Determining unilateral or bilateral hearing aid preference in adults: a prospective study.

OBJECTIVE: Despite high rates of bilateral hearing aid fitting globally, a number of adults continue to reject one hearing aid. The current study aimed to identify a clinically suitable tool for determining, pre-fitting, which clients might prefer one hearing aid.Study Sample: Ninety-five new adult hearing aid candidates, aged 49-87 years, were assessed prior to a first hearing aid fitting. Sixty-eight participants adhered to the prescribed protocol for both bilateral and unilateral hearing aid use. DESIGN: Performance was assessed on a modified version of the Listening in Spatialised Noise - Sentences test (LiSN-S), the Dichotic Digits difference Test, the Experiential Hearing Aid simulator, and the Grooved Pegboard Test. All participants were fitted bilaterally, but were instructed to alternate between unilateral and bilateral hearing aid use over fourteen weeks post-fitting. Participants' wearing preferences were assessed via a short questionnaire. RESULTS: 78% of participants expressed an overall preference for bilateral hearing aid use. Only the LiSN-S bilateral advantage test outcomes significantly correlated with overall wearing preference. CONCLUSIONS: Although the LiSN-S bilateral advantage score related to overall wearing preference, the accuracy of the predictor was too low to warrant implementation of this test prior to hearing aid fitting. The current practice of recommending bilateral hearing aid use continues to be the best option for clinicians.

The Dichotic Digits difference Test (DDdT): Development, Normative Data, and Test-Retest Reliability Studies Part 1.

BACKGROUND: The dichotic digits test is one of the most widely used assessment tools for central auditory processing disorder. However, questions remain concerning the impact of cognitive factors on test results. PURPOSE: To develop the Dichotic Digits difference Test (DDdT), an assessment tool that could differentiate children with cognitive deficits from children with genuine dichotic deficits based on differential test results. The DDdT consists of four subtests: dichotic free recall (FR), dichotic directed left ear (DLE), dichotic directed right ear (DRE), and diotic. Scores for six conditions are calculated (FR left ear [LE], FR right ear [RE], and FR total, as well as DLE, DRE, and diotic). Scores for four difference measures are also calculated: dichotic advantage, right-ear advantage (REA) FR, REA directed, and attention advantage. RESEARCH DESIGN: Experiment 1 involved development of the DDdT, including error rate analysis. Experiment 2 involved collection of normative and test-retest reliability data. STUDY SAMPLE: Twenty adults (aged 25 yr 10 mo to 50 yr 7 mo, mean 36 yr 4 mo) took part in the development study; 62 normal-hearing, typically developing, primary-school children (aged 7 yr 1 mo to 11 yr 11 mo, mean 9 yr 4 mo) and 10 adults (aged 25 yr 0 mo to 51 yr 6 mo, mean 34 yr 10 mo) took part in the normative and test-retest reliability study. DATA COLLECTION AND ANALYSIS: In Experiment 1, error rate analysis was conducted on the 36 digit-pair combinations of the DDdT. Normative data collected in Experiment 2 were arcsine transformed to achieve a distribution that was closer to a normal distribution and z-scores calculated. Pearson product-moment correlations were used to determine the strength of relationships between DDdT conditions. RESULTS: The development study revealed no significant differences in the adult population between test and retest on any DDdT condition. Error rates on 36 digit pairs ranged from 1.5% to 16.7%. The most and the least error-prone digits were removed before commencement of the normative data study, leaving 25 unique digit pairs. Average z-scores calculated from the arcsine-transformed data collected from the 62 children who took part in the normative data study revealed that FR dichotic processing (LE, RE, and total) was highly correlated with diotic processing (r ranging from 0.5 to 0.6; p < 0.0001). Significant improvements in performance on retest occurred for the FR LE, RE, total, and diotic conditions (p ranging from 0.05 to 0.0004), the conditions that would be expected to improve with practice if the participant's response strategies are better the second time around. CONCLUSIONS: The addition of a diotic control task-that shares many response demands with the usual dichotic tasks-opens up the possibility of differentiating children who perform below expectations because of poor dichotic processing skills from those who perform poorly because of impaired attention, memory, or other cognitive abilities. The high correlation between dichotic and diotic performance suggests that factors other than dichotic performance play a substantial role in a child's ability to perform a dichotic listening task. This hypothesis is investigated further in the cognitive correlation study that follows in the companion paper (DDdT Study Part 2; Cameron et al, 2016).

Investigating the Interaction between Dichotic Deficits and Cognitive Abilities Using the Dichotic Digits difference Test (DDdT) Part 2.

BACKGROUND: The Dichotic Digits difference Test (DDdT) was developed to investigate the relationship between dichotic processing and cognitive abilities and, through the use of differential test scores, to provide professionals with a clinical tool that could aid in differentiation of clients with genuine dichotic deficits from those where cognitive disorders affect test performance. The DDdT consists of four subtests: dichotic free recall (FR), dichotic directed left ear, dichotic directed right ear, and diotic. Scores are calculated for six conditions: FR left ear (LE), right ear (RE), and total, as well as the directed left ear, directed right ear, and diotic, and four difference measures: dichotic advantage, RE advantage FR, RE advantage directed, and attention advantage. PURPOSE: To investigate the role of cognitive abilities on DDdT test performance. RESEARCH DESIGN: Correlational analysis between the various DDdT conditions and difference measures, as well as between dichotic, diotic, and cognitive factors (memory, intelligence, and attention). STUDY SAMPLE: Fifty typically developing children (aged 7 yr 0 mo to 12 yr 1 mo, mean = 9 yr 2 mo) and ten children recruited from the Australian Hearing CAPD Service who were diagnosed with a memory or dichotic deficit (aged 7 yr 0 mo to 15 yr 0 mo, mean = 9 yr 5 mo) took part in the study. DATA COLLECTION AND ANALYSIS: The Pearson product moment correlations were used to determine the strength of relationships between DDdT conditions as well as relationships between scores on these conditions and performance on the various cognitive assessment tools, which included the number memory forward and reversed subtests of the Test of Auditory Processing Skills - Third Edition, IVA + Plus Continuous Performance Test, and the Test of Non-Verbal Intelligence-4 (TONI-4). A parent questionnaire (Fisher's Auditory Checklist) and a participant questionnaire (Listening Inventory for Education) were also administered. RESULTS: Diotic performance was significantly correlated with performance on all the DDdT dichotic FR conditions (r = 0.6-0.8; p < 0.00001). Further, significant correlations were found between the FR LE, total, and diotic conditions, and the cognitive measures of attention and memory, with r ranging from 0.4 to 0.5 (p < 0.01-0.001). Right-ear performance was not significantly correlated to any cognitive measure, except for FR RE and number memory forward (r = 0.35; p = 0.006). The DDdT dichotic advantage measure was investigated in a subset of clinical children and found to aid in differentiating true dichotic from spurious results. CONCLUSIONS: As found in the DDdT normative data study that precedes in the companion paper (DDdT Study Part 1; Cameron et al, 2016), the high correlation between dichotic and diotic performances by the clinical and typically developing participants suggests that factors other than dichotic performance play a substantial role in a child's ability to perform a dichotic listening task. Indeed, 61% of the variance in FR total scores for the children in this study was accounted for by factors that do not involve the perception of dichotic stimuli. This view is supported by the correlations between measures of attention and memory and dichotic scores. This result has wide-spread implications in respect to interpretation of central auditory processing disorder test results and further investigation of the use of the DDdT in a clinical population is warranted.

On the Contribution of Target Audibility to Performance in Spatialized Speech Mixtures.

Hearing loss has been shown to reduce speech understanding in spatialized multitalker listening situations, leading to the common belief that spatial processing is disrupted by hearing loss. This paper describes related studies from three laboratories that explored the contribution of reduced target audibility to this deficit. All studies used a stimulus configuration in which a speech target presented from the front was masked by speech maskers presented symmetrically from the sides. Together these studies highlight the importance of adequate stimulus audibility for optimal performance in spatialized speech mixtures and suggest that reduced access to target speech information might explain a substantial portion of the "spatial" deficit observed in listeners with hearing loss.

Effect of audibility on spatial release from speech-on-speech masking.

This study investigated to what extent spatial release from masking (SRM) deficits in hearing-impaired adults may be related to reduced audibility of the test stimuli. Sixteen adults with sensorineural hearing loss and 28 adults with normal hearing were assessed on the Listening in Spatialized Noise-Sentences test, which measures SRM using a symmetric speech-on-speech masking task. Stimuli for the hearing-impaired listeners were delivered using three amplification levels (National Acoustic Laboratories - Revised Profound prescription (NAL-RP) +25%, and NAL-RP +50%), while stimuli for the normal-hearing group were filtered to achieve matched audibility. SRM increased as audibility increased for all participants. Thus, it is concluded that reduced audibility of stimuli may be a significant factor in hearing-impaired adults' reduced SRM even when hearing loss is compensated for with linear gain. However, the SRM achieved by the normal hearers with simulated audibility loss was still significantly greater than that achieved by hearing-impaired listeners, suggesting other factors besides audibility may still play a role.

Results from a National Central Auditory Processing Disorder Service: A Real-World Assessment of Diagnostic Practices and Remediation for Central Auditory Processing Disorder.

This article describes the development and evaluation of a national service to diagnose and remediate central auditory processing disorder (CAPD). Data were gathered from 38 participating Australian Hearing centers over an 18-month period from 666 individuals age 6, 0 (years, months) to 24, 8 (median 9, 0). A total of 408 clients were diagnosed with either a spatial processing disorder (n = 130), a verbal memory deficit (n = 174), or a binaural integration deficit (n = 104). A hierarchical test protocol was used so not all children were assessed on all tests in the battery. One hundred fifty clients decided to proceed with deficit-specific training (LiSN & Learn or Memory Booster) and/or be fitted with a frequency modulation system. Families were provided with communication strategies targeted to a child's specific listening difficulties and goals. Outcomes were measured using repeat assessment of the relevant diagnostic test, as well as the Client Oriented Scale of Improvement measure and Listening Inventories for Education teacher questionnaire. Group analyses revealed significant improvements postremediation for all training/management options. Individual posttraining performance and results of outcome measures also are discussed.

Remediation of spatial processing deficits in hearing-impaired children and adults.

BACKGROUND: The ability to use interaural cues to segregate target speech from competing signals allows people with normal hearing to understand speech at significantly poorer signal-to-noise ratios. This ability, referred to as spatial processing ability or spatial release from masking, has been shown to be deficient in people with a sensorineural hearing loss even after amplification is applied. Spatial processing deficits in a population of children with auditory processing deficits have been found to be remediable through the use of a deficit-specific auditory training program called the LiSN & Learn. PURPOSE: The aim of the present study was to determine whether LiSN & Learn auditory training could improve the spatial processing ability of hearing-impaired adults and children. In addition, the research investigated whether the age of the participant would affect the efficacy of the training program. RESEARCH DESIGN: In a repeated-measures design, participants' spatial processing ability was assessed pretraining and posttraining using the Listening in Spatialized Noise-Sentences Test (LiSN-S). Questionnaire responses were also collected from participants pretraining and posttraining to provide a subjective measure of real-life listening difficulty. Between the two assessment periods, participants were asked to train with the LiSN & Learn for 15 min per day, 5 days per week for 60 training sessions. STUDY SAMPLE: Participants were five children (aged 6-11 yr) and five adults (aged 60-74 yr) with up to a moderate sensorineural hearing loss. DATA COLLECTION AND ANALYSIS: The LiSN & Learn auditory training software incorporates five computer games in which target sentences, processed with head-related transfer functions, are perceived as coming from 0° azimuth, and simultaneous distracting speech streams are perceived as coming from ±90° azimuth. Participants are tasked with identifying a word from the target sentence and selecting the corresponding picture from a selection of four images displayed on the screen. The signal-to-noise ratio is adapted based on whether the response given is correct or incorrect. RESULTS: Despite an average improvement of 10 dB on the LiSN & Learn training program, no significant improvements were seen posttraining in either of the spatially separated conditions of the LiSN-S (p ranging 0.47-0.75). A 1.2 dB improvement was found in the baseline condition of the LiSN-S, which incorporates no spatial separation between distracter and target stimuli (p < 0.01). Age did not significantly affect training outcomes (p = 0.21). No significant improvements were found posttraining on the self-report questionnaires (p = 0.84 and p = 0.20). CONCLUSIONS: This study has demonstrated that LiSN & Learn training does not significantly improve spatial processing deficits in adults or children with a sensorineural hearing loss. As auditory training did not prove to be effective, further research should be directed toward the development of hearing aid processing schemes that will compensate for the degraded interaural time difference and interaural level difference cues which underpin spatial processing.

Prevalence and remediation of spatial processing disorder (SPD) in Indigenous children in regional Australia.

OBJECTIVE: This study aimed to determine the prevalence of spatial processing disorder (SPD) in the Indigenous Australian population and the benefit of and logistical issues arising from remediation of the disorder. DESIGN: Participants were assessed for SPD with the Listening in Spatialized Noise - Sentences test (LiSN-S). Participants diagnosed with SPD were instructed to use the LiSN & Learn auditory training software until 100 games had been completed. STUDY SAMPLE: Participants were 144 Indigenous Australian children (aged between 6;0 [years;months] and 12;2). RESULTS: Ten participants (6.9%) presented with SPD. Nine took part in the auditory training study. Post-training LiSN-S performance improved on average by 0.9 population standard deviations (1.4 dB). There was a significant correlation (r = 0.71, p = 0.031, η(2) = 0.51) between total number of LiSN & Learn games played (mean = 65, SD = 27) and improvement in LiSN-S performance. Teachers rated all participants as improving in their listening abilities post-intervention. CONCLUSIONS: There is a high prevalence of SPD in the Indigenous Australian population. LiSN & Learn training is effective in remediating SPD in this population and is considered a beneficial intervention by teachers, however improvement in spatial processing is dependent on training program uptake.

The effect of better-ear glimpsing on spatial release from masking.

The current experiment investigated whether better-ear glimpsing can explain the spatial release achieved by normal-hearing adults when situations are high in informational masking. Both modeling and behavioral methods were used. The speech reception thresholds of 38 young adults were measured for co-located, spatially separated and two better-ear glimpsed conditions. In the better-ear glimpsed conditions the binaural signals were processed so that in each time-frequency segment, the signal with the better SNR (left or right ear) was presented diotically. To investigate the effect of widening auditory filters on better-ear glimpsing, adjacent frequency bands were combined in one of the better-ear glimpsing conditions. Twenty-two participants were tested with maskers high in informational masking, while 16 participants were tested with maskers lower in informational masking. The mean speech reception thresholds achieved in the glimpsed conditions were significantly worse than in the spatially separated condition. This suggests that better-ear glimpsing can explain some but not all of the observed spatial release from masking. The difference between performance in the spatially separated and glimpsed conditions was largest when informational masking was high, suggesting better-ear glimpsing may release energetic rather than informational masking. Reducing the number of frequency bands sampled had a small effect on performance.

The importance of interaural time differences and level differences in spatial release from masking.

Numerous studies have described improvements in speech understanding when interaural time differences (ITDs) and interaural level differences (ILDs) are present. The present study aimed to investigate whether either cue in isolation can elicit spatial release from masking (SRM) in a speech-on-speech masking paradigm with maskers positioned symmetrically around the listener. Twelve adults were tested using three presentations of the Listening in Spatialized Noise-Sentences Test, with each presentation modified to contain different interaural cues in the stimuli. Results suggest that ILDs provide a similar amount of SRM as ITDs and ILDs combined. ITDs alone provide significantly less benefit.

The effects of hearing impairment and aging on spatial processing.

OBJECTIVES: Difficulty in understanding speech in background noise is frequently reported by hearing-impaired people despite well-fitted amplification. Understanding speech in the presence of background noise involves segregating the various auditory stimuli into distinct streams using cues such as pitch characteristics, spatial location of speakers, and contextual information. One possible cause of listening difficulties in noise is reduced spatial-processing ability. Previous attempts to investigate spatial processing in hearing-impaired people have often been confounded by inadequate stimulus audibility. The present research aimed to investigate the effects of hearing impairment and aging on spatial-processing ability. The effect of cognitive ability on spatial processing was also explored. In addition, the relationship between spatial-processing ability and self-report measures of listening difficulty was examined to investigate how much effect spatial-processing ability has in real-world situations. DESIGN: Eighty participants aged between 7 and 89 years took part in the study. Participants' hearing thresholds ranged from within normal limits to a moderately severe sensorineural hearing loss. All participants had English as their first language and no reported learning disabilities. The study sample included both hearing aid users and non-hearing aid users. Spatial-processing ability was assessed with a modified version of the Listening in Spatialized Noise-Sentences test (LiSN-S). The LiSN-S was modified to incorporate a prescribed gain amplifier that amplified the target and distracting stimulus according to the National Acoustic Laboratories-Revised Profound (NAL-RP) prescription. In addition, participants aged 18 years and above completed the Neurobehavioral Cognitive Status examination and the Speech, Spatial and Qualities questionnaire. Participants aged under 18 years completed the Listening Inventory for Education questionnaire. RESULTS: Spatial-processing ability, as measured by the spatial advantage measure of the LiSN-S, was negatively affected by hearing impairment. Aging was not significantly correlated with spatial-processing ability. No significant relationship was found between cognitive ability and spatial processing. Self-reported listening difficulty in children, as measured with the Listening Inventory for Education, and spatial-processing ability were not correlated. Self-reported listening difficulty in adults, as measured by the Speech, Spatial and Qualities questionnaire, was significantly correlated with spatial-processing ability. CONCLUSIONS: All hearing-impaired people will have a spatial processing deficit of some degree. This should be given due consideration when counseling patients in regard to realistic expectations of how they will perform in background noise. Further research is required into potential remediation for spatial-processing deficits and the cause of these deficits.

An opinion on the assessment of people who may have an auditory processing disorder.

We need to rethink how we assess auditory processing disorder (APD). The current use of test batteries, while necessary and well accepted, is at risk of failing as the size of these batteries increases. To counter the statistical, fatigue, and clinical efficiency problems of large test batteries, we propose a hierarchical approach to APD assessment. This begins with an overall test of listening difficulty in which performance is measurably affected for anyone with an impaired ability to understand speech in difficult listening conditions. It proceeds with a master test battery containing a small number of single tests, each of which assesses a different group of skills necessary for understanding speech in difficult listening conditions. It ends with a detailed test battery, where the individual tests administered from this battery are only those that differentiate the skills assessed by the failed test(s) from the master test battery, so that the specific form of APD can be diagnosed. An example of how hierarchical interpretation of test results could be performed is illustrated using the Listening in Spatialized Noise-Sentences test (LiSN-S). Although consideration of what abilities fall within the realm of auditory processing should remain an important issue for research, we argue that patients will be best served by focusing on whether they have difficulty understanding speech, identifying the specific characteristics of this difficulty, and specifically remediating and/or managing those characteristics.

Efficacy of the LiSN & Learn auditory training software: randomized blinded controlled study.

Children with a spatial processing disorder (SPD) require a more favorable signal-to-noise ratio in the classroom because they have difficulty perceiving sound source location cues. Previous research has shown that a novel training program - LiSN & Learn - employing spatialized sound, overcomes this deficit. Here we investigate whether improvements in spatial processing ability are specific to the LiSN & Learn training program. Participants were ten children (aged between 6;0 [years;months] and 9;9) with normal peripheral hearing who were diagnosed as having SPD using the Listening in Spatialized Noise - Sentences test (LiSN-S). In a blinded controlled study, the participants were randomly allocated to train with either the LiSN & Learn or another auditory training program - Earobics - for approximately 15 min per day for twelve weeks. There was a significant improvement post-training on the conditions of the LiSN-S that evaluate spatial processing ability for the LiSN & Learn group (P=0.03 to 0.0008, η(2)=0.75 to 0.95, n=5), but not for the Earobics group (P=0.5 to 0.7, η(2)=0.1 to 0.04, n=5). Results from questionnaires completed by the participants and their parents and teachers revealed improvements in real-world listening performance post-training were greater in the LiSN & Learn group than the Earobics group. LiSN & Learn training improved binaural processing ability in children with SPD, enhancing their ability to understand speech in noise. Exposure to non-spatialized auditory training does not produce similar outcomes, emphasizing the importance of deficit-specific remediation.

Problems hearing in noise in older adults: a review of spatial processing disorder.

Difficulty understanding speech in background noise, even with amplification to restore audibility, is a common problem for hearing-impaired individuals and is especially frequent in older adults. Despite the debilitating nature of the problem the cause is not yet completely clear. This review considers the role of spatial processing ability in understanding speech in noise, highlights the potential impact of disordered spatial processing, and attempts to establish if aging leads to reduced spatial processing ability. Evidence supporting and opposing the hypothesis that spatial processing is disordered among the aging population is presented. With a few notable exceptions, spatial processing ability was shown to be reduced in an older population in comparison to young adults, leading to poorer speech understanding in noise. However, it is argued that to conclude aging negatively effects spatial processing ability may be oversimplified or even premature given potentially confounding factors such as cognitive ability and hearing impairment. Further research is required to determine the effect of aging and hearing impairment on spatial processing and to investigate possible remediation options for spatial processing disorder.

Listening in Spatialized Noise-Sentences Test (LiSN-S): normative and retest reliability data for adolescents and adults up to 60 years of age.

BACKGROUND: The Australian version of the Listening in Spatialized Noise-Sentences Test (LiSN-S) was originally developed to assess auditory stream segregation skills in children aged 6 to 11 yr with suspected central auditory processing disorder. The LiSN-S creates a three-dimensional auditory environment under headphones. A simple repetition-response protocol is used to assess a listener's speech reception threshold (SRT) for target sentences presented in competing speech maskers. Performance is measured as the improvement in SRT in decibels gained when either pitch, spatial, or both pitch and spatial cues are incorporated in the maskers. PURPOSE: To collect additional normative data on the Australian LiSN-S for adolescents and adults up to 60 yr of age, to analyze the effects of age on LiSN-S performance, to examine retest reliability in the older population, and to extrapolate findings from the Australian data so that the North American version of the test can also be used clinically with older adults. RESEARCH DESIGN: In a descriptive design, normative and test-retest reliability data were collected from adolescents and adults and combined with previously published data from Australian children aged 6 to 11 yr. STUDY SAMPLE: One hundred thirty-two participants with normal hearing aged 12 yr, 0 mo, to 60 yr, 7 mo, took part in the normative data study. Fifty-five participants returned between 2 and 4 mo after the initial assessment for retesting. RESULTS: Analysis of variance revealed a significant effect of age on LiSN-S performance (p < .01 for all LiSN-S measures, ηp2 ranging from 0.16 to 0.54). On the low and high cue SRT measures, planned contrasts revealed significant differences between adults and children aged 13 yr and younger, as well as between 50- to 60-yr-olds and younger adults aged 18-29 yr. Whereas there were significant differences between adults and children on the talker, spatial, and total advantage measures, there were no significant differences in performance in adults aged 18-60 yr. There was a small but significant improvement on retest ranging from 0.5 to 1.2 dB across the four LiSN-S test conditions (p ranging from .01 to <.001). However, there was no significant difference between test and retest on the advantage measures (p ranging from .143 to .768). Test-retest differences across all LiSN-S measures were significantly correlated (r ranging from 0.2 to 0.7, p ranging from .023 to <.00000001) and did not differ as a function of age (p ranging from .178 to .980). CONCLUSIONS: As there was no significant difference among adults aged 18-60 yr on the LiSN-S talker, spatial, and total advantage measures, it appears that the decline in ability to understand speech in noise experienced by 50- to 60-yr-olds is not related to their ability to use either spatial or pitch cues. This result suggests that some other factor/s contributes to the decline in speech perception in noise experienced by older adults that is reported in the literature and was demonstrated in this study on the LiSN-S low and high cue SRT measures.