In cases where you detect a symmetrical hearing loss, it is usually sufficient to perform traditional audiometry without masking. However, in cases of asymmetrical hearing loss, you cannot be certain that the sound is heard by the ear tested or the opposite ear. Therefore, it is necessary to apply masking where you occupy the good ear (non-test ear) while testing the other.
The need to mask the better hearing ear is linked to the interaural attenuation, which equals the amount of attenuation the sound is exposed to on its way through the skull. You can apply masking to air conduction, bone conduction and speech audiometry.
We recommend that you apply masking if the difference between the ears is greater than the interaural attenuation (IaA).
1. If the air-bone gap is 15 dB or more: reassess the bone conduction threshold while applying masking to the non-test ear
2. If the difference between the air conduction threshold of the worse ear and the bone conduction threshold of the good ear exceeds interaural attenuation of 40 dB (50 dB if using insert phones):
Recommended masking procedure:
1. Perform air conduction audiometry unmasked for both ears
2. Perform bone conduction audiometry unmasked for both ears
3. Apply masking
4. Select NB in channel 2
5. Select the ear to be masked (right or left) and choose the appropriate masking transducer (head phones or insert phones). This will activate the masking noise.
6. Proceed to do a masked threshold search and press Store once a correct threshold has been obtained. The symbol will appear in the audiogram as masked.
7. To display the masking level information on the screen, select Mask info.Interacoustics offers an auto masking feature to ease the effort required in order to mask with correct masking levels. Learn more here in our quick guide