# Bilateral Fitting of Bone-Anchored Hearing Devices: Speech Recognition and Sound Localization

## TL;DR

This study shows that using two bone-anchored hearing devices improves speech recognition and sound localization compared to using one device.

## Contribution

The study provides empirical evidence supporting the benefits of bilateral over unilateral bone-anchored hearing device fitting.

## Key findings

- Bilateral BAHD users had 78.2% speech recognition in silence versus 71.5% with unilateral fitting.
- Bilateral fitting improved sound localization accuracy with a mean angular deviation of 68.08° versus 80.48° for unilateral fitting.
- Better performance was observed in noise conditions with bilateral fitting (72.2%) compared to unilateral (61%).

## Abstract

Bilateral fitting of bone-anchored hearing devices (BAHD) remains a contentious topic, as the use of a single device can direct sound to both cochleae. However, the interplay of interaural attenuation and time delay may result in different responses in each ear; thus, greater challenges for unilateral BAHD users.

To assess the auditory performance of BAHD users with unilateral and bilateral fitting regarding speech recognition in silence and noise and sound localization.

Cross-sectional study. Unilateral BAHD users treated at a Brazilian public hospital underwent a speech recognition test, containing a list of monosyllables at 65dBSPL in silence and noise (S/N ratio = 0dB). The sound localization test employed eight speakers arranged at 45° distance. A recorded trisyllabic word served as the stimulus. For bilateral fitting, an elastic band with a device similar to the implant was used; patients underwent the same tests under identical conditions.

Sixteen patients were assessed (mean age = 24.2 years). The average monosyllable recognition in silence rate was 71.5% in unilateral fitting and 78.2% in bilateral fitting. In noise, 61% in unilateral fitting and 72.2% in bilateral fitting. The mean angular deviation for the sound localization test was 80.48° in unilateral fitting and 68.08° in bilateral fitting. The bilateral fitting outcomes were better for all tests.

Users with bilateral BAHD fitting had better outcomes for speech recognition and sound localization.