Assessment of Binaural Benefits in Hearing and Hearing-Impaired Listeners.

PURPOSE: The purpose of this study was to (a) investigate which speech material is most appropriate as stimulus in head shadow effect (HSE) and binaural squelch (SQ) tests, (b) obtain normative values of both tests using the material decided to be optimal, and (c) explore the results in bilateral cochlear implant (CI) users. METHOD: Study participants consisted of 30 normal-hearing (NH) persons and 34 bilateral CI users. This study consisted of three phases. In the first phase, three different speech materials (1) monosyllabic words, (2) spondee words, and (3) sentences were compared in terms of (a) effect size, (b) test-retest reliability, and (c) interindividual variability. In the second phase, the speech material selected in the first phase was used to test a further 24 NHs to obtain normative values for both tests. In the third phase, tests were administered to a further 23 bilateral CI users, together with localization test and the Speech, Spatial, and Qualities of Hearing scale. RESULTS: The results of the first phase indicated that spondees and sentences were more robust materials compared with monosyllables. Although the effect size and interindividual variability were comparable for spondees and sentences, sentences had higher test-retest reliability in this sample of CI users. With sentences, the mean (± standard deviation) HSE and SQ in the NH group were 58 ± 14% and 22 ± 11%, respectively. In the CI group, the mean HSE and SQ were 49 ± 13% and 13 ± 14%, respectively. There were no statistically significant correlations between the test results and the interval between the implantations, the length of binaural listening experience, or the asymmetry between the ears. CONCLUSIONS: Sentences are preferred as stimulus material in the binaural HSE and SQ tests. Normative data are given for HSE and SQ with the LiCoS (linguistically controlled sentences) test. HSE is present for all bilateral CI users, whereas SQ is present in approximately seven out of 10 cases.

American Cochlear Implant Alliance Task Force Guidelines for Clinical Assessment and Management of Adult Cochlear Implantation for Single-Sided Deafness.

The indications for cochlear implantation have expanded to include individuals with profound sensorineural hearing loss in the impaired ear and normal hearing (NH) in the contralateral ear, known as single-sided deafness (SSD). There are additional considerations for the clinical assessment and management of adult cochlear implant candidates and recipients with SSD as compared to conventional cochlear implant candidates with bilateral moderate to profound sensorineural hearing loss. The present report reviews the current evidence relevant to the assessment and management of adults with SSD. A systematic review was also conducted on published studies that investigated outcomes of cochlear implant use on measures of speech recognition in quiet and noise, sound source localization, tinnitus perception, and quality of life for this patient population. Expert consensus and systematic review of the current literature were combined to provide guidance for the clinical assessment and management of adults with SSD.

Toward Assessment of Sound Localization in Disorders of Consciousness Using a Hybrid Audiovisual Brain-Computer Interface.

Behavioral assessment of sound localization in the Coma Recovery Scale-Revised (CRS-R) poses a significant challenge due to motor disability in patients with disorders of consciousness (DOC). Brain-computer interfaces (BCIs), which can directly detect brain activities related to external stimuli, may thus provide an approach to assess DOC patients without the need for any physical behavior. In this study, a novel audiovisual BCI system was developed to simulate sound localization evaluation in CRS-R. Specifically, there were two alternatively flashed buttons on the left and right sides of the graphical user interface, one of which was randomly chosen as the target. The auditory stimuli of bell sounds were simultaneously presented by the ipsilateral loudspeaker during the flashing of the target button, which prompted patients to selectively attend to the target button. The recorded electroencephalography data were analyzed in real time to detect event-related potentials evoked by the target and further to determine whether the target was attended to or not. A significant BCI accuracy for a patient implied that he/she had sound localization. Among eighteen patients, eleven and four showed sound localization in the BCI and CRS-R, respectively. Furthermore, all patients showing sound localization in the CRS-R were among those detected by our BCI. The other seven patients who had no sound localization behavior in CRS-R were identified by the BCI assessment, and three of them showed improvements in the second CRS-R assessment after the BCI experiment. Thus, the proposed BCI system is promising for assisting the assessment of sound localization and improving the clinical diagnosis of DOC patients.

AVATAR Assesses Speech Understanding and Multitask Costs in Ecologically Relevant Listening Situations.

OBJECTIVES: There is a high need among clinicians and researchers for an ecologically valid measure of auditory functioning and listening effort. Therefore, we developed AVATAR: an "Audiovisual True-to-life Assessment of Auditory Rehabilitation" which takes important characteristics of real-life listening situations into account, such as multimodal speech presentation, spatial separation of sound sources and multitasking. As such, AVATAR aims to assess both auditory functioning and the amount of allocated processing resources during listening in a realistic yet controllable way. In the present study, we evaluated AVATAR and investigated whether speech understanding in noise and multitask costs during realistic listening environments changed with increasing task complexity. DESIGN: Thirty-five young normal-hearing participants performed different task combinations of an auditory-visual speech-in-noise task and three secondary tasks on both auditory localization and visual short-term memory in a simulated restaurant environment. Tasks were combined in increasing complexity and multitask costs on the secondary tasks were investigated as an estimate of the amount of cognitive resources allocated during listening and multitasking. In addition to behavioral measures of auditory functioning and effort, working memory capacity and self-reported hearing difficulties were established using a reading span test and a questionnaire on daily hearing abilities. RESULTS: Whereas performance on the speech-in-noise task was not affected by task complexity, multitask costs on one of the secondary tasks became significantly larger with increasing task complexity. Working memory capacity correlated significantly with multitask costs, but no association was observed between behavioral outcome measures and self-reported hearing abilities or effort. CONCLUSIONS: AVATAR proved to be a promising model to assess speech intelligibility and auditory localization abilities and to gauge the amount of processing resources during effortful listening in ecologically relevant multitasking situations by means of multitask costs. In contrast with current clinical measures of auditory functioning, results showed that listening and multitasking in challenging listening environments can require a considerable amount of processing resources, even for young normal-hearing adults. Furthermore, the allocation of resources increased in more demanding listening situations. These findings open avenues for a more realistic assessment of auditory functioning and individually tuned auditory rehabilitation for individuals of different age and hearing profiles.

The frequency-following response as an assessment of spatial processing.

Objective: It is important to detect children with difficulties distinguishing speech-in-noise early. Prompt identification may be assisted by an evoked potential. The aims of the present study were: 1) to evaluate the frequency-following response (FFR) as a measure of binaural processing and spatial listening and, 2) to investigate the relationship between the FFR and a behavioural measure of binaural processing and spatial listening. Design: A single group, repeated measures design. The FFR was recorded in two different spatial conditions and amplitudes compared to spatial listening ability. Study Sample: Thirty-two children (aged 6.0 to 13.1 years) with a range of spatial processing abilities as measured behaviourally using the Listening in Spatialised Noise Sentences test (LiSN-S). Results: FFR waveforms were elicited using speech-like stimuli in co-located and separated conditions. A significant (p≤0.005) spatial advantage effect was observed with larger amplitudes in the separated condition. No correlations were observed between FFR amplitude and LiSN-S results. Conclusions: The FFR shows promise as a measure of binaural processing and spatial listening, but could be measuring different processes to those measured by the LiSN-S.

Validation of the Egyptian Arabic Assessment of Auditory Skills development using children with Cochlear Implants.

INTRODUCTION: Audition is the gateway to spoken language, and infants' early accomplishments in acquiring the sound structure of their native language lays a critical ground work for subsequent learning. The development of pre-lingual auditory perceptual skills for cochlear implanted children is crucial for initial development of oral language. OBJECTIVE: The aims of the present study were to validate the Egyptian Arabic Assessment of Auditory Skills, and to track the development of auditory skills in Egyptian children fitted with CI during the first three years post implantation. METHODS: The study included 90 Arabic Egyptian children attending the phoniatric unit, Kasr El Aini hospital. Their chronological age ranged from 36 to 72 months. The study lasted for 18 months from July 2015 to January 2017. The children were divided into six groups according to their cochlear age i.e., amount of implant experience. An Arabic assessment chart of auditory skills was tailored that included six auditory skills' domains; detection, identification, short term auditory memory, supra-segmental discrimination, segmental discrimination and linguistic auditory processing. This chart was then used to develop an assessment tool which was then applied to all the study participants. All children had bilateral Sensorineural Hearing Loss (SNHL) since birth. None of the participants had prior Cochlear Implant (CI), but all had tried conventional hearing aids. All participants were implanted unilateral, with CI devices. All met selection criteria applied in the Egyptian national insurance committee for cochlear implantation. RESULTS: All auditory skills domains improved with cochlear age. There was significant improvement between 1-6 and 7-12 months in the scores of the Detection (DET) domain. There was significant difference between 1-6 and 7-12 months, 7-12 and 13-18 months, 19-24 and 25-30 months in the scores of the Identification (IDENT) domain. Regarding the Short Term Auditory Memory (STAM) domain scores and the Supra-segmental Discrimination (SSD) domain scores there was significant difference between all the groups. Regarding the Segmental Discrimination (SGD) domain scores, there was significant difference between group 1-6 and 7-12 months, 7-12 and 13-18 months, 19-24 and 25-30 months, 25-30 and 31-36 months. Regarding the Linguistic Auditory Processing (LAP) domain, there was significant difference between group 1-6 and 7-12 months, 7-12 and 13-18 months, 25-30 and 31-36 months. CONCLUSIONS: Children fitted with Cochlear Implants (CIs) appeared to show improvement in acquisition of auditory skills over a period of three years that followed a hierarchy of development dependent on the cochlear age.

Hearing in Real-Life Environments (HERE): Structure and Reliability of a Questionnaire on Perceived Hearing for Older Adults.

OBJECTIVES: The ability to hear in a variety of social situations and environments is vital for social participation and a high quality of life. One way to assess hearing ability is by means of self-report questionnaire. For questionnaires to be useful, their measurement properties, based on careful validation, have to be known. Only recently has consensus been reached concerning how to perform such validation and been published as COSMIN (consensus-based standards for the selection of health status measurement instruments) guidelines. Here the authors use these guidelines to evaluate the measurement properties of the "Hearing in Real-Life Environments" (HERE) questionnaire, a newly developed self-report measure that assesses speech perception, spatial orientation, and the social-emotional consequences of hearing impairment in older adults. The aim is to illustrate the process of validation and encourage similar examinations of other frequently used questionnaires. DESIGN: The HERE questionnaire includes 15 items with a numeric rating scale from 0 to 10 for each item and allows the assessment of hearing with and without hearing aids. The evaluation was performed in two cohorts of community-dwelling older adults from Finland (n = 581, mean 82 years) and the United Kingdom (n = 50, mean 69 years). The internal structure of the questionnaire and its relationship to age, hearing level, and self-reported and behavioral measures of speech perception was assessed and, when possible, compared between cohorts. RESULTS: The results of the factor analysis showed that the HERE's internal structure was similar across cohorts. In both cohorts, the factor analysis showed a satisfactory solution for three factors (speech hearing, spatial hearing, and socio-emotional consequences), with a high internal consistency for each factor (Cronbach's α's for the factors from 0.90 to 0.97). Test-retest analysis showed the HERE overall mean score to be stable and highly replicable over time (intraclass correlation coefficient = 0.86, standard error of measurement of the test score = 0.92). The HERE overall mean score correlated highly with another self-report measure of speech perception, the Speech Spatial Qualities of Hearing questionnaire (standardized regression coefficient [ß] = -0.75, p < 0.001), moderately highly with behaviorally assessed hearing level (best-ear average: ß = 0.45 to 0.46), and moderately highly with behaviorally measured intelligibility of sentences in noise (ß = -0.50, p < 0.001). CONCLUSIONS: Using the COSMIN guidelines, the authors show that the HERE is a valid, reliable, and stable questionnaire for the assessment of self-reported speech perception, sound localization, and the socio-emotional consequences of hearing impairment in the context of social functioning. The authors also show that cross-cultural data collected using different data collection strategies can be combined with a range of statistical methods to validate a questionnaire.

Human-Machine Interaction Assessment by Neurophysiological Measures: A Study on Professional Air Traffic Controllers.

This study aims at investigating the possibility to employ neurophysiological measures to assess the humanmachine interaction effectiveness. Such a measure can be used to compare new technologies or solutions, with the final purpose to enhance operator's experience and increase safety. In the present work, two different interaction modalities (Normal and Augmented) related to Air Traffic Management field have been compared, by involving 10 professional air traffic controllers in a control tower simulated environment. Experimental task consisted in locating aircrafts in different airspace positions by using the sense of hearing. In one modality (i.e. "Normal"), all the sound sources (aircrafts) had the same amplification factor. In the "Augmented" modality, the amplification factor of the sound sources located along the participant head sagittal axis was increased, while the intensity of sound sources located outside this axis decreased. In other words, when the user oriented his head toward the aircraft position, the related sound was amplified. Performance data, subjective questionnaires (i.e. NASA-TLX) and neurophysiological measures (i.e. EEG-based) related to the experienced workload have been collected. Results showed higher significant performance achieved by the users during the "Augmented" modality with respect to the "Normal" one, supported by a significant decreasing in experienced workload, evaluated by using EEG-based index. In addition, Performance and EEG-based workload index showed a significant negative correlation. On the contrary, subjective workload analysis did not show any significant trend. This result is a demonstration of the higher effectiveness of neurophysiological measures with respect to subjective ones for Human-Computer Interaction assessment.

Spectrotemporal window of binaural integration in auditory object formation.

Binaural integration of interaural temporal information is essential for sound source localization and segregation. Current models of binaural interaction have shown that accurate sound localization in the horizontal plane depends on the resolution of phase ambiguous information by across-frequency integration. However, as such models are mostly static, it is not clear how proximate in time binaural events in different frequency channels should occur to form an auditory object with a unique lateral position. The present study examined the spectrotemporal window required for effective integration of binaural cues across frequency to form the perception of a stationary position. In Experiment 1, listeners judged whether dichotic frequency-modulated (FM) sweeps with a constant large nominal interaural delay (1500 µs), whose perceived laterality was ambiguous depending on the sweep rate (1500, 3000, 6000, and 12,000 Hz/s), produced a percept of continuous motion or a stationary image. Motion detection performance, indexed by d-prime (d') values, showed a clear effect of sweep rate, with auditory motion effects most pronounced for low sweep rates, and a punctate stationary image at high rates. Experiment 2 examined the effect of modulation rate (0.5, 3, 20, and 50 Hz) on lateralizing sinusoidally frequency-modulated (SFM) tones to confirm the effect of sweep rate on motion detection, independent of signal duration. Lateralization accuracy increased with increasing modulation rate up to 20 Hz and saturated at 50 Hz, with poorest performance occurring below 3 Hz depending on modulator phase. Using the transition point where percepts changed from motion to stationary images, we estimated a spectrotemporal integration window of approximately 150 ms per octave required for effective integration of interaural temporal cues across frequency channels. A Monte Carlo simulation based on a cross-correlation model of binaural interaction predicted 90% of the variance on perceptual motion detection performance as a function of FM sweep rate. Findings suggest that the rate of frequency channel convergence of binaural cues is essential to binaural lateralization.

Considerations for Pediatric Cochlear Implant Recipients With Unilateral or Asymmetric Hearing Loss: Assessment, Device Fitting, and Habilitation.

PURPOSE: The purpose of this clinical report is to present case studies of children who are nontraditional candidates for cochlear implantation because they have significant residual hearing in 1 ear and to describe outcomes and considerations for their audiological management and habilitation. METHOD: Case information is presented for 5 children with profound hearing loss in 1 ear and normal or mild-to-moderate hearing loss in the opposite ear and who have undergone unilateral cochlear implantation. Pre- and postoperative assessments were performed per typical clinic routines with modifications described. Postimplant habilitation was customized for each recipient using a combination of traditional methods, newer technologies, and commercial materials. RESULTS: The 5 children included in this report are consistent users of their cochlear implants and demonstrate speech recognition in the implanted ear when isolated from the better hearing ear. CONCLUSIONS: Candidacy criteria for cochlear implantation are evolving. Children with single-sided deafness or asymmetric hearing loss who have traditionally not been considered candidates for cochlear implantation should be evaluated on a case-by-case basis. Audiological management of these recipients is not vastly different compared with children who are traditional cochlear implant recipients. Assessment and habilitation techniques must be modified to isolate the implanted ear to obtain accurate results and to provide meaningful therapeutic intervention.

Accumulation and decay of visual capture and the ventriloquism aftereffect caused by brief audio-visual disparities.

Visual capture and the ventriloquism aftereffect resolve spatial disparities of incongruent auditory visual (AV) objects by shifting auditory spatial perception to align with vision. Here, we demonstrated the distinct temporal characteristics of visual capture and the ventriloquism aftereffect in response to brief AV disparities. In a set of experiments, subjects localized either the auditory component of AV targets (A within AV) or a second sound presented at varying delays (1-20 s) after AV exposure (A2 after AV). AV targets were trains of brief presentations (1 or 20), covering a ±30° azimuthal range, and with ±8° (R or L) disparity. We found that the magnitude of visual capture generally reached its peak within a single AV pair and did not dissipate with time, while the ventriloquism aftereffect accumulated with repetitions of AV pairs and dissipated with time. Additionally, the magnitude of the auditory shift induced by each phenomenon was uncorrelated across listeners and visual capture was unaffected by subsequent auditory targets, indicating that visual capture and the ventriloquism aftereffect are separate mechanisms with distinct effects on auditory spatial perception. Our results indicate that visual capture is a 'sample-and-hold' process that binds related objects and stores the combined percept in memory, whereas the ventriloquism aftereffect is a 'leaky integrator' process that accumulates with experience and decays with time to compensate for cross-modal disparities.

Delays in Sound Recognition and Imitation in Underinsured Children Receiving Cochlear Implantation.

Importance: Barriers to early pediatric cochlear implantation in underinsured populations have been previously reported. However, to our knowledge, the effect of this delay on the development of auditory and speech-language objectives has not been evaluated. Objective: To determine if health care insurance status affects the achievement of proficiency in basic sound access and imitation tasks in children with cochlear implants. Design, Setting, and Participants: A retrospective review of 123 children aged 1 to 12 years receiving cochlear implants at the single tertiary referral academic free-standing Children's National Health System in Washington, DC, between January 1, 2008, and December 31, 2015. Main Outcomes and Measures: Auditory function after cochlear implantation, time to proficiency in Ling-6 scores, and number of speech therapy and audiological appointments, as well as current educational setting, were compared with patient age at diagnosis of hearing loss, age at cochlear implantation, cochlear implantation insertion technique, and health care insurance status for recipients of cochlear implants. Results: A total of 123 children aged 1 to 12 years (mean [SD] age, 64.0 [57.4] years) with cochlear implants were included in the study. Of 37 patients with complete and accurate Ling-6 test scores, 23 (62.1%) were able to have proficiency a mean of 5.1 months at follow-up. Despite equal auditory performance on pure-tone audiometry after cochlear implantation, publicly insured recipients had Ling-6 proficiency a mean of 6.0 months (95% CI, 5.5-6.5 months) later than privately insured recipients (11.0 vs 5.0 months). When controlling for patient age, time to cochlear implantation, number of therapy sessions, and cochlear implantation insertion technique, multivariable logistic regression analysis revealed health care insurance status to be the independent variable associated with inadequate Ling-6 discrimination scores (odds ratio, 46.2; 95% CI, 2.9-729.4). Conclusions and Relevance: Despite equal speech detection scores, publicly insured recipients of cochlear implantation had a significant and critical delay in attaining proficiency in a fundamental measure of sound recognition and imitation.

An assessment of the direction-finding accuracy of bat biosonar beampatterns.

In the biosonar systems of bats, emitted acoustic energy and receiver sensitivity are distributed over direction and frequency through beampattern functions that have diverse and often complicated geometries. This complexity could be used by the animals to determine the direction of incoming sounds based on spectral signatures. The present study has investigated how well bat biosonar beampatterns are suited for direction finding using a measure of the smallest estimator variance that is possible for a given direction [Cramér-Rao lower bound (CRLB)]. CRLB values were estimated for numerical beampattern estimates derived from 330 individual shape samples, 157 noseleaves (used for emission), and 173 outer ears (pinnae). At an assumed 60 dB signal-to-noise ratio, the average value of the CRLB was 3.9°, which is similar to previous behavioral findings. Distribution for the CRLBs in individual beampatterns had a positive skew indicating the existence of regions where a given beampattern does not support a high accuracy. The highest supported accuracies were for direction finding in elevation (with the exception of phyllostomid emission patterns). No large, obvious differences in the CRLB (greater 2° in the mean) were found between the investigated major taxonomic groups, suggesting that different bat species have access to similar direction-finding information.

A study of language development and affecting factors in children aged 5 to 27 months.

We conducted a study to assess the factors that affect language development in infants and toddlers using data obtained during developmental screening. Our study group consisted of 505 children-244 (48.3%) boys and 261 (51.7%) girls, aged 5 to 27 months. The children were divided into four age groups: group 1, which we designated as the "6 months" group (age range: 5 to 7 mo); group 2, designated as the "12 months" group (11 to 13 mo); group 3, designated as the "18 months" group (17 to 19 mo); and group 4, designated as the "24 months" group (23 to 27 mo). In addition to demographic data, we compiled data using the Denver II Developmental Screening Test, as well as neurologic examination findings and medical histories. At 6 months, the social item "Works for toy out of reach" was positively related to all language development items. Two gross motor development items-"Pull to sit, no head lag" and "Lifts chest with arm support"-were related to the "Turns to sound" and "Turns to voice" items, respectively. Overall, children whose mothers had higher education levels and who were living in higher socioeconomic areas showed significantly greater language development, as did boys, specifically. At 12 months, higher maternal ages, some gross motor development items, and some social items were related to better language development, and children living in higher socioeconomic areas had a significantly increased ability to pass the "4 words other than mama/dada" item. At 18 months, the ability of girls to pass the "4 words other than mama/dada" item increased, and children who passed the "4 words other than mama/dada" item did not pass the "Throws ball" gross motor item. At 24 months, children whose mothers were older had better "Combines 2 words" and "Speech half intelligible" items, girls had better "Comprehends prepositions (such as under/above)" skills, and boys had better "Shows 4 parts of doll" skills. We conclude that language items appear to change together with gross motor items and social development, and that they can be influenced by a family's socioeconomic level. However, as children get older, language development diverges from gross motor development.

Corneal-Reflection Eye-Tracking Technique for the Assessment of Horizontal Sound Localization Accuracy from 6 Months of Age.

OBJECTIVES: The evaluation of sound localization accuracy (SLA) requires precise behavioral responses from the listener. Such responses are not always possible to elicit in infants and young children, and procedures for the assessment of SLA are time consuming. The aim of this study was to develop a fast, valid, and objective method for the assessment of SLA from 6 months of age. To this end, pupil positions toward spatially distributed continuous auditory and visual stimuli were recorded. DESIGN: Twelve children (29 to 157 weeks of age) who passed the universal newborn hearing screening and eight adults (18 to 40 years of age) who had pure-tone thresholds ≤20 dB HL in both ears participated in this study. Horizontal SLA was measured in a sound field with 12 loudspeaker/display (LD)-pairs placed in an audiological test room at 10 degrees intervals in the frontal horizontal plane (±55 degrees azimuth). An ongoing auditory-visual stimulus was presented at 63 dB SPL(A) and shifted to randomized loudspeakers simultaneously with pauses of the visual stimulus. The visual stimulus was automatically reintroduced at the azimuth of the sounding loudspeaker after a sound-only period of 1.6 sec. A corneal-reflection eye-tracking technique allowed the acquisition of the subjects' pupil positions relative to the LD-pairs. The perceived azimuth was defined as the median of the intersections between gaze and LD-pairs during the final 500 msec of the sound-only period. Overall SLA was quantified by an Error Index (EI), where EI = 0 corresponded to perfect match between perceived and presented azimuths, whereas EI = 1 corresponded to chance. RESULTS: SLA was rapidly measured in children (mean = 168 sec, n = 12) and adults (mean = 162 sec, n = 8). Visual inspection of gaze data indicated that gaze shifts occurred in sound-only periods. The medians of the perceived sound-source azimuths either coincided with the presenting sound-source azimuth or were offset by a maximum of 20 degrees in children. In contrast, adults revealed a perfect match from -55 to 55 degrees, except at 15 degrees azimuth (median = 20 degrees), with 9/12 of the quartile ranges = 0 degrees. Children showed a mean (SD) EI of 0.42 (0.17), which was significantly higher than that in adults (p < 0.0001). However, children revealed a distinct age-related EI improvement of 16 percentage points per year (r = -0.68, p = 0.015, n = 12), suggesting an ongoing maturation of SLA in the studied age range (29 to 157 weeks). The eight adults showed high SLA and high reliability as demonstrated by the low mean (SD) EI (0.054 [0.021]) and the low variability in test-retest differences (95% confidence interval = -0.020 to 0.046). CONCLUSIONS: Corneal-reflection eye-tracking provides an objective and fast assessment of horizontal SLA from about 6 months of age and may enable gaze to be used as an objective measure for sound localization in this age group. Infant SLA is immature and improvements are related to increasing age. Adults show high overall SLA and low intra- and intersubject variability in SLA. The technique may be used as a clinical tool for the evaluation of very early intervention in a young, preverbal population and throughout the life span.

Assessment of the contralateral routing of signal system in unilateral cochlear implantation.

OBJECTIVES: The purpose of this study was to evaluate the contribution of a contralateral routing of signal (CROS) system in unilateral cochlear implants (CI) users. DESIGN: Single-centre prospective interventional study. SETTING: Tertiary referral centre. PARTICIPANTS: Eight unilateral cochlear implants patients with >30% speech perception in silence and >6 months' implantation. MAIN OUTCOME MEASURES: Free-field speech perception assessed by 'vowel-consonant-vowel' pseudoword test and free-field spatial localisation by Fournier lists on five loudspeakers (in silence and in noise). Subjective benefit assessed on the abbreviated profile of hearing aid benefit (APHAB) questionnaire. These tests were performed on the 1st and 15th day of the trial (denoted by D1 and D15, respectively). RESULTS: Contralateral routing of signal-cochlear implants provided significant improvement in speech perception at D1 and D15 in silence (P, respectively, 0.03 and 0.025) and in noise (P 0.012 and 0.036). No improvement in spatial localisation was demonstrated. The abbreviated profile of hearing aid benefit quality of life questionnaire administered at D15 showed overall benefit and a significant difference in ease of communication with versus without contralateral routing of signal. By 6 months, however, 75% of the patients (6/8) had abandoned the system due to trouble in noise (5/6), trouble with the device's wiring (3/6) and onset of headache (4/6). CONCLUSION: Contralateral routing of signal-cochlear implants is an interesting novel option, restoring a binaural effect and providing improved speech perception and non-negligible comfort of hearing in certain patients, without the medical and economic costs of bilateral cochlear implants. However, the drawbacks (especially the difficulty of modulating the signal-to-noise ratio) do not presently allow it to be an effective alternative to bilateral cochlear implants.

Automated acoustic localization and call association for vocalizing humpback whales on the Navy's Pacific Missile Range Facility.

Time difference of arrival (TDOA) methods for acoustically localizing multiple marine mammals have been applied to recorded data from the Navy's Pacific Missile Range Facility in order to localize and track humpback whales. Modifications to established methods were necessary in order to simultaneously track multiple animals on the range faster than real-time and in a fully automated way, while minimizing the number of incorrect localizations. The resulting algorithms were run with no human intervention at computational speeds faster than the data recording speed on over forty days of acoustic recordings from the range, spanning multiple years. Spatial localizations based on correlating sequences of units originating from within the range produce estimates having a standard deviation typically 10 m or less (due primarily to TDOA measurement errors), and a bias of 20 m or less (due primarily to sound speed mismatch). An automated method for associating units to individual whales is presented, enabling automated humpback song analyses to be performed.

Simultaneous Assessment of Speech Identification and Spatial Discrimination: A Potential Testing Approach for Bilateral Cochlear Implant Users?

With increasing numbers of children and adults receiving bilateral cochlear implants, there is an urgent need for assessment tools that enable testing of binaural hearing abilities. Current test batteries are either limited in scope or are of an impractical duration for routine testing. Here, we report a behavioral test that enables combined testing of speech identification and spatial discrimination in noise. In this task, multitalker babble was presented from all speakers, and pairs of speech tokens were sequentially presented from two adjacent speakers. Listeners were required to identify both words from a closed set of four possibilities and to determine whether the second token was presented to the left or right of the first. In Experiment 1, normal-hearing adult listeners were tested at 15° intervals throughout the frontal hemifield. Listeners showed highest spatial discrimination performance in and around the frontal midline, with a decline at more eccentric locations. In contrast, speech identification abilities were least accurate near the midline and showed an improvement in performance at more lateral locations. In Experiment 2, normal-hearing listeners were assessed using a restricted range of speaker locations designed to match those found in clinical testing environments. Here, speakers were separated by 15° around the midline and 30° at more lateral locations. This resulted in a similar pattern of behavioral results as in Experiment 1. We conclude, this test offers the potential to assess both spatial discrimination and the ability to use spatial information for unmasking in clinical populations.

The flip side of the auditory spatial selection benefit: larger attentional mixing costs for target selection by ear than by gender in auditory task switching.

In cued auditory task switching, one of two dichotically presented number words, spoken by a female and a male, had to be judged according to its numerical magnitude. One experimental group selected targets by speaker gender and another group by ear of presentation. In mixed-task blocks, the target-defining feature (male/female vs. left/right) was cued prior to each trial, but in pure blocks it remained constant. Compared to selection by gender, selection by ear led to better performance in pure blocks than in mixed blocks, resulting in larger "global" mixing costs for ear-based selection. Selection by ear also led to larger "local" switch costs in mixed blocks, but this finding was partially mediated by differential cue-repetition benefits. Together, the data suggest that requirements of attention shifting diminish the auditory spatial selection benefit.

Assessment of auditory spatial awareness in complex listening environments.

In the real world, listeners often need to track multiple simultaneous sources in order to maintain awareness of the relevant sounds in their environments. Thus, there is reason to believe that simple single source sound localization tasks may not accurately capture the impact that a listening device such as a hearing aid might have on a listener's level of auditory awareness. In this experiment, 10 normal hearing listeners and 20 hearing impaired listeners were tested in a task that required them to identify and localize sound sources in three different listening tasks of increasing complexity: a single-source localization task, where listeners identified and localized a single sound source presented in isolation; an added source task, where listeners identified and localized a source that was added to an existing auditory scene, and a remove source task, where listeners identified and localized a source that was removed from an existing auditory scene. Hearing impaired listeners completed these tasks with and without the use of their previously fit hearing aids. As expected, the results show that performance decreased both with increasing task complexity and with the number of competing sound sources in the acoustic scene. The results also show that the added source task was as sensitive to differences in performance across listening conditions as the standard localization task, but that it correlated with a different pattern of subjective and objective performance measures across listeners. This result suggests that a measure of complex auditory situation awareness such as the one tested here may be a useful tool for evaluating differences in performance across different types of listening devices, such as hearing aids or hearing protection devices.