What indicates that masking may be required for air conduction testing?

Masking is used in air conduction testing to ensure that the results are accurate, particularly when there is a significant difference in hearing ability between the two ears. In this context, a 40 dB difference between the test ear (the ear being examined) and the non-test ear (the ear that is not being tested) is particularly critical. This threshold indicates sufficient asymmetry in hearing sensitivity, suggesting that sound presented to the test ear could cross over and be heard by the non-test ear, leading to inaccurate results.

When a significant difference of 40 dB is noted, it is a clear indicator that masking is necessary to isolate the test ear and obtain a true representation of its hearing ability without interference from the other ear. In audiometric practice, this is a common criterion employed by audiologists to determine when masking should be applied to ensure the validity of the air conduction threshold measurements.

While a 15 dB difference between ears and a flat audiogram can indicate potential issues, they do not meet the specific criterion that necessitates masking as definitively as the 40 dB difference does. Therefore, the option stating a 40 dB difference is the most relevant and appropriate reason for requiring masking during air conduction testing.