Effect of Sound Source Location and Spatial Hearing on the Vestibulo-Ocular Reflex.

BACKGROUND: There have been conflicting results on the effect of auditory stimulation on the vestibulo-ocular reflex (VOR) with some studies indicating suppression, enhancement, or no effect. No studies to date have assessed the effect of sound source location on VOR gain or the relationship between spatial hearing ability and VOR gain. PURPOSE: The purpose of the present study was to determine if VOR gain was affected by moving the location of the sound source within participants and to determine if these effects were related to spatial hearing ability. RESEARCH DESIGN: A between subjects repeated measures experimental design was utilized. STUDY SAMPLE: Two groups of participants (adult and child) with normal otologic, vestibular, and neurologic function. 22 adults (20 female and 2 male; average age = 23 years) and 16 children (9 female and 7 male; average age = 7.5 years) were included in data analysis. DATA COLLECTION AND ANALYSIS: VOR gain was measured using rotational chair stimulation in the following auditory conditions: silent, insert earphones, external loudspeaker at 0° azimuth rotating with participant, and external stationary speaker. Localization ability was measured using root mean square (RMS) error. RESULTS: Results indicated a significant effect for sound source location on VOR gain and VOR difference gain in both groups. RMS error was positively correlated for the moving and fixed sound source locations for both adults and children. CONCLUSION: VOR gain was significantly affected by location of the sound source. Findings suggest the presence and location of an auditory stimulus during rotational testing can alter results during the assessment.

Effects of Unilateral Hearing Loss on Speech-Evoked Auditory Brainstem Responses and Reading: A Preliminary Study.

PURPOSE: The purpose of this study was to determine whether the speech-evoked auditory brainstem responses (sABRs) obtained by stimulating the ear with normal sensitivity in children with unilateral hearing loss (UHL) were different from that of children with normal hearing (NH), and to explore correlations between the sABR findings and measures of reading. METHOD: Eleven children with UHL and 11 children with NH were tested via the BioMARK sABR protocol using the syllable /da/; latency and amplitudes of Waves V, A, C, D, E, F, and O were measured. Participants also were tested on the Phonemic Synthesis Test (PST) and the Woodcock Reading Mastery Test-Revised (WRMT-R), particularly the Reading Readiness, Basic Skills, and Comprehension subtests. RESULTS: Multivariate analysis of variance testing showed a significantly higher amplitude for Wave A for the NH group as compared to the UHL group. Separate ANOVAs also found significantly lower scores for the UHL group compared to the NH group on Basic Skills and Comprehension subtests of the Woodcock. Significant positive Spearman rho correlations were found for the UHL group between wave amplitudes for V, A, and O and the Reading Readiness score, and between wave amplitudes for V, A, D, and O and the Reading Comprehension score. A significant correlation also was found between the Total Reading score and wave amplitudes for V and A. No such correlations were found between wave amplitude and Woodcock scores for the NH group. Further testing of the UHL data found significant relationships between the pure-tone average of the hearing loss ear and the Basic Skills, Comprehension, and Total Reading scores from the WRMT-R. There was also a significant correlation between the PST score and Wave C amplitude. CONCLUSION: There may be a connection between speech encoding and measures of reading in children with UHL.

Acceptable Noise Levels and Preferred Signal-to-noise Ratios for Speech and Music.

OBJECTIVES: The objective of this study was to evaluate the influence of music versus speech on a listener's signal-to-noise ratio (SNR) preferences when listening in a noise background. SNR preferences were quantified using acceptable noise level (ANL) and preferred SNR metrics. The measurement paradigm for ANL allows the listener to adjust the level of background noise while listening to the target at their most comfortable loudness level. A higher ANL indicates less tolerance for noise and a lower ANL indicates high tolerance for noise. The preferred SNR is simply the SNR the listener prefers when attending to a target in a fixed-amount (level) of background noise. In contrast to the ANL, the listener does not have control over the noise. Rather, they are only able to manipulate the target level. The first aim of the study was to determine if listeners' tolerances for noise, quantified using the ANL, when listening to music is different from that when listening to speech. The second aim of the study was to determine if listeners' tolerances for noise, quantified using their preferred SNR, when listening to music is different from that when listening to speech. The third aim of the study was to quantify the relationship between ANL and preferred SNR. DESIGN: Ninety-nine normal-hearing, native-English speakers participated in this study. The ANL and preferred SNR were measured for speech and music targets. Music targets included two variations (with lyrics and without lyrics) of the song "Rocky Top." Measurements were made in the sound field at 0° azimuth, 1.5 m from a loud speaker. For both ANL and preferred SNR, targets were presented in 12-talker babble noise. The level of the noise was adjusted by the listener during ANL measurement but was fixed in level during the preferred SNR measurement (75 dB A). Repeated-measures analysis of variance was performed to identify any significant effect of target on the ANL and preferred SNR. Correlation analysis was performed to evaluate the relationship between ANL and preferred SNR. RESULTS: Findings demonstrate a significant effect of target on ANL and preferred SNR. ANLs were highest for speech (mean = 7.2 dB), followed by music with lyrics (6.1 dB), and music without lyrics (2.5 dB). Preferred SNRs were highest for music with lyrics (mean = 2.3 dB), followed by speech (1.2 dB), and music without lyrics (-0.1 dB). A listener's ANL for a given target was strongly correlated with their ANL for a different target (the same was true for preferred SNR); however, ANL for a given target was not a statistically significant predictor of preferred SNR for the same target. CONCLUSIONS: When listening in a background of noise, the listener's tolerance for noise depends on the target to which they are attending, whether music or speech. This dependence is especially evident for ANL measures, and less so for preferred SNR measures. Despite differences in ANL and preferred SNR across targets, a listener's ANL and preferred SNR for one target predicts their ANL and preferred SNR, respectively, for a different target. The lack of correlation between ANL and preferred SNR suggests different mechanisms underly these listener-preference metrics.

Multidimensional Timbre Spaces of Cochlear Implant Vocoded and Non-vocoded Synthetic Female Singing Voices.

Many post-lingually deafened cochlear implant (CI) users report that they no longer enjoy listening to music, which could possibly contribute to a perceived reduction in quality of life. One aspect of music perception, vocal timbre perception, may be difficult for CI users because they may not be able to use the same timbral cues available to normal hearing listeners. Vocal tract resonance frequencies have been shown to provide perceptual cues to voice categories such as baritone, tenor, mezzo-soprano, and soprano, while changes in glottal source spectral slope are believed to be related to perception of vocal quality dimensions such as fluty vs. brassy. As a first step toward understanding vocal timbre perception in CI users, we employed an 8-channel noise-band vocoder to test how vocoding can alter the timbral perception of female synthetic sung vowels across pitches. Non-vocoded and vocoded stimuli were synthesized with vibrato using 3 excitation source spectral slopes and 3 vocal tract transfer functions (mezzo-soprano, intermediate, soprano) at the pitches C4, B4, and F5. Six multi-dimensional scaling experiments were conducted: C4 not vocoded, C4 vocoded, B4 not vocoded, B4 vocoded, F5 not vocoded, and F5 vocoded. At the pitch C4, for both non-vocoded and vocoded conditions, dimension 1 grouped stimuli according to voice category and was most strongly predicted by spectral centroid from 0 to 2 kHz. While dimension 2 grouped stimuli according to excitation source spectral slope, it was organized slightly differently and predicted by different acoustic parameters in the non-vocoded and vocoded conditions. For pitches B4 and F5 spectral centroid from 0 to 2 kHz most strongly predicted dimension 1. However, while dimension 1 separated all 3 voice categories in the vocoded condition, dimension 1 only separated the soprano stimuli from the intermediate and mezzo-soprano stimuli in the non-vocoded condition. While it is unclear how these results predict timbre perception in CI listeners, in general, these results suggest that perhaps some aspects of vocal timbre may remain.

The Use of Static and Dynamic Cues for Vowel Identification by Children Wearing Hearing Aids or Cochlear Implants.

OBJECTIVE: To examine vowel perception based on dynamic formant transition and/or static formant pattern cues in children with hearing loss while using their hearing aids or cochlear implants. We predicted that the sensorineural hearing loss would degrade formant transitions more than static formant patterns, and that shortening the duration of cues would cause more difficulty for vowel identification for these children than for their normal-hearing peers. DESIGN: A repeated-measures, between-group design was used. Children 4 to 9 years of age from a university hearing services clinic who were fit for hearing aids (13 children) or who wore cochlear implants (10 children) participated. Chronologically age-matched children with normal hearing served as controls (23 children). Stimuli included three naturally produced syllables (/ba/, /bi/, and /bu/), which were presented either in their entirety or segmented to isolate the formant transition or the vowel static formant center. The stimuli were presented to listeners via loudspeaker in the sound field. Aided participants wore their own devices and listened with their everyday settings. Participants chose the vowel presented by selecting from corresponding pictures on a computer screen. RESULTS: Children with hearing loss were less able to use shortened transition or shortened vowel centers to identify vowels as compared to their normal-hearing peers. Whole syllable and initial transition yielded better identification performance than the vowel center for /ɑ/, but not for /i/ or /u/. CONCLUSIONS: The children with hearing loss may require a longer time window than children with normal hearing to integrate vowel cues over time because of altered peripheral encoding in spectrotemporal domains. Clinical implications include cognizance of the importance of vowel perception when developing habilitative programs for children with hearing loss.

Using Microphone Technology to Improve Speech Perception in Noise in Children with Cochlear Implants.

BACKGROUND: Cochlear implant (CI) users are affected more than their normal hearing (NH) peers by the negative consequences of background noise on speech understanding. Research has shown that adult CI users can improve their speech recognition in challenging listening environments by using dual-microphone beamformers, such as adaptive directional microphones (ADMs) and wireless remote microphones (RMs). The suitability of these microphone technologies for use in children with CIs is not well-understood nor widely accepted. PURPOSE: To assess the benefit of ADM or RM technology on speech perception in background noise in children and adolescents with cochlear implants (CIs) with no previous or current use of ADM or RM. RESEARCH DESIGN: Mixed, repeated measures design. STUDY SAMPLE: Twenty (20) children, ten (10) CI users (mean age 14.3 yrs) who used Advanced Bionics HiRes90K implants with research Naida processors, and ten (10) NH age-matched controls participated in this prospective study. INTERVENTION: CI users listened with an ear-canal level microphone, T-Mic (TM), an ADM, and a wireless RM at different audio-mixing ratios. Speech understanding with five microphone settings (TM 100%, ADM, RM + TM 50/50, RM + TM 75/25, RM 100%) was evaluated in quiet and in noise. DATA COLLECTION AND ANALYSIS: Speech perception ability was measured using children's spondee words to obtain a speech recognition threshold for 80% accuracy (SRT80%) in 20-talker babble where the listener sat in a sound booth 1 m (3.28') from the target speech (front) and noise (behind) to test five microphone settings (TM 100%, ADM, RM + TM 50/50, RM + TM 75/25, RM 100%). Group performance-intensity functions were computed for each listening condition to show the effects of microphone configuration with respect to signal-to-noise ratio (SNR). A difference score (CI Group minus NH Group) was computed to show the effect of microphone technology at different SNRs relative to NH. Statistical analysis using a repeated-measures analysis of variance evaluated the effects of the microphone configurations on SRT80% and performance at SNRs. Between-groups analysis of variance was used to compare the CI group with the NH group. RESULTS: The speech recognition was significantly poorer for children with CI than children with NH in quiet and in noise when using the TM alone. Adding the ADM or RM provided a significant improvement in speech recognition for the CI group over use of the TM alone in noise (mean dB advantage ranged from 5.8 for ADM to 16 for RM100). When children with CI used the RM75 or RM100 in background babble, speech recognition was not statistically different from the group with NH. CONCLUSION: Speech recognition in noise performance improved with the use of ADM and RM100 or RM75 over TM-only for children with CIs. Alhough children with CI remain at a disadvantage as compared with NH children in quiet and more favorable SNRs, microphone technology can enhance performance for some children with CI to match that of NH peers in contexts with negative SNRs.

Open-Fit Domes and Children with Bilateral High-Frequency Sensorineural Hearing Loss: Benefits and Outcomes.

BACKGROUND: Open-fit domes (OFDs) coupled with behind-the-ear (BTE) hearing aids were designed for adult listeners with moderate-to-severe bilateral high-frequency hearing loss (BHFL) with little to no concurrent loss in the lower frequencies. Adult research shows that BHFL degrades sound localization accuracy (SLA) and that BTE hearing aids with conventional earmolds (CEs) make matters worse. In contrast, research has shown that OFDs enhance spatial hearing percepts in adults with BHFL. Although the benefits of OFDs have been studied in adults with BHFL, no published studies to date have investigated the use of OFDs in children with the same hearing loss configuration. This study seeks to use SLA measurements to assess efficacy of bilateral OFDs in children with BHFL. PURPOSE: To measure SLA in children with BHFL to determine the extent to which hearing loss, age, duration of CE use, and OFDs affect localization accuracy. RESEARCH DESIGN: A within-participant experimental design using repeated measures was used to determine the effect of OFDs on localization accuracy in children with BHFL. A between-participant experimental design was used to compare localization accuracy between children with BHFL and age-matched controls with normal hearing (NH). STUDY SAMPLE: Eighteen children with BHFL who used CE and 18 age-matched NH controls. Children in both groups were divided into two age groups: older children (10-16 yr) and younger children (6-9 yr). DATA COLLECTION AND ANALYSIS: All testing was done in a sound-treated booth with a horizontal array of 15 loudspeakers (radius of 1 m). The stimulus was a spondee word, "baseball": the level averaged 60 dB SPL and randomly roved (±8 dB). Each child was asked to identify the location of a sound source. Localization error was calculated across the loudspeaker array for each listening condition. RESULTS: A significant interaction was found between immediate benefit from OFD and duration of CE usage. Longer CE usage was associated with degraded localization accuracy using OFDs. Regardless of chronological age, children who had used CEs for <6 yr showed immediate localization benefit using OFDs, whereas children who had used CEs for >6 yr showed immediate localization interference using OFDs. Development, however, may play a role in SLA in children with BHFL. When unaided, older children had significantly better localization acuity than younger children with BHFL. When compared to age-matched controls, children with BHFL of all ages showed greater localization error. Nearly all (94% [17/18]) children with BHFL spontaneously reported immediate own-voice improvement when using OFDs. CONCLUSIONS: OFDs can provide sound localization benefit to younger children with BHFL. However, immediate benefit from OFDs is reduced by prolonged use of CEs. Although developmental factors may play a role in improving localization abilities over time, children with BHFL will rarely equal that of peers without early use of minimally disruptive hearing aid technology. Also, the occlusion effect likely impacts children far more than currently thought.

Auditory and visual localization accuracy in young children and adults.

OBJECTIVE: This study aimed to measure and compare sound and light source localization ability in young children and adults who have normal hearing and normal/corrected vision in order to determine the extent to which age, type of stimuli, and stimulus order affects sound localization accuracy. METHODS: Two experiments were conducted. The first involved a group of adults only. The second involved a group of 30 children aged 3 to 5 years. Testing occurred in a sound-treated booth containing a semi-circular array of 15 loudspeakers set at 10° intervals from -70° to 70° azimuth. Each loudspeaker had a tiny light bulb and a small picture fastened underneath. Seven of the loudspeakers were used to randomly test sound and light source identification. The sound stimulus was the word "baseball". The light stimulus was a flashing of a light bulb triggered by the digital signal of the word "baseball". Each participant was asked to face 0° azimuth, and identify the location of the test stimulus upon presentation. Adults used a computer mouse to click on an icon; children responded by verbally naming or walking toward the picture underneath the corresponding loudspeaker or light. A mixed experimental design using repeated measures was used to determine the effect of age and stimulus type on localization accuracy in children and adults. A mixed experimental design was used to compare the effect of stimulus order (light first/last) and varying or fixed intensity sound on localization accuracy in children and adults. RESULTS: Localization accuracy was significantly better for light stimuli than sound stimuli for children and adults. Children, compared to adults, showed significantly greater localization errors for audition. Three-year-old children had significantly greater sound localization errors compared to 4- and 5-year olds. Adults performed better on the sound localization task when the light localization task occurred first. CONCLUSIONS: Young children can understand and attend to localization tasks, but show poorer localization accuracy than adults in sound localization. This may be a reflection of differences in sensory modality development and/or central processes in young children, compared to adults.

Relationship among the physiologic channel interactions, spectral-ripple discrimination, and vowel identification in cochlear implant users.

The hypothesis of this study was that broader patterns of physiological channel interactions in the local region of the cochlea are associated with poorer spectral resolution in the same region. Electrically evoked compound action potentials (ECAPs) were measured for three to six probe electrodes per subject to examine the channel interactions in different regions across the electrode array. To evaluate spectral resolution at a confined location within the cochlea, spectral-ripple discrimination (SRD) was measured using narrowband ripple stimuli with the bandwidth spanning five electrodes: Two electrodes apical and basal to the ECAP probe electrode. The relationship between the physiological channel interactions, spectral resolution in the local cochlear region, and vowel identification was evaluated. Results showed that (1) there was within- and across-subject variability in the widths of ECAP channel interaction functions and in narrowband SRD performance, (2) significant correlations were found between the widths of the ECAP functions and narrowband SRD thresholds, and between mean bandwidths of ECAP functions averaged across multiple probe electrodes and broadband SRD performance across subjects, and (3) the global spectral resolution reflecting the entire electrode array, not the local region, predicts vowel identification.

Spatial hearing in a child with auditory neuropathy spectrum disorder and bilateral cochlear implants.

OBJECTIVE: The neural dys-synchrony associated with auditory neuropathy spectrum disorder (ANSD) causes a temporal impairment that could degrade spatial hearing, particularly sound localization accuracy (SLA) and spatial release from masking (SRM). Unilateral cochlear implantation has become an accepted treatment for ANSD but treatment options for the contralateral ear remain controversial. We report spatial hearing measures in a child with ANSD before and after receiving a second cochlear implant (CI). STUDY SAMPLE: An 11-year-7-month old boy with ANSD and expressive and receptive language delay received a second CI eight years after his first implant. DESIGN: The SLA and SRM were measured four months before sequential bilateral CIs (with the contralateral ear plugged and unplugged), and after nine months using both CIs. RESULTS: Testing done before the second CI, with the first CI alone, suggested that residual hearing in the contralateral ear contributed to sound localization accuracy, but not word recognition in quiet or noise. Nine-months after receiving a second CI, SLA improved by 12.76° and SRM increased to 3.8-4.2 dB relative to pre-operative performance. Results were compared to published outcomes for children with bilateral CIs. CONCLUSIONS: The addition of a second CI in this child with ANSD improved spatial hearing.

Using the Extended Parallel Process Model to create and evaluate the effectiveness of brochures to reduce the risk for noise-induced hearing loss in college students.

Brochures containing messages developed according to the Extended Parallel Process Model were deployed to increase intentions to use hearing protection for college students. These brochures were presented to one-half of a college student sample, after which a questionnaire was administered to assess perceptions of threat, efficacy, and behavioral intentions. The other half of the sample completed the questionnaire and then received brochures. Results indicated that people receiving the brochure before the questionnaire reported greater perceptions of hearing loss threat and efficacy to use ear plugs when in loud environments, however, intentions to use ear plugs were unchanged. Distribution of the brochure also resulted in greater perceptions of hearing loss threat and efficacy to use over-the-ear headphones when using devices such as MP3 players. In this case, however, intentions to use over-the-ear headphones increased. Results are discussed in terms of future research and practical applications.

Sound localization acuity in children with unilateral hearing loss who wear a hearing aid in the impaired ear.

BACKGROUND: Disrupted binaural hearing is thought to contribute in part to the academic, social, and communication problems often associated with unilateral hearing loss (UHL) in childhood. It is not known, however, if putting a hearing aid in the impaired ear of a child with UHL will lead to bilateral or binaural benefit. This study seeks to utilize sound localization acuity measurements to assess hearing aid amplification efficacy in children with UHL. PURPOSE: To measure sound localization ability in children with UHL who use a hearing aid in the impaired ear to determine the extent to which amplification, age, early intervention, and degree of hearing loss affects localization acuity. RESEARCH DESIGN: A within-subjects experimental design using repeated measures is used to determine the effect of amplification on localization acuity in children with UHL. A between-subjects experimental design is used to compare localization acuity between children with UHL and age-matched controls with normal hearing. STUDY SAMPLE: Twelve children with UHL who used a hearing aid in the impaired ear and 12 age-matched controls with normal hearing. Children with UHL were divided into two groups based on degree of hearing loss. Children in both groups were divided into two age groups: older children (10-14 yr) and younger children (6-9 yr). DATA COLLECTION AND ANALYSIS: All testing was done in a sound-treated booth with a horizontal array of 15 loudspeakers (radius of 1 m). The stimulus was a spondee word, "baseball": the level averaged 60 dB SPL and randomly roved (±8 dB). Each child was asked to identify the location of a sound source. RESULTS: In the experimental study a significant interaction was found between hearing aid amplification and child age. A hearing aid significantly improved localization acuity in younger children with UHL and significantly impaired localization acuity in older children. A significant correlation was found between age at intervention and localization bilateral benefit. Children who were fit earlier showed bilateral benefit whereas children who were fit later showed bilateral interference. Development, however, may play a role in sound localization acuity. When unaided, older children had significantly better localization acuity than younger children with UHL. CONCLUSIONS: A hearing aid can provide bilateral localization benefit to some children with UHL. Early intervention may increase the likelihood of bilateral benefit. However, developmental factors appear to play a role in improving localization abilities over time for children with UHL. Nonetheless, without a means of establishing bilateral benefit with hearing aid amplification, localization performance in children with UHL will rarely equal that of peers.

The effects of receiver placement on probe microphone, performance, and subjective measures with open canal hearing instruments.

BACKGROUND: Open canal hearing instruments differ in method of sound delivery to the ear canal, distance between the microphone and the receiver, and physical size of the devices. Moreover, RITA (receiver in the aid) and RITE (receiver in the ear) hearing instruments may also differ in terms of retention and comfort as well as ease of use and care for certain individuals. What remains unclear, however, is if any or all of the abovementioned factors contribute to hearing aid outcome. PURPOSE: To determine the effect of receiver location on performance and/or preference of listeners using open canal hearing instruments. RESEARCH DESIGN: An experimental study in which subjects were exposed to a repeated measures design. STUDY SAMPLE: Twenty-five adult listeners with mild sloping to moderately severe sensorineural hearing loss (mean age 67 yr). DATA COLLECTION AND ANALYSIS: Participants completed two six-week trial periods for each device type. Probe microphone, objective, and subjective measures (quiet, noise) were conducted unaided and aided at the end of each trial period. RESULTS: Occlusion effect results were not significantly different between the RITA and RITE instruments; however, frequency range was extended in the RITE instruments, resulting in significantly greater maximum gain for the RITE instruments than the RITA instruments at 4000 and 6000 Hz. Objective performance in quiet or in noise was unaffected by receiver location. Subjective measures revealed significantly greater satisfaction ratings for the RITE than for the RITA instruments. Similarly, preference in quiet and overall preference were significantly greater for the RITE than for the RITA instruments. CONCLUSIONS: Although no occlusion differences were noted between instruments, the RITE did demonstrate a significant difference in reserve gain before feedback at 4000 and 6000 Hz. Objectively; no positive benefit was noted between unaided and aided conditions on speech recognition tests. These results suggest that such testing may not be sensitive enough to determine aided benefit with open canal instruments. However, the subjective measures (Abbreviated Profile of Hearing Aid Benefit [APHAB] and subjective ratings) did indicate aided benefit for both instruments when compared to unaided. This further suggests the clinical importance of subjective measures as a way to measure aided benefit of open-fit devices.

Developing an "essential functions" rubric: purposes and applications for speech-language-hearing academic programs.

This article describes the purpose and application of an essential functions rubric for prospective and current students engaged in the study of communication sciences and disorders. Adopted in 2007 by the Council on Academic Programs in Communication Sciences and Disorders (CAPCSD), the essential functions rubric identifies core skills and attributes in five areas: communication, motor, intellectual-cognitive, sensory/observational, and behavioral/social. CAPCSD does not intend the rubric to be prescriptive but rather expects that it will be adapted to reflect the unique mission or circumstances of each academic program. The value of an essential functions rubric for academic programs is the opportunity it provides to educate students about the roles and responsibilities of the disciplines. A rubric also allows academic programs an objective basis for counseling students about professional expectations. Importantly, an essential functions rubric gives both students and programs opportunities to determine what, if any, accommodations might be employed to allow students who are otherwise qualified to help them succeed both academically and clinically.

A comparison of video versus conventional visual reinforcement in 7- to 16-month-old infants.

PURPOSE: To compare response patterns to video visual reinforcement audiometry (VVRA) and conventional visual reinforcement audiometry (CVRA) in infants 7-16 months of age. METHOD: Fourteen normal-hearing infants aged 7-16 months (8 male, 6 female) participated. A repeated measures design was used. Each infant was tested with VVRA and CVRA over 2 different sessions. The total number of head turns prior to habituation, hit rate (response consistency), false alarm rate, and sensitivity for each reinforcement condition were evaluated. RESULTS: No significant differences were found between the 2 reinforcement methods for total number of head turns, hit rate, false alarm rate, or sensitivity. Overall, results showed no difference between the 2 reinforcer conditions in infants 7-16 months of age. CONCLUSION: The results of the present study suggest that infants in the 7- to 16-month-old age range respond similarly to VVRA and CVRA as measured by response consistency and false alarm rate. VVRA is, therefore, a viable option for testing hearing in infants. However, prior to clinical implementation, the effectiveness of VVRA should be explored in infants with hearing loss.

Effect of masker type and age on speech intelligibility and spatial release from masking in children and adults.

Speech recognition in noisy environments improves when the speech signal is spatially separated from the interfering sound. This effect, known as spatial release from masking (SRM), was recently shown in young children. The present study compared SRM in children of ages 5-7 with adults for interferers introducing energetic, informational, and/or linguistic components. Three types of interferers were used: speech, reversed speech, and modulated white noise. Two female voices with different long-term spectra were also used. Speech reception thresholds (SRTs) were compared for: Quiet (target 0 degrees front, no interferer), Front (target and interferer both 0 degrees front), and Right (interferer 90 degrees right, target 0 degrees front). Children had higher SRTs and greater masking than adults. When spatial cues were not available, adults, but not children, were able to use differences in interferer type to separate the target from the interferer. Both children and adults showed SRM. Children, unlike adults, demonstrated large amounts of SRM for a time-reversed speech interferer. In conclusion, masking and SRM vary with the type of interfering sound, and this variation interacts with age; SRM may not depend on the spectral peculiarities of a particular type of voice when the target speech and interfering speech are different sex talkers.

Benefits of bilateral cochlear implants and/or hearing aids in children.

This study evaluated functional benefits from bilateral stimulation in 20 children ages 4-14, 10 use two CIs and 10 use one CI and one HA. Localization acuity was measured with the minimum audible angle (MAA). Speech intelligibility was measured in quiet, and in the presence of 2-talker competing speech using the CRISP forced-choice test. Results show that both groups perform similarly when speech reception thresholds are evaluated. However, there appears to be benefit (improved MAA and speech thresholds) from wearing two devices compared with a single device that is significantly greater in the group with two CI than in the bimodal group. Individual variability also suggests that some children perform similarly to normal-hearing children, while others clearly do not. Future advances in binaural fitting strategies and improved speech processing schemes that maximize binaural sensitivity will no doubt contribute to increasing the binaurally-driven advantages in persons with bilateral CIs.

Bilateral cochlear implants in children: localization acuity measured with minimum audible angle.

OBJECTIVE: To evaluate sound localization acuity in a group of children who received bilateral (BI) cochlear implants in sequential procedures and to determine the extent to which BI auditory experience affects sound localization acuity. In addition, to investigate the extent to which a hearing aid in the nonimplanted ear can also provide benefits on this task. DESIGN: Two groups of children participated, 13 with BI cochlear implants (cochlear implant + cochlear implant), ranging in age from 3 to 16 yrs, and six with a hearing aid in the nonimplanted ear (cochlear implant + hearing aid), ages 4 to 14 yrs. Testing was conducted in large sound-treated booths with loudspeakers positioned on a horizontal arc with a radius of 1.5 m. Stimuli were spondaic words recorded with a male voice. Stimulus levels typically averaged 60 dB SPL and were randomly roved between 56 and 64 dB SPL (+/-4 dB rove); in a few instances, levels were held fixed (60 dB SPL). Testing was conducted by using a "listening game" platform via computerized interactive software, and the ability of each child to discriminate sounds presented to the right or left was measured for loudspeakers subtending various angular separations. Minimum audible angle thresholds were measured in the BI (cochlear implant + cochlear implant or cochlear implant + hearing aid) listening mode and under monaural conditions. RESULTS: Approximately 70% (9/13) of children in the cochlear implant + cochlear implant group discriminated left/right for source separations of

Bilateral cochlear implants in adults and children.

OBJECTIVE: To measure the benefit (ie, sound localization and speech intelligibility in noise) of bilateral cochlear implants (CIs) in adults and in children. DESIGN, SETTING, AND PATIENTS: Seventeen adults and 3 children underwent testing 3 months after activation of bilateral hearing. Adults received their devices in a simultaneous procedure and children in sequential procedures (3-8 years apart). Adults underwent testing of sound localization and speech intelligibility, with a single CI and bilaterally. Children underwent testing of sound localization, right/left discrimination, and speech intelligibility, with the first CI alone and bilaterally. We used computer games to attract the children's attention and engage them in the psychophysical tasks for long periods of time. RESULTS: Preliminary findings suggest that, for adults, bilateral hearing leads to better performance on the localization task, and on the speech task when the noise is near the poorer of the 2 ears. In children, localization and discrimination are slightly better under bilateral conditions, but not remarkably so. On the speech tasks, 1 child did not benefit from bilateral hearing. Two children showed consistent improvement with bilateral hearing when the noise was near the side that underwent implantation first. CONCLUSIONS: Bilateral CIs may offer advantages to some listeners. The tasks described in this study might offer a powerful tool for measuring such advantages, especially in young children. The extent of the advantage, however, is difficult to ascertain after 3 months of bilateral listening experience, and might require a more prolonged period of adjustment and learning. Future work should be aimed at examining these issues.