How to perform audiometric masking with Equinox Evo
Required equipment
- Equinox Evo
- A patient response button
- A calibrated bone conductor (B81)
- Licensed AC440 Audiometry module
- Calibrated headphones or insert phones
Test procedure
Perform air conduction and bone conduction audiometry unmasked for both ears.
In case there is an air-bone gap of 15 dB or more, the bone conduction threshold must be reassessed while applying masking to the non-test ear.
If the difference between the air conduction threshold of the worse ear and the bone conduction threshold of the good ear exceeds an interaural attenuation of 40 dB (50 dB if using insert phones), masking will be needed for the air conduction audiometry of the worse ear.
Select NB on channel 2.
Select the ear to be masked (right or left) and choose the appropriate masking transducer (headphones or insert phones). This will activate the masking noise.
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.
There are many ways of applying clinical masking. Which one to use is your decision. Regardless of the masking method, channel 2 is used to occupy the better ear.
When storing a threshold while masking, the final masking level is stored in the masking table under the ear that is being tested. The term 'Effective masking' in this situation refers to the fact that the narrowband noise level was loud enough to effectively mask a pure tone of the indicated level heard by the masked ear.
Auto masking
Interacoustics auto masking is available to ease the effort required to mask with correct masking levels. When auto masking is enabled, channel 2 is controlled by the system and is set to the appropriate intensity level.
Auto masking is activated by selecting the icon that shows the mask with a letter A. There will be a green, amber, or purple indicator at the level of channel 2 indicating the following (Table 1).
| Indicator | Meaning |
| Green | Masking is correctly applied. |
| Amber | Masking should be louder, and extended range needs to be activated. |
| Purple | Masking is needed but not possible. |
Table 1: Auto masking indicators.
Masking help
Interacoustics masking help is available to make it easier to decide on a safe and correct masking intensity. When masking help is activated, a status light on channel 2 indicates if masking is applied correctly.
Masking help is activated by selecting the icon that shows the mask without a letter A. There will be a grey, green, amber, or purple indicator at the level of channel 2 indicating the following (Table 2).
| Indicator | Meaning |
| Grey | Masking help is not active. |
| Green | Masking is correctly applied. May also provide a suggested masking level. |
| Amber | Masking should be increased or decreased to suggested level. |
| Purple | Masking is needed but not possible. |
Table 2: Masking help indicators.
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