Extended high-frequency hearing thresholds, distortion product otoacoustic emissions (DPOAEs), and speech recognition in noise: their relationship with age.

Abstract

Previous research has looked into the effects of age on the auditory system. This study focused on assessing particularly the EHF range and its significance for early age-related hearing diagnosis (Škerková et al., 2023) and speech perception skills (Hunter et al. 2020). The available evidence indicates the presence of significant information at EHFs ranging from 8 to 20 kHz may have an impact on speech intelligibility. However, it is yet to be determined whether this information is utilised during difficult listening situations (Motlagh Zadeh et al., 2019).

A cross sectional study of forty-eight adults aged 18 to 70 with normal hearing thresholds in the 0.25-4 kHz frequency range was conducted, to examine how well age correlates with conventional PTA, EHFA, DPOAE, and speech perception in noise scores and to investigate test score correlation and obtain normative test values. The speech perception tests were conducted through; fixed and roving speech in noise using the crescent of sound rig with speech material recorded to capture high-frequency components up to 20 kHz.

To investigate the age effects, participants were divided into two age groups: Group 1 (18–40 years) n=27 and Group 2 (50–70 years) n=21. For conventional frequencies and EHFs, a statistically significant difference (p<0.0045) was found between the two groups for all tested frequencies 4-20 kHz. The mean and median across all frequencies were lower in Group 1 than in Group 2 for right and left ears. For DPOAE, the SNR (dB) and DP (dB SPL) values were analysed for the (65/55 and 70 dB SPL) stimulus levels, and a significant difference between both groups (p<0.05) was found for the DP and SNR measurement (when the data were not divided into specific frequency) for both levels paradigm, in right and left ears. The mean values of DP measurement for Group 1 were generally higher than Group 2 across all frequencies (842-9509 Hz) for (65/55 and 70/70 dB SPL) stimulus levels. For CRM task (fixed speech and roving speech in noise), the age effect was not evident in both of the speech test values, with no statistical difference between groups (p>0.05). For the correlation between test results, the correlation between DPOAE and PTA conventional frequencies resulted in a moderate negative linear correlation with statistically significant correlation (p<0.05). Regarding the EHF range with the (9509 Hz in DPOAE), results revealed no relationship between both tests. A notable absence of a statistically significant correlation exist between the outcomes of PTA and speech perception skills through (fixed and roving speech in noise tests) (p>0.05) in both conventional and EHF ranges.

The results concluded that age has a noticeable effect on the PTA and DPOAEs test values. The age effect was not evident on fixed speech and roving speech in noise, suggesting other factors might have affected the test values: attention, encouragement, and other cognitive skills. The only significant correlation between the test values was between PTA and DPOAE in the conventional range. The weak and lack of significant correlation between the test values does not mean the test values do not reflect the same results; it suggests other factors than the hearing status might have affected the tests. It was concluded by this study that the EHF range might still be beneficial for speech perception but not particularly for the CRM task, as it is considered a cognitive more than a speech test. Further research is needed to investigate this.