AJA

Research Article

The Spatial Hearing Questionnaire: Data From Individuals With Normal Hearing Ann E. Perreau,a Bryn Spejcher,a Hua Ou,b and Richard Tylerc

Purpose: Although a number of questionnaires are available to assess hearing aid benefit and general hearing disability, relatively few investigate spatial hearing ability in more complex listening situations. The aim of this study was to document the performance of individuals with normal hearing using the Spatial Hearing Questionnaire (SHQ; Tyler, Perreau, & Ji, 2009) and to compare performance with published data from cochlear implant (CI) users. Method: Fifty-one participants with normal hearing participated. All participants completed the 24-item SHQ. Also, a factor analysis and reliability tests were performed. Results: Performance on the SHQ was high (87%) for the participants with normal hearing. Subjective ratings varied across different listening situations: Understanding speech in

quiet (98%) was rated higher than sound localization (84%) and understanding speech in a background of noise (85%). Compared with previously published data (Tyler, Perreau, & Ji, 2009), listeners with normal hearing rated their spatial hearing ability significantly better than bilateral and unilateral CI users. Results confirmed that the SHQ is a reliable measure of spatial hearing ability for listeners with normal hearing. Conclusions: Overall, results indicated that the SHQ is able to capture expected differences between individuals with normal hearing and CI users. These new data can be used as targets following the provision of hearing devices.

H

Correspondence to Ann E. Perreau: [email protected] Editor: Larry Humes

Jacobson, & Hug, 1990; Ventry & Weinstein, 1982). Other questionnaires have been developed to measure the effects of specific hearing disorders, such as tinnitus. For example, the Tinnitus Handicap Questionnaire (Kuk, Tyler, Russell, & Jordan, 1990) and the Tinnitus Functional Index (Meikle et al., 2011) were developed to measure treatment-related changes of tinnitus. Despite numerous questionnaires assessing the social, emotional, and physical aspects of hearing loss or hearing disorders, relatively few focus on situations that emphasize the spatial perception of sound. Spatial hearing is the ability of a listener to perceive sounds in more complex listening situations, which requires binaural, or two-eared, processing of important auditory cues. These interaural timing and level differences provide the cues necessary to localize sound sources and segregate different speech and noise sources (Blauert, 1997). Patients with hearing loss often report difficulty in these situations in which spatial hearing is emphasized, yet their hearing abilities in these specific, complex situations are often not directly assessed either subjectively or objectively in routine clinical practice. Two questionnaires are available for measuring selfreported localization ability, including the Speech, Spatial and Qualities of Hearing Scale (SSQ; Gatehouse & Noble, 2004) and the Spatial Hearing Questionnaire (SHQ; Tyler, Perreau, & Ji, 2009). The SSQ assesses the difficulties faced

Received September 17, 2013 Revision received November 17, 2013 Accepted December 27, 2013 DOI: 10.1044/2014_AJA-13-0049

Disclosure: The authors have declared that no competing interests existed at the time of publication.

earing self-report outcome measures, such as patient surveys and questionnaires, provide clinicians with valuable information about a patient’s personal perspectives on their hearing abilities related to their hearing impairment and the degree of handicap associated with their hearing loss. In this way, a patient’s hearing abilities can be evaluated subjectively and compared with objective hearing test results, such as pure-tone or speech audiometry, to provide a more comprehensive representation of the patient’s current functioning level and help to identify target areas for intervention. Multiple questionnaires have been developed for gathering selfassessment outcomes from individuals with a hearing impairment, with the emphasis mostly on hearing aid benefit and satisfaction (e.g., Cox & Alexander, 1995, 1999, 2001, 2002; Dillon, James, & Ginis, 1997; Gatehouse, 1999; Tyler, Baker, & Armstrong-Bednall, 1983; Tyler & Smith, 1983) and general hearing disability and handicap (e.g., Giolas, Owens, Lamb, & Schubert, 1979; Newman, Weinstein,

a

Augustana College, Rock Island, IL Illinois State University, Normal c University of Iowa, Iowa City b

Key Words: spatial hearing, questionnaires, cochlear implants

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by individuals with hearing loss in a wide range of listening domains via three distinct scales: (a) speech; (b) spatial (direction, distance, and movement); and (c) other qualities of hearing (segregation of sounds, naturalness and clarity of sound). The SSQ has 49 items and is intended to be administered in an interview (Gatehouse & Noble, 2004), although more recently five- and 12-item screening versions have been developed (Demeester et al., 2012; Noble, Jensen, Naylor, Bhullar, & Akeroyd, 2013). Research on the SSQ has revealed that the questionnaire is sensitive to performance differences among various patient groups, including cochlear implant (CI) and hearing aid users, and between patients with asymmetrical and symmetrical hearing loss (Beijen, Snik, & Mylanus, 2007; Noble, 2010; Noble & Gatehouse, 2004, 2006; Noble, Tyler, Dunn, & Bhullar, 2008). The SHQ (see the Appendix; Tyler et al., 2009) was specifically developed to measure an individual’s subjective hearing abilities in situations in which binaural hearing is emphasized. Eight subscales were used to differentiate characteristics important for binaural hearing, including the perception of male voices (Items 1, 5, 9, 13, and 17), female voices (Items 2, 6, 10, 14, and 18), children’s voices (Items 3, 7, 11, 15, and 19), music listening (Items 4, 8, 12, 16, and 20), sound localization (Items 13–24), speech perception in quiet (Items 1–4), speech perception in noise with target and noise sources from the front (Items 5–8), and speech perception in noise with target and noise sources spatially separate (Items 9–12). Previous psychometric evaluation has been performed for the SHQ using bilateral and unilateral CI users (Tyler et al., 2009). The results suggested high reliability (Cronbach’s a = 0.98) and scores that loaded onto three factors that represent the subscales of Localization, Speech in Noise and Music, and Speech in Quiet and explain over 80% of the variance in scores (Tyler et al., 2009). Additionally, previous studies have revealed that the SHQ is well correlated to that of the SSQ (Potvin, Punte, & Van de Heyning, 2011; Tyler et al., 2009) as well as performance on objective test measures, including speech perception in quiet (e.g., consonant-nucleus-consonant monosyllabic words; Tillman & Carhart, 1966) and the Hearing in Noise Test (Nilsson, Soli, & Sullivan, 1994), speech perception in noise (i.e., an adaptive spondee word test; Tyler, Noble, Dunn, & Witt, 2006), and localization (i.e., a horizontal localization test using eight loudspeakers; Dunn, Tyler, & Witt, 2005). In sum, research indicates that both the SSQ and SHQ are reliable and valid questionnaires assessing spatial hearing performance for patients with hearing loss and sensitive to differences among different hearing profiles. Although the questionnaires appear to overlap in their assessment of listener traits, there are important differences in the SSQ and SHQ that may suggest use of one questionnaire over the other. First, the SSQ was validated using an interview format between the participant and administrator (Gatehouse & Noble, 2004), whereas the SHQ was validated in a self-administered format (Tyler et al., 2009). Using a selfadministered format has several advantages over an interview style in that it is a more time-efficient approach with less

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influence from the administrator, albeit with more demands on the participant. Studies have since evaluated the use of the SSQ in a self-administered approach, and results suggested similar scores between the two administration methods, but lower test–retest reliability when the SSQ is self-administered, especially for the spatial subscale (Singh & Pichora-Fuller, 2010). Second, the length of the SHQ is shorter with 24 questions, whereas the SSQ contains 49 questions. In testing or clinical situations in which time is a factor, the SHQ may be more advantageous given its shorter length. Finally, the two questionnaires assess different aspects of hearing disability. For example, the SSQ contains several general questions not specifically related to spatial hearing (i.e., “Does your own voice sound natural to you?” and “When you listen to music, can you make out which instruments are playing?”). The SHQ focuses specifically on spatial hearing and attempts to separate spatial hearing performance with stimuli of different frequency content (e.g., male voices vs. children’s voices). Although normative data are available for the SSQ (Banh, Singh, & Pichora-Fuller, 2012), similar data from individuals with normal hearing have not been previously investigated using the SHQ. This could be a valuable contribution in the clinical utility of the tool in audiological assessment in several ways. Namely, performance from individuals with normal hearing establishes the best possible outcome that can be documented from those with relatively good hearing across different listening situations. In this way, performance from individuals with normal hearing can be compared with that of individuals with hearing impairment to gauge the overall differences in performance due to hearing loss. In addition, this also serves as a baseline for comparing the change in performance following hearing aid and/or CI fittings, which will be important as the demands for documenting improvements in patient performance increase. Here, we measured SHQ scores using listeners with normal hearing to determine what constitutes best performance on the questionnaire and then compared these scores from individuals with normal hearing with the scores of those who have severe-to-profound hearing loss using one or two CIs. By comparing scores from listeners with normal hearing with unilateral and bilateral CI users, we can assess the impact of hearing loss on subjective performance in situations in which binaural hearing is emphasized. We also conducted psychometric evaluation of the SHQ using data from individuals with normal hearing by investigating the factor structure and reliability of the questionnaire and compared these data with previously published results on the SHQ (Potvin et al., 2011; Tyler et al., 2009).

Method Participants Participants over the age of 18 years with normal hearing in both ears were invited to participate in this study. The participants were recruited from a small, private college

campus in an urban setting. Of the total 58 adult participants who were recruited, 51 had normal hearing and were eligible to participate. Of the 51 participants, there were seven men and 44 women. Participants’ ages ranged from 18 to 61 years, with the average age at 34.2 years (SD = 14.2). For all participants, the mean education level was 15.4 years (SD = 3.8). Participants were provided with a small honorarium for their participation. The local institutional review board approved this study.

Procedure Pure-tone air conduction audiometric testing was performed bilaterally for octave frequencies of 250 Hz– 8000 Hz using a GSI-61 clinical audiometer. Testing was conducted in a sound-treated booth on the Augustana College campus (Rock Island, IL). Audiometric testing was performed using supra-aural headphones, and a push button was used by the participants to report their responses. The right ear was tested first before the left ear for the participants. The criterion for normal hearing for the study included hearing thresholds between 0 and 25 dB HL across the frequencies of 250 Hz–8000 Hz. Figure 1 displays the mean pure-tone audiometric thresholds for both ears averaged across all participants. Next, the SHQ (Tyler et al., 2009) was administered to the participants by a research assistant in a quiet setting. Participants used paper and pencil to report a score to each question on the SHQ using a scale ranging from 0 to 100, where 0 indicates that the situation is very difficult and 100 indicates that the situation is very easy (see the Appendix). Figure 1. Mean pure-tone hearing thresholds (in dB HL) for both ears for all 51 participants. Mean thresholds are plotted in the filled circles. The minimum threshold is shown in the dotted line, and the maximum thresholds are shown in the dashed line. Brackets represent ±1 standard deviation.

All participants were independently able to report their answers on the SHQ without any modifications or outside assistance. The participants completed each question; no items were left blank.

Data Analysis SHQ ratings for the participants with normal hearing were reported descriptively for the eight subscales and the total score, as well as for the 24 individual items. In addition, scores on the eight subscales and the total score for participants in this study were compared with that of CI users previously published by Tyler et al. (2009). The previous data were from bilateral (n = 42) and unilateral (n = 100) CI users who had completed an identical SHQ after using their CI for 12 months or more. The data were analyzed using two-tailed, independent-samples t tests to compare total and subscale mean scores on the SHQ for the participants with normal hearing and unilateral CI participants and the participants with normal hearing and bilateral CI participants. Factor analysis. A factor analysis was also performed to determine the relationship among the items in the SHQ based on these data obtained from listeners with normal hearing. First, the Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy was computed to determine whether factor analysis was appropriate for the data. This score provides an estimate of the proportion of variance in the variables due to underlying factors. Here, a KMO score of 0.77, or close to 1, indicated that factor analysis was an appropriate test. As done in previous psychometric evaluations of the SHQ (Potvin et al., 2011; Tyler et al., 2009), a principal factor analysis was also conducted here using varimax rotation to spread the variation more evenly across the factor loadings.

Reliability To determine reliability of the SHQ for normal hearing listeners with normal hearing Cronbach’s a and item-total correlation coefficients were computed. Additionally, Pearson correlation coefficients were used to compare results for each of the eight subscales with the total SHQ score. High correlation coefficients, or scores close to 1, are indicative of good reliability. For all statistical tests, statistical significance was defined as a p < .05. Data were analyzed using the Statistical Package for the Social Sciences (SPSS; Version 21.0).

Results The mean subscale and total scores for the 51 listeners with normal hearing on the SHQ are displayed in Table 1. Subscale scores were highest for the Understanding Speechin-Quiet subscale (M = 98.3, SD = 1.8; SE = 0.26) and lowest for the Localization subscale (M = 84.1, SD = 13.2; SE = 1.9). Further, scores were similar across many subscales, including those corresponding to adult male, adult female, and children’s voices (M = 89.5, 89.4, and 87.0, respectively), and between the Speech-in-Noise subscales

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Table 1. Mean Spatial Hearing Questionnaire subscale and the total scores for the participants with normal hearing (n = 51). Test measure

M (SD, SE)

[95% CI]

Male Female Children Music Localization Quiet Noise-front Noise-separate Total

89.5 (7.3, 1.0) 89.4 (7.1, 1.0) 87.0 (9.2, 1.3) 87.7 (8.9, 1.2) 84.2 (13.1, 1.8) 98.3 (1.8, 0.3) 84.9 (11.0, 1.5) 85.8 (10.7, 1.5) 86.6 (8.9, 1.2)

[87.5, 91.6] [87.4, 91.4] [84.5, 89.6] [85.2, 90.2] [80.5, 87.9] [97.8, 98.8] [81.8, 88.0] [82.8, 88.7] [84.3, 89.3]

Note. CI = confidence interval.

comparing target and noise sources front or spatially separated (M = 84.9 and 85.75). The total score was computed by calculating the average of all 24 items, which revealed an overall mean of 86.8% (SD = 8.9; SE = 1.3). Of importance, the distribution of SHQ scores was highly negatively skewed, suggesting that, for these participants with normal hearing, the SHQ scores were not normally distributed. Table 2 displays mean scores averaged across all 51 participants with normal hearing for each of the 24 items from the SHQ. Individual item scores ranged from 76.8% to 98.8%, with the lowest performance reported on Item 22, which related to the ability to perceive distance of a sound (e.g., “You hear a car off in the distance, but you cannot see it. How accurately can you tell where it is coming from?”) and the highest performance on Item 1, related to the ability

Table 2. Mean scores for all 24 items of the Spatial Hearing Questionnaire for the participants with normal hearing (n = 51). Item

M

SD

SE

1. Man’s voice in quiet 2. Woman’s voice in quiet 3. Child’s voice in quiet 4. Music in quiet 5. Man in front, noise behind 6. Woman in front, noise behind 7. Child in front, noise behind 8. Music and noise in front 9. Man in front, noise to side 10. Woman in front, noise to side 11. Child in front, noise to side 12. Music in front, noise to side 13. Location of man’s voice 14. Location of woman’s voice 15. Location of child’s voice 16. Location of music 17. Location of man’s voice, behind 18. Location of woman’s voice, behind 19. Location of child’s voice, behind 20. Location of music, behind 21. Location of airplane 22. Direction of car 23. Movement of car 24. Distance of sound source

98.8 98.7 97.1 98.4 86.8 86.5 82.9 82.9 87.1 86.8 83.4 85.1 86.7 86.9 85.0 85.1 88.2 88.2 86.6 87.0 77.5 76.8 83.3 78.1

1.7 2.0 3.9 2.6 10.4 10.5 13.0 13.4 10.6 10.3 12.7 11.0 12.3 11.9 13.2 13.5 13.0 12.8 13.9 13.5 16.8 19.4 18.0 19.8

0.3 0.4 0.8 0.5 1.8 1.7 2.3 2.4 2.0 1.9 2.3 1.9 2.1 2.1 2.4 2.4 2.6 2.6 2.8 2.7 2.9 3.2 3.3 3.7

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to understand speech in quiet (e.g., “A man talking to you is standing in front of you. It is a very quiet room. How well can you understand him?”). In addition, the standard error, or estimation of variability, was also quite small for Items 1–4 assessing speech in quiet (0.2–0.5) as compared with Items 21–24 on localization and distance (2.4–2.8). Figure 2 shows results on the SHQ for the participants with normal hearing and participants using one or two CIs. The data for the 100 unilateral and 42 bilateral CI users were previously published by Tyler et al. (2009). Comparing scores among individuals with normal hearing with those with severe-to-profound hearing loss using CIs revealed several important findings. First, SHQ scores were significantly higher for individuals with normal hearing as compared with both groups of CI users for all eight subscale and total scores. Total scores on the SHQ averaged 84%–98% for the participants with normal hearing, whereas scores averaged 39%–78% and 56%–84% for the unilateral and CI users, respectively. Comparing the individuals with normal hearing with the unilateral CI users, results were highly significant: male voices, t(139) = 13.77, p < .0001; female voices, t(135) = 13.55, p < .0001; children’s voices, t(142) = 14.54, p < .0001; music, t(136) = 15.22, p < .0001; localization, t(149) = 14.00, p = .0001; speech in quiet, t(103) = 11.75, p < .0001; speech in noise from the front, t(144) = 10.61, p < .0001; speech in noise with spatially separate target and noise sources, t(143) = 10.67, p < .0001; and total SHQ score, t(145) = 14.42, p < .0001. Again, comparing listeners with normal hearing with bilateral CI users, the results were highly

Figure 2. Mean performance for listeners with normal hearing (NH; black bars; n = 51), unilateral cochlear implant (CI) users (white bars; n = 100), and bilateral CI users (gray bars; n = 42) for all eight subscales and the total Spatial Hearing Questionnaire score. Higher scores indicate better subjective hearing abilities. Error bars represent standard errors.

significant: male voices, t(49) = 6.42, p < .0001; female voices, t(51) = 6.94, p < .0001; children’s voices, t(52) = 7.49, p < .0001; music, t(50) = 7.60, p < .0001; localization, t(58) = 6.24, p < .0001; speech in quiet, t(42) = 6.37, p < .001; speech in noise from the front, t(57) = 6.45, p < .0001; speech in noise with spatially separate target and noise sources, t(56) = 6.96, p < .0001; and total SHQ score, t(54) = 7.10, p < .0001. Across all participant groups, including the listeners with normal hearing, the same pattern of results as would be expected was found in the subscale scores of the SHQ. For example, the highest mean score was found on the Understanding Speech-in-Quiet subscale; that is, scores of 98.2%, 78.0%, and 84.1% were obtained for the normalhearing, unilateral CI, and bilateral CI groups, respectively. In contrast, the lowest mean score across all three groups was found on the Localization subscale, with scores of 84.1%, 38.6%, and 56.3% for the participants with normal hearing, a unilateral CI, and bilateral CIs. Similarly, subjective ability was also described as more difficult for all groups for the perception of children’s voices and music compared with that of adult male and female voices, although not as drastic of a change in scores for the participants with normal hearing (difference scores of È2%) compared with the CI users (difference scores of È10% for unilateral and bilateral CI users). Further, understanding speech in quiet was rated significantly higher compared with understanding speech in noise-front; that is, difference scores of 13.5%, 25.7%, and 23.7% emerged between these subscales for normal hearing, unilateral CI, and bilateral CI, respectively. Finally, there was no difference in scores for any of the groups when comparing understanding of speech in a background of noise for target and noise sources from the front and when spatially separated (difference scores between the two subscales of 0.8%, 0.9%, and 1.5% for participants with normal hearing, unilateral CI, and bilateral CIs, respectively). In sum, although fairly predictable, the SHQ results adequately reflect the increasing demands on listeners as the level of difficulty in each situation increases. Factor analysis. The factor structure of the SHQ was evaluated using the extraction method of principalcomponent analysis. Prior to factor analysis, however, a logit transformation was initially performed to normalize the SHQ scores due to the observed skewness in the data (i.e., SHQ scores from the participants with normal hearing were clustered near the ceiling). The logit transformation redistributes the scores along a percentage from 0% to 100%, which improves the results of an analysis when data are highly skewed. First, a proportion, p, is calculated by dividing each SHQ score by 100. Then the logit transformation is computed using the following equation: Logit (p) = log(p) – log(1 – p). Because Logit (p) cannot be computed when the value of p is 0 or 1, an adjustment was applied so that when p = 1, a value of 0.9999 was entered, and when p = 0, a value of 0.0001 was entered. This transformation was conducted for each participant’s item, subscale, and total score on the SHQ. The results of factor analysis are displayed in Table 3. To determine the shared features among the items, the

Table 3. Rotated component matrix for the four factors. Factor Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

1

2

3

4

0.07 0.08 0.22 0.00 0.06 0.08 0.26 0.07 0.42 0.42 0.23 0.04 0.90 0.90 0.88 0.89 0.86 0.86 0.90 0.86 0.47 0.58 0.57 0.49

0.14 0.11 0.11 –0.07 0.86 0.90 0.89 0.62 0.81 0.80 0.87 0.58 0.29 0.30 0.32 0.15 0.07 0.07 0.10 0.22 0.22 0.20 0.12 0.13

0.93 0.95 0.78 0.67 0.14 0.07 –0.03 0.10 0.09 0.08 0.04 0.08 –0.01 –0.04 –0.03 0.01 0.19 0.19 0.14 0.17 0.08 0.01 0.10 –0.06

–0.02 –0.04 –0.04 0.39 0.18 0.15 0.17 0.58 –0.06 –0.08 0.26 0.62 0.15 0.14 0.13 0.18 0.19 0.18 0.15 0.14 0.58 0.72 0.54 0.74

Note. Variables are grouped by factor (in bold).

communality values, or proportion of variance in each item, were first examined. All communality values were at least 0.60, and most values (17 of 24) were at least 0.80. Communality values that are greater than 0.50 indicate high correlations between the items and the factors. The number of factors is determined by analyzing eigenvalues. The eigenvalue represents the amount of variance in the items accounted for by each component or factor. Often only those factors with eigenvalues greater than 1.0 are retained. In this study, four factors with eigenvalues greater than 1.0 emerged from the questionnaire data. For Factors 1, 2, 3, and 4, the eigenvalues were 11.4, 3.6, 2.8, and 1.7, respectively. The four factors explained 47.6%, 14.8%, 11.7%, and 7.0% of the variance, respectively, and in total, over 81.1% of the variance. Factor loadings were rotated using varimax rotation with Kaiser normalization, which spreads the variance more equally among the components. Shown in Table 3 is the rotated component matrix for the four factors. Evaluating the factor structure of the SHQ revealed eight items loaded on Factor 1, eight items on Factor 2, four items on Factor 3, and four items on Factor 4. The first factor consisted of Items 13–20 and represents sound localization abilities with speech or music as the sound source. Factor 2 consisted of Items 5–12 and represents recognizing speech and music in a background of noise. Factor 3 consisted of Items 1–4 and correlates to the recognizing speech and music in quiet. Finally, Factor 4 consisted of Items 21–24 and correlates to spatial hearing with other sound sources (e.g., car, airplane, music). There

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were three items that overlapped or loaded equally on two factors. These included Item 8, relating to recognizing music in front with noise in front (loaded on Factors 2 and 4); Item 12, music in front with noise to side (loaded on Factors 2 and 4); and Item 23, movement of a car (loaded on Factors 1 and 4). All three of these items relate to the fourth factor of spatial hearing with other sound sources. However, for Items 8 and 12, it was determined that the most appropriate placement for these items was with Factor 2, representing recognition of speech and music in background noise.

Reliability Reliability was assessed using Cronbach’s a, itemtotal correlations, and subscale and total correlations based on data obtained from the listeners with normal hearing. Cronbach’s a was 0.93 for the SHQ, which indicates good internal consistency reliability. Item-total correlations were computed and revealed significant findings. For Items 1 through 4, these values ranged from .14 to .22, whereas for Items 5 through 24, item-total correlations ranged from .63 to .79. Therefore, low correlations were found for the first four items of the questionnaire, which represent recognition of speech and music in quiet. The remaining 20 items of the questionnaire correlated well with the SHQ total score. Finally, Pearson correlation coefficients were computed to compare scores from the eight subscales and the SHQ total score. Here, we found significant correlations for seven of the subscales to the total score, including male voices, female voices, children’s voices, music, localization, noise-front, and noise-separate (r = .78–.96; p < .001). The correlation between the Speech-in-Quiet subscale and the total SHQ score was not significant (r = .233; p = .10). Overall, the results of the item-total correlations and the Pearson correlation between the subscales and total score indicate that, based on the data from these participants with normal hearing, Items 1–4 representing recognition of speech and music in quiet are not related to the remaining items of the SHQ assessing spatial hearing performance. This point is discussed more thoroughly in the Discussion.

Discussion The primary aim of this investigation was to describe the subjective abilities of individuals with normal hearing on spatial hearing tasks as assessed using the SHQ that would serve to establish a criterion or “benchmark” for comparison across different groups of individuals, including CI users. Here, we found that performance on the SHQ was quite high as would be expected for listeners with normal hearing, with scores averaging 87% overall. In addition, for the participants with normal hearing, subjective ratings were varied across different listening situations: Understanding speech in quiet (98%) was rated higher than sound localization (84%) and understanding speech in a background of noise (È85%). No other performance differences were found across the other four domains on the SHQ related to the perception of male, female, and children’s voices and music, indicating that

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individuals with normal hearing perceive these listening situations to be relatively similar. Additionally, scores from individual items on the SHQ suggest that even participants with normal hearing reported some degree of difficulty in certain situations. For instance, Items 21–24 assessing the direction of moving sound sources, the movement of a car, and the distance of a stationary sound source were found to be the most difficult for the participants with normal hearing. Scores averaged 77%–83% across these four items. In addition, Items 7 and 8 (82.9% and 82.9%, respectively) assessing the ability to hear a child’s voice or music in the presence of a masker were also moderately difficult for the participants. These listening situations represent more complex acoustical environments that are encountered in everyday life, which rely on binaural cues as well as top-down and bottom-up processing (Colburn, Shinn-Cunningham, Kidd, & Durlach, 2006). In comparison, other listening situations presented only slight or no difficulty to the participants with normal hearing, such as determining the location of a man’s voice with out a visual representation (85%–87%) and speech understanding in quiet (97%–98%). Overall, the data from the SHQ indicate that individuals with normal hearing report a similar level of difficulty that would be expected as the complexity of the listening situation increases, from listening in quiet, to locating sounds in space, to tracking the movement and direction of sound coming from a moving object. In addition, this predicted change in SHQ scores with increasing levels of difficulty suggests that the SHQ is sensitive to differences in performance among various situations and stimuli as designed. To investigate the differences in spatial hearing ability among different groups of listeners, this study’s results from listeners with normal hearing on the SHQ were also compared with previously published results of CI users. In the previous study by Tyler et al. (2009), subjective performance was assessed for 100 unilateral and 42 bilateral CI users. In that study, significantly higher scores were reported for the bilateral CI users compared with the unilateral CI users for the total SHQ score, as well as six of the eight subscales. Here, we found that listeners with normal hearing rate their spatial hearing ability significantly better than both bilateral and unilateral CI groups across all aspects assessed with the SHQ, which included speech-in-quiet, speech-innoise, and localization tasks. For the SHQ total score, scores from the participants with normal hearing were 35.5% and 24.1% higher compared with the unilateral and bilateral CI users, respectively. Interestingly, although the scores were significantly different among the groups with normal hearing and the CI groups, the pattern of responses were similar, revealing similar challenges in a variety of listening situations assessed with the SHQ regardless of hearing profile. More specifically, the easiest listening situation for listeners with normal hearing and CI users alike was understanding speech in quiet, whereas the most difficult listening situation was sound localization. Previous studies comparing performance among individuals with symmetric and asymmetric hearing loss have also found significant differences in scores on the SHQ (Potvin et al., 2011). Taken together, these results

suggest that the SHQ is sensitive to differences in subjective spatial hearing ability that may be observed among different hearing profiles, including those with and without hearing loss. The results of the factor analysis revealed four underlying factors correlating to the scores of participants with normal hearing. Factor 1 represented sound localization with speech or music sound sources. Factor 2 related to understanding speech and music in background noise. Factor 3 represented understanding speech and music in quiet. Finally, Factor 4 related to spatial hearing with other sound sources (i.e., a moving car or airplane). Previously, investigations of the SHQ using CI users (Tyler et al., 2009) and a Dutch version using patients with symmetrical and asymmetrical hearing loss (Potvin et al., 2011) have shown similar results with three to four underlying factors. Overall, this suggests that, although the SHQ is composed of eight subscales representing different characteristics important to binaural hearing, the data from listeners with normal hearing indicates that there are four separate factors that explain their responses on the questionnaire. From the data reported here, it appears that the subscales on the SHQ overlap on these factors to a certain extent; however, this is not surprising given that the individual items do overlap among many of the subscales (e.g., Item 16 contributes to both the Music and Localization subscales). In addition, the data from listeners with normal hearing resulted in high scores on all spatial hearing tasks. These high scores on the SHQ make it difficult for the factor analysis to distinguish and group different spatial hearing functions. Additional work will be needed from a more diverse population to accurately document different factors relevant to spatial hearing. As suggested by Potvin et al. (2011), the majority of the SHQ items relate to spatial hearing abilities, with the exception of Items 1 through 4. These items specifically refer to speech or music recognition in quiet. Analyzing the reliability results in this study, we found low item-total correlations for these first four items and a nonsignificant correlation between the Speech-in-Quiet subscale (consisting of Items 1 through 4) and the total SHQ score. By comparison, the remaining item-total correlations were high, and the other seven subscales were highly correlated to the total SHQ score. As well, the Cronbach’s a was high at 0.93 and comparable to 0.98 that has been reported in previous investigations of the SHQ (Potvin et al., 2011; Tyler et al., 2009). In sum, these results suggest that the SHQ is a reliable assessment of spatial hearing ability; however, when applied to listeners with normal hearing, it is important that the subscale of Speech in Quiet be separated from the remaining subscales assessing spatial hearing ability. Further, the results from this study provide a means to compare SHQ scores among listeners with normal hearing and listeners with hearing impairment on tasks of spatial perception. Because most clinics do not have access to the equipment (e.g., a localization array) necessary to test spatial hearing skills directly with their patients, we must rely on subjective outcome measures to assess the spatial hearing difficulties of patients faced in everyday life. The SHQ can be

helpful to clinicians to determine the degree of disability for a given patient related to localization and spatial hearing ability that might otherwise be ignored in standard clinical practice. This study has several limitations that should be mentioned. First, questionnaire data, which are subjective in nature, can lead to unreliable results if not obtained properly. However, every effort was taken to ensure that these results were accurate, including describing the questionnaire and the scaling to the participants prior to obtaining any data. Second, this study was limited to only a subset of individuals with normal hearing who have a high degree of education and who were also younger (Mage = 32.4 and 34.5 years for male and female participants, respectively) than the CI participants (Mage = 54.2 and 55.8 years for male and female participants, respectively) tested in the Tyler et al. (2009) study. However, the age range of the participants in this study was fairly large, ranging from 18 to 61 years as compared with ranging from 18 to 89 years in Tyler et al. (2009). Additional attempts to gather data from elderly patients with normal hearing across all speech frequencies of 250–8000 Hz may prove difficult due to the age-related onset of hearing loss. Despite these limitations, this study supported the high sensitivity of the SHQ in teasing out differences in spatial perception among listeners with normal hearing and listeners with severe-to-profound hearing loss using one or two CIs. In addition, the results revealed that the relative difficulty experienced by listeners with normal hearing as evidenced in their subjective responses correlate well with the increasing complexity of various listening situations, further supporting the sensitivity of this measurement tool. Future studies should investigate use of the questionnaire with other patient populations and various degrees of hearing loss, including unilateral and bilateral hearing aid users, and individuals using a hearing aid and CI in opposite ears, and compare subjective responses on the SHQ with results from objective measures (e.g., localization testing and speech-in-noise tasks).

Acknowledgments This research was supported in part by the New Faculty Research Award and Larry Jones Research Fellowship awarded to Ann E. Perreau from Augustana College. This research was also supported by the National Institute on Deafness and Other Communication Disorders, National Institutes of Health Research Grant 2P50DC000242-26A1; General Clinical Research Centers Program, Division of Research Resources, National Institutes of Health Grant RR00059; the Lions Clubs International Foundation; and the Iowa Lions Foundation. We thank Elizabeth Hughes for her efforts with data collection and Fen A. Fenwick for statistical support. We also thank the participants for their time.

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Appendix The Spatial Hearing Questionnaire ___________________________________________________________________________________________________________________ Name: _______________________________ Date: _______________________________ Please respond to each question with a number from 0 to 100. Number 0 means the situation would be very difficult. Number 100 means the situation would be very easy. 0 = Very Difficult

100 = Very Easy

1.

A man talking to you is standing in front of you. It is a very quiet room. How well can you understand him?

2.

A woman talking to you is standing in front of you. It is a very quiet room. How well can you understand her?

3.

A child talking to you is standing in front of you. It is a very quiet room. How well can you understand the child?

4.

You are listening to music that is comfortably loud coming from in front of you. It is a very quiet room. How easy or difficult is it to hear the music clearly?

5.

A man talking to you is standing in front of you. There is a loud fan directly behind him. How well can you understand him?

6.

A woman talking to you is standing in front of you. There is a loud fan directly behind her. How well can you understand her?

7.

A child talking to you is standing in front of you. There is a loud fan directly behind them. How well can you understand the child?

8.

You are listening to comfortably loud music coming from in front of you. There is also a loud fan in front of you. How easy or difficult is it to hear the music clearly?

9.

A man talking to you is standing in front of you. There is a loud fan off to one side. How well can you understand him?

10.

A woman talking to you is standing in front of you. There is a loud fan off to one side. How well can you understand her?

11.

A child talking to you is standing in front of you. There is a loud fan off to one side. How well can you understand the child?

12.

You are listening to comfortably loud music coming from in front of you. There is also a loud fan off to one side. How easy or difficult is it to hear the music clearly?

13.

How well are you able to determine the location of a man’s voice when you cannot see him?

14.

How well are you able to determine the location of a woman’s voice when you cannot see her?

15.

How well are you able to determine the location of a child’s voice when you cannot see the child?

16.

How well are you able to determine the location of a music source, say a radio, when you cannot see it?

17.

How well are you able to determine the location of a man’s voice when he is behind you?

18.

How well are you able to determine the location of a woman’s voice when she is behind you?

19.

How well are you able to determine the location of a child’s voice when the child is behind you?

20.

How well are you able to determine the location of a music source, say a radio, when it is behind you?

21.

How well are you able to determine the location of a flying airplane when you cannot see it?

22.

You hear a car off in the distance, but you cannot see it. How accurately can you tell where it is coming from?

23.

If you were to stand beside a road and close your eyes, how well could you tell what direction a car was going as it passed by?

24.

You are in a room in a house and hear a loud sound. How easily can you tell how far away the sound was?

Note. The Spatial Hearing Questionnaire has been translated into 10 other languages: French, Spanish, Swedish, Hebrew, German, Polish, Korean, Chinese (both Simplified and Traditional dialects), and Dutch. Please contact Rich Tyler ([email protected]) for more information.

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