Introduction
In clinical practice, it is common to identify individuals who report hearing difficulties but do not have hearing loss. Studies have reported that 15% of adults with normal hearing thresholds experience hearing difficulties [1], often associated with auditory processing disorders, auditory neuropathy, and hidden hearing loss [2]. However, the reasons for this remain unclear and multifactorial.
Age-related changes, auditory processing deficits, and cognitive factors contribute to difficulties in understanding speech in challenging environments and localizing sounds despite normal hearing thresholds [3-5]. Older adults with normal hearing thresholds can present with deficits in spatial hearing and temporal processing [4,6], and auditory processing deficits in general are found to be associated with higher levels of self-reported hearing difficulties [5,7]. For instance, temporal deficits are associated with poor performance in understanding speech in noisy environments, while spatial deficits can affect the ability to segregate sounds in complex auditory environments, impacting speech understanding and communication [4].
These self-reported difficulties may be explained to some extent by deficits in extended high frequencies (EHFs). There is growing evidence that EHFs are important in improving listening skills. Roup, et al. [8] reported that adults with poor EHF hearing benefit less from spatial separation, which may influence their speech perception in challenging environments. Mishra, et al. [9] reported that EHF loss compromised frequency resolution, even when hearing thresholds were within the normal range. This could contribute to the difficulties experienced by some individuals in understanding speech in noisy environments. This finding is further supported by Saxena, et al. [10], who investigated the functional effects of EHF hearing loss in adults with normal audiograms. Their results showed that participants with EHF hearing loss reported higher levels of hearing difficulties than the normal EHF hearing group, indicating that individuals with impaired EHF may experience difficulty understanding speech in challenging environments, impaired spatial hearing abilities, and compromised hearing quality.
These abilities are particularly crucial in everyday situations, such as following conversations in crowded spaces or identifying the direction of approaching sounds, which are often compromised in older adults with EHF hearing loss.
Despite evidence of the importance of EHFs, their relationship with self-reported difficulties remains unclear. While reports indicate the contribution of EHFs to several listening skills, such as spatial separation and frequency resolution [11], how EHF hearing loss, auditory processing, and self-reported difficulties have not been systematically explored. Furthermore, many studies have focused on younger individuals or individuals who report hearing problems, limiting the understanding of how these factors interact in older adults with clinically normal-hearing thresholds. This is particularly relevant, as individuals in their 50s often exhibit EHF hearing loss, which has a more pronounced impact than in younger adults on their listening abilities [11,12].
This study investigated self-perceptions of listening abilities in younger (<30 years) and older (≥50 years) adults with normal hearing, focusing on the role of auditory processing skills and EHFs in perceived difficulties. This will help understand the mechanisms underlying the difficulties experienced in particular by older adults with clinically normal hearing.
Subjects and Methods
Participants
Fifty adults (32 females) aged 19–71 years (mean=40.3, standard deviation=17.4) with clinically normal hearing participated in this study (Table 1), which was conducted at the Audiology Clinic of Andrés Bello University, Viña del Mar, Chile, and approved by the institution’s Faculty of Medicine Ethics Committee. All participants provided written informed consent.
The inclusion criteria for participants were: 1) aged 18–30 or ≥50 years; 2) pure tone thresholds ≤20 dB at 0.25–3 kHz, ≤25 dB at 4 kHz, and ≤30 dB at 6 and 8 kHz, with interaural asymmetry ≤10 dB HL at 0.5, 1, 2, and 3 kHz [3]; 3) type “A” (bilateral) tympanograms; 4) ipsilateral acoustic reflexes at 0.5, 1, and 2 kHz; and 5) native Spanish speaking. The exclusion criteria were: 1) diagnosed hearing loss and 2) self-reported neurological issues (e.g., stroke, degenerative disease, head injury).
Participants were allocated into two age groups: the younger group (YG) comprising individuals under 30 years, and the older group (OG) comprising individuals aged 50 years and older. This age group was based on previous reports that observed significant differences in the Speech, Spatial and Qualities of Hearing Scale (SSQ12) scores between groups [13], and individuals in their 50s often experience increased EHF hearing thresholds and changes in auditory processing abilities [12-14]. Thus, this age range was selected to maximize the contrast between YG and OG, which would not be the case for similar age ranges.
Sample size calculation
Statistical power analyses using G*Power 3.1 (Heinrich-Heine-Universität Düsseldorf) estimated a target sample size of 44 participants for the SSQ12 questionnaire, based on prior studies of individuals with normal hearing (α=5%, power 80%, effect size 0.9) [13].
Procedures
The participants’ assessments included: 1) pure-tone audiometry (0.25–8 kHz); 2) EHF audiometry (9–16 kHz); 3) middle ear assessment; 4) the dichotic digits test (DDT) [15]; 5) speech recognition in noise (SIN, 0 dB SNR) [15]; 6) the gaps in noise test (GIN) [16]; 7) SSQ12 [17], and 8) Amsterdam Inventory for Auditory Disability and Handicap (AIADH) [18] questionnaires (Supplementary Material in the online-only Data Supplement). The tests were administered via an AC40 audiometer (Interacoustics) using the Audacity software (version 3.1.3; The Muse Group, www.audacityteam.org), and an ASUS VivoBook laptop in a sound booth. The participants completed the questionnaires during on-site interviews.
Data analysis
Nonparametric tests were used to compare groups when assumptions of normality were not met. Between-group comparisons of young and older adults were conducted using Mann–Whitney U-tests, and Spearman rank correlations were used to test the correlation between variables. Bonferroni correction was used to correct for multiple comparisons. p-values set at <0.05 were considered statistically significant. IBM SPSS Statistics software (version 26.0; IBM Corp.) was used for data analysis.
Results
Questionnaires
Group comparison of the SSQ12 questionnaire
Mann–Whitney U test results revealed that the OG reported greater difficulty on the spatial subscale (U=147.500, p=0.001, r=0.455) compared to the YG, indicating that older adults experienced more difficulties in localizing sounds and determining the distance and movement of sounds. Lower overall SSQ12 scores also indicated greater difficulty in the OG (U=194.500, p=0.022, r=0.324) (Table 2).
When analyzing individual items, the OG reported higher listening difficulties when understanding speech in noise (U=188.000, p=0.012, r=-0.355) and multiple speakers (U=210.000, p=0.043, r=0.286) compared to the YG. Additionally, the OG showed more difficulty identifying sounds than the YG (U=209.000, p=0.035, r=0.285) (Table 2). Lastly, the OG experienced significant difficulties in judging the distance and movement of a sound (Item 7: U=148.500, p=0.001, r=0.461 and Item 8: U=133.000, p<0.001, r=0.517). This suggests that older adults may struggle in crowded environments, such as family gatherings or work meetings, with tasks like following conversations, localizing outdoor sounds, or recognizing alarm signals.
Comparison of groups for AIADH
In AIADH, the OG reported greater difficulty understanding speech in quiet environments (U=208.000, p=0.030, r=-0.307) and differentiating sounds (U=193.500, p=0.015, r=0.344) than the YG. Overall scores also indicate that the OG experienced more hearing difficulties than the YG group (U=201.500, p=0.031, r=0.305) (Table 3). The findings suggest that challenges are not limited to noisy environments; older adults may also experience difficulties with auditory processing in quieter settings, such as at home.
Auditory processing tests
Dichotic digits test
The OG performed significantly worse in both ears compared to the YG (right ear: U=134.500, p<0.001, r=0.515; left ear: U=108.000, p<0.001, r=0.569) (Table 4 and Fig. 1). When comparing the asymmetry between ears, it was observed that the difference was larger in the OG (U=433.000, p=0.018, r=0.701). The asymmetry index was calculated as [(RE-LE)/(RE+LE)]×100 [19]. Overall DDT performance (%) was higher in the YG (U=81.000, p<0.001, r=0.639).
Gaps in noise
No significant differences were observed between the ears for threshold and performance (%). Thus, composite scores were used for the analysis. The OG showed a higher threshold and lower performance (%) than the YG (U=506.000, p<0.001, r=0.534; U=95.500, p<0.001, r=0.596, respectively) (Table 4 and Fig. 1). This indicates that the OG required larger gaps to achieve detection and was less accurate in detecting the gaps presented. Elevated GIN thresholds suggest a clinical reduction in temporal resolution of auditory processing, which can contribute to challenges in speech perception, particularly in noisy environments.
Speech in noise
No significant differences were observed between the ears regarding performance (%); therefore, composite scores were used for the analysis. No significant differences in speech recognition in noise scores were observed between the YG and OG (U=308.000, p=0.930) (Table 4 and Fig. 1).
Puretone thresholds average for 0.5, 1, 2 and 4 kHz (PTA4) differed between groups; therefore, we conducted a correlation analysis between auditory processing tests and hearing thresholds. The Spearman’s correlations revealed that higher hearing thresholds were associated with poorer performance on the DDT (right and left ears %) (rs=-0.485, p<0.0033; rs=-0.464, p<0.0033, respectively) and the GIN test (%) (rs=-0.464, p<0.0033). This suggests a connection between audibility and age in test performance, as PTA4 thresholds are higher in the OG.
EHF audiometry
No significant differences were observed between the ears for the PTA4-high frequencies (HF) (11.2, 12.5, 14, and 16 kHz) composite scores. These frequencies were selected because they demonstrated consistent responses across all participants and have been widely used in previous research [11].
The OG had higher EHF thresholds than the YG (U=195.000, p=0.022, r=0.849) (Table 1). Spearman’s correlations indicated significant positive relationships between GIN thresholds and PTA4-HF (rs=0.553, p<0.001), indicating that individuals with higher hearing thresholds had poorer (higher) GIN thresholds. Additionally, there was a significant negative correlation between PTA4-HF and DDT scores in both ears (right ear: rs=-0.532, p<0.001; left ear: rs=-0.561, p<0.001). No correlations were found between PTA4-HF and the SSQ12 or AIADH subscales or their respective overall scores after applying a Bonferroni correction for multiple comparisons.
Correlations between questionnaires and auditory processing tests
Spearman’s correlations showed a significant positive relationship between the overall scores from the SSQ12 and AIADH questionnaires (Table 5), indicating that higher SSQ12 ratings were related to higher AIADH ratings. In addition, DDT-LE scores correlated with AIADH ratings, indicating that people with higher performance on DDT-LE demonstrated better listening abilities (Table 5). The DDT-LE results offer valuable insights into cognitive functions, particularly memory, making it useful for assessing auditory and cognitive abilities in clinical settings.
Discussion
This study aimed to identify differences in self-reported listening difficulties between older and younger adults with clinically normal hearing. Auditory processing deficits and EHF loss were also explored to evaluate their potential contributions to these difficulties. Findings showed that older adults experienced significantly more listening difficulties than young adults, mainly in spatial hearing tasks. Also, older adults performed worse on binaural separation and temporal resolution tasks. Further analysis revealed that older adults exhibited EHF hearing loss, which may contribute to difficulty handling complex auditory information in daily life situations.
These findings highlight the need for early identification of subtle auditory deficits in older adults, even those with clinically normal hearing. Routine audiological assessments may benefit from incorporating EHF testing and central auditory processing evaluations to detect early signs of auditory decline. Clinically, interventions such as auditory training programs targeting spatial hearing and temporal processing, as well as communication strategies for challenging listening environments, may help mitigate the impact of these deficits on daily life.
Self-perceived listening abilities
The OG reported spatial and dynamic listening challenges, including sound localization, movement detection, and following group conversations. Helfer, et al. [20] reported that middle-aged adults experienced more difficulties in understanding speech than younger adults, suggesting that hearing difficulties may emerge relatively early in the ageing process and before hearing loss is clinically detected.
The age effect on SSQ results has been modest but consistent across several studies. Von Gablenz, et al. [21] reported a general trend of decreasing SSQ scores with age, particularly in the spatial subscale. Similarly, Banh, et al. [3] reported that younger adults scored higher on most SSQ items than older adults. These findings align with our results, where the older adults scored lower on the spatial subscale (YG: 9.1; OG: 7.9), indicating an age-related decline in spatial auditory abilities.
Given the spatial hearing difficulties reported by older adults, targeted interventions could mitigate their impact. Auditory training programs focusing on sound localization and spatial awareness could be beneficial. Spatially oriented auditory training and dichotic listening tasks can enhance binaural processing. Additionally, assistive listening devices, such as remote microphones or hearing aids with directional microphones, can improve speech perception in complex environments. Cognitive training programs that strengthen attention and working memory may support the processing of spatial auditory cues.
Interestingly, older adults also reported difficulties in understanding speech in quiet but consistently in noisy environments. Mukari, et al. [22] found that poorer high-frequency thresholds (4 and 8 kHz) significantly contributed to speech recognition in a quiet environment. Although all participants in our study had normal hearing (PTA4 ≤20 dB HL), the older adults had poorer hearing thresholds than the younger participants. This is consistent with Kamerer, et al. [2], who reported that individuals with thresholds ≥10 dB HL had difficulties similar to those with moderate hearing loss.
Older adults might report fewer listening difficulties in noisy environments, indicating the development of compensatory mechanisms to manage noisy environments [23]. For example, older adults often rely on top-down cognitive resources to compensate for declines in peripheral auditory processing, which can aid in segregating and attending to target speech signals [24]. Age-related changes in auditory processing abilities may trigger mechanisms to compensate for noisy environments, but increase their awareness of difficulties in quiet environments [25].
Auditory processing performance
The older adults presented deficits in auditory processing, particularly binaural separation and temporal resolution, as evidenced by poorer DDT and GIN performance. These changes are likely associated with age-related changes in the central auditory system, reflecting reduced interhemispheric communication [26] and deficits in separating competitive stimuli [6,27] and processing complex auditory stimuli.
Increased GIN thresholds and lower performance demonstrated temporal resolution deficits in the older group. These deficits impact speech intelligibility in noisy environments and indicate broader age-related central auditory changes [6].
These deficits could be clinically assessed using more challenging speech-in-noise tests, temporal processing assessments, and objective measures like auditory evoked potentials.
Unexpectedly, no significant group differences were observed in the SIN performance. These may reflect limitations in the test material, as the 0 dB SNR used may not have been sufficiently challenging to detect deficits.
The significant correlations between PTA4, DDT, and GIN suggest that subtle changes in hearing sensitivity within the normal range can impact auditory processing. These results highlight the connection between peripheral hearing and central auditory processing, particularly for temporal resolution and binaural hearing.
Self-reported and objective measures
No consistent correlations were observed between self-reported difficulties and auditory processing test scores, except DDT (LE) and AIADH scores. This correlation suggests that left ear performance may reflect cognitive changes affecting listening abilities [14]. However, these results differ from Bamiou, et al. [5], who reported significant correlations between auditory processing tests (e.g., DDT, GIN) and hearing questionnaires (SSQ50 and modified AIADH). Differences in sample characteristics, such as including individuals with clinically diagnosed auditory processing disorder, may explain these differences. This discrepancy between objective and subjective assessment suggests the complexity of auditory perception and suggests that additional factors, such as the interaction listening environment, may influence self-reported challenges [27] and cognitive abilities [3,20]. From a clinical perspective, relying solely on standard audiometric evaluations or auditory processing tests may not fully capture the functional listening difficulties experienced by older adults. Incorporating self-report questionnaires, such as the SSQ12 and AIADH, can provide valuable insights into real-world auditory challenges and support more tailored intervention strategies.
Interestingly, better temporal resolution was associated with better DDT-LE performance, indicating shared neural networks underlying these abilities. However, the mechanisms driving this relationship remain unclear.
Our study did not establish a consistent link between auditory processing performance and self-reported measures, suggesting the questionnaires might not have been sensitive enough to detect age-related auditory changes, despite differences between older and younger adults. This could also be due to individual performance variations. For example, Sammeth, et al. [28] found greater variability in spatial hearing and temporal processing tasks among older adults, which could influence self-perceived difficulties. Questionnaires specifically designed to evaluate distinct auditory abilities, such as spatial hearing [29], might prove more effective in detecting age-related changes.
EHF hearing
The EHF hearing plays an important role in auditory processing, supporting spatial and temporal cues required for speech recognition in noise and binaural separation [11,30]. Our findings showed significant differences in EHFs between older and younger adults, associated with differences in temporal resolution (GIN) and binaural separation (DDT). These findings are consistent with those of Sammeth, et al. [28] who also reported a correlation between EHF hearing, spatial hearing, and temporal processing performance. These findings highlight EHF hearing’s role in auditory processing, particularly spatial hearing and temporal resolution. Incorporating EHF testing into standard audiological assessments could detect subtle auditory deficits that conventional pure-tone audiometry fails to identify. This approach would enable earlier intervention and more tailored rehabilitation strategies for older adults with clinically normal hearing thresholds.
Despite these associations, no significant correlations were observed between EHF hearing and self-reported measures (SSQ12 and AIADH). This may reflect the reliance on mid-frequency sounds for speech recognition. Additionally, cognitive and language abilities, and auditory processing compensatory strategies may mediate the effects of EHF hearing loss.
Our findings contrast with those of Saxena, et al. [10], where normal-hearing adults (18–37 years) with EHF hearing loss reported significant difficulties compared to those without EHF hearing loss, differences in listening demands and expectations may explain these differences. Younger adults may face more demanding situations, such as noisy environments or group conversations, increasing their awareness of listening difficulties, while older adults may have developed compensatory mechanisms.
These compensatory strategies include relying on context cues, linguistic knowledge, and cognitive resources to fill in missing information. Older adults can also use visual cues more effectively. They could also use strategies to position themselves closer to the speakers and avoid nosy environments. These adaptations may help handle perceptual challenges associated with EHF hearing loss, leading to lower self-reported impact despite auditory deficits.
Spatial hearing tasks showed the greatest group differences, consistent with Best, et al. [31], who concluded that frequencies below 8 kHz suffice for speech recognition; high-frequency information (>8 kHz) is essential for accurate localization. Some studies suggest EHF hearing loss leads to greater listening challenges, but this has not been systematically studied in older adults with clinically normal hearing. To address this, EHF audiometry should be included in clinical assessments to address these deficits to detect subtle spatial hearing impairments. Additionally, spatially focused auditory training programs can enhance sound source localization and improve communication in complex environments.
Limitations and future research
The lack of significant group differences in speech-in-noise performance was an unexpected finding, potentially highlighting limitations in the test methodology. Future studies could consider using a range of SNR levels to address this limitation, including more challenging conditions such as -5 dB or -10 dB SNR.
Noise exposure history and cognitive processing can impact self-perception of listening abilities. However, our study could not collect data or measure cognitive capacity, leaving their impact undetermined. Our findings suggest that self-reported difficulties in auditory perception may not be entirely due to peripheral hearing loss (EHF) but could also reflect underlying cognitive contributions, such as working memory. Future research should explore these interactions more explicitly, as cognitive factors may help explain differences between objective measures and self-reported difficulties.
These limitations highlight the need for further research to explore interactions between auditory processing, EHF hearing, cognitive capacity, and other age-related factors to explain self-perceived challenges in older adults with clinically normal hearing. While we found a significant correlation between PTA4, DDT, and GIN performance, the results should be interpreted with caution due to study limitations. Future research should examine how subtle hearing threshold variations affect auditory processing using a larger sample.
Conclusion
Older adults reported significant difficulties in dynamic listening environments, sound localization, and speech perception. Objective assessments show deficits in dichotic listening, temporal resolution, and elevated EHF thresholds compared to younger adults. These findings highlight the need for a comprehensive auditory assessment considering central auditory processing and EHF to address the challenges faced by older adults with normal clinical audiograms.
PDF Links
PubReader
ePub Link
XML Download
Full text via DOI
Download Citation
Supplement
Print
