypothesis that auditory-visual facilitation is distinct to properties of natural, dynamic speech gestures was partially supported.

Variability in speech understanding in noise by listeners with hearing loss

Listeners with sensorineural hearing loss (SNHL) report significant difficulties when listening to speech in the presence of background noise and are highly variable in their tolerance to such noise. In our studies of speech perception, audibility predicts understanding of speech in quiet for most young listeners with SNHL. In background noise, however, the speech recognition performance of some young listeners with SNHL deviates significantly from audibility predictions. We hypothesize that vulnerability to background noise may be related to listeners’ broader auditory filters, to a loss of discrimination ability for rapid spectral changes, or to a disruption of the speech temporal envelopes by the addition of noise. Measures of spectral resolution, spectral change detection, and envelope confusion will be presented for listeners with SNHL. Relationships between those estimates and speech recognition in noise will be described. Results may suggest a range of custom strategies for improving tolerance for background noise. Work supported by NIDCD R018306 to the first author.

Presbycusis: A Brain Disorder? “The Ears Listen, the Brain Hears”

Age-related hearing loss (presbycusis) is the most common cause of hearing loss. The audiometric profile of peripheral presbycusis is well known, but little attention has been paid to the role of central auditory dysfunction in both the diagnosis and management of presbycusis. Central presbycusis is typified by difficulty understanding speech in noise. Central presbycusis appears to involve or arise from decrements in executive functioning, which may be age-related or dementia-related. Tests employing speech in noise are appropriate measures for identifying patients who understand speech relatively normally in quiet but have undue difficulty understanding in background noise. The message of this discussion is that such testing should be done routinely for patients complaining of this problem. Identification of central presbycusis with such testing is important for proper auditory rehabilitation.

Cochlear Implantation in Adults With Asymmetric Hearing Loss

Bilateral severe to profound sensorineural hearing loss is a standard criterion for cochlear implantation. Increasingly, patients are implanted in one ear and continue to use a hearing aid in the nonimplanted ear to improve abilities such as sound localization and speech understanding in noise. Patients with severe to profound hearing loss in one ear and a more moderate hearing loss in the other ear (i.e., asymmetric hearing) are not typically considered candidates for cochlear implantation. Amplification in the poorer ear is often unsuccessful because of limited benefit, restricting the patient to unilateral listening from the better ear alone. The purpose of this study was to determine whether patients with asymmetric hearing loss could benefit from cochlear implantation in the poorer ear with continued use of a hearing aid in the better ear. Ten adults with asymmetric hearing between ears participated. In the poorer ear, all participants met cochlear implant candidacy guidelines; seven had postlingual onset, and three had pre/perilingual onset of severe to profound hearing loss. All had open-set speech recognition in the better-hearing ear. Assessment measures included word and sentence recognition in quiet, sentence recognition in fixed noise (four-talker babble) and in diffuse restaurant noise using an adaptive procedure, localization of word stimuli, and a hearing handicap scale. Participants were evaluated preimplant with hearing aids and postimplant with the implant alone, the hearing aid alone in the better ear, and bimodally (the implant and hearing aid in combination). Postlingual participants were evaluated at 6 mo postimplant, and pre/perilingual participants were evaluated at 6 and 12 mo postimplant. Data analysis compared the following results: (1) the poorer-hearing ear preimplant (with hearing aid) and postimplant (with cochlear implant); (2) the device(s) used for everyday listening pre- and postimplant; and (3) the hearing aid-alone and bimodal listening conditions postimplant. The postlingual participants showed significant improvements in speech recognition after 6 mo cochlear implant use in the poorer ear. Five postlingual participants had a bimodal advantage over the hearing aid-alone condition on at least one test measure. On average, the postlingual participants had significantly improved localization with bimodal input compared with the hearing aid-alone. Only one pre/perilingual participant had open-set speech recognition with the cochlear implant. This participant had better hearing than the other two pre/perilingual participants in both the poorer and better ear. Localization abilities were not significantly different between the bimodal and hearing aid-alone conditions for the pre/perilingual participants. Mean hearing handicap ratings improved postimplant for all participants indicating perceived benefit in everyday life with the addition of the cochlear implant. Patients with asymmetric hearing loss who are not typical cochlear implant candidates can benefit from using a cochlear implant in the poorer ear with continued use of a hearing aid in the better ear. For this group of 10, the 7 postlingually deafened participants showed greater benefits with the cochlear implant than the pre/perilingual participants; however, further study is needed to determine maximum benefit for those with early onset of hearing loss.

Auditory Processing Deficits in Children With Friedreich Ataxia

Friedreich ataxia is a neurodegenerative disease with an average age of onset of 10 years. The authors sought to investigate the presence and functional consequences of auditory neuropathy in a group of affected children and to evaluate the ability of personal FM-listening systems to improve perception. Nineteen school-aged individuals with Friedreich ataxia and a cohort of matched control subjects underwent a battery of auditory function tests. Sound detection was relatively normal, but auditory temporal processing and speech understanding in noise were severely impaired, with children with Friedreich ataxia typically able to access less than 40% of the information available to controls. Use of FM-listening devices did, however, improve the speech perception performance of those with Friedreich ataxia to the level of their unaffected peers in conditions designed to replicate the listening environment of the average school classroom.

Speech-in-Noise and Subjective Benefit With Active Middle Ear Implant Omnidirectional and Directional Microphones

1) To evaluate speech understanding in noise by comparing signal-to-noise ratios for 50% correct word understanding (SNR50) using an omnidirectional and a directional microphone audio processor (AP) in 4 different noise conditions. 2) To compare subjective speech understanding abilities, spatial hearing abilities, and qualitative hearing performance with the 2 processors. A prospective, single-subjects repeated-measures study design was used to compare speech understanding performance with the 2 APs acutely and after 6 weeks' acclimatization time. Tertiary referral center. Thirteen experienced unilateral German-speaking active middle ear implant users with either mixed or conductive hearing loss were enrolled. Directional audio processor. SNR50 obtained from 4 different noise conditions. SNR50s with the directional AP were lower (better) than with the omnidirectional AP in all noise conditions, although there were no changes in aided PTA thresholds. In acute testing, the mean SNR50 showed a significant directional advantage (DA) for the directional AP in the S0N0 condition of 1.3 dB, in S0NVSB 2.3 dB, in S0Ncont 3.1 dB, and in S0N180 4.5 dB. As expected, the largest DA was found in the S0N180 condition. No DA was expected in the S0N0 condition but was present. After 6 weeks of acclimatization time, no significant change from the acute testing was found, suggesting that patients experienced improved performance with the directional AP, even without acclimatization time. There was no significant change in subjective questionnaire outcomes. The directional AP yields immediately improved speech understanding in noise.

Studies on Bilateral Cochlear Implants at the University of Wisconsin’s Binaural Hearing and Speech Laboratory

This report highlights research projects relevant to binaural and spatial hearing in adults and children. In the past decade we have made progress in understanding the impact of bilateral cochlear implants (BiCIs) on performance in adults and children. However, BiCI users typically do not perform as well as normal hearing (NH) listeners. In this article we describe the benefits from BiCIs compared with a single cochlear implant (CI), focusing on measures of spatial hearing and speech understanding in noise. We highlight the fact that in BiCI listening the devices in the two ears are not coordinated; thus binaural spatial cues that are available to NH listeners are not available to BiCI users. Through the use of research processors that carefully control the stimulus delivered to each electrode in each ear, we are able to preserve binaural cues and deliver them with fidelity to BiCI users. Results from those studies are discussed as well, with a focus on the effect of age at onset of deafness and plasticity of binaural sensitivity. Our work with children has expanded both in number of subjects tested and age range included. We have now tested dozens of children ranging in age from 2 to 14 yr. Our findings suggest that spatial hearing abilities emerge with bilateral experience. While we originally focused on studying performance in free field, where real world listening experiments are conducted, more recently we have begun to conduct studies under carefully controlled binaural stimulation conditions with children as well. We have also studied language acquisition and speech perception and production in young CI users. Finally, a running theme of this research program is the systematic investigation of the numerous factors that contribute to spatial and binaural hearing in BiCI users. By using CI simulations (with vocoders) and studying NH listeners under degraded listening conditions, we are able to tease apart limitations due to the hardware/software of the CI systems from limitations due to neural pathology.

Speech in noise and ease of language understanding: when and how working memory capacity plays a role

A working memory based model for Ease of Language Understanding (ELU) has been developed (Rönnberg, 2003; Rönnberg et al., 2008; Rönnberg et al., 2011). It predicts that speech understanding in adverse, mismatching noise conditions is dependent on explicit processing resources such as working memory capacity (WMC). This presentation will examine the details of this prediction by addressing some recent data on (1) how brainstem responses are modulated by working memory load and WMC, (2) how cortical correlates of speech understanding in noise are modulated by WMC, and (3) how WMC determines episodic long-term memory for spoken discourse masked by speech.

French Muticenter Study on Vibroplasty

These last years, different papers have demonstrated good surgical and audiological results in patients with conductive and mixed hearing losses, when the FMT is placed on the round window, on the stapes or on the incus. We present the preliminary results of a prospective multicenter French study comparing the results of the VSB in mixed hearing loss with BAHA and conventional hearing aids. Materials and methods: 30 patients whose pathologies were mainly chronic otitis (22 cases) and otosclerosis (8 cases) were implanted with a VSB middle ear implant. The surgical approaches used consisted in the classical approach (FMT on long process of the incus) in 8 cases, in placement of the FMT on the stapes in 12 cases, and in placement of the FMT on the round window in 10 cases. Thresholds in air conduction, bone conduction, speech understanding and speech understanding in noise were measured at 1, 3, 6, and 12 months, and compared with preoperative measurements with numeric conventional hearing aid and head set BAHA Results: No surgical complications were reported. 4 patients expressed a lack of hearing improvement and the FMTs were replaced under local anesthesia. In these four cases, the FMT had been placed on the round window. There were no change in bone conduction hearing thresholds and all patients are showing significant gain with VSB and improvement 17 dB below the air conduction thresholds in average. In average, speech understanding was better for VSB than BAHA and hearing aids. Results in speech understanding were identical between VSB and BAHA for pure conductive heanring loss, and were better for VSB than BAHA when the bone conduction thresholds were higher than 40 dB. Conclusion: Preliminaty results have shown that the VSB middle ear implant can be a good alternative for the rehabilitation of mixed hearing losses.

Efficacy of a Reverse Cardioid Directional Microphone

Directional microphones have been shown to improve a listener's ability to communicate in noise by improving the signal to noise ratio. However, their efficacy may be questioned in situations where the listener needs to understand speech originating from the back. The goal of the study was to examine the performance of a directional microphone mode that has an automatic reverse cardioid polar pattern. A single-blinded, factorial repeated-measures design was used to study the effect of microphone modes (reverse cardioid, omnidirectional, and front hypercardioid) and stimulus azimuths (front and back) on three outcome variables (aided thresholds, nonsense syllable identification in quiet, and sentence recognition in noise). Twenty adults with a mild-to-severe bilaterally symmetrical (±5 dB) sensorineural hearing loss participated. Audibility in quiet was evaluated by obtaining aided sound field thresholds and speech identification at an input level of 50 dB SPL presented at 0 and 180° azimuths. In addition, speech understanding in noise was also assessed with the Hearing In Noise Test (HINT) sentences presented at both azimuths (0 and 180°) with a diffuse noise. Repeated-measures analyses of variance (ANOVAs) were conducted to examine the effects of microphone mode (omnidirectional, front hypercardioid, reverse cardioid) and stimulus azimuth (0°, 180°) on aided thresholds, nonsense syllable identification, and HINT performance. Results with the reverse cardioid directional microphone in both quiet conditions were similar to the omnidirectional microphone. The results of the reverse cardioid microphone in noise were significantly better than the omnidirectional microphone and front hypercardioid microphone when speech was presented from the back (p < 0.001). These results support the possible benefits of a reverse cardioid directional microphone when used in specific listening situations.

Age-related changes in consonant and sentence processing

Speech understanding in noise declines with age, even in older subjects with normal hearing (ONH). These age-related declines could reflect reductions in phonological processing ability or impairments in semantic and lexical processing required for sentence understanding. In experiment 1, we used the California Syllable Test (CaST) to examine age-related changes in the ability of subjects to identify consonants in consonant-vowel-consonant syllables in noise. ONH subjects showed impaired performance in comparison with younger subjects with normal hearing, particularly for hard-to-identify consonants, but otherwise showed similar influences of consonant position, lexicality, and vowel nuclei. Regression analyses showed that CaST performance was independently affected by both age and audiometric thresholds. In experiment 2, we examined sentence reception thresholds (SeRTs) using the Quick Speech in Noise Test and Hearing in Noise Test. No significant age-related changes in SeRTs were observed for either test. SeRT preservation in ONH subjects appeared to reflect the age-resistant ability to identify easy consonants in noise as well as intact top-down contextual and lexical processing. These results establish benchmark values that can be used to evaluate the success of audiological rehabilitation in older subjects with hearing impairment.

Relationship Between Consonant Recognition in Noise and Hearing Threshold

Although poorer understanding of speech in noise by listeners who are hearing-impaired (HI) is known not to be directly related to audiometric hearing threshold, HT (f), grouping HI listeners with HT (f) is widely practiced. In this article, the relationship between consonant recognition and HT (f) is considered over a range of signal-to-noise ratios (SNRs). Confusion matrices (CMs) from 25 HI ears were generated in response to 16 consonant-vowel syllables presented at 6 different SNRs. Individual differences scaling (INDSCAL) was applied to both feature-based matrices and CMs in order to evaluate the relationship between HT (f) and consonant recognition among HI listeners. The results showed no predictive relationship between the percent error scores (Pe) and HT (f) across SNRs. The multiple regression models showed that the HT (f) accounted for 39% of the total variance of the slopes of the Pe. Feature-based INDSCAL analysis showed consistent grouping of listeners across SNRs, but not in terms of HT (f). Systematic relationship between measures was also not defined by CM-based INDSCAL analysis across SNRs. HT (f) did not account for the majority of the variance (39%) in consonant recognition in noise when the complete body of the CM was considered.

Interference in dichotic listening: the effect of contralateral noise on oscillatory brain networks

Coupling of thalamocortical networks through synchronous oscillations at gamma frequencies (30-80 Hz) has been suggested as a mechanism for binding of auditory sensory information into an object representation, which then becomes accessible for perception and cognition. This study investigated whether contralateral noise interferes with this step of central auditory processing. Neuromagnetic 40-Hz oscillations were examined in young healthy participants while they listened to amplitude-modulated sound in one ear and a multi-talker masking noise in the contralateral ear. Participants were engaged in a gap-detection task, for which their behavioural performance declined under masking. The amplitude modulation of the stimulus elicited steady 40-Hz oscillations with sources in bilateral auditory cortices. Analysis of the temporal dynamics of phase synchrony between source activity and the stimulus revealed two oscillatory components; the first was indicated by an instant onset in phase synchrony with the stimulus while the second showed a 200-ms time constant of gradual increase in phase synchrony after phase resetting by the gap. Masking abolished only the second component. This coincided with masking-related decrease of the P2 wave of the transient auditory-evoked responses whereas the N1 wave, reflecting early sensory processing, was unaffected. Given that the P2 response has been associated with object representation, we propose that the first 40-Hz component is related to representation of low-level sensory input whereas the second is related to internal auditory processing in thalamocortical networks. The observed modulation of oscillatory activity is discussed as reflecting a neural mechanism critical for speech understanding in noise.

On the Use of the Distortion-Sensitivity Approach in Examining the Role of Linguistic Abilities in Speech Understanding in Noise

Researchers have used the distortion-sensitivity approach in the psychoacoustical domain to investigate the role of auditory processing abilities in speech perception in noise (van Schijndel, Houtgast, & Festen, 2001; Goverts & Houtgast, 2010). In this study, the authors examined the potential applicability of the distortion-sensitivity approach for investigating the role of linguistic abilities in speech understanding in noise. The authors applied the distortion-sensitivity approach by measuring the processing of visually presented masked text in a condition with manipulated syntactic, lexical, and semantic cues and while using the Text Reception Threshold (George et al., 2007; Kramer, Zekveld, & Houtgast, 2009; Zekveld, George, Kramer, Goverts, & Houtgast, 2007) method. Two groups that differed in linguistic abilities were studied: 13 native and 10 non-native speakers of Dutch, all typically hearing university students. As expected, the non-native subjects showed substantially reduced performance. The results of the distortion-sensitivity approach yielded differentiated results on the use of specific linguistic cues in the 2 groups. The results show the potential value of the distortion-sensitivity approach in studying the role of linguistic abilities in speech understanding in noise of individuals with hearing impairment.

A neural basis of speech-in-noise perception in older adults.

We investigated a neural basis of speech-in-noise perception in older adults. Hearing loss, the third most common chronic condition in older adults, is most often manifested by difficulty understanding speech in background noise. This trouble with understanding speech in noise, which occurs even in individuals who have normal-hearing thresholds, may arise, in part, from age-related declines in central auditory processing of the temporal and spectral components of speech. We hypothesized that older adults with poorer speech-in-noise (SIN) perception demonstrate impairments in the subcortical representation of speech. In all participants (28 adults, age 60-73 yr), average hearing thresholds calculated from 500 to 4000 Hz were ≤ 25 dB HL. The participants were evaluated behaviorally with the Hearing in Noise Test (HINT) and neurophysiologically using speech-evoked auditory brainstem responses recorded in quiet and in background noise. The participants were divided based on their HINT scores into top and bottom performing groups that were matched for audiometric thresholds and intelligent quotient. We compared brainstem responses in the two groups, specifically, the average spectral magnitudes of the neural response and the degree to which background noise affected response morphology. In the quiet condition, the bottom SIN group had reduced neural representation of the fundamental frequency of the speech stimulus and an overall reduction in response magnitude. In the noise condition, the bottom SIN group demonstrated greater disruption in noise, reflecting reduction in neural synchrony. The role of brainstem timing is particularly evident in the strong relationship between SIN perception and quiet-to-noise response correlations. All physiologic measures correlated with SIN perception. Adults in the bottom SIN group differed from the audiometrically matched top SIN group in how speech was neurally encoded. The strength of subcortical encoding of the fundamental frequency appears to be a factor in successful speech-in-noise perception in older adults. Given the limitations of amplification, our results suggest the need for inclusion of auditory training to strengthen central auditory processing in older adults with SIN perception difficulties.

Improving Hearing Aid Function in Noisy Situations

Improving Hearing Aid Function in Noisy Situations