This study is about learning how hearing is affected in early stages of diseases like Alzheimer's and Parkinson's. Researchers are looking at hearing problems in people who seem to hear tones fine but have trouble understanding speech in noisy places. This is called *hidden hearing loss*. They want to find markers in the blood that might be linked to this type of hearing loss. Participants will go through many hearing tests, like checking how they hear sounds and speech, both in quiet and noisy settings, and measuring ear responses. The results will be compared to blood tests and health information.

• The study is for people aged 50-85 who speak French and have good health and mobility.
• Participants should not have certain illnesses like diabetes, hearing problems, or be using certain drugs.
• Participants need to visit the study location for tests and must be part of Public Health Insurance.