How will I determine voice notes?

Question:

How will I determine voice notes?

My co Mariah Carey fans are always present when it comes to comparing her into another singers in youtube. They say she can hit an e2 above but how do they determine an e2 to a e3, e4, e5 and so on and so forth?

Best Answer - Chosen by Asker: You ever see one of those electric guitar tuners? I assume you'd use something similar but instead of strumming a guitar, you would sing into it. With practice, people can guess pretty closely what note they're hearing.