Suggest Remedy For Loss Of Voice

Good morning! I have a question regarding to my grandfather who is 83 years of age. About three weeks ago my grandfather woke up with a lost voice. He says he doesnt have pain or anything. He went to the doctor and he told gave him medicine but it is not working. The doctor also told him that if he doesnt get better that he should get another doctor. I was wondering what could the problem be and what treatment should be getting?