It's like the Pure Tone Audiometry/PTA test in a sound booth where you click a button when you hear the tone in each frequency.
Except, instead of hearing tones played by your Audi in earphones, you play the tones yourself (for each frequency in one ear at a time) and hear the tones directly in your hearing aids.
When you finish measuring both ears in all the frequencies; Voila; You have a new in-Situ Audiogram and you can Calculate/Rx/Prescribe a new fitting based on the in-Situ measurements.
