The green line is the target 'aided
threshold' for a severely deaf person.
The gap between the red and the green
lines is the 'gain' needed for this person to hear most
The best hearing aid for this person
will give 'aided thresholds' like the green line.
This person has a
Hearing aids cannot give enough 'gain'
for a profoundly deaf person to hear all speech sounds.
Target 'aided thresholds' for
a profoundly deaf person are for the green line to be inside the 'speech