Http://localhost/mp3

i am using apache server and my root www folder contains mp3 folder,when i run my http://localhost/ page everything works fine but when i type http://localhost/mp3 it shows me my mp3 folders contains and i dont want it to happen in a such way,how i can lock or disable http://localhost/mp3 dir so that it doesn’t appear when i type http://localhost/mp3 in my browser