Abstract
Objective:
This study aims to analyze the impact of single-sided deafness (SSD) on listening behavior to evaluate sound localization ability, speech-in-noise performance, and quantifying and comparing compensatory head movements in individuals with normal hearing (NH) and SSD, with and without a cochlear implant (CI).
Study Design:
Non-randomized, prospective human-subject study.
Setting:
Tertiary academic medical center.
Methods:
NH, SSD, and SSD-CI subjects were presented with Harvard IEEE sentences at varying target azimuths in a darkened, semi-anechoic chamber in background noise while head position was monitored. Head movement (total absolute head displacement, onset delay, and response time), localization accuracy, and speech-in-noise performance were analyzed.
Results:
SSD subjects demonstrated less accurate speech-in-noise and sound localization performance with a significant effect of hearing status and signal-to-noise ratio (SNR). Sound localization benefit with CI was limited and did not improve with increasingly optimal SNR and speech-in-noise performance reached the level of NH controls with more optimal SNR. Head movements varied with and without CI for total response time, whereby CI users had shortest response times. There was no difference between the SSD and SSD-CI conditions for onset delay and head displacement, despite significant differences compared to NH controls.
Conclusions:
Speech-in-noise performance may be the most significant improvement in CI use for SSD. While sound localization abilities are present, there may be modest clinical significance. Head movement dynamics may highlight adaptive mechanisms that, if integrated into training or device programming, may further improve speech-in-noise and localization abilities.
Keywords: Single-sided deafness, SSD, binaural hearing, cochlear implant, speech-in-noise, sound localization, head movement
Introduction
Participation in everyday activities such as following a conversation in a noisy restaurant or safely navigating a busy street rely on binaural hearing. Spatially distinct auditory input to the brain provided by normal hearing in two ears is essential for sound localization and understanding speech in noise, the binaural hearing mechanisms that underly these skills. As such, binaural hearing is crucial for maintaining independence and safety as other senses diminish with age.
Single-sided deafness (SSD) refers to unilateral hearing loss that is not amenable to traditional amplification in the impaired ear. Approximately 60,000 new cases of SSD are diagnosed annually in the United States1. Due to lack of access to binaural acoustical cues, individuals with SSD demonstrate larger errors in sound localization2. They may develop compensatory head movements to optimize signal-to-noise ratio (SNR) in the hearing ear, achieving some level of localization ability through intact monaural cues3. However, these head movements may not effectively optimize acoustical SNR if binaural auditory input is restored with cochlear implantation (CI) and patients continue to rely on monaural cue optimization2,4.
With recent FDA approval for CI in SSD and rising implantation rates, optimizing binaural task performance benefits for these patients is critical. When individuals with SSD undergo CI, sound access in the deaf ear is restored, theoretically providing binaural cues and the benefits of binaural hearing. However, these cues are often altered and incomplete5, and the ability to localize sound is not fully restored6, with significant variability in localization performance post-implantation2,7–9. How individuals with SSD optimize for monaural cues in complex listening environments and the impact of compensatory head movements on binaural acoustical cues post-rehabilitation is poorly understood10.
A recent systematic review by Daher et al (2023) showed variability in testing paradigms for individuals who have undergone implantation for this indication (SSD-CI), with improvements noted in sound localization and speech-in-noise (SIN) performance, and significant quality of life improvements8. Unfortunately, some SSD patients perceive no benefit and don’t use their devices effectively11. Testing protocols for SIN and localization vary, as well as metrics for tests of binaural hearing12, with performance improvement margins across individual studies averaging about 25 degrees8, which may not result in appreciable benefits in real-world interactions as the clinical significance of these changes remain unknown. In addition to wide variability in research protocols, the ecologic validity of these assessments may also be brough into question, as testing frequently directs speech to the deafened ear and restricts head movement – conditions that far from mimic real-world listening behavior.
To address these gaps, we have developed a novel, combined task of SIN and speech-sound localization, allowing free head movement to better assess changes in binaural task performance in individuals with SSD with CI. This study aims to investigate sound localization ability, SIN performance, and compensatory head movements in individuals with normal hearing (NH) and SSD, with and without a CI.
Methods
This study was approved by the Institutional Review Board at the University of Michigan (HUM00190678).
Study Design, Recruitment, and Audiometric evaluation
Eligible participants were those with SSD and a CI, implanted at least six months before the study. Subjects were recruited from University of Michigan Otolaryngology and Audiology Clinics and an institutional research participant registry (https://umhealthresearch.org/). Adults 18 years or older were included. Patients with retrocochlear pathology, neurodegenerative diseases, history of middle ear disease, or abnormal middle ear function on screening audiometry were excluded. All subjects underwent otoscopic examination, and, if they did not have a diagnostic audiogram within the previous 12 months, they underwent audiometric testing with pure tone thresholds to bone and air conduction in both ears using the modified Hughson-Westlake technique, with masking where appropriate.
Combined Speech-in-Noise and Sound Localization Test
Subjects completed a combination SIN and localization task in a dark, semi-anechoic chamber equipped with 24 loudspeakers placed 15° apart in a 360° array. A highly salient, non-target orienting stimulus was presented followed by Harvard IEEE Sentences at 70 dB SPL, with a background masker of pink noise presented diffusely at seven levels (−10, −5, −2, 0, 2, +5, and +10 dB SNR). Subjects were instructed to repeat the target sentence and indicate the perceived stimulus location via head turn (Figure 1). Sentences were scored by testers in real-time for accuracy (% target words correct). A head-worn electromagnetic tracking system with fixed reference (Polhemus Fastrak, Colchester, VT) captured real-time head position while subjects were simultaneously video-monitored to ensure protocol compliance.
Figure 1:
Illustration of the combined speech-in-noise and localization testing paradigm. Head movement, sound localization, and speech-in-noise performance are measured simultaneously.
Data Analysis
Head movements, localization accuracy, and SIN performance were analyzed and compared between subject groups. Localization accuracy was characterized as both the mean absolute error (MAE) and the average slope (m) of the target-response line of best fit, where a slope of one indicates no localization errors. Three head movement characteristics were analyzed: onset delay (seconds), absolute displacement (degrees), and total response time (seconds).
Statistical analyses were performed using MATLAB (R2024a; The Mathworks, Inc., Natick, MA). For SIN tasks, performance differences among NH, unaided, and aided groups were compared using a Wilcoxon rank sum test to account for non-normally distributed data. Localization accuracy underwent two distinct analyses: individual trial response error calculation (MAE) and summarized performance across the azimuthal array (slope). First, we calculated MAE by computing the absolute difference between each target and response azimuth using circular metrics. The absolute error is calculated based on a 360-degree scale to account for full-circle angular differences. This value is then “wrapped” to a 180-degree scale to reframe large angular discrepancies, ensuring large errors (e.g., 355o) are correctly represented as small errors (e.g., 5o). Any residual errors greater than 270o are adjusted to their correct values to maintain accuracy. Second, we used a robust linear regression to estimate the slope of target-response data for each subject across target azimuth, handling outliers and high-variance responses. The robust linear regression method, using an iteratively reweighted least-squares algorithm, provided stable and appropriate estimates of individual localization abilities by accounting for outliers.
The Speech, Spatial, and Qualities of Hearing Scale (SSQ)
The SSQ is a validated questionnaire measuring a range of hearing abilities, including hearing speech in competing contexts, the directional, distance, and movement components of spatial hearing, and the ability to segregate sounds and attend to simultaneous speech streams, mimicking real-world hearing13. SSD subjects completed the survey, responding to Form A based on their experiences without their CI and to Form B based on their aided experiences. Form B assesses changes in experience with the device compared to unaided experience. Form A is scored from 0–10, while Form B ranges from −5 to +5, with 0 indicating no change, negative values suggesting worsened aided experiences, and positive values indicating improvements.
Results
Subject Demographics
Twenty-eight NH subjects (mean age = 39, 61% female) and ten adults with SSD (mean age = 61, 60% female) were included. SSD subjects (n=10) were tested in both their unaided and CI conditions. The average age of onset of deafness was 57.2 years, average age of implantation was 59.3, and average age at time of testing was 61.3. 9/10 (90%) of subjects were implanted with a Cochlear America™ device, while one was implanted with a Med El™ implant. All subjects had severe to profound unilateral sensorineural hearing loss in relatively flat configurations. Without meaningful residual hearing, none were utilizing electroacoustic stimulation. A subset of data analyzed for SSD subjects has been previously presented14, but within subject comparisons to assess device benefit for SSD subjects is unique to this manuscript. Detailed demographic information for hearing impaired subjects are summarized in Table 1.
TABLE 1.
Subject demographic data
| Subject ID | Gender | Etiology | Deaf Ear | Age at Onset of SSD | Age at Implantation | Age at Testing (yr) | Internal Device | ADI National Percentile |
|---|---|---|---|---|---|---|---|---|
|
| ||||||||
| SSD023 | F | Sudden idiopathic | Left | 65.00 | 66.00 | 68.00 | Mi250 Synchrony 2 Flex 28 | 45.00 |
| SSD024 | F | Viral labyrinthitis | Left | 59.00 | 59.00 | 62.00 | Nucleus CI632 | 18.00 |
| SSD025 | F | Viral labyrinthitis | Right | 58.00 | 59.00 | 61.00 | Nucleus CI612 | 10.00 |
| SSD031 | M | Sudden idiopathic | Left | 69.00 | 71.00 | 78.00 | Nucleus CI532 | 39.00 |
| SSD032 | M | Viral labyrinthitis | Right | 53.00 | 54.00 | 55.00 | Nucleus CI612 | 32.00 |
| SSD035 | F | Post SSC plugging | Right | 56.00 | 57.00 | 58.00 | Nucleus CI612 | 58.00 |
| SSD036 | F | SSNHL | Left | 50.00 | 50.00 | 51.00 | Nucleus CI632 | 65.00 |
| SSD037 | F | Sudden idiopathic | Right | 40.00 | 48.00 | 49.00 | Nucleus CI632 | 42.00 |
| SSD038 | M | SSNHL | Right | 66.00 | 70.00 | 71.00 | Nucleus CI612 | 67.00 |
| SSD039 | M | SSNHL | Right | 56.00 | 59.00 | 60.00 | Nucleus CI622 | |
ADI =Area Deprivation Index, CI= cochlear implant, SSNHL = sudden sensorineural hearing loss, SSC= superior semicircular canal, SSD = single-sided deafness
Head Movement
Three components of head movement were analyzed: onset delay (seconds), absolute head displacement (degrees), and total response time (seconds). Onset delay measured the time before a subject began moving their head in response to a stimulus. Absolute head displacement quantified the total movement of the head in during the task. Total response time indicates how long a subject took from move onset to indicating localization response.
Total Absolute Head Displacement
NH controls had proportionally more total absolute head movement when the target sound was presented further away from center (Figure 2A; see supplemental Table 2A). The proportional pattern of increased head displacement with increasing distance from center (0°) is most accurate with more positive SNR (+10, +5, +2 dB), whereas there is more variability at more negative SNR (−10, −5, −2 dB), with increased total head displacement across all target locations. SSD and SSD-CI subjects did not demonstrate this pattern of proportional head movement and had relatively more total displacement at all conditions for all targets.
Figure 2:
Head movement data by SNR and target azimuth, corrected for side of deafness (positive values indicate targets or responses to the normal hearing ear).
In comparing NH and SSD-CI subjects, three-way ANOVA showed statistical significance for all main effects of Hearing Status (HS), SNR, and Target Azimuth (TA) [F=1.05e04, p<0.001], SNR [F=91.7, p<0.001], and TA [F=106, p<0.001], respectively, and all two-way and three-way interactions [p<0.001]. Repeated measures ANOVA, to compare SSD and SSD-CI conditions, revealed a significant main effect of TA [F=2.14, p=0.024] and a significant interaction of SNR:TA [F=2.26, p<0.001]. All other effects were not significant.
Head Movement Onset Delay
NH controls took an average of 1.45 seconds (s) before initiating head movement, while SSD and SSD-CI subjects waited 2.63 and 2.60 s, respectively. SSD and SSD-CI subject delay prior to initiating head movement was similar across all targets when averaged across all SNRs (Figure 2B; see supplemental Table 2B). Irrespective of SNR and TA, the NH group showed the least onset delay, followed SSD-CI.
In comparing NH and SSD-CI subjects, three-way ANOVA revealed significant main effects of HS [F=596, p<0.001], SNR [F=14.5, p<0.001], and TA [F=6.07, p<0.001], as well as a significant two-way interaction HS:TA [F=3.19, p<0.001]. The two-way interactions HS:SNR and SNR:TA, as well as the three-way interaction HS:SNR:TA were not significant. Repeated measures ANOVA, to compare SSD and SSD-CI conditions, revealed a significant effect of SNR [F=17.3, p<0.001] and TA [F=5.69, p<0.001]. The main effect of CI status, the two-way interactions of CI:SNR, CI:TA, and SNR:TA, as well as the three-way interaction CI:SNR:TA were not significant.
Total Response Time
Total response time varied between the three groups. NH controls averaged a total response time of 7.88 s, while SSD and SSD-CI subjects average total response time was 7.67 and 6.99 s, respectively (see supplemental Table 2C). SSD-CI condition shortened total response time beyond that of NH controls. While NH controls demonstrate a pattern of longer total response time proportional to increased degrees away from center (0°), SSD and SSD-CI subjects did not demonstrate the same pattern (Figure 2C).
In comparing NH and SSD-CI subjects, three-way ANOVA revealed a significant main effect of HS only [F=46.0, p<0.001]. All other effects were not significant. Repeated measures ANOVA, to compare SSD and SSD-CI conditions, revealed a significant main effect of CI status [F=5.16, p=0.049] and of TA [F=2.55, p=0.007], as well a significant two-way interaction SNR:TA [F=1.51, p=0.008] and a significant three-way interaction CI:SNR:TA [F=1.39, p=0.027]. The two-way interaction CI:TA were not significant [F=1.71, p=0.081]. The main effect of SNR and the two-way interaction CI:SNR were not significant.
Sound Localization
Sound localization accuracy was analyzed via both MAE (Figure 3A) and the slope of the target-response line of best fit (Figure 4A). To better visualize differences between groups and effects of SNR, localization accuracy (MAE, slope of the target-response line of best fit) was plotted by SNR (Figure 3B, 4B).
Figure 3:
Swarmplot of Mean Absolute Error (MAE) in localization performance for each trial for NH, SSD, and SSD-CI groups, across all SNR. Width reflects response frequency, and the blue line depicts the mean across trials (A). Mean Absolute Error (MAE) values by SNR for all groups. Error bars represent the standard error of the mean (SEM) (B).
Figure 4:
SSD-CI localization per SNR. Response (crosshatch) and target-response best fit lines (red line) (A). Mean slopes generated from (A) and depicted in (B). Error bars represent SEM.
In comparing NH and SSD-CI subjects MAE, three-way ANOVA revealed significant main effects of HS [F=4140, p<0.001], SNR [F=36.3, p<0.001], and TA [F=41.8, p<0.001], as well as significant interactions of all factors [p<0.001]. The two-way interaction of HS:SNR [F=21.9, p<0.001], HS:TA [F=8.86, p<0.001], and SNR:TA were all significant [F=2.69; p<0.001], as well as the three-way interaction [F=2.48, p<0.001]. Post-hoc analysis showed significant differences in MAE between control and experimental groups across all HS, SNR, and TA combinations [p<0.05].
Repeated measures ANOVA, to compare SSD and SSD-CI conditions, revealed a significant effect of CI status [F=4140, p<0.001] and SNR [F=19.0, p<0.001], but no significant effect of TA[F=1.52, p=0.135]. There is a significant interactions of CI status and SNR [F=9.47, p<0.001], of SNR and TA [F=1520; p=0.04], and of CI, SNR, and TA [F=420, p=0.011], however there is no significant interaction of CI and TA [F=0.66, p=0.78]. Post-hoc comparisons show that SNR-10 was significantly different from all other SNRs [p<0.001].
NH subjects showed the highest slope values overall, followed by SSD-CI, and SSD regardless of SNR. Consistent with MAE, NH continued to show the best overall accuracy, followed by SSD-CI. To further characterize localization performance between groups by SNR, the mean slope of the line of best fit for each group per SNR is demonstrated in Figure 4.
Comparing NH and SSD-CI subjects in a two-way ANOVA, there are significant main effects of HS [F=324, p<0.001] and SNR [F=5.56, p<0.001]. The two-way interaction between HS:SNR was also significant [F=5.78, p<0.001]. Repeated measures ANOVA to compare SSD and SSD-CI groups showed significant main effects of CI status [F=12.1, p=0.008] and SNR [F=4.15, p=0.002], and the interaction between CI status and SNR was significant [F=4.5, p=0.001]. Post-hoc comparisons show that SNR −10 was significantly different from all other SNR except −5 [p<0.02].
Though there is a significant improvement in localization accuracy between SSD and SSD-CI, the improvement seen by SSD-CI groups does not reach the level of NH controls at any SNR and does not increasingly improve as SNR becomes more positive.
SIN Performance
NH controls were compared to SSD-unaided, and additional comparison was made for SSD subjects with and without CI for SIN performance (Figure 5A). Examining NH and SSD-CI subjects in a two-way ANOVA, there are significant main effects of HS [F=33.1, p<0.001], SNR [F=1.33e03, p<0.001], and target ear (TE) [F=11.2, p<0.001]. The two-way interactions between HS:SNR and SNR:TE were not significant [p>0.05], while SNR:TE [F=3.7; p<0.001] and the three-way interaction of HS:SNR:TEar [F=2.16, p=0.044] were significant. Repeated measures ANOVA between SSD and SSD-CI reveals CI status as a significant main effect [F=140, p<0.001]. Two-way interactions between SNR:CI [F=64.0, p<0.001], and TE:CI are significant [F=16.4, p<0.001], and there was no significant difference in the three-way interaction SNR:TE:CI. In the unaided condition, speech sounds in noise presented to the hearing ear yielded better performance (Figure 5B), while in the CI condition this differential between presentation direction was no longer present (Figure 5C). When SNR was matched, results showed no difference between NH and SSD-CI across any of the SNRs.
Figure 5:
Speech performance by SNR for all groups (A) and by presentation direction for unaided (B) and aided (C) SSD subjects. Error bars represent the SEM
The Speech, Spatial, and Qualities of Hearing Scale (SSQ)
Eight of the 10 SSD subjects completed both Form A&B. Form A assessed unaided scores in each domain, and the average scores per domain were calculated per subject (see supplemental Table 3). SSD-unaided subjects experienced relative difficulty in spatial hearing compared to the other domains (see supplemental Figure 6). Form B assessed relative benefit with CI. Form B median values for overall scores (see supplemental Table 3; see supplemental Figure 6) demonstrate meager improvement in aided experience with a wide variability in responses
Discussion
Compared to individuals with NH, patients with SSD face increased difficulty interacting with their environment and a diminished quality of life15–18. Binaural hearing is essential for sound localization and understanding SIN. Head movements in response to auditory and dynamic ear-level acoustical cues are essential to localization19–22, and individuals with NH use head movements to alter acoustical cues to optimize performance on binaural tasks23–25.
Limited studies indicate that patients with SSD, as monaural listeners, generally exhibit compensatory head movements and greater errors when localizing sound2,4,26, continuing to rely on monaural cue optimization2,3,27. How individuals with SSD optimize monaural cues in complex listening environments is poorly understood. The study utilizes a novel combination SIN and localization testing paradigm designed to allow for natural head movements, closely mimicking real-world human behavior in complex listening tasks. Elucidating the relationship between simultaneous real-time localization, speech-in-noise ability, head movements, and CI device use are fundamental to advancing individualized device programming and adding a novel testing metric to the current audiometric and evaluative battery for device benefit.
Head Movements
In examining total absolute head displacement, NH subjects showed proportional displacement relative to the target source, while SSD subjects demonstrated less variability, with no significant difference between displacements toward the deaf or hearing ear. Although previous studies have shown that CI use can reduce gross head movements during sound localization for SSD subjects4, our results showed that SNR and TA impacted total movement, but CI use did not have a significant effect.
Little is known about the timing of head movements during listening in SSD subjects. In our study, NH subjects initiated head movement shortly after stimulus onset, while SSD subjects waited much longer, in some cases until after stimulus presentation, to begin to move. It has been well established that head movement during listening tasks improves localization accuracy23,25. Permissive head movements generate dynamic head-related transfer functions and the resulting available acoustical cues contain additional salient information to optimize performance when compared to similar tasks restricting head movement. In our dataset, the lost opportunity to generate these more salient cues resulting from SSD does not appear to be mitigated by the presence of a CI. SSD subjects also demonstrated reduced overall response time. Though potentially shortened by delayed movement onset, the reduced response time may also indicate less engagement or reliance on sound lateralization rather than localization.
Sound Localization
Though there is a significant improvement in localization accuracy between SSD and SSD-CI, SSD-CI performance does not reach NH performance at any SNR and does not increasingly improve with favorable SNR. While SSD individuals show generally poor unaided localization ability, regardless of SNR, there is improvement in MAE and slope of the target-response best fit line with a CI. The sound localization improvements and reductions in mean absolute error seen with CI use reach a point at which no additional gains are noted, despite the easiest listening conditions. This improvement may reflect a degree of monoaural cue contribution to localization3, and the asymptotic nature of the improvement may reflect limitations in the device and ITD resolution10,28,29 such that individuals are lateralizing rather than localizing sound. Though improvements with CI use in localization accuracy reach statistical significance for SSD subjects, the large remaining discrepancy from normal hearing performance brings into question the real-world benefits of the improvement. As such, the clinical significance of these changes remains largely unknown.
SIN Performance
This study assessed SIN performance while listeners localized speech sounds, allowing free head movement across varying SNRs and TAs. Although previous literature shows varied results, our SSD-CI group performed similarly to NH controls. Additionally, speech performance improved when sounds were presented to the deaf ear with a CI compared to without, approximating NH performance in the best.
Speech, Spatial, and Qualities of Hearing Scale (SSQ)
SSD subjects reported the greatest challenge in spatial hearing without their CI but noted benefits across all subscales with their CI. Previous studies support significant improvements in spatial and speech-hearing subscales with CI use, although there is more variability in hearing quality8,9,11,30,31.
Limitations
Restricted sample size, given the extensive in-person testing required of each participant, is a limitation of this study. Long testing hours over multiple days and rare discomfort with the protocol limited the ability to collect a larger data pool. NH controls were on average 39 years old, while SSD subjects averaged 57 years old. While NH controls were on average younger than SSD subjects, a barrier to age matching was the strict criteria to have audiometrically-verified normal hearing bilaterally. Finally, future studies may consider using multi-talker babble with this protocol as the background noise to better simulate the real-world experience. Continued protocol expansion and additional subject recruitment are required to extrapolate these findings on a broader scale and inform clinical changes to audiometric testing protocols.
Conclusion
Although cochlear implants provide individuals with SSD a statistically significant improvement in sound-source localization, the clinical significance of the changes remains challenging to quantify. Contrastingly, the cochlear implant does improve speech understanding in noise to that of normal hearing controls. Head movement analysis highlights compensatory behaviors in SSD individuals. Understanding the relationship between simultaneous localization, the ability to understand speech-in-noise, head movements, and CI use is crucial for advancing individualized device programming and adding novel testing metrics to the current audiometric battery.
Most crucially in this rapidly growing patient population, we recognize that cochlear implantation for SSD enhances binaural hearing but requires proper patient expectation counseling to improve selection and reduce non-use. With the rise of personalized medicine, this study aims to optimize device performance and increase the usage of hearing assistive devices by tailoring them to individual needs.
Supplementary Material
Figure 6: Box plots for SSQ Form A and Form B. Shaded area above the median = first quartile. Shaded area below the median = third quartile. Whiskers = minimum to maximum values.
TABLE 2a.
Mean total head displacement per target location (degrees)
| Target | Response | Response Differences | |||
|---|---|---|---|---|---|
| NH | SSD | SSD-CI | Δ NH - SSD-CI | Δ SSD-CI - SSD | |
|
| |||||
| −180 | 172.71 | 127.93 | 150.07 | 22.64 | 22.14 |
| −150 | 163.10 | 126.06 | 143.22 | 19.89 | 17.15 |
| −120 | 143.65 | 125.33 | 137.44 | 6.21 | 12.11 |
| −90 | 112.49 | 126.04 | 139.66 | −27.17 | 13.62 |
| −60 | 97.55 | 120.10 | 131.62 | −34.06 | 11.52 |
| −30 | 74.57 | 123.27 | 133.81 | −59.24 | 10.54 |
| 0 | 63.23 | 122.31 | 149.47 | −86.24 | 27.16 |
| 30 | 68.34 | 132.07 | 155.12 | −86.78 | 23.05 |
| 60 | 89.11 | 129.47 | 163.16 | −74.05 | 33.69 |
| 90 | 112.65 | 133.90 | 166.73 | −54.08 | 32.83 |
| 120 | 137.08 | 139.37 | 163.79 | −26.72 | 24.42 |
| 150 | 157.84 | 135.60 | 154.97 | 2.87 | 19.37 |
Target = Target sound location in the azimuth plane. NH = normal hearing control, SSD = single-sided deaf (unaided), SSD-CI =single-sided deaf with CI (aided).
Within Δ Group A - Group B, negative values indication that Group B waited longer before initiating head movement than Group A.
TABLE 2b.
Mean movement onset delay per target location (seconds)
| Target | Response | Response Differences | |||
|---|---|---|---|---|---|
| NH | SSD | SSD-CI | Δ NH - SSD-CI | Δ SSD-CI - SSD | |
|
| |||||
| −180 | 2.11 | 2.81 | 2.74 | −0.63 | −0.08 |
| −150 | 1.45 | 2.83 | 2.67 | −1.22 | −0.15 |
| −120 | 1.30 | 2.87 | 2.90 | −1.59 | 0.02 |
| −90 | 1.27 | 2.71 | 2.77 | −I.SO | 0.06 |
| −60 | 1.35 | 2.62 | 2.51 | −1.16 | −0.11 |
| −30 | 1.60 | 2.66 | 2.54 | −0.93 | −0.13 |
| 30 | 1.48 | 2.32 | 2.64 | −1.16 | 0.32 |
| 60 | 1.28 | 2.37 | 2.41 | −1.13 | 0.04 |
| 90 | 1.29 | 2.49 | 2.29 | −1.00 | −0.20 |
| 120 | 1.32 | 2.61 | 2.43 | −1.11 | −0.18 |
| 150 | 1.54 | 2.67 | 2.65 | −1.11 | −0.02 |
Target = Target sound location in the azimuth plane. NH = normal hearing control, SSD = single-sided deaf (unaided), SSD-CI =single-sided deaf with CI (aided).
Within Δ Group A - Group B, negative values indication that Group B waited longer before initiating head movement than Group A.
TABLE 2c.
Mean total response time per target location (seconds)
| Target | Response | Response Differences | |||
|---|---|---|---|---|---|
| NH | SSD | SSD-CI | Δ NH - SSD-CI | Δ SSD-CI - SSD | |
|
| |||||
| −180 | 8.48 | 7.87 | 7.24 | 1.24 | −0.63 |
| −150 | 8.14 | 7.93 | 7.13 | I.OJ | −0.80 |
| −120 | 7.92 | 7.75 | 6.99 | 0.92 | −0.75 |
| −90 | 7.61 | 7.97 | 6.95 | 0.65 | −1.02 |
| −60 | 7.67 | 7.63 | 6.76 | 0.90 | −0.87 |
| −30 | 7.72 | 7.59 | 6.77 | 0.96 | −0.83 |
| 30 | 7.44 | 7.42 | 6.93 | 0.51 | −0.49 |
| 60 | 7.58 | 7.31 | 6.83 | 0.76 | −0.48 |
| 90 | 7.87 | 7.42 | 7.00 | 0.86 | −0.42 |
| 120 | 7.98 | 7.77 | 7.10 | 0.87 | −0.67 |
| 150 | 8.26 | 7.66 | 7.14 | 1.12 | −0.51 |
Target = Target sound location in the azimuth plane. NH = normal hearing control, SSD = single-sided deaf (unaided), SSD-CI =single-sided deaf with CI (aided).
Within Δ Group A - Group B, negative values indication that Group B waited longer before initiating head movement than Group A.
TABLE 3.
The Speech, Spatial and Qualities of Hearing Scale (SSQ)
| SSQA | |||||
|---|---|---|---|---|---|
| Overall | Speech Hearing | Spatial Hearing | Qualities of Hearing | ||
|
| |||||
| Mean | 4.57 | 4.54 | 2.75 | 6.31 | |
| SD | 0.71 | 0.89 | 1.21 | 1.11 | |
| Min | 3.59 | 3.19 | 0.74 | 5.13 | |
| 0.25 | 4.05 | 4.01 | 2.38 | 5.57 | |
| 0.50 | 4.52 | 4.66 | 2.91 | 5.78 | |
| 0.75 | 4.98 | 5.13 | 3.39 | 7.12 | |
| Max | 5.71 | 5.65 | 4.40 | 8.06 | |
|
| |||||
| SSQB | |||||
| Overall | Speech Hearing | Spatial Hearing | Qualities of Hearing | ||
|
| |||||
| Mean | 0.79 | 0.81 | 0.53 | 1.01 | |
| SD | 1.25 | 1.32 | 1.14 | 1.63 | |
| Min | −1.20 | −1.09 | −2.00 | −0.89 | |
| 0.25 | 0.00 | −0.29 | 0.31 | −0.16 | |
| 0.50 | 0.77 | 1.07 | 1.00 | 0.58 | |
| 0.75 | 1.56 | 1.63 | 1.06 | 1.88 | |
| Max | 2.55 | 2.57 | 1.71 | 3.94 | |
Funding:
American Academy of Otolaryngology—Head and Neck Surgery Foundation Resident Research Grant, AwardID 1053411 (NII), NIH R25 Research Education Program: 5R25DC020262-02 (OA)
Footnotes
Conflicts of Interest: None
References
- 1.Baguley D m., Bird J, Humphriss R l., Prevost A t. The evidence base for the application of contralateral bone anchored hearing aids in acquired unilateral sensorineural hearing loss in adults. Clin Otolaryngol. 2006;31(1):6–14. doi: 10.1111/j.1749-4486.2006.01137.x [DOI] [PubMed] [Google Scholar]
- 2.Ludwig AA, Meuret S, Battmer RD, Schönwiesner M, Fuchs M, Ernst A. Sound Localization in Single-Sided Deaf Participants Provided With a Cochlear Implant. Front Psychol. 2021;12:753339. doi: 10.3389/fpsyg.2021.753339 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Slattery WH 3rd, Middlebrooks JC. Monaural sound localization: acute versus chronic unilateral impairment. Hear Res. 1994. May;75(1–2):38–46. doi: 10.1016/0378-5955(94)90053-1. [DOI] [PubMed] [Google Scholar]
- 4.Bernstein JGW, Phatak SA, Schuchman GI, Stakhovskaya OA, Rivera AL, Brungart DS. Single-Sided Deafness Cochlear Implant Sound-Localization Behavior With Multiple Concurrent Sources. Ear Hear. 2022;43(1):206–219. doi: 10.1097/AUD.0000000000001089 [DOI] [PubMed] [Google Scholar]
- 5.Wilson B, Dorman M. The Design of Cochlear Implants; in Niparko J (Ed): Cochlear Implants, Principals and Practices. Lippincott, Philadelphia, 2009, Pp 95–136. [Google Scholar]
- 6.Dorman MF, Zeitler D, Cook SJ, et al. Interaural Level Difference Cues Determine Sound Source Localization by Single-Sided Deaf Patients Fit with a Cochlear Implant. Audiol Neurotol. 2015;20(3):183–188. doi: 10.1159/000375394 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Dirks C, Nelson PB, Sladen DP, Oxenham AJ. Mechanisms of Localization and Speech Perception with Colocated and Spatially Separated Noise and Speech Maskers Under Single-Sided Deafness with a Cochlear Implant. Ear Hear. 2019;40(6):1293–1306. doi: 10.1097/AUD.0000000000000708 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Daher GS, Kocharyan A, Dillon MT, Carlson ML. Cochlear Implantation Outcomes in Adults With Single-Sided Deafness: A Systematic Review and Meta-analysis. Otol Neurotol. 2023;44(4):297–309. doi: 10.1097/MAO.0000000000003833 [DOI] [PubMed] [Google Scholar]
- 9.Marx M, Mosnier I, Venail F, et al. Cochlear Implantation and Other Treatments in Single-Sided Deafness and Asymmetric Hearing Loss: Results of a National Multicenter Study Including a Randomized Controlled Trial. Audiol Neurotol. 2021;26(6):414–424. doi: 10.1159/000514085 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Wess JM, Brungart DS, Bernstein JGW. The Effect of Interaural Mismatches on Contralateral Unmasking With Single-Sided Vocoders. Ear Hear. 2017;38(3):374. doi: 10.1097/AUD.0000000000000374 [DOI] [PubMed] [Google Scholar]
- 11.Távora-Vieira D, Acharya A, Rajan GP. What can we learn from adult cochlear implant recipients with single-sided deafness who became elective non-users? Cochlear Implants Int. 2020;21(4):220–227. doi: 10.1080/14670100.2020.1733746 [DOI] [PubMed] [Google Scholar]
- 12.Anidi C, Abdulrazzak O, Jones G, Epperson MV, Ibrahim NI, Banakis Hartl RM. Auditory Localization Performance in Cochlear Implant Recipients With Single-Sided Deafness: The Challenges and Limitations of Current Outcome Metrics. Otol Neurotol. 2024;45(8):878–886. doi: 10.1097/MAO.0000000000004273 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Gatehouse S, Noble W. The Speech, Spatial and Qualities of Hearing Scale (SSQ). Int J Audiol. 2004;43(2):85–99. doi: 10.1080/14992020400050014 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Abdulrazzak O, Banakis Hartl RM. Comparing Bilateral and Single-Sided Deaf Cochlear Implant Recipients in a Novel Speech-in-Noise and Localization Task. Otolaryngol Head Neck Surg. 2025. (in press; ). doi: 10.1002/ohn.1187 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Harris MS, Boyce L, Pisoni DB, Shafiro V, Moberly AC. The Relationship Between Environmental Sound Awareness and Speech Recognition Skills in Experienced Cochlear Implant Users. Otol Neurotol. 2017;38(9):e308–e314. doi: 10.1097/MAO.0000000000001514 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Lin FR, Thorpe R, Gordon-Salant S, Ferrucci L. Hearing Loss Prevalence and Risk Factors Among Older Adults in the United States. J Gerontol A Biol Sci Med Sci. 2011;66A(5):582–590. doi: 10.1093/gerona/glr002 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Giolas TG, Wark DJ. Communication Problems Associated with Unilateral Hearing Loss. J Speech Hear Disord. 1967;32(4):336–343. doi: 10.1044/jshd.3204.336 [DOI] [PubMed] [Google Scholar]
- 18.Wie OB, Pripp AH, Tvete O. Unilateral deafness in adults: Effects on communication and social interaction. Ann Otol Rhinol Laryngol. 2010;119(11):772–781. [PubMed] [Google Scholar]
- 19.Ito S, Si Y, Feldheim DA, Litke AM. Spectral cues are necessary to encode azimuthal auditory space in the mouse superior colliculus. Nat Commun. 2020;11(1):1087. doi: 10.1038/s41467-020-14897-7 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Grothe B, Pecka M, McAlpine D. Mechanisms of Sound Localization in Mammals. Physiol Rev. 2010;90(3):983–1012. doi: 10.1152/physrev.00026.2009 [DOI] [PubMed] [Google Scholar]
- 21.Moore DR. Anatomy and Physiology of Binaural Hearing. Audiology. 1991;30(3):125–134. doi: 10.3109/00206099109072878 [DOI] [PubMed] [Google Scholar]
- 22.Dubno JR, Ahlstrom JB, Horwitz AR. Binaural Advantage for Younger and Older Adults With Normal Hearing. J Speech Lang Hear Res. 2008;51(2):539–556. doi: 10.1044/1092-4388(2008/039) [DOI] [PubMed] [Google Scholar]
- 23.Pollack I, Rose M. Effect of head movement on the localization of sounds in the equatorial plane. Percept Psychophys. 1967;2(12):591–596. doi: 10.3758/BF03210274 [DOI] [Google Scholar]
- 24.Perrott DR, Ambarsoom H, Tucker J. Changes in head position as a measure of auditory localization performance: Auditory psychomotor coordination under monaural and binaural listening conditions. J Acoust Soc Am. 1987;82(5):1637–1645. doi: 10.1121/1.395155 [DOI] [PubMed] [Google Scholar]
- 25.Thurlow WR, Runge PS. Effect of Induced Head Movements on Localization of Direction of Sounds. J Acoust Soc Am. 1967;42(2):480–488. doi: 10.1121/1.1910604 [DOI] [PubMed] [Google Scholar]
- 26.Brimijoin WO, McShefferty D, Akeroyd MA. Undirected head movements of listeners with asymmetrical hearing impairment during a speech-in-noise task. Hear Res. 2012;283(1):162–168. doi: 10.1016/j.heares.2011.10.009 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Loiselle LH, Dorman MF, Yost WA, Cook SJ, Gifford RH. Using ILD or ITD Cues for Sound Source Localization and Speech Understanding in a Complex Listening Environment by Listeners With Bilateral and With Hearing-Preservation Cochlear Implants. J Speech Lang Hear Res. 2016;59(4):810–818. doi: 10.1044/2015_JSLHR-H-14-0355 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Zirn S, Arndt S, Aschendorff A, Wesarg T. Interaural stimulation timing in single sided deaf cochlear implant users. Hear Res. 2015;328:148–156. doi: 10.1016/j.heares.2015.08.010 [DOI] [PubMed] [Google Scholar]
- 29.Dillon MT, Rooth MA, Canfarotta MW, Richter ME, Thompson NJ, Brown KD. Sound Source Localization by Cochlear Implant Recipients with Normal Hearing in the Contralateral Ear: Effects of Spectral Content and Duration of Listening Experience. Audiol Neurotol. 2022;27(6):437–448. doi: 10.1159/000523969 [DOI] [PubMed] [Google Scholar]
- 30.Arndt S, Laszig R, Aschendorff A, Hassepass F, Beck R, Wesarg T. Cochlear implant treatment of patients with single-sided deafness or asymmetric hearing loss. HNO. 2017;65(Suppl 2):98–108. doi: 10.1007/s00106-016-0297-5 [DOI] [PubMed] [Google Scholar]
- 31.Dillon MT, Buss E, Rooth MA, et al. Effect of Cochlear Implantation on Quality of Life in Adults with Unilateral Hearing Loss. Audiol Neurotol. 2018;22(4–5):259–271. doi: 10.1159/000484079 [DOI] [PubMed] [Google Scholar]
Associated Data
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Supplementary Materials
Figure 6: Box plots for SSQ Form A and Form B. Shaded area above the median = first quartile. Shaded area below the median = third quartile. Whiskers = minimum to maximum values.