The purpose of this document is to provide a Quick Guide for instructions on how to administer the Acceptable Noise Level (ANL) test with the AC440 Audiometry module in the Equinox 2.0, Affinity 2.0 and Callisto™.
What is the ANL test?
The ANL Test is a method of determining how much noise the patient is able to tolerate whilst listening to a target signal/speaker (Nabalek et al., 1991). It is used as a predictor for how well a patient will cope with amplification when receiving a hearing aid (Nabalek et al., 2006).
The ANL test is designed to be performed via loudspeaker as it is a free field test. However, it can be configured to perform monaurally via selection of headphones and routing the signal to the relevant ear-side. The Equinox and Affinity systems can perform the test binaurally via the R+L feature.
The ANL Test can use any of the materials you have already ripped into your Interacoustics Suite software.
When should I perform the ANL test?
The ANL test is typically performed before the patient is given any form of amplification as a rehabilitative action for their hearing loss.
MCL High – This is the loudest comfortable level the patient can listen to without any competing noise
MCL Low – This is the lowest comfortable level the patient can listen to without any competing noise
MCL Real – This is the patient most comfortable level without any competing noise
BNL – This is the actual ANL test where the MCL Real is presented and the competing noise is manipulated to find an ANL value
It is not essential to perform MCL High and MCL Low for the ANL test, but these are also good indicators of the patients’ comfortable hearing range.
Instructions for the patient will always be displayed at the bottom of the screen.
Click on the MCL High Icon and click play. This will loop your speech material.
Increase and decrease the stimulus intensity to match the patients loudest MCL.
There will be no other change in the display to represent this, only the level in the MCL High icon box.
The display will change within the icon but also a predicted MCL Real will be generated as a midpoint between the MCL High and MCL Low.
What does my ANL value mean?
On performing the ANL test you will obtain an ANL value (in dB) and a percentage. The percentage gives a likelihood of success with amplification (Nabalek et al., 2006) and the ANL value is the outcome of the following calculation:
ANL = MCL - BNL
For response categories the following outcome criteria was determined as an effect of the Nabalek et al. (2006) investigation into ANL outcomes in relation to amplification:
ANL Score 7 dB or less: These individuals have a great prognosis for regular use and acceptance of hearing aids; may not need as much follow-up counseling and guidance as the average patient.
ANL Score 8-12 dB: These are your more common patients and have a good (8) or bad (12) prognosis for regular use and acceptance of hearing aids. These patients may need more follow-up counseling and are excellent candidates for noise reduction technologies.
ANL Score 13 dB or more: These patients are “at risk” for reduced utilization of hearing aids and may need additional post-fitting counseling, guidance, and require noise reduction technologies.
Nabelek, A.K., Tucker, F.M., & Letowski, T.R. (1991). Toleration of background noises: Relationship with patterns of hearing aid use by elderly persons. Journal of Speech and Hearing Research, 34, 679-685.
Nabelek, A., Freyaldenhoven, M., Tampas, J., & Burchfield, S. (2006). Acceptable noise level as a predictor of hearing aid use. Journal of the American Academy of Audiology, 17(9), 626-639.