The validity of LENA technology for assessing the linguistic environment and interactions of infants learning Hebrew and Arabic.

The present study assessed LENA's suitability as a tool for monitoring future language interventions by evaluating its reliability, construct validity, and criterion validity in infants learning Hebrew and Arabic, across low and high levels of maternal education. Participants were 32 infants aged 3 to 11 months (16 in each language) and their mothers, whose socioeconomic status (SES) was determined based on their years of education (H-high or L-low ME-maternal education). The results showed (1) good reliability for the LENA's automatic count on adult word count (AWC), conversational turns (CTC), and infant vocalizations (CVC), based on the positive associations and fair to excellent agreement between the manual and automatic counts; (2) good construct validity based on significantly higher counts for HME vs. LME and positive associations between LENA's automatic vocal assessment (AVA) and developmental questionnaire (DA) and age; and (3) good concurrent criterion validity based on the positive associations between the LENA counts for CTC, CVC, AVA, and DA and the scores on the preverbal parent questionnaire (PRISE). The present study supports the use of LENA in early intervention programs for infants whose families speak Hebrew or Arabic. The LENA could be used to monitor the efficacy of these programs as well as to provide feedback to parents on the amount of language experience their infants are getting and their progress in vocal production. The results also indicate a potential utility of LENA in assessing linguistic environments and interactions in Hebrew- and Arabic-speaking infants with developmental disorders, such as hearing impairment and cerebral palsy.

Identification and Comprehension of Narrow Focus by Arabic-Speaking Adolescents With Moderate-to-Profound Hearing Loss.

PURPOSE: Processing narrow focus (NF), the stressed word in the sentence, includes both the perceptual ability to identify the stressed word in the sentence and the pragmatic-semantic ability to comprehend the nonexplicit linguistic message. NF and its underlying meaning can be conveyed only via the auditory modality. Therefore, NF can be considered as a measure for assessing the efficacy of the hearing aid (HA) and cochlear implants (CIs) for acquiring nonexplicit language skills. The purpose of this study was to assess identification and comprehension of NF by HA and CI users who are native speakers of Arabic and to associate NF outcomes with speech perception and cognitive and linguistic abilities. METHOD: A total of 46 adolescents (age range: 11;2-18;8) participated: 18 with moderate-to-severe hearing loss who used HAs, 10 with severe-to-profound hearing loss who used CIs, and 18 with typical hearing (TH). Test materials included the Arabic Narrow Focus Test (ANFT), which includes three subtests assessing identification (ANFT1), comprehension of NF in simple four-word sentences (ANFT2), and longer sentences with a construction list at the clause or noun phrase level (ANFT3). In addition, speech perception, vocabulary, and working memory were assessed. RESULTS: All the participants successfully identified the word carrying NF, with no significant difference between the groups. Comprehension of NF in ANFT2 and ANFT3 was reduced for HA and CI users compared with TH peers, and speech perception, hearing status, and memory for digits predicted the variability in the overall results of ANFT1, ANFT2, and ANFT3, respectively. CONCLUSIONS: Arabic speakers who used HAs or CIs were able to identify NF successfully, suggesting that the acoustic cues were perceptually available to them. However, HA and CI users had considerable difficulty in understanding NF. Different factors may contribute to this difficulty, including the memory load during the task as well as pragmatic-linguistic knowledge on the possible meanings of NF.

Difficulties Experienced by Older Listeners in Utilizing Voice Cues for Speaker Discrimination.

Human listeners are assumed to apply different strategies to improve speech recognition in background noise. Young listeners with normal hearing (NH), e.g., have been shown to follow the voice of a particular speaker based on the fundamental (F0) and formant frequencies, which are both influenced by the gender, age, and size of the speaker. However, the auditory and cognitive processes that underlie the extraction and discrimination of these voice cues across speakers may be subject to age-related decline. The present study aimed to examine the utilization of F0 and formant cues for voice discrimination (VD) in older adults with hearing expected for their age. Difference limens (DLs) for VD were estimated in 15 healthy older adults (65-78 years old) and 35 young adults (18-35 years old) using only F0 cues, only formant frequency cues, and a combination of F0 + formant frequencies. A three-alternative forced-choice paradigm with an adaptive-tracking threshold-seeking procedure was used. Wechsler backward digit span test was used as a measure of auditory working memory. Trail Making Test (TMT) was used to provide cognitive information reflecting a combined effect of processing speed, mental flexibility, and executive control abilities. The results showed that (a) the mean VD thresholds of the older adults were poorer than those of the young adults for all voice cues, although larger variability was observed among the older listeners; (b) both age groups found the formant cues more beneficial for VD, compared to the F0 cues, and the combined (F0 + formant) cues resulted in better thresholds, compared to each cue separately; (c) significant associations were found for the older adults in the combined F0 + formant condition between VD and TMT scores, and between VD and hearing sensitivity, supporting the notion that a decline with age in both top-down and bottom-up mechanisms may hamper the ability of older adults to discriminate between voices. The present findings suggest that older listeners may have difficulty following the voice of a specific speaker and thus implementing doing so as a strategy for listening amid noise. This may contribute to understanding their reported difficulty listening in adverse conditions.

Infants' Preference for Child-Directed Speech Over Time-Reversed Speech in On-Channel and Off-Channel Masking.

Purpose This study aims to examine the development of auditory selective attention to speech in noise by examining the ability of infants to prefer child-directed speech (CDS) over time-reversed speech (TRS) presented in "on-channel" and "off-channel" noise. Method A total of 32 infants participated in the study. Sixteen typically developing infants were tested at 7 and 11 months of age using the central fixation procedure with CDS and TRS in two types of noise at +10 dB signal-to-noise ratio. One type of noise was an "on-channel" masker with a spectrum overlapping that of the CDS (energetic masking), and the second was an "off-channel" masker with frequencies that were outside the spectrum of the CDS (distractive masking). An additional group of sixteen 11-month-old infants were tested in quiet and served as controls for the "off-frequency" masker condition. Results Infants preferred CDS over TRS in both age groups, but this preference was more pronounced with "off-channel" masker regardless of age. Also, older infants demonstrated longer looking time for the target stimuli when presented with an "off-channel" masker compared to the "on-channel" masker. Looking time in quiet was similar to looking time in the "off-channel" condition, and looking time for CDS was longer in quiet compared to the "on-channel" condition. Conclusions These findings support the notion that (a) infants as young as 7 months of age are already showing preference for speech in noise, regardless of type of masker; (b) by 11 months of age, listening with the "off-channel" condition did not yield different results than in quiet. Thus, by 11 months of age, infants' cognitive-attentional abilities may be more developed.

The Effect of Soft Tissue Stimulation on Skull Vibrations and Hearing Thresholds in Humans.

HYPOTHESIS: Hearing via soft tissue stimulation involves an osseous pathway. BACKGROUND: A recent study that measured both hearing thresholds and skull vibrations found that vibratory stimulation of soft tissue led to hearing sensation that correlated with skull vibrations, supporting the hypothesis of an osseous pathway. It is possible, however, that a lower application force of the vibrator on the stimulated soft tissue would not be sufficient to elicit skull vibration suggesting hearing via a nonosseous pathway. The purpose of the present study was to confirm the osseous pathway by measuring skull vibrations and behavioral thresholds using a low application force on a layer of ultrasound gel. Gel was used to mimic soft tissue because of its similar acoustic impedance and to control for variability between participants. METHODS: Hearing thresholds and the skull vibrations of five patients who were implanted with bone-anchored implants were assessed in two conditions when the bone vibrator was applied on the forehead: 1) direct application with 5N force; 2) through a layer of ultrasound gel with minimal application force. Skull vibrations were measured in both conditions by a laser Doppler vibrometer focused on the bone-anchored implant. RESULTS: Skull vibrations were present even when minimal application force was applied on soft tissue. The difference in skull vibrations when the vibrator was directly on the forehead compared with the gel condition was consistent with the variability in hearing thresholds between the two conditions. CONCLUSION: These results reinforce the hypothesis that skull vibrations are involved in hearing when sound is transmitted via either soft tissue or bone.

Practice Makes Transfer Imperfect: Evidence From Auditory Learning.

BACKGROUND: Evidence from motor and visual studies suggests that the ability to generalize learning gains to untrained conditions decreases as the training progresses. This decrease in generalization was suggested to reflect a shift from higher to lower levels of neuronal representations of the task following prolonged training. In the auditory modality, however, the few studies that tested the influence of prolonging training on generalization ability showed no decrease and sometimes even an increase in generalization. OBJECTIVE: To test the impact of extending training in a basic psychoacoustic task on the ability to generalize the gains attained in training to untrained conditions. DESIGN: Eighty-two young adults participated in two experiments that differed in the specific training regimen. In both experiments, training was conducted using a difference limen for frequency (DLF) task with an adaptive forced-choice procedure, for either a single- or nine-session training. Following training, generalization to the untrained ear and to an untrained frequency was assessed. RESULTS: (a) Training induced significant learning (i.e., smaller DLF thresholds) following a single session of training, and more so following nine training sessions; (b) results from the combined data from both experiments showed that the ability to generalize the learning gains to the untrained ear and frequency was limited after the extended DLF training; (c) larger improvements under the trained condition resulted in smaller generalization to the untrained conditions. CONCLUSIONS: The findings of increased specificity with training in the auditory modality support the notion that gradual changes, both quantitative and qualitative, occur in the neural representations of an auditory task during its acquisition. These findings suggest common underlying mechanisms in basic skill learning across different modalities.

Listening in Noise Remains a Significant Challenge for Cochlear Implant Users: Evidence from Early Deafened and Those with Progressive Hearing Loss Compared to Peers with Normal Hearing.

Cochlear implants (CIs) are the state-of-the-art therapy for individuals with severe to profound hearing loss, providing them with good functional hearing. Nevertheless, speech understanding in background noise remains a significant challenge. The purposes of this study were to: (1) conduct a novel within-study comparison of speech-in-noise performance across ages in different populations of CI and normal hearing (NH) listeners using an adaptive sentence-in-noise test, and (2) examine the relative contribution of sensory information and cognitive-linguistic factors to performance. Forty CI users (mean age 20 years) were divided into "early-implanted" <4 years (n = 16) and "late-implanted" >6 years (n = 11), all prelingually deafened, and "progressively deafened" (n = 13). The control group comprised 136 NH subjects (80 children, 56 adults). Testing included the Hebrew Matrix test, word recognition in quiet, and linguistic and cognitive tests. Results show poorer performance in noise for CI users across populations and ages compared to NH peers, and age at implantation and word recognition in quiet were found to be contributing factors. For those recognizing 50% or more of the words in quiet (n = 27), non-verbal intelligence and receptive vocabulary explained 63% of the variance in noise. This information helps delineate the relative contribution of top-down and bottom-up skills for speech recognition in noise and can help set expectations in CI counseling.

Children With Normal Hearing Are Efficient Users of Fundamental Frequency and Vocal Tract Length Cues for Voice Discrimination.

BACKGROUND: The ability to discriminate between talkers assists listeners in understanding speech in a multitalker environment. This ability has been shown to be influenced by sensory processing of vocal acoustic cues, such as fundamental frequency (F0) and formant frequencies that reflect the listener's vocal tract length (VTL), and by cognitive processes, such as attention and memory. It is, therefore, suggested that children who exhibit immature sensory and/or cognitive processing will demonstrate poor voice discrimination (VD) compared with young adults. Moreover, greater difficulties in VD may be associated with spectral degradation as in children with cochlear implants. OBJECTIVES: The aim of this study was as follows: (1) to assess the use of F0 cues, VTL cues, and the combination of both cues for VD in normal-hearing (NH) school-age children and to compare their performance with that of NH adults; (2) to assess the influence of spectral degradation by means of vocoded speech on the use of F0 and VTL cues for VD in NH children; and (3) to assess the contribution of attention, working memory, and nonverbal reasoning to performance. DESIGN: Forty-one children, 8 to 11 years of age, were tested with nonvocoded stimuli. Twenty-one of them were also tested with eight-channel, noise-vocoded stimuli. Twenty-one young adults (18 to 35 years) were tested for comparison. A three-interval, three-alternative forced-choice paradigm with an adaptive tracking procedure was used to estimate the difference limens (DLs) for VD when F0, VTL, and F0 + VTL were manipulated separately. Auditory memory, visual attention, and nonverbal reasoning were assessed for all participants. RESULTS: (a) Children' F0 and VTL discrimination abilities were comparable to those of adults, suggesting that most school-age children utilize both cues effectively for VD. (b) Children's VD was associated with trail making test scores that assessed visual attention abilities and speed of processing, possibly reflecting their need to recruit cognitive resources for the task. (c) Best DLs were achieved for the combined (F0 + VTL) manipulation for both children and adults, suggesting that children at this age are already capable of integrating spectral and temporal cues. (d) Both children and adults found the VTL manipulations more beneficial for VD compared with the F0 manipulations, suggesting that formant frequencies are more reliable for identifying a specific speaker than F0. (e) Poorer DLs were achieved with the vocoded stimuli, though the children maintained similar thresholds and pattern of performance among manipulations as the adults. CONCLUSIONS: The present study is the first to assess the contribution of F0, VTL, and the combined F0 + VTL to the discrimination of speakers in school-age children. The findings support the notion that many NH school-age children have effective spectral and temporal coding mechanisms that allow sufficient VD, even in the presence of spectrally degraded information. These results may challenge the notion that immature sensory processing underlies poor listening abilities in children, further implying that other processing mechanisms contribute to their difficulties to understand speech in a multitalker environment. These outcomes may also provide insight into VD processes of children under listening conditions that are similar to cochlear implant users.

Logarithmic Versus Linear Change in Step Size When Using an Adaptive Threshold-Seeking Procedure in a Frequency Discrimination Task: Does It Matter?

Different rules for changing step sizes (e.g., logarithmic, linear) are alternately used in adaptive threshold-seeking procedures, with no clear justification. We hypothesized that the linear rule may yield more accurate thresholds for poor performers because the step sizes are predetermined and fixed across listeners and thus can be small, in contrast to the logarithmic rule, in which step sizes are changed with respect to the listener's performance. Purpose The aim of this study was to test the effect of logarithmic and linear rules on frequency discrimination (FD) thresholds. Method Three experiments involving human subjects and Monte Carlo computer simulations were designed and conducted. In the 1st experiment, FD thresholds were estimated in 40 young adults with either 3-interval 2-alternative forced choice (3I2AFC; n = 19) or 2-interval 2AFC (n = 21) in a within-subject design. In the 2nd experiment, thresholds were estimated in 16 children (7-8 years old) in a within-subject design, using 3I2AFC. In the 3rd experiment, thresholds were estimated in 30 young adults in a between-subjects design using 3I2AFC. Results No significant differences were shown between the 2 rules, regardless of age group, method, or level of FD performance. Computer simulations supported the empirical findings, predicting similar FD thresholds for both rules in the majority of runs. However, they also yielded more accurate thresholds with the linear rule, but with a larger number of outliers, which increased as the listener's attention level decreased. Conclusion Overall, the use of a particular rule has little influence on FD thresholds. Possible outliers may be minimized by monitoring the participant's attention at the beginning of the run.

Deficits in Explicit Language Problem Solving Rather Than in Implicit Learning in Specific Language Impairment: Evidence From Learning an Artificial Morphological Rule.

Purpose The purpose of this study was to delineate differences between children with specific language impairment (SLI), typical age-matched (TAM) children, and typical younger (TY) children in learning and mastering an undisclosed artificial morphological rule (AMR) through exposure and usage. Method Twenty-six participants (eight 10-year-old children with SLI, 8 TAM children, and ten 8-year-old TY children) were trained to master an AMR across multiple training sessions. The AMR required a phonological transformation of verbs depending on a semantic distinction: whether the preceding noun was animate or inanimate. All participants practiced the application of the AMR to repeated and new (generalization) items, via judgment and production tasks. Results The children with SLI derived significantly less benefit from practice than their peers in learning most aspects of the AMR, even exhibiting smaller gains compared to the TY group in some aspects. Children with SLI benefited less than TAM and even TY children from training to judge and produce repeated items of the AMR. Nevertheless, despite a significant disadvantage in baseline performance, the rate at which they mastered the task-specific phonological regularities was as robust as that of their peers. On the other hand, like 8-year-olds, only half of the SLI group succeeded in uncovering the nature of the AMR and, consequently, in generalizing it to new items. Conclusions Children with SLI were able to learn language aspects that rely on implicit, procedural learning, but experienced difficulties in learning aspects that relied on the explicit uncovering of the semantic principle of the AMR. The results suggest that some of the difficulties experienced by children with SLI when learning a complex language regularity cannot be accounted for by a broad, language-related, procedural memory disability. Rather, a deficit-perhaps a developmental delay in the ability to recruit and solve language problems and establish explicit knowledge regarding a language task-can better explain their difficulties in language learning.

Training of Speech Perception in Noise in Pre-Lingual Hearing Impaired Adults With Cochlear Implants Compared With Normal Hearing Adults.

BACKGROUND: Speech perception in noise remains a significant challenge for cochlear implant (CI) users in everyday life. It has been argued that training to use the information provided by the CI is as important as technological advances. So far, however, only few studies have trained speech perception in noise, most (if not all) included postlingually deafened CI adult users using non-sentence training material. OBJECTIVE: To assess the effect of training on a speech perception in noise task in prelingually hearing-impaired CI users with years of CI experience, as compared with normal-hearing (NH) young adults, following single- and multi-session training using the same training protocol. METHODS: Participants included 22 CI users with prelingual hearing loss and 30 NH. The Hebrew version of the Matrix sentence-in-noise test was used for training. All participants took part in a single training session. Six NH and seven CI continued training for four additional training sessions. All seven CI users trained for additional 5 days, totaling 10 training sessions. Generalization and retention of learning gains were assessed. RESULTS: Following single-session training, CI users showed speech reception thresholds in noise (SRTn) that were 9 to 10 dB higher than NH. After 5 first days of training, five of seven CI users reduced this disadvantage by half. After 10 days of training the CI improved performance by 4.1 dB SNR. No generalization and partial retention of learning were demonstrated. CONCLUSIONS: The present study is the first to demonstrate the course of learning and improvements in SRTn following training speech perception in noise in CI users with prelingual hearing loss.

Does hearing in response to soft-tissue stimulation involve skull vibrations? A within-subject comparison between skull vibration magnitudes and hearing thresholds.

Hearing can be elicited in response to bone as well as soft-tissue stimulation. However, the underlying mechanism of soft-tissue stimulation is under debate. It has been hypothesized that if skull vibrations were the underlying mechanism of hearing in response to soft-tissue stimulation, then skull vibrations would be associated with hearing thresholds. However, if skull vibrations were not associated with hearing thresholds, an alternative mechanism is involved. In the present study, both skull vibrations and hearing thresholds were assessed in the same participants in response to bone (mastoid) and soft-tissue (neck) stimulation. The experimental group included five hearing-impaired adults in whom a bone-anchored hearing aid was implanted due to conductive or mixed hearing loss. Because the implant is exposed above the skin and has become an integral part of the temporal bone, vibration of the implant represented skull vibrations. To ensure that middle-ear pathologies of the experimental group did not affect overall results, hearing thresholds were also obtained in 10 participants with normal hearing in response to stimulation at the same sites. We found that the magnitude of the bone vibrations initiated by the stimulation at the two sites (neck and mastoid) detected by the laser Doppler vibrometer on the bone-anchored implant were linearly related to stimulus intensity. It was therefore possible to extrapolate the vibration magnitudes at low-intensity stimulation, where poor signal-to-noise ratio limited actual recordings. It was found that the vibration magnitude differences (between soft-tissue and bone stimulation) were not different than the hearing threshold differences at the tested frequencies. Results of the present study suggest that bone vibration magnitude differences can adequately explain hearing threshold differences and are likely to be responsible for the hearing sensation. Thus, the present results support the idea that bone and soft-tissue conduction could share the same underlying mechanism, namely the induction of bone vibrations. Studies with the present methodology should be continued in future work in order to obtain further insight into the underlying mechanism of activation of the hearing system.

Voice Discrimination by Adults with Cochlear Implants: the Benefits of Early Implantation for Vocal-Tract Length Perception.

Cochlear implant (CI) users find it extremely difficult to discriminate between talkers, which may partially explain why they struggle to understand speech in a multi-talker environment. Recent studies, based on findings with postlingually deafened CI users, suggest that these difficulties may stem from their limited use of vocal-tract length (VTL) cues due to the degraded spectral resolution transmitted by the CI device. The aim of the present study was to assess the ability of adult CI users who had no prior acoustic experience, i.e., prelingually deafened adults, to discriminate between resynthesized "talkers" based on either fundamental frequency (F0) cues, VTL cues, or both. Performance was compared to individuals with normal hearing (NH), listening either to degraded stimuli, using a noise-excited channel vocoder, or non-degraded stimuli. Results show that (a) age of implantation was associated with VTL but not F0 cues in discriminating between talkers, with improved discrimination for those subjects who were implanted at earlier age; (b) there was a positive relationship for the CI users between VTL discrimination and speech recognition score in quiet and in noise, but not with frequency discrimination or cognitive abilities; (c) early-implanted CI users showed similar voice discrimination ability as the NH adults who listened to vocoded stimuli. These data support the notion that voice discrimination is limited by the speech processing of the CI device. However, they also suggest that early implantation may facilitate sensory-driven tonotopicity and/or improve higher-order auditory functions, enabling better perception of VTL spectral cues for voice discrimination.

Comprehension of "Narrow Focus" by Adolescents in the Autism Spectrum.

OBJECTIVE: The study compared the performance of adolescents with autistic spectrum disorder (ASD) to that of age-matched peers with typical development (TD) and cognitive language-matched peers with TD on measures of identification and comprehension of "narrow focus." PARTICIPANTS: Forty-nine participants, 17 autistic, 17 TD peers matched for age and sex, and 15 TD children matched for expressive vocabulary participated in the study. METHOD: The Hebrew Narrow Focus Test (HNFT) was used. The HNFT includes 3 subtests. The first subtest (A) required identification of the stressed word in the sentence based on psychoacoustic abilities alone. The second (B) and third (C) subtests required understanding the meaning of focused stress in different contexts. In subtest B, the meaning of "narrow focus" was to contrast other possibilities related to the lexical-grammatical role of the stressed word in the sentence, whereas in subtest C, the meaning was to indicate a mistake. RESULTS: ASD participants showed reduced performance compared to peers across all the subtests of the HNFT, but similar performance compared to TD children in subtests A and B and better performance on subtest C. A significant correlation was found between the Raven test for assessing nonverbal intelligence and subtests B and C of the HNFT in the group of adolescents with ASD. CONCLUSIONS: Comprehension of narrow focus in adolescents with ASD who study in a special educational system is related to their cognitive-linguistic abilities and not to the autistic condition by itself or to its severity.

Is the Role of External Feedback in Auditory Skill Learning Age Dependent?

Purpose: The purpose of this study is to investigate the role of external feedback in auditory perceptual learning of school-age children as compared with that of adults. Method: Forty-eight children (7-9 years of age) and 64 adults (20-35 years of age) conducted a training session using an auditory frequency discrimination (difference limen for frequency) task, with external feedback (EF) provided for half of them. Results: Data supported the following findings: (a) Children learned the difference limen for frequency task only when EF was provided. (b) The ability of the children to benefit from EF was associated with better cognitive skills. (c) Adults showed significant learning whether EF was provided or not. (d) In children, within-session learning following training was dependent on the provision of feedback, whereas between-sessions learning occurred irrespective of feedback. Conclusions: EF was found beneficial for auditory skill learning of 7-9-year-old children but not for young adults. The data support the supervised Hebbian model for auditory skill learning, suggesting combined bottom-up internal neural feedback controlled by top-down monitoring. In the case of immature executive functions, EF enhanced auditory skill learning. This study has implications for the design of training protocols in the auditory modality for different age groups, as well as for special populations.

Recognition and Comprehension of "Narrow Focus" by Young Adults With Prelingual Hearing Loss Using Hearing Aids or Cochlear Implants.

Purpose: The stressed word in a sentence (narrow focus [NF]) conveys information about the intent of the speaker and is therefore important for processing spoken language and in social interactions. The ability of participants with severe-to-profound prelingual hearing loss to comprehend NF has rarely been investigated. The purpose of this study was to assess the recognition and comprehension of NF by young adults with prelingual hearing loss compared with those of participants with normal hearing (NH). Method: The participants included young adults with hearing aids (HA; n = 10), cochlear implants (CI; n = 12), and NH (n = 18). The test material included the Hebrew Narrow Focus Test (Segal, Kaplan, Patael, & Kishon-Rabin, in press), with 3 subtests, which was used to assess the recognition and comprehension of NF in different contexts. Results: The following results were obtained: (a) CI and HA users successfully recognized the stressed word, with the worst performance for CI; (b) HA and CI comprehended NF less well than NH; and (c) the comprehension of NF was associated with verbal working memory and expressive vocabulary in CI users. Conclusions: Most CI and HA users were able to recognize the stressed word in a sentence but had considerable difficulty understanding it. Different factors may contribute to this difficulty, including the memory load during the task itself and linguistic and pragmatic abilities. Supplemental Material: https://doi.org/10.23641/asha.5572792.

Intelligibility of bandpass filtered speech: The effect of filter types.

Many studies have examined the contribution of different spectral bands to speech intelligibility, measuring recognition scores of filtered speech stimuli. For a given filter bandwidth, the influence of filter properties on such experiments has been studied mainly with respect to transition band slopes. The objective of the present study was to determine whether nominal transition band slope is a sufficient characterization of filter properties. Several types of filters, both finite impulse response and infinite impulse response types were examined in three experiments to determine if details of the transition band behavior, as well as group delay properties, had any influence on recognition scores. The results of a total of 72 participants showed that for 1/3 octave passbands, differences between filters having the same nominal transition band slopes, but of different types, were large and statistically significant. Linearity of phase response, however, did not influence the results. Further experiments using passband widths of 1/2 and 2/3 octaves revealed that only for the latter the difference in recognition scores between filter types ceased to be significant. These results have important implications for studies which involve filtered speech as well as models that employ different types of filters to emulate peripheral auditory processing.

Soft tissue conduction as a possible contributor to the limited attenuation provided by hearing protection devices.

CONTEXT: Damage to the auditory system by loud sounds can be avoided by hearing protection devices (HPDs) such as earmuffs, earplugs, or both for maximum attenuation. However, the attenuation can be limited by air conduction (AC) leakage around the earplugs and earmuffs by the occlusion effect (OE) and by skull vibrations initiating bone conduction (BC). AIMS: To assess maximum attenuation by HPDs and possible flanking pathways to the inner ear. SUBJECTS AND METHODS: AC attenuation and resulting thresholds were assessed using the real ear attenuation at threshold (REAT) procedure on 15 normal-hearing participants in four free-field conditions: (a) unprotected ears, (b) ears covered with earmuffs, (c) ears blocked with deeply inserted customized earplugs, and (d) ears blocked with both earplugs and earmuffs. BC thresholds were assessed with and without earplugs to assess the OE. RESULTS: Addition of earmuffs to earplugs did not cause significantly greater attenuation than earplugs alone, confirming minimal AC leakage through the external meatus and the absence of the OE. Maximum REATs ranged between 40 and 46 dB, leading to thresholds of 46-54 dB HL. Furthermore, calculation of the acoustic impedance mismatch between air and bone predicted at least 60 dB attenuation of BC. CONCLUSION: Results do not support the notion that skull vibrations (BC) contributed to the limited attenuation provided by traditional HPDs. An alternative explanation, supported by experimental evidence, suggests transmission of sound to inner ear via non-osseous pathways such as skin, soft tissues, and fluid. Because the acoustic impedance mismatch between air and soft tissues is smaller than that between air and bone, air-borne sounds would be transmitted to soft tissues more effectively than to bone, and therefore less attenuation is expected through soft tissue sound conduction. This can contribute to the limited attenuation provided by traditional HPDs. The present study has practical implications for hearing conservation protocols.

Auditory Discrimination of Lexical Stress Patterns in Hearing-Impaired Infants with Cochlear Implants Compared with Normal Hearing: Influence of Acoustic Cues and Listening Experience to the Ambient Language.

OBJECTIVES: To assess discrimination of lexical stress pattern in infants with cochlear implant (CI) compared with infants with normal hearing (NH). While criteria for cochlear implantation have expanded to infants as young as 6 months, little is known regarding infants' processing of suprasegmental-prosodic cues which are known to be important for the first stages of language acquisition. Lexical stress is an example of such a cue, which, in hearing infants, has been shown to assist in segmenting words from fluent speech and in distinguishing between words that differ only the stress pattern. To date, however, there are no data on the ability of infants with CIs to perceive lexical stress. Such information will provide insight to the speech characteristics that are available to these infants in their first steps of language acquisition. This is of particular interest given the known limitations that the CI device has in transmitting speech information that is mediated by changes in fundamental frequency. DESIGN: Two groups of infants participated in this study. The first group included 20 profoundly hearing-impaired infants with CI, 12 to 33 months old, implanted under the age of 2.5 years (median age of implantation = 14.5 months), with 1 to 6 months of CI use (mean = 2.7 months) and no known additional problems. The second group of infants included 48 NH infants, 11 to 14 months old with normal development and no known risk factors for developmental delays. Infants were tested on their ability to discriminate between nonsense words that differed on their stress pattern only (/dóti/ versus /dotí/ and /dotí/ versus /dóti/) using the visual habituation procedure. The measure for discrimination was the change in looking time between the last habituation trial (e.g., /dóti/) and the novel trial (e.g., /dotí/). RESULTS: (1) Infants with CI showed discrimination between lexical stress pattern with only limited auditory experience with their implant device, (2) discrimination of stress patterns in infants with CI was reduced compared with that of infants with NH, (3) both groups showed directional asymmetry in discrimination, that is, increased discrimination from the uncommon to the common stress pattern in Hebrew (/dóti/ versus /dotí/) compared with the reversed condition. CONCLUSIONS: The CI device transmitted sufficient acoustic information (amplitude, duration, and fundamental frequency) to allow discrimination between stress patterns in young hearing-impaired infants with CI. The present pattern of results is in support of a discrimination model in which both auditory capabilities and "top-down" interactions are involved. That is, the CI infants detected changes between stressed and unstressed syllables after which they developed a bias for the more common weak-strong stress pattern in Hebrew. The latter suggests that infants with CI were able to extract the statistical distribution of stress patterns by listening to the ambient language even after limited auditory experience with the CI device. To conclude, in relation to processing of lexical stress patterns, infants with CI followed similar developmental milestones as hearing infants thus establishing important prerequisites for early language acquisition.

The effect of listening experience on the discrimination of /ba/ and /pa/ in Hebrew-learning and Arabic-learning infants.

UNLABELLED: Infant speech discrimination can follow multiple trajectories depending on the language and the specific phonemes involved. Two understudied languages in terms of the development of infants' speech discrimination are Arabic and Hebrew. PURPOSE: The purpose of the present study was to examine the influence of listening experience with the native language on the discrimination of the voicing contrast /ba-pa/ in Arabic-learning infants whose native language includes only the phoneme /b/ and in Hebrew-learning infants whose native language includes both phonemes. METHOD: 128 Arabic-learning infants and Hebrew-learning infants, 4-to-6 and 10-to-12-month-old infants, were tested with the Visual Habituation Procedure. RESULTS: The results showed that 4-to-6-month-old infants discriminated between /ba-pa/ regardless of their native language and order of presentation. However, only 10-to-12-month-old infants learning Hebrew retained this ability. 10-to-12-month-old infants learning Arabic did not discriminate the change from /ba/ to /pa/ but showed a tendency for discriminating the change from /pa/ to /ba/. CONCLUSIONS: This is the first study to report on the reduced discrimination of /ba-pa/ in older infants learning Arabic. Our findings are consistent with the notion that experience with the native language changes discrimination abilities and alters sensitivity to non-native contrasts, thus providing evidence for 'top-down' processing in young infants. The directional asymmetry in older infants learning Arabic can be explained by assimilation of the non-native consonant /p/ to the native Arabic category /b/ as predicted by current speech perception models.