Age-related benefits of digital noise reduction for short-term word learning in children with hearing loss

The effect of telepractice on vocal turn-taking between a provider, children with cochlear implants, and caregivers: A preliminary report

OBJECTIVES

To examine the effect of telepractice on vocal turn-taking between one clinical provider and children with cochlear implants and their caregivers during child-centered auditory rehabilitation intervention.

METHODS

Seven dyads of children with cochlear implants (mean age 4:11 years) and their hearing mothers and one speech-language pathologist participated together in a telepractice session and an in-person intervention session. Dependent variables were vocalization rate, turn taking rate, rate of speech overlap per second, and between-speaker pause duration.

RESULTS

The speech-language pathologist and children had lower rates of vocalization in the telepractice session than the in-person session. However, maternal vocalization rate was higher in the telepractice than in-person session. The rate of turn-taking between the provider and children was lower in telepractice than in-person sessions but the rate of turn taking between mothers and children was higher in telepractice than in-person sessions. Between-speaker pause duration between children and the provider and between mothers and children was longer in telepractice than in-person sessions. Rate of speech overlap did not vary significantly by session type.

DISCUSSION

The quantity and temporal characteristics of vocal turn-taking were impacted by remote communication during tele-intervention suggesting a potential increase in the cognitive effort required of participants.

Evaluation of Potential Benefits and Limitations of Noise Management Technologies for Children with Hearing Aids

BACKGROUND

 Children with hearing loss frequently experience difficulty understanding speech in the presence of noise. Although remote microphone systems are likely to be the most effective solution to improve speech recognition in noise, the focus of this study centers on the evaluation of hearing aid noise management technologies including directional microphones, adaptive noise reduction (ANR), and frequency-gain shaping. These technologies can improve children's speech recognition, listening comfort, and/or sound quality in noise. However, individual contributions of these technologies as well as the effect of hearing aid microphone mode on localization abilities in children is unknown.

PURPOSE

 The objectives of this study were to (1) compare children's speech recognition and subjective perceptions across five hearing aid noise management technology conditions and (2) compare localization abilities across three hearing aid microphone modes.

RESEARCH DESIGN

 A single-group, repeated measures design was used to evaluate performance differences and subjective ratings.

STUDY SAMPLE

 Fourteen children with mild to moderately severe hearing loss.

DATA COLLECTION AND ANALYSIS

 Children's sentence recognition, listening comfort, sound quality, and localization were assessed in a room with an eight-loudspeaker array.

RESULTS AND CONCLUSION

 The use of adaptive directional microphone technology improves children's speech recognition in noise when the signal of interest arrives from the front and is spatially separated from the competing noise. In contrast, the use of adaptive directional microphone technology may result in a decrease in speech recognition in noise when the signal of interest arrives from behind. The use of a microphone mode that mimics the natural directivity of the unaided auricle provides a slight improvement in speech recognition in noise compared with omnidirectional use with limited decrement in speech recognition in noise when the signal of interest arrives from behind. The use of ANR and frequency-gain shaping provide no change in children's speech recognition in noise. The use of adaptive directional microphone technology, ANR, and frequency-gain shaping improve children's listening comfort, perceived ability to understand speech in noise, and overall listening experience. Children prefer to use each of these noise management technologies regardless of whether the signal of interest arrives from the front or from behind. The use of adaptive directional microphone technology does not result in a decrease in children's localization abilities when compared with the omnidirectional condition. The best localization performance occurred with use of the microphone mode that mimicked the directivity of the unaided auricle.

Perceived Listening Difficulty in the Classroom, Not Measured Noise Levels, Is Associated With Fatigue in Children With and Without Hearing Loss

PURPOSE

The purpose of this study was to examine if classroom noise levels and perceived listening difficulty were related to fatigue reported by children with and without hearing loss.

METHOD

Measures of classroom noise and reports of classroom listening difficulty were obtained from 79 children (ages 6-12 years) at two time points on two different school days. Forty-four children had mild to moderately severe hearing loss in at least one ear. Multiple regression analyses were conducted to evaluate if measured noise levels, perceived listening difficulty, hearing status, language abilities, or grade level would predict self-reported fatigue ratings measured using the Pediatric Quality of Life Inventory Multidimensional Fatigue Scale.

RESULTS

Higher perceived listening difficulty was the only predictor variable that was associated with greater self-reported fatigue.

CONCLUSIONS

Measured classroom noise levels showed no systematic relationship with fatigue ratings, suggesting that actual classroom noise levels do not contribute to increased reports of subjective fatigue. Instead, perceived challenges with listening appears to be an important factor for consideration in future work examining listening-related fatigue in children with and without hearing loss.

Learning and Retention of Novel Words in Musicians and Nonmusicians

Purpose The purpose of this study was to determine whether long-term musical training enhances the ability to perceive and learn new auditory information. Listeners with extensive musical experience were expected to detect, learn, and retain novel words more effectively than participants without musical training. Advantages of musical training were expected to be greater for words learned in multitalker babble compared to quiet. Method Participants consisted of 20 young adult musicians and 20 age-matched nonmusicians, all with normal hearing. In addition to completing word recognition and nonword detection tasks, each participant learned 10 novel words in a rapid word-learning paradigm. All tasks were completed in quiet and in multitalker babble. Next-day retention of the learned words was examined in isolation (recall) and in the context of continuous discourse (detection). Performance was compared across groups and listening conditions. Results Performance was significantly poorer in babble than in quiet on word recognition and nonword detection, but not on word learning, learned-word recall, or learned-word detection. No differences were observed between groups (musicians vs. nonmusicians) on any of the tasks. Conclusions For young normal-hearing adults, auditory experience resulting from long-term music training did not enhance their learning of new auditory information in either favorable (quiet) or unfavorable (babble) listening conditions. This suggests that the formation of semantic and musical representations in memory may be supported by the same underlying auditory processes, such that musical training is simply an extension of an auditory expertise that both musicians and nonmusicians possess.

What Can a Child Do With One Normal-Hearing Ear? Speech Perception and Word Learning in Children With Unilateral and Bilateral Hearing Losses Relative to Peers With Normal Hearing

OBJECTIVES

To examine the effects of unilateral hearing loss on children's ability to perceive familiar words and to learn and retain new words. Because children with unilateral hearing loss receive full auditory input in one ear, their performance was expected to be consistent with that of children with normal hearing rather than that of children with moderate bilateral hearing loss.

DESIGN

Participants were 36 school-age children with normal hearing bilaterally, 11 children with moderate bilateral hearing loss, and 11 children with mild-to-profound unilateral hearing loss (six right and five left). Half of the normally hearing children and two-thirds of the children with unilateral hearing loss were from bilingual Spanish/English-speaking homes. One of the 11 children with bilateral hearing loss was from a bilingual Spanish/English-speaking home. All children completed a word recognition test in English and in Spanish, a word-learning task comprised of nonsense words constructed using the phonotactic rules of English, Spanish, and Arabic, and a next-day word-retention test.

RESULTS

Word recognition did not differ across groups in English or Spanish. Learning and retention of nonsense words was highest for the children with normal hearing in all three languages. The children with unilateral and bilateral losses learned and recalled the English nonsense words as well as their normally hearing peers, but performance for the Spanish and Arabic nonsense words was significantly and similarly reduced by hearing loss in either ear.

CONCLUSIONS

Failure to learn and retain new words given a full auditory representation in one ear suggests that children with unilateral and bilateral hearing losses may share a unifying feature of impairment at the level of the central auditory system.

Individual Differences Offer Insight Into Clinical Recommendations for Directional and Remote Microphone Technology Use in Children

Purpose This study sought to evaluate the effects of common hearing aid microphone technologies on speech recognition and listening effort, and to evaluate potential predictive factors related to microphone benefits for school-age children with hearing loss in a realistic listening situation. Method Children (n = 17, ages 10-17 years) with bilateral, sensorineural hearing loss were fitted with hearing aids set to include three programs: omnidirectional, adaptive directional, and omnidirectional + remote microphone. Children completed a dual-task paradigm in a moderately reverberant room. The primary task included monosyllabic word recognition, with target speech presented at 60 dB A from 0° (front) or 180° (back) azimuth. The secondary task was a "go/no-go," visual shape-recognition task. Multitalker babble noise created a +5 dB SNR. Children were evaluated in two speaker conditions (front, back) using all three hearing aid programs. The remote microphone transmitter remained at the front speaker throughout testing. Speech recognition performance was calculated from the primary task while listening effort was measured as response time during the secondary task. Results Speech presented from the back significantly increased listening effort and caused a reduction in speech perception when directional and remote microphones were used. Considerable variability was found in pattern of benefit across microphones and source location. Clinical measures did not predict benefit patterns with directional or remote microphones; however, child age and performance with omnidirectional microphones did. Conclusions When compared to a traditional omnidirectional setting, the directional and remote microphone configurations evaluated in this study have the potential to provide benefit for some children and increase difficulty for others when used in dynamic environments. A child's performance with omnidirectional hearing aids could be used to better inform clinical recommendations for these technologies.

Bone Conduction Amplification in Children: Stimulation via a Percutaneous Abutment versus a Transcutaneous Softband

OBJECTIVES

Research suggests that the speech perception of children using bone conduction amplification improves if the device is coupled to an implanted abutment rather than to a softband. The purpose of the present study was to determine if the benefit of direct stimulation via an abutment is limited to small improvements in speech perception or if similar or greater benefits occur for other auditory tasks important for learning and communication.

DESIGN

Fourteen children (7 to 15 years of age) with bilateral conductive and three children with unilateral conductive or sensorineural hearing loss were enrolled. Each child completed four tasks while using a bone conduction device coupled to an implanted abutment and with the device coupled to a softband. The two devices were worn at the same time and activated one at a time for testing. The children completed four tasks under each coupling condition: (a) a traditional word recognition task, (b) an auditory lexical decision task in which the children repeated aloud, and indicated the category of, real and nonsense words, (c) a nonsense-word detection task which required the children to identify nonsense words within short sentences, and (d) a rapid word learning task in which the children learned to associate nonsense words with novel images.

RESULTS

Regression analyses revealed that age, duration of device use, in-situ hearing thresholds, or device output did not account for a significant portion of the variability in performance for any of the four tasks. Repeated-measures analysis of variance revealed significant increases in word recognition with the abutment as well as significantly better performance for the lexical decision and word learning tasks. The data indicated that the children with the poorest performance with the softband tended to benefit most with the abutment. Also, the younger children showed improved performance for more tasks with the abutment than the older children. No difference between coupling conditions was observed for nonsense-word detection.

CONCLUSIONS

The improved recognition of familiar words, categorization and repetition of nonsense words, and speed of word learning with the abutment suggests that direct stimulation provides a higher-quality signal than indirect stimulation through a softband. Because these processes are important for vocabulary acquisition and language development, children may experience long-term benefits of direct stimulation for academic, social, and vocational purposes in addition to immediate improvement in communication.

Assistive Hearing Technology for Deaf and Hard-of-Hearing Spoken Language Learners

Radical advancements in hearing technology in the last 30 years have offered some deaf and hard-of-hearing (DHH) children the adequate auditory access necessary to acquire spoken language with high-quality early intervention. However, meaningful achievement gaps in reading and spoken language persist despite the engineering marvel of modern hearing aids and cochlear implants. Moreover, there is enormous unexplained variability in spoken language and literacy outcomes. Aspects of signal processing in both hearing aids and cochlear implants are discussed as they relate to spoken language outcomes in preschool and school-age children. In suggesting areas for future research, a case is made for not only expanding the search for mechanisms of influence on outcomes outside of traditional device- and child-related factors, but also for framing the search within Biopsychosocial systems theories. This theoretical approach incorporates systems of risk factors across many levels, as well as the bidirectional and complex ways in which factors influence each other. The combination of sophisticated hearing technology and a fuller understanding of the complex environmental and biological factors that shape development will help maximize spoken language outcomes in DHH children and contribute to laying the groundwork for successful literacy and academic development.

Effects of Adaptive Hearing Aid Directionality and Noise Reduction on Masked Speech Recognition for Children Who Are Hard of Hearing

Purpose The purpose of this study was to evaluate speech-in-noise and speech-in-speech recognition associated with activation of a fully adaptive directional hearing aid algorithm in children with mild to severe bilateral sensory/neural hearing loss. Method Fourteen children (5-14 years old) who are hard of hearing participated in this study. Participants wore laboratory hearing aids. Open-set word recognition thresholds were measured adaptively for 2 hearing aid settings: (a) omnidirectional (OMNI) and (b) fully adaptive directionality. Each hearing aid setting was evaluated in 3 listening conditions. Fourteen children with normal hearing served as age-matched controls. Results Children who are hard of hearing required a more advantageous signal-to-noise ratio than children with normal hearing to achieve comparable performance in all 3 conditions. For children who are hard of hearing, the average improvement in signal-to-noise ratio when comparing fully adaptive directionality to OMNI was 4.0 dB in noise, regardless of target location. Children performed similarly with fully adaptive directionality and OMNI settings in the presence of the speech maskers. Conclusions Compared to OMNI, fully adaptive directionality improved speech recognition in steady noise for children who are hard of hearing, even when they were not facing the target source. This algorithm did not affect speech recognition when the background noise was speech. Although the use of hearing aids with fully adaptive directionality is not proposed as a substitute for remote microphone systems, it appears to offer several advantages over fixed directionality, because it does not depend on children facing the target talker and provides access to multiple talkers within the environment. Additional experiments are required to further evaluate children's performance under a variety of spatial configurations in the presence of both noise and speech maskers.

Predictors of Vocabulary Outcomes in Children Who Are Deaf or Hard of Hearing From Spanish-Speaking Families

Purpose

The goal of this study was to identify predictors of expressive vocabulary in young Spanish-speaking children who are deaf or hard of hearing living in the United States.

Method

This cross-sectional study considered 53 children with bilateral hearing loss between 8 and 34 months of age ( M = 24, SD = 6.9). Demographic variables, variables related to the hearing loss, and intervention variables were included in a hierarchical regression analysis to predict expressive vocabulary quotients from the MacArthur Inventario del Desarrollo de Habilidades Comunicativas (Communicative Development Inventories; Jackson-Maldonado et al., 2003 ).

Results

Chronological age, degree of hearing loss, functional hearing ability ratings, age of enrollment in early intervention, and the interaction between chronological age and age of intervention accounted for 61.5% of the vocabulary variance. Children who received intervention by 6 months of age achieved significantly higher vocabulary outcomes than children who started intervention later.

Conclusion

The children's mean vocabulary outcomes were below average when compared with hearing peers. This was especially true for older children, children with moderately-severe-to-profound hearing loss, and children who began intervention after 6 months of age. This delay in vocabulary outcomes has the potential to interfere with future reading and academic outcomes.

Word Recognition and Learning: Effects of Hearing Loss and Amplification Feature

Two amplification features were examined using auditory tasks that varied in stimulus familiarity. It was expected that the benefits of certain amplification features would increase as the familiarity with the stimuli decreased. A total of 20 children and 15 adults with normal hearing as well as 21 children and 17 adults with mild to severe hearing loss participated. Three models of ear-level devices were selected based on the quality of the high-frequency amplification or the digital noise reduction (DNR) they provided. The devices were fitted to each participant and used during testing only. Participants completed three tasks: (a) word recognition, (b) repetition and lexical decision of real and nonsense words, and (c) novel word learning. Performance improved significantly with amplification for both the children and the adults with hearing loss. Performance improved further with wideband amplification for the children more than for the adults. In steady-state noise and multitalker babble, performance decreased for both groups with little to no benefit from amplification or from the use of DNR. When compared with the listeners with normal hearing, significantly poorer performance was observed for both the children and adults with hearing loss on all tasks with few exceptions. Finally, analysis of across-task performance confirmed the hypothesis that benefit increased as the familiarity of the stimuli decreased for wideband amplification but not for DNR. However, users who prefer DNR for listening comfort are not likely to jeopardize their ability to detect and learn new information when using this feature.

A critical review of hearing-aid single-microphone noise-reduction studies in adults and children

PURPOSE

Single-microphone noise reduction (SMNR) is implemented in hearing aids to suppress background noise. The purpose of this article was to provide a critical review of peer-reviewed studies in adults and children with sensorineural hearing loss who were fitted with hearing aids incorporating SMNR.

METHOD

Articles published between 2000 and 2016 were searched in PUBMED and EBSCO databases.

RESULTS

Thirty-two articles were included in the final review. Most studies with adult participants showed that SMNR has no effect on speech intelligibility. Positive results were reported for acceptance of background noise, preference, and listening effort. Studies of school-aged children were consistent with the findings of adult studies. No study with infants or young children of under 5 years old was found. Recent studies on noise-reduction systems not yet available in wearable hearing aids have documented benefits of noise reduction on memory for speech processing for older adults.

CONCLUSIONS

This evidence supports the use of SMNR for adults and school-aged children when the aim is to improve listening comfort or reduce listening effort. Future research should test SMNR with infants and children who are younger than 5 years of age. Further development, testing, and clinical trials should be carried out on algorithms not yet available in wearable hearing aids. Testing higher cognitive level for speech processing and learning of novel sounds or words could show benefits of advanced signal processing features. These approaches should be expanded to other populations such as children and younger adults. Implications for rehabilitation The review provides a quick reference for students and clinicians regarding the efficacy and effectiveness of SMNR in wearable hearing aids. This information is useful during counseling session to build a realistic expectation among hearing aid users. Most studies in the adult population suggest that SMNR may provide some benefits to adult listeners in terms of listening comfort, acceptance of background noise, and release of cognitive load in a complex listening condition. However, it does not improve speech intelligibility. Studies that examined SMNR in the paediatric population suggest that SMNR may benefit older school-aged children, aged between 10 and 12 years old. The evidence supports the use of SMNR for adults and school-aged children when the aim is to improve listening comfort or reduce listening effort.

Detecting and Learning New Words: The Impact of Advancing Age and Hearing Loss

PURPOSE

Lexical acquisition was examined in children and adults to determine if the skills needed to detect and learn new words are retained in the adult years. In addition to advancing age, the effects of hearing loss were also examined.

METHOD

Measures of word recognition, detection of nonsense words within sentences, and novel word learning were obtained in quiet for 20 children with normal hearing and 21 with hearing loss (8-12 years) as well as for 15 adults with normal hearing and 17 with hearing loss (58-79 years). Listeners with hearing loss were tested with and without high-frequency acoustic energy to identify the type of amplification (narrowband, wideband, or frequency lowering) that yielded optimal performance.

RESULTS

No differences were observed between the adults and children with normal hearing except for the adults' better nonsense word detection. The poorest performance was observed for the listeners with hearing loss in the unaided condition. Performance improved significantly with amplification to levels at or near that of their counterparts with normal hearing. With amplification, the adults performed as well as the children on all tasks except for word recognition.

CONCLUSIONS

Adults retain the skills necessary for lexical acquisition regardless of hearing status. However, uncorrected hearing loss nearly eliminates these skills.

Commentary: listening can be exhausting--fatigue in children and adults with hearing loss

Anecdotal reports of fatigue after sustained speech-processing demands are common among adults with hearing loss; however, systematic research examining hearing loss-related fatigue is limited, particularly with regard to fatigue among children with hearing loss (CHL). Many audiologists, educators, and parents have long suspected that CHL experience stress and fatigue as a result of the difficult listening demands they encounter throughout the day at school. Recent research in this area provides support for these intuitive suggestions. In this article, the authors provide a framework for understanding the construct of fatigue and its relation to hearing loss, particularly in children. Although empirical evidence is limited, preliminary data from recent studies suggest that some CHL experience significant fatigue-and such fatigue has the potential to compromise a child's performance in the classroom. In this commentary, the authors discuss several aspects of fatigue including its importance, definitions, prevalence, consequences, and potential linkage to increased listening effort in persons with hearing loss. The authors also provide a brief synopsis of subjective and objective methods to quantify listening effort and fatigue. Finally, the authors suggest a common-sense approach for identification of fatigue in CHL; and, the authors briefly comment on the use of amplification as a management strategy for reducing hearing-related fatigue.

Subjective fatigue in children with hearing loss: some preliminary findings

PURPOSE

In this study, the authors examined the effect of hearing loss on subjective reports of fatigue in school-age children using a standardized measure.

METHODS

As part of a larger ongoing study, the authors obtained subjective ratings of fatigue using the Pediatric Quality of Life Inventory (PedsQL) Multidimensional Fatigue Scale ( Varni, Burwinkle, Katz, Meeske, & Dickinson, 2002). This standardized scale provides a measure of general fatigue, sleep/rest fatigue, cognitive fatigue, and an overall composite measure of fatigue. To date, data from 10 children with hearing loss (CHL) and 10 age-matched children with normal hearing (CNH) have been analyzed.

RESULTS

These preliminary results show that subjective fatigue is increased in school-age children with hearing loss (Cohen's d = 0.78-1.90). In addition, the impact of hearing loss on fatigue in school-age children appears pervasive across multiple domains (general, sleep/rest, and cognitive fatigue).

CONCLUSION

School-age CHL reported significantly more fatigue than did CNH. These preliminary data are important given the negative academic and psychosocial consequences associated with fatigue. Further research is needed to determine the underlying mechanisms responsible for this increased fatigue in school-age children with hearing loss, and to identify factors that may modulate (e.g., degree of loss) and mediate (e.g., hearing aid or cochlear implant use) its impact.

Listening effort and perceived clarity for normal-hearing children with the use of digital noise reduction

OBJECTIVES

The goal of this study was to evaluate how digital noise reduction (DNR) impacts listening effort and judgment of sound clarity in children with normal hearing. It was hypothesized that when two DNR algorithms differing in signal-to-noise ratio (SNR) output are compared, the algorithm that provides the greatest improvement in overall output SNR will reduce listening effort and receive a better clarity rating from child listeners. A secondary goal was to evaluate the relation between the inversion method measurements and listening effort with DNR processing.

DESIGN

Twenty-four children with normal hearing (ages 7 to 12 years) participated in a speech recognition task in which consonant-vowel-consonant nonwords were presented in broadband background noise. Test stimuli were recorded through two hearing aids with DNR off and DNR on at 0 dB and +5 dB input SNR. Stimuli were presented to listeners and verbal response time (VRT) and phoneme recognition scores were measured. The underlying assumption was that an increase in VRT reflects an increase in listening effort. Children rated the sound clarity for each condition. The two commercially available HAs were chosen based on: (1) an inversion technique, which was used to quantify the magnitude of change in SNR with the activation of DNR, and (2) a measure of magnitude-squared coherence, which was used to ensure that DNR in both devices preserved the spectrum.

RESULTS

One device provided a greater improvement in overall output SNR than the other. Both DNR algorithms resulted in minimal spectral distortion as measured using coherence. For both devices, VRT decreased for the DNR-on condition, suggesting that listening effort decreased with DNR in both devices. Clarity ratings were also better in the DNR-on condition for both devices. The device showing the greatest improvement in output SNR with DNR engaged improved phoneme recognition scores. The magnitude of this improved phoneme recognition was not accurately predicted with measurements of output SNR. Measured output SNR varied in the ability to predict other outcomes.

CONCLUSIONS

Overall, results suggest that DNR effectively reduces listening effort and improves subjective clarity ratings in children with normal hearing but that these improvements are not necessarily related to the output SNR improvements or preserved speech spectra provided by the DNR.

The Complexities of Fatigue in Children with Hearing Loss

Fatigue is a common phenomenon in our society, and it can have a major impact on an individual's performance and wellbeing. Parents and teachers have long believed that children with hearing loss (CHL) are at increased risk for fatigue. One could easily speculate that toward the end of a school day, CHL may be “physically and mentally spent” as a result of focusing so intently on a teacher's speech, as well as conversations with other students. Moreover, the increased listening effort, stress, and subsequent fatigue experienced by CHL could jeopardize the ability to learn in a noisy classroom environment, thus increasing the risk for problems in school. Only recently, however, have we begun to see empirical studies supporting the notion that CHL experience more fatigue than children with normal hearing (CNH).

This review was developed to enhance the awareness of fatigue among those audiologists interested in serving CHL. To this end, we have presented an overview on fatigue in CHL, including its importance, definitions, prevalence, consequences, and recent developments. The complexity and multifaceted nature of fatigue has been highlighted and the need for additional research on fatigue in CHL is emphasized.

Effect of phonotactic probability and neighborhood density on word-learning configuration by preschoolers with typical development and specific language impairment

PURPOSE

In this study, the authors assessed the effects of phonotactic probability and neighborhood density on word-learning configuration by preschoolers with specific language impairment (SLI) and typical language development (TD).

METHOD

One hundred thirty-one children participated: 48 with SLI, 44 with TD matched on age and gender, and 39 with TD matched on vocabulary and gender. Referent identification and naming were assessed in a computer-based learning context.

RESULTS

For referent identification, preschoolers with TD benefited from high phonotactic probability, and the younger group also benefited from low neighborhood density. In contrast, the SLI group benefited only from high neighborhood density. For naming, older preschoolers with TD benefited most from low-density words, younger preschoolers with TD benefited most from words with high phonotactic probability, and the SLI group showed no advantage.

CONCLUSION

Phonotactic probability and neighborhood density had different effects on each group that may be related to children's ability to store well-specified word forms and to the size of their extant lexicon. The authors argue that cross-study comparisons of word learning are needed; therefore, researchers should describe word, referent, and learner characteristics and the learning context and should situate their studies in a triggering → configuration + engagement model of word learning.

An evidence-based systematic review of directional microphones and digital noise reduction hearing aids in school-age children with hearing loss

PURPOSE

The purpose of this evidence-based systematic review was to evaluate the efficacy of digital noise reduction and directional microphones for outcome measures of audibility, speech recognition, speech and language, and self- or parent-report in pediatric hearing aid users.

METHOD

The authors searched 26 databases for experimental studies published after 1980 addressing one or more clinical questions and meeting all inclusion criteria. The authors evaluated studies for methodological quality and reported or calculated p values and effect sizes when possible.

RESULTS

A systematic search of the literature resulted in the inclusion of 4 digital noise reduction and 7 directional microphone studies (in 9 journal articles) that addressed speech recognition, speech and language, and/or self- or parent-report outcomes. No digital noise reduction or directional microphone studies addressed audibility outcomes.

CONCLUSIONS

On the basis of a moderate level of evidence, digital noise reduction was not found to improve or degrade speech understanding. Additional research is needed before conclusions can be drawn regarding the impact of digital noise reduction on important speech, language, hearing, and satisfaction outcomes. Moderate evidence also indicates that directional microphones resulted in improved speech recognition in controlled optimal settings; however, additional research is needed to determine the effectiveness of directional microphones in actual everyday listening environments.