persistent cough mainly in evening and loss of voice

wondering what i can do to alleviate symptoms. visited dr who said i have a respritory infection that would clear up on its own. but i am unable to rest in the evenings because of this persistent cough. Sleeping in daytime is fine because i dont cough nearly as much. the cough seems to be aggrivated by dampness. I also need my voice back. What can you recomend?