PP305 - Combined Effects of High-Frequency Hearing Loss, Fitting Formula, and Venting on Real-Ear Sound Level and Patient Perception

Abstract:
This study investigated how acoustic options and fitting formulae affect hearing aid fitting for high-frequency hearing losses (HFHLs). Real ear measures were completed on Kemar (25 HFHL configurations per HL) and adults with three groups of HFHLs, with 14 eartip options for three fitting formulae. Subjective responses were obtained for nine HL combinations.  Results revealed significant impacts of the HL, eartip/venting, and fitting formula on sound level in the ear canal and perception. Participants with HL did not perceive sound the same as those with normal hearing. Further effects of multiple aspects were reported for a better fitting with HFHLs.

Summary:
High-frequency hearing loss (HFHL), the most common HL configuration, can lead to communication difficulties and impact the quality of life (e.g., Furman, et al. 2013). Hearing aids can help address speech clarity issues, but commonly may introduce occlusion when closing the ear canal, or cause feedback and undesired speech intelligibility when opening the canal (e.g., Dillon, 2012; Hengen et al. 2020). Our preliminary study with software simulation indicated clear effects of the degree and configuration of HFHL, fitting formula, vent size on the gain, and the gain restriction presented may negatively affect speech intelligibility for moderately-severe and greater HLs.
It is not clear of their combined effects on listeners with HLs. Also, clinically there is no guideline regarding choosing specific fitting parameters for an HFHL. This study evaluated the acoustic and perceptual effects of different acoustic options and fitting formulae on hearing aid fitting for moderately severe to severe HFHLs with various degrees and configurations of HFHL. Real ear measures (REMs) were completed on Kemar and adults with normal hearing (NH), moderately severe, and severe HF-SNHLs. Simulated HLs for Kemar included five low frequency (LF) thresholds (0,10,20,30,35dB), and five HFHL configurations (HL ranged at 2-8,3-8,4-8,6-8,8kHz) for each LF threshold for moderately-severe and severe-SNHLs.

Real ear occluded gain, aided gain for 20dB insertion gain, and aided gain and output for each HL (simulated mild HL for NH), and maximum gain before feedback were recorded for different domes (open, vented, cap, & power), earmolds (c-shell & slimTip with occluded, 1,2,3mm vent sizes), and fitting formulae (NAL-NL1, NAL-NL2, & DSL-Pediatric). Subjective responses were obtained for the individual’s perceptions of their own and other’s voices with different domes/earmolds and fitting formulae for a total of nine HL combinations, including the participant’s HL and simulated HLs with the above five LF thresholds and five HFHL configurations when fixing H/LF thresholds, respectively.

Results revealed significant effects of the HL, eartip/venting, and fitting formula on sound level in the ear canal and perception (p < .0001). Increasing the degree of LFHL increased the output for most of the frequencies, but increasing the HF cutoff frequency decreased output at 1500-8000Hz. Dome and earmold had different acoustics, although increasing the eartip opening scale decreased the output for all frequencies but will not affect the verifit prescriptive targets, leading to the need of more occluded venting to meet the targets when necessary. The sound level was highest for DSL, which had similar trend as NAL-NL2 focusing on mid-high frequencies. NAL-NL1 provided more output at mid-frequencies. All participants were sensitive to the sound level change and mostly associated louder perception with less sound quality and comfort, and mostly more occlusion sensation. Participants with HL did not perceive sound the same as those with NH, although NAL-NL2 and more opening eartips were preferred, and DSL perceived significantly more occlusion (p < .0001). One moderately severe participant preferred DSL and perceived NAL-NL1 the least quality and comfort. One Severe participant did not perceive much difference among different fitting formulae and eartips. More information will be reported which will be useful for fitting with HFHLs.