Acoustic features of auditory medical alarms-An experimental study of alarm volume.

Audible alarms are a ubiquitous feature of all high-paced, high-risk domains such as aviation and nuclear power where operators control complex systems. In such settings, a missed alarm can have disastrous consequences. It is conventional wisdom that for alarms to be heard, "louder is better," so that alarm levels in operational environments routinely exceed ambient noise levels. Through a robust experimental paradigm in an anechoic environment to study human response to audible alerting stimuli in a cognitively demanding setting, akin to high-tempo and high-risk domains, clinician participants responded to patient crises while concurrently completing an auditory speech intelligibility and visual vigilance distracting task as the level of alarms were varied as a signal-to-noise ratio above and below hospital background noise. There was little difference in performance on the primary task when the alarm sound was -11 dB below background noise as compared with +4 dB above background noise-a typical real-world situation. Concurrent presentation of the secondary auditory speech intelligibility task significantly degraded performance. Operator performance can be maintained with alarms that are softer than background noise. These findings have widespread implications for the design and implementation of alarms across all high-consequence settings.

Binaural masking release in children with Down syndrome.

OBJECTIVES: Binaural hearing results in a number of listening advantages relative to monaural hearing, including enhanced hearing sensitivity and better speech understanding in adverse listening conditions. These advantages are facilitated in part by the ability to detect and use interaural cues within the central auditory system. Binaural hearing for children with Down syndrome could be impacted by multiple factors including, structural anomalies within the peripheral and central auditory system, alterations in synaptic communication, and chronic otitis media with effusion. However, binaural hearing capabilities have not been investigated in these children. This study tested the hypothesis that children with Down syndrome experience less binaural benefit than typically developing peers. DESIGN: Participants included children with Down syndrome aged 6 to 16 years (n = 11), typically developing children aged 3 to 12 years (n = 46), adults with Down syndrome (n = 3), and adults with no known neurological delays (n = 6). Inclusionary criteria included normal to near-normal hearing sensitivity. Two tasks were used to assess binaural ability. Masking level difference (MLD) was calculated by comparing threshold for a 500-Hz pure-tone signal in 300-Hz wide Gaussian noise for N0S0 and N0Sπ signal configurations. Binaural intelligibility level difference was calculated using simulated free-field conditions. Speech recognition threshold was measured for closed-set spondees presented from 0-degree azimuth in speech-shaped noise presented from 0-, 45- and 90-degree azimuth, respectively. The developmental ability of children with Down syndrome was estimated and information regarding history of otitis media was obtained for all child participants via parent survey. RESULTS: Individuals with Down syndrome had higher masked thresholds for pure-tone and speech stimuli than typically developing individuals. Children with Down syndrome had significantly smaller MLDs than typically developing children. Adults with Down syndrome and control adults had similar MLDs. Similarities in simulated spatial release from masking were observed for all groups for the experimental parameters used in this study. No association was observed for any measure of binaural ability and developmental age for children with Down syndrome. Similar group psychometric functions were observed for children with Down syndrome and typically developing children in most instances, suggesting that attentiveness and motivation contributed equally to performance for both groups on most tasks. CONCLUSIONS: The binaural advantages afforded to typically developing children, such as enhanced hearing sensitivity in noise, were not as robust for children with Down syndrome in this study. Children with Down syndrome experienced less binaural benefit than typically developing peers for some stimuli, suggesting that they could require more favorable signal-to-noise ratios to achieve optimal performance in some adverse listening conditions. The reduced release from masking observed for children with Down syndrome could represent a delay in ability rather than a deficit that persists into adulthood. This could have implications for the planning of interventions for individuals with Down syndrome.

Blind and sighted pedestrians' road-crossing judgments at a single-lane roundabout.

OBJECTIVE: The aim of this study was to evaluate the relative risk and efficiency of road crossing experienced by blind and sighted pedestrians at a single-lane roundabout with two levels of traffic volume and at two distances from the roundabout. BACKGROUND: With the rapid spread of modern roundabouts across the United States,their accessibility to blind pedestrians has become an important concern. To date, accessibility research relevant to blind pedestrians has focused on multilane roundabouts, and single-lane roundabouts have been virtually ignored. METHOD: Blind and sighted participants made judgments about when they would cross a single-lane roundabout with high and low traffic volumes, at exit and entry lanes, and at the actual crosswalks and at locations farther from the roundabout. RESULTS: Relative to sighted participants, blind participants' judgments about when to cross were more frequently risky, especially when traffic volume was high. Blind participants also were slower to make crossing judgments and accepted fewer crossing opportunities. Both groups made somewhat safer and more efficient judgments at locations farther from the roundabout. CONCLUSION: Some single-lane roundabouts may pose greater risk to blind pedestrians than to sighted pedestrians, especially when traffic volume is high. Crosswalk location merits further investigation as a design issue. APPLICATION: These findings are relevant to transportation planners and engineers who are responsible for the accessibility of public rights-of-way.

Comparison of ventilation and voice outcomes between unilateral laryngeal pacing and unilateral cordotomy for the treatment of bilateral vocal fold paralysis.

BACKGROUND/AIMS: Rehabilitation of the bilaterally paralyzed human larynx remains a complex clinical problem. Conventional treatment generally involves surgical enlargement of the compromised airway, but often with resultant dysphonia and risk of aspiration. In this retrospective study, we compared one such treatment, posterior cordotomy, with unilateral laryngeal pacing: reanimation of vocal fold opening by functional electrical stimulation of the posterior cricoarytenoid muscle. METHODS: Postoperative peak inspiratory flow (PIF) values and overall voice grade ratings were compared between the two surgical groups, and pre- and postoperative PIF were compared within the pacing group. RESULTS: There were 5 patients in the unilateral pacing group and 12 patients in the unilateral cordotomy group. Within the pacing group, postoperative PIF values were significantly improved from preoperative PIF values (p = 0.04) without a significant effect on voice (grade; p = 0.62). Within the pacing group, the mean postoperative PIF value was significantly higher than that in the cordotomy group (p = 0.05). Also, the mean postoperative overall voice grade values in the pacing group were significantly lower (better) than those of the cordotomy group (p = 0.03). CONCLUSION: Unilateral pacing appears to be an effective treatment superior to posterior cordotomy with respect to postoperative ventilation and voice outcome measures.

Human sensitivity to differences in the rate of auditory cue change.

Measurement of sensitivity to differences in the rate of change of auditory signal parameters is complicated by confounds among duration, extent, and velocity of the changing signal. Dooley and Moore [(1988) J. Acoust. Soc. Am. 84(4), 1332-1337] proposed a method for measuring sensitivity to rate of change using a duration discrimination task. They reported improved duration discrimination when an additional intensity or frequency change cue was present. The current experiments were an attempt to use this method to measure sensitivity to the rate of change in intensity and spatial position. Experiment 1 investigated whether duration discrimination was enhanced when additional cues of rate of intensity change, rate of spatial position change, or both were provided. Experiment 2 determined whether participant listening experience or the testing environment influenced duration discrimination task performance. Experiment 3 assessed whether duration discrimination could be used to measure sensitivity to rates of changes in intensity and spatial position for stimuli with lower rates of change, as well as emphasizing the constancy of the velocity cue. Results of these experiments showed that duration discrimination was impaired rather than enhanced by the additional velocity cues. The findings are discussed in terms of the demands of listening to concurrent changes along multiple auditory dimensions.

Auditory perception of motor vehicle travel paths.

OBJECTIVE: These experiments address concerns that motor vehicles in electric engine mode are so quiet that they pose a risk to pedestrians, especially those with visual impairments. BACKGROUND: The "quiet car" issue has focused on hybrid and electric vehicles, although it also applies to internal combustion engine vehicles. Previous research has focused on detectability of vehicles, mostly in quiet settings. Instead, we focused on the functional ability to perceive vehicle motion paths. METHOD: Participants judged whether simulated vehicles were traveling straight or turning, with emphasis on the impact of background traffic sound. RESULTS: In quiet, listeners made the straight-or-turn judgment soon enough in the vehicle's path to be useful for deciding whether to start crossing the street. This judgment is based largely on sound level cues rather than the spatial direction of the vehicle. With even moderate background traffic sound, the ability to tell straight from turn paths is severely compromised. The signal-to-noise ratio needed for the straight-or-turn judgment is much higher than that needed to detect a vehicle. CONCLUSION: Although a requirement for a minimum vehicle sound level might enhance detection of vehicles in quiet settings, it is unlikely that this requirement would contribute to pedestrian awareness of vehicle movements in typical traffic settings with many vehicles present. APPLICATION: The findings are relevant to deliberations by government agencies and automobile manufacturers about standards for minimum automobile sounds and, more generally, for solutions to pedestrians' needs for information about traffic, especially for pedestrians with sensory impairments.

Horizontal plane localization in single-sided deaf adults fitted with a bone-anchored hearing aid (Baha).

OBJECTIVES: : One purpose of this investigation was to evaluate the effect of a unilateral bone-anchored hearing aid (Baha) on horizontal plane localization performance in single-sided deaf adults who had either a conductive or sensorineural hearing loss in their impaired ear. The use of a 33-loudspeaker array allowed for a finer response measure than has previously been used to investigate localization in this population. In addition, a detailed analysis of error patterns allowed an evaluation of the contribution of random error and bias error to the total rms error computed in the various conditions studied. A second purpose was to investigate the effect of stimulus duration and head-turning on localization performance. DESIGN: : Two groups of single-sided deaf adults were tested in a localization task in which they had to identify the direction of a spoken phrase on each trial. One group had a sensorineural hearing loss (SNHL group; N = 7), and the other group had a conductive hearing loss (CHL group; N = 5). In addition, a control group of four normal-hearing adults was tested. The spoken phrase was either 1250 msec in duration (a male saying "Where am I coming from now?") or 341 msec in duration (the same male saying "Where?"). For the longer-duration phrase, subjects were tested in conditions in which they either were or were not allowed to move their heads before the termination of the phrase. The source came from one of nine positions in the front horizontal plane (from -79° to +79°). The response range included 33 choices (from -90° to +90°, separated by 5.6°). Subjects were tested in all stimulus conditions, both with and without the Baha device. Overall rms error was computed for each condition. Contributions of random error and bias error to the overall error were also computed. RESULTS: : There was considerable intersubject variability in all conditions. However, for the CHL group, the average overall error was significantly smaller when the Baha was on than when it was off. Further analysis of error patterns indicated that this improvement was primarily based on reduced response bias when the device was on; that is, the average response azimuth was nearer to the source azimuth when the device was on than when it was off. The SNHL group, on the other hand, had significantly greater overall error when the Baha was on than when it was off. Collapsed across listening conditions and groups, localization performance was significantly better with the 1250 msec stimulus than with the 341 msec stimulus. However, for the longer-duration stimulus, there was no significant beneficial effect of head-turning. Error scores in all conditions for both groups were considerably larger than those in the normal-hearing control group. CONCLUSIONS: : On average, single-sided deaf adults with CHL showed improved localization ability when using the Baha, whereas single-sided deaf adults with SNHL showed a decrement in performance when using the device. These results may have implications for clinical counseling for patients with unilateral hearing impairment.

Interaural time and level difference thresholds for acoustically presented signals in post-lingually deafened adults fitted with bilateral cochlear implants using CIS+ processing.

OBJECTIVES: The main purpose of the study was to measure thresholds for interaural time differences (ITDs) and interaural level differences (ILDs) for acoustically presented noise signals in adults with bilateral cochlear implants (CIs). A secondary purpose was to assess the correlation between the ILD and ITD thresholds and error scores in a horizontal-plane localization task, to test the hypothesis that localization by individuals with bilateral implants is mediated by the processing of ILD cues. DESIGN: Eleven adults, all postlingually deafened and all bilaterally fitted with MED-EL COMBI 40+ CIs, were tested in ITD and ILD discrimination tasks in which signals were presented acoustically through headphones that fit over their two devices. The stimulus was a 200-msec burst of Gaussian noise bandpass filtered from 100 to 4000 Hz. A two-interval forced-choice adaptive procedure was used in which the subject had to respond on each trial whether the lateral positions of the two sound images (with the interaural difference favoring the left and right sides in the two intervals) moved from left-to-right or right-to-left. RESULTS: In agreement with previously reported data, ITD thresholds for the subjects with bilateral implants were poor. The best threshold was approximately 400 microsec, and only five of 11 subjects tested achieved thresholds <1000 microsec. In contrast, ILD thresholds were relatively good; mean threshold was 3.8 dB with the initial compression circuit on the implant devices activated and 1.9 dB with the compression deactivated. The ILD and ITD thresholds were higher than previously reported thresholds obtained with direct electrical stimulation (generally, <1.0 dB and 100 to 200 microsec, respectively). When the data from two outlying subjects were omitted, ILD thresholds were highly correlated with total error score in a horizontal-plane localization task, computed for sources near midline (r = 0.87, p < 0.01). CONCLUSIONS: The higher ILD and ITD thresholds obtained in this study with acoustically presented signals (when compared with prior data with direct electrical stimulation) can be attributed-at least partially-to the signal processing carried out by the CI in the former case. The processing strategy effectively leaves only envelope information as a basis for ITD discrimination, which, for the acoustically presented noise stimuli, is mainly coded in the onset information. The operation of the compression circuit reduces the ILDs in the signal, leading to elevated ILD thresholds for the acoustically presented signals in this condition. The large magnitude of the ITD thresholds indicates that ITDs could not have contributed to the performance in the horizontal-plane localization task. Overall, the results suggest that for subjects using bilateral implants, localization of noise signals is mediated entirely by ILD cues, with little or no contribution from ITD information.

Visual attention and hearing loss: past and current perspectives.

BACKGROUND: It is reasonable to expect that deaf individuals require the use of vision for purposes other than those needed by hearing persons. For example, without the use of hearing, one would need to scan the environment visually to determine if someone was approaching rather than listening for footsteps or a name being called. Furthermore, these experiential differences could alter the development of neural organization of sensory systems of deaf persons. PURPOSE: To review the evidence-based literature in the area of visual attention and deafness with an emphasis on a series of visual attention studies utilizing several paradigms including the Continuous Performance Task, the Letter Cancellation Task, the Flanker Task, and a self-designed task of target identification in the periphery under distracter and nondistracter conditions conducted at Vanderbilt University. RESEARCH DESIGN: Systematic review. RESULTS: Collectively, the Vanderbilt studies pointed to a compensatory role that the visual system plays for deaf individuals. Specifically, the visual system appears to play an important role in directing a deaf individual's attention to the near visual periphery. CONCLUSIONS: Studies of visual attention in deaf individuals have been mixed in their conclusions about whether altered neural organization results in better or worse visual attention abilities by those who are deaf relative to those with normal hearing. The notion of across-the-board deficits or enhancements in the visual function of deaf individuals is not supported by the literature, nor is there support for the idea that fundamental visual sensory abilities such as acuity or light detection differ between deaf and hearing persons.

Localization by postlingually deafened adults fitted with a single cochlear implant.

OBJECTIVE: : The main purpose of the study was to assess the ability of adults with unilateral cochlear implants to localize noise and speech signals in the horizontal plane. DESIGN: : Six unilaterally implanted adults, all postlingually deafened and all fitted with MED-EL COMBI 40+ devices, were tested with a modified source identification task. Subjects were tested individually in an anechoic chamber, which contained an array of 43 numbered loudspeakers extending from -90 degrees to +90 degrees azimuth. On each trial, a 200 millisecond signal (either a noise burst or a speech sample) was presented from one of nine active loudspeakers, and the subject had to identify which source (from the 43 loudspeakers in the array) produced the signal. RESULTS: : The relationship between source azimuth and response azimuth was characterized in terms of the adjusted constant error (C). C for three subjects was near chance (50.5 degrees ), whereas C for the remaining three subjects was significantly better than chance (35 degrees -44 degrees ). By comparison, C for a group of normal-hearing listeners was 5.6 degrees . For two of the three subjects who performed better than chance, monaural cues were determined to be the basis for their localization performance. CONCLUSIONS: : Some unilaterally implanted subjects can localize sounds at a better than chance level, apparently because they can learn to make use of subtle monaural cues based on frequency-dependent head-shadow effects. However, their performance is significantly poorer than that reported in previous studies of bilaterally implanted subjects, who are able to take advantage of binaural cues.

Horizontal-plane localization of noise and speech signals by postlingually deafened adults fitted with bilateral cochlear implants.

OBJECTIVES: The main purpose of the study was to assess the ability of adults with bilateral cochlear implants to localize noise and speech signals in the horizontal plane. A second objective was to measure the change in localization performance in these adults between approximately 5 and 15 mo after activation. A third objective was to evaluate the relative roles of interaural level difference (ILD) and interaural temporal difference (ITD) cues in localization by these subjects. DESIGN: Twenty-two adults, all postlingually deafened and all bilaterally fitted with MED-EL COMBI 40+ cochlear implants, were tested in a modified source identification task. Subjects were tested individually in an anechoic chamber, which contained an array of 43 numbered loudspeakers extending from -90 degrees to +90 degrees azimuth. On each trial, a 200-msec signal (either a noise burst or a speech sample) was presented from one of 17 active loudspeakers (span: +/-80 degrees ), and the subject had to identify which source from the 43 loudspeakers in the array produced the signal. Subjects were tested in three conditions: left device only active, right device only active, and both devices active. Twelve of the 22 subjects were retested approximately 10 mo after their first test. In Experiment 2, the spectral content and rise-decay time of the noise stimulus were manipulated. RESULTS: The relationship between source azimuth and response azimuth was characterized in terms of the adjusted constant error (c). (1) With both devices active, c for the noise stimulus varied from 8.1 degrees to 43.4 degrees (mean: 24.1 degrees ). By comparison, c for a group of listeners with normal hearing ranged from 3.5 degrees to 7.8 degrees (mean: 5.6 degrees ). When subjects listened in unilateral mode (with one device turned off), c was at or near chance (50.5 degrees ) in all cases. However, when considering unilateral performance on each subject's better side, average c for the speech stimulus was 47.9 degrees , which was significantly (but only slightly) better than chance. (2) When listening bilaterally, error score was significantly lower for the speech stimulus (mean c = 21.5 degrees ) than for the noise stimulus (mean c = 24.1 degrees ). (3) As a group, the 12 subjects who were retested 10 mo after their first visit showed no significant improvement in localization performance during the intervening time. However, two subjects who performed very poorly during their first visit showed dramatic improvement (error scores were halved) over the intervening time. In Experiment 2, removing the high-frequency content of noise signals resulted in significantly poorer performance, but removing the low-frequency content or increasing the rise-decay time did not have an effect. CONCLUSIONS: In agreement with previously reported data, subjects with bilateral cochlear implants localized sounds in the horizontal plane remarkably well when using both of their devices, but they generally could not localize sounds when either device was deactivated. They could localize the speech signal with slightly, but significantly better accuracy than the noise, possibly due to spectral differences in the signals, to the availability of envelope ITD cues with the speech but not the noise signal, or to more central factors related to the social salience of speech signals. For most subjects the remarkable ability to localize sounds has stabilized by 5 mo after activation. However, for some subjects who perform poorly initially, there can be substantial improvement past 5 mo. Results from Experiment 2 suggest that ILD cues underlie localization ability for noise signals, and that ITD cues do not contribute.

Speech recognition for unilateral and bilateral cochlear implant modes in the presence of uncorrelated noise sources.

OBJECTIVE: The purpose of the current investigation was to compare speech recognition in noise for bilateral and unilateral modes within postlingually deafened, adult bilateral cochlear implant recipients. In addition, it was of interest to evaluate the time course of the bilateral speech-recognition advantage and the effect of changing signal-to-noise ratio (SNR) on the magnitude of the bilateral advantage. DESIGN: In the first experiment, 16 postlingually deafened adults who were bilaterally implanted with the MED-EL C40+ cochlear device were evaluated in unilateral left, unilateral right, and bilateral conditions 4 to 7 mo after activation. Speech recognition in the presence of five spatially separated, uncorrelated noise sources was evaluated using both a single fixed SNR of +10 dB and an adaptive-SNR method. In a follow-up study, a subset of 10 participants was re-evaluated using an identical fixed-SNR method 12 to 17 mo after activation to examine the time course of speech-recognition performance in both unilateral and bilateral modes at a single SNR. A third study was performed with a subset of six participants to examine performance over a range of SNRs. In this study, speech recognition was measured 12 to 17 mo after activation in quiet and at +5, +10, +15, and +20 dB SNRs using the same five uncorrelated noise sources. RESULTS: The speech-recognition data revealed a significant bilateral advantage of 3.3 dB using the adaptive-SNR method. A significant bilateral advantage of 9% was also measured using a fixed +10 dB SNR. Results from the second study revealed that experience resulted in a significant (11 to 20%) increase in speech-recognition-in-noise performance for both unilateral and bilateral modes; however, the magnitude of the bilateral advantage was not affected by experience. Results from the third study revealed the largest bilateral advantage at the poorest SNR evaluated. In addition, performance in quiet was significantly better than that measured in the presence of noise, even at the +20 dB SNR. CONCLUSIONS: The results of these experiments support a small but significant bilateral speech-recognition-in-noise advantage for cochlear implant recipients in an environment with multiple noise sources. This advantage is presumed to be attributable to the combined effects of binaural squelch and diotic summation. Although experience generally improved speech-recognition-in-noise performance in both unilateral and bilateral modes, a consistent bilateral advantage (approximately 10%) was measured at 4 to 7 mo and at 12 to 17 mo postactivation.

Blind and sighted pedestrians' judgments of gaps in traffic at roundabouts.

This paper reports two experiments about street crossing under conditions of free flowing traffic, with a focus on modem roundabout intersections. Experiment 1 was conducted at three roundabouts varying in size and traffic volume. Six totally blind and six sighted adults judged whether gaps in traffic were long enough to permit crossing to the median (splitter) island before the next vehicle arrived. Gap distributions and measures of judgment quality are reported. Overall, blind participants were about 2.5 times less likely to make correct judgments than sighted participants, took longer to detect crossable gaps, and were more likely to miss crossable gaps altogether. However, the differences were significant only at the two higher volume roundabouts. In Experiment 2, we evaluated the response of drivers to pedestrians with and without mobility devices (i.e., long canes, dog guides). The experiment was conducted at a single-lane roundabout, a midblock crossing, and a two-way-stop-controlled intersection. Site-specific characteristics appeared to have a greater impact on drivers' yielding than did a mobility device. Actual or potential applications of this research include the development of methods for assessing pedestrian safety and driver behavior as well as identifying intersections that may require modification in order to be accessible to blind pedestrians.

Reduced order modeling of head related impulse responses for virtual acoustic displays.

This study investigated the use of reduced order head related impulse response (HRIR) models to improve the computational efficiency in acoustic virtual displays. State space models of varying order were generated from zero-elevation HRIRs using a singular value decomposition technique. A source identification experiment was conducted under anechoic conditions in which three subjects were required to localize sounds in the front horizontal plane. The sounds were either (1) real sources (emitted by individual loudspeakers in a semi-circular array), (2) virtual sources generated from the original HRIRs, or (3) virtual sources generated using reduced order state space models. All virtual sources were created by simultaneous activation of two loudspeakers at +/- 30 degrees using a virtual source imaging technique based on either the measured or modeled HRIRs. The errors in the perceived direction of the virtual sources generated from the reduced order models were compared to errors in localization using the original HRIRs. The results demonstrate that a very significant reduction in model size can be achieved without significantly affecting the fidelity of the virtual display of horizontally placed sources.

Visual attention in deaf and normal hearing adults: effects of stimulus compatibility.

Visual perceptual skills of deaf and normal hearing adults were measured using the Eriksen flanker task. Participants were seated in front of a computer screen while a series of target letters flanked by similar or dissimilar letters was flashed in front of them. Participants were instructed to press one button when they saw an H, and another button when they saw an N. Targets H and N were flashed with flanking letters that were either H or N, creating response-compatible and response-incompatible arrays. Flankers were presented at different distances from the targets and reaction times were measured. In the present study, reaction times were significantly faster for the hearing group than for the deaf group. However, the hearing group had significantly more errors on this task than the deaf group, suggesting that the deaf participants may have been more deliberate in their responses. In addition, the deaf group revealed a significantly greater interference effect than the hearing group at a parafoveal (i.e., 1.0 degrees ) eccentricity. These findings suggest that deaf individuals may allocate their visual resources over a wider range than those with normal hearing.

Directional guidance from audible pedestrian signals for street crossing.

Typical audible pedestrian signals indicate when the pedestrian walk interval is in effect but provide little, or even misleading information for directional alignment. In three experiments, blind and blindfolded sighted adults crossed a simulated crossing with recorded traffic noise to approximate street sounds. This was done to investigate how characteristics of signal presentation affected usefulness of the auditory signal for guiding crossing behaviour. Crossing was more accurate when signals came only from the far end of the crossing rather than the typical practice of presenting signals simultaneously from both ends. Alternating the signal between ends of the crossing was not helpful. Also, the customary practice of signalling two parallel crossings at the same time drew participants somewhat toward the opposite crossing. Providing a locator tone at the end of the crossing during the pedestrian clearance interval improved crossing accuracy. These findings provide a basis for designing audible pedestrian signals to enhance directional guidance. The principal findings were the same for blind and sighted participants and applied across a range of specific signals (e.g. chirps, clicks, voices).

Responses to targets in the visual periphery in deaf and normal-hearing adults.

The purpose of this study was to compare the response times of deaf and normal-hearing individuals to the onset of target events in the visual periphery in distracting and nondistracting conditions. Visual reaction times to peripheral targets placed at 3 eccentricities to the left and right of a center fixation point were measured in prelingually deafened adults and normal-hearing adults. Deaf participants responded more slowly than normal-hearing participants to targets in the near periphery in the nondistracting condition and to targets in the near and distant periphery when distracting stimuli were present. One interpretation of these findings is that deaf individuals may be more deliberate than normal-hearing individuals in responding to near peripheral events and to peripheral events that occur in the presence of distracting stimuli.

Visual attention in children with normal hearing, children with hearing aids, and children with cochlear implants.

Previous studies have reported both positive and negative effects of deafness on visual attention. The purpose of this study was to replicate and expand findings of previous studies by examining visual attention abilities in children with deafness and children with normal hearing. Twenty-eight children, ages 8-14 years, were evaluated. There were two groups of children with prelingual deafness and one group with normal hearing. The children with deafness were divided further into two groups: those with cochlear implants and those with conventional hearing aids. Unlike previous studies, the current study found no substantial differences in performance among these three groups of children on a continuous-performance visual attention task or on a letter cancellation task. Children in all three groups performed very well on the visual attention tasks. Furthermore, there was little association between performance on the visual attention tasks and parent or teacher ratings of behavior and attention. Age and nonverbal intelligence were significantly correlated with performance on visual attention tasks. The theoretical implications of these findings are discussed, along with directions for future research.