MASKING TECHNIQUES REVISITED: APPLICATION OF LIDÉN’S FORMULAS IN BONE CONDUCTION SPEECH AUDIOMETRY

Introduction Bone conduction speech audiometry is a complementary tool required by many otologists, particularly in assessing cochlear reserve and estimating postoperative results in patients undergoing stapedectomy. However, when clinical masking of the non-test ear is needed for these tests, it introduces a significant methodological challenge. This study aims to establish a systematic approach for determining safe and effective masking levels in bone conduction speech audiometry. In this context, the proposed framework offers quantitative tools designed to help reduce the risk of masking dilemmas, which are a persistent challenge in audiologic practice. Material and methods Adaptation and application of Lidén’s formulas to determine the minimum and maximum masking levels for bone conduction speech audiometry and analysis of four frequently encountered audiometric configurations. Results The minimum and maximum masking levels for each configuration were determined. In cases of large ear-bone gaps in the non-test ear, and/or good bone conduction thresholds in the test ear, masking at supra-threshold levels may be difficult due to the risk of overmasking. In one or more of these configurations, a masking dilemma is sometimes detected at levels close to the speech recognition threshold. In such challenging situations, we recommend the use of insert earphones to extend the range of safe stimulus levels and masking levels that can be presented to the patient. Conclusions Speech audiometry holds considerable predictive value for otologic surgeons, so it is important to use techniques that minimise the risks of cross-hearing and inappropriate masking. These limitations are important when using bone-conduction stimulation and need to be carefully evaluated. This paper shows how Lidén’s formulas can be used for calculating safe masking levels.