In pure-tone audiometry, what is the primary clinical reason for delivering masking noise to the non-test ear?

• A. To calibrate the audiometer's bone conduction transducer dynamically
• B. To prevent cross-hearing from interfering with the thresholds of the test ear
• C. To measure the binaural fusion capabilities of the brainstem
• D. To improve the patient's attention and concentration during a long test

Answer: (B)

Masking in pure-tone audiometry is used to isolate the test ear by preventing the non-test ear from hearing the signal. If the non-test ear can pick up the tone (through cross-hearing or skull conduction), it can respond, making the measured threshold for the test ear inaccurate. Delivering masking noise to the non-test ear raises its threshold for that signal, effectively rendering the tone inaudible to the non-test ear and ensuring the response comes only from the test ear. This is especially important when there’s a potential asymmetry in hearing or when the stimulus level could cross over due to the transducer’s interaural attenuation. It’s not about calibrating equipment, measuring binaural fusion, or improving attention.