What is the primary function of automatic gain control in hearing aids?

The primary function of automatic gain control (AGC) in hearing aids is to maintain a consistent output level regardless of the variations in input sound intensity. This is particularly important in preventing feedback, which can occur when the amplified sound from the hearing aid itself gets re-amplified, creating an undesirable squealing sound.

By controlling the sound intensity associated with feedback circuits, AGC ensures that the amplified sound is comfortable for the user and minimizes sudden volume fluctuations that could be jarring or unpleasant. This capacity to manage output levels effectively supports individuals in navigating complex auditory environments, ensuring that softer sounds are heard without amplifying louder sounds to a level that could be uncomfortable or harmful.

In contrast, enhancing background noise would typically detract from speech understanding, measuring sound pressure levels at the eardrum is more about assessing auditory input rather than controlling output, and filtering out high frequencies serves a different purpose related to sound clarity and individual acoustic preferences. Thus, the focus of AGC is specifically on sound intensity control, making option B the correct choice.