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Why are each ear tested separately during pure-tone audiometry?

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In pure-tone audiometry, each ear is tested separately to ensure an accurate assessment of individual hearing thresholds. This separation is necessary because sound can cross from one side of the head to the other, a phenomenon known as cross-hearing.1

If a listener has poor hearing in the ear being tested, a sufficiently intense signal may cross the skull and be detected by the opposite ear, which may have better hearing. To prevent this, audiologists use masking noise in the nontest ear to ensure the results reflect the sensitivity of the specific ear under examination. Testing each ear individually, while shielding the other, allows for a precise determination of the degree and nature of any hearing impairment for each side independently.12