Evaluation of Hearing Aid Manufacturers' Software-Derived Fittings to DSL v5.0 Pediatric Targets

Abstract

Background Hearing aid prescriptive methods are a commonly recommended component of evidence-based preferred practice guidelines and are often implemented in the hearing aid programming software. Previous studies evaluating hearing aid manufacturers' software-derived fittings to prescriptions have shown significant deviations from targets. However, few such studies examined the accuracy of software-derived fittings for the Desired Sensation Level (DSL) v5.0 prescription. Purpose The purpose of this study was to evaluate the accuracy of software-derived fittings to the DSL v5.0 prescription, across a range of hearing aid brands, audiograms, and test levels. Research Design This study is a prospective chart review with simulated cases. Data Collection and Analysis A set of software-derived fittings were created for a six-month-old test case, across audiograms ranging from mild to profound. The aided output from each fitting was verified in the test box at 55-, 65-, 75-, and 90-dB SPL, and compared with DSL v5.0 child targets. The deviations from target across frequencies 250-6000 Hz were calculated, together with the root-mean-square error (RMSE) from target. The aided Speech Intelligibility Index (SII) values generated for the speech passages at 55- and 65-dB SPL were compared with published norms. Study Sample Thirteen behind-the-ear style hearing aids from eight manufacturers were tested. Results The amount of deviation per frequency was dependent on the test level and degree of hearing loss. Most software-derived fittings for mild-to-moderately severe hearing losses fell within ± 5 dB of the target for most frequencies. RMSE results revealed more than 84% of those hearing aid fittings for the mild-to-moderate hearing losses were within 5 dB at all test levels. Fittings for severe to profound hearing losses had the greatest deviation from target and RMSE. Aided SII values for the mild-to-moderate audiograms fell within the normative range for DSL pediatric fittings, although they fell within the lower portion of the distribution. For more severe losses, SII values for some hearing aids fell below the normative range. Conclusions In this study, use of the software-derived manufacturers' fittings based on the DSL v5.0 pediatric targets set most hearing aids within a clinically acceptable range around the prescribed target, particularly for mild-to-moderate hearing losses. However, it is likely that clinician adjustment based on verification of hearing aid output would be required to optimize the fit to target, maximize aided SII, and ensure appropriate audibility across all degrees of hearing loss.

Listening Preferences of New Adult Hearing Aid Users: A Registered, Double-Blind, Randomized, Mixed-Methods Clinical Trial of Initial Versus Real-Ear Fit

“…For example, 20% of custom earmold initial fittings were within 10 dB of target in compared to 67% in the current study. Similar improvements in the manufacturers' initial fits were also observed in recently published studies that found small initial fit deviations from targets and greater consistency between manufacturers (Folkeard et al, 2019;Narayanan et al, 2022). Although the differences in the overall gain between initial fit and REM were relatively small, they were enough to elicit a preference for most participants.…”

“…This study compared the two fitting approaches for new adult users with mild-to-moderate sensorineural hearing loss, using one hearing aid prescription, the same fitting software and the primary outcome of listening preference. The findings of this study could be generalized to other prescription methods, given the similarity between prescription methods (Johnson & Dillon, 2011) and the lack of noticeable deviations of initial fits from targets that were found with the Desired Sensation Level prescription method (Folkeard et al, 2019). However, caution should be exercised when generalizing the results of this experiment to other manufacturers' fitting software, as there are mixed reports of deviation from target values (Narayanan et al, 2022;Sanders et al, 2015).…”

“…In addition, it is unclear whether the findings can be generalized to other types and severities of hearing loss. Previously published studies have indicated that the more severe the hearing loss, the less accurate the manufacturer's initial fits, irrespective of the hearing aid model (Folkeard et al, 2019;Quar et al, 2019). In addition, these studies also found that using the REM for this particular group did little to improve the matches to the prescribed targets (Dao et al, 2021;Quar et al, 2019).…”

“…Based on the findings of our review, it is evident that there is a need for high-quality evidence on clinical and costeffectiveness of REM, given that it requires resources and time (perhaps up to ten minutes of a typical NHS fitting appointment), which could be otherwise directed to nontechnical procedures such as addressing the specific listening needs of the patient. In addition, the accuracy of the manufacturers' initial fit, as mentioned above, has improved over time (Folkeard et al, 2019;Narayanan et al, 2022). However, a lack of statistically significant gain difference between the REM and initial fittings would not mean patients will not have a preference for either of the fitting approaches.…”

“…In earlier reports, manufacturer's initial fit was found to provide inadequate amplification compared to Real Ear Measurement (REM) fitting, with deviations between the two approaches most prominent at high frequencies and low input levels (Aazh & Moore, 2007;Aazh et al, 2012;Sanders et al, 2015;Valente et al, 2018). However, accuracy of the manufacturer's initial fits has improved over time (Folkeard et al, 2019;Narayanan et al, 2022), presumably because (a) hearing aids have become more adjustable and (b) manufacturers have more information about how to allow for low-frequency venting and high-frequency tubing effects (Dillon, 2012). For example, Aazh and Moore (2007) found that only 36% of initial fittings were within 10 dB tolerance of NAL-NL1 target from 0.5 to 4 kHz.…”