Comparison of Prescribed and REIG Gain of Two Manufacturer’s RIC Hearing aids using Similar Acoustic Coupling

Abstract

Aims and Objectives: This study investigated the mismatch between two manufacturer’s hearing aids with similar acoustic coupling with respect to NAL NL2 prescriptive gain and real-ear insertion gain (REIG) and compared their speech perception in noise performance. The study also examined the target mismatch associated with different types of coupling open and tulip domes. Method: This study employed a within-subject design using purposive non-random sampling. Eighteen participants, with a mean age of 67.6 years, with moderate to moderately severe sloping sensorineural hearing loss were selected. Hearing aids from two manufacturers were programmed and tested under four conditions (open dome and tulip dome for each). Real ear measurements (REIG) and Speech in Noise (SPIN) tests were conducted. The study compared NAL NL 2 gain and REIG across three input levels (50 dB, 65 dB, and 80 dB) and four frequencies (500 Hz, 1k Hz, 2k Hz, and 4k Hz). We also examined target mismatch and evaluated speech perception in noise performance. Data were analyzed using SPSS version 26, and statistical tests were conducted to determine significance of differences. Results and Discussion : The findings were tested using a 4-way repeated measure ANOVA to analyze the effects and interactions of various factors (manufacturer, domes, frequency, and levels) on hearing aids, revealing significant interactions among these variables. Further pairwise comparisons using paired-t-tests showed that NAL-NL2 gain differed significantly across manufacturers (HA-1 and HA-2) at different input levels (50, 65, 80 dB SPL) and frequencies (500 Hz to 4000 Hz) for both open and tulip domes, with HA-2 generally prescribing higher gains, especially at lower frequencies. Real Ear Insertion Gain (REIG) measurements indicated significant differences between manufacturers for open domes at specific frequencies and input levels, while differences for tulip domes were less pronounced. Target Mismatch (TM) analysis also highlighted significant discrepancies in the performance of the two manufacturers’ hearing aids across the tested conditions. Speech in noise performance was better for HA 1 compared to HA 2. This could be due to HA 2 providing high gain at low frequencies leading to more noisy listening as well as HA1 providing higher gain at high frequencies yielding better speech in noise ratio at these speech frequencies. Conclusion : This study indicated significant differences in NAL NL2 gain prescriptions across manufacturers and corresponding REIG differences between manufacturers, affecting patient’s speech perception in noise. Our study highlight the critical role of REM and speech in noise test in verifying hearing aid fittings.