When is bone conduction masking necessary?

Bone conduction masking is necessary when the difference in air conduction (AC) thresholds between the two ears exceeds a specific level. Generally, when the difference is around 10 dB or greater, there is a risk that the test results may not accurately represent the functional capacity of each ear separately. This threshold is particularly crucial to ensure that the sound presented to the better hearing ear does not cross over and mask the response of the poorer hearing ear.

In scenarios where the difference in thresholds is at or above this level, masking is employed to isolate the ear being tested from any influences of the non-test ear, which could lead to misleading results. This ensures that the results obtained are valid and reflect the actual hearing thresholds of the specific ear being assessed.

Conversely, if the threshold difference is 5 dB or less, it is typically considered safe to test without masking, as the risk of crossover is minimal. Testing both ears simultaneously generally raises concerns about potential cross-hearing, but it does not automatically necessitate bone conduction masking unless the threshold differences warrant it. Lastly, while masking is often used during air conduction testing, it is not required in every instance, specifically when the threshold differences are within acceptable limits.