A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations.A hearing aid is a small electronic device that you wear in or behind your ear. It makes some sounds louder so that a person with hearing loss can listen, communicate, and participate more fully in daily activities. A hearing aid can help people hear more in both quiet and noisy situations.The majority of people with mild to moderate hearing loss can benefit from hearing aids. However, hearing aids don't work for everyone, including people with severe to profound nerve deafness, or sensorineural hearing loss in both ears.It's also very important to know that hearing aids do not work right away.