Masking (Audiology)

In audiology, masking is a technique used during hearing testing to prevent the non-test ear from responding to sounds presented to the test ear. When a sound is loud enough, it can travel through the skull and be detected by the opposite ear, a phenomenon called cross-hearing or shadow hearing. Without masking, the audiologist may record a falsely better threshold for a poor-hearing ear because the better ear is actually detecting the test signal.

To prevent this, a masking noise (usually a narrow-band noise calibrated to the test frequency) is presented to the non-test ear at a controlled level to keep it occupied while the test ear is being assessed. The rules governing when and how much masking to apply are established in audiological guidelines and require clinical judgment. Too little masking fails to prevent cross-hearing. Too much masking (over-masking) can produce falsely elevated thresholds in the test ear.

Masking is applied routinely during both air and bone conduction testing whenever the difference between ears warrants it.