Final answer:
When a hearing aid is set at a person's Most Comfortable Level, it provides functional gain, which is the benefit of hearing sounds at a comfortable volume level that would otherwise not be heard. The term functional gain is different from usable gain, which refers to the amount of amplification without discomfort or feedback.
Step-by-step explanation:
When the hearing aid is set at a person's Most Comfortable Level (MCL), you have c) functional gain. The MCL is the level at which sound is perceived as neither too soft nor too loud, but comfortable. A hearing aid's main purpose is to amplify sounds so that they reach the wearer's MCL, thereby providing a functional benefit that allows the wearer to hear sounds they would otherwise not be able to hear. This is different from usable gain, which refers to the amount of amplification a hearing aid provides without causing feedback or discomfort.
Hearing loss in terms of decibels (dB) can be calculated by understanding the level of sound amplification needed. If a woman requires an amplification of 5.0 × 1012 times the threshold intensity to hear at all frequencies, her overall hearing loss would be significant, with smaller amplifications being more appropriate for more intense sounds, to prevent damage from levels above 90 dB.