Masking is a testing technique used during a comprehensive hearing evaluation to ensure that the ear which is being tested is not being assisted by the opposite ear. Masking is done by presenting a narrow-band noise to the opposite ear of the ear being tested. There is a specific formula used by the evaluator to ensure that an effective amount of masking noise is being used. Even under headphones, a sound presented to one ear may be picked up by the opposite ear, especially if the opposite ear is a better-hearing ear. It is common for the tester to use masking when there is a difference between the hearing in each ear, or when there is a conductive hearing loss.
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