I can only speak from personal experience. I have defective hearing. I am not profoundly deaf but it is still a frustrating handicap in a social context.. The defect is greater in one ear than the other. I was advised to wear a hearing aid in both ears. The reason for this is best ezplained by a trained audiologist. I would strongly advise taking out insurance against hearing aid loss . They are very expensive if you buy them privately! I didn't initally have insurance and lived to regret it!