When is it necessary to mask air conduction?

Masking for air conduction is necessary when there is a significant difference in air conduction thresholds between the two ears, specifically a 40 dB or greater difference. This procedure is essential to ensure accurate hearing test results and to prevent crossover or false results from the non-test ear. If the difference in thresholds is 40 dB or more, sound presented to the test ear may also be heard by the non-test ear, potentially leading to an underestimation of the hearing loss in the test ear.

In cases where there is not a significant difference in thresholds, such as a 20 dB difference or even no difference at all, masking is not typically needed. This is because the sound being tested is unlikely to crossover to the non-test ear, allowing for accurate testing without interference. Thus, the procedure is primarily focused on ensuring that each ear's thresholds are tested independently, especially when there is a considerable discrepancy in their ability to hear sounds.