How can I truely know whether I am a soprano or alto?

Answer 1

Depends on your range; generally speaking, a soprano is a singer with a voice that ranges from, approximately, the A below middle C to "high C", while a typical alto will have a range from around the F below middle C to the E a tenth above middle C. Not much of a difference between them, really, and obviously, individuals vary, so it comes down not so much to what notes you can hit but which ones you can sing comfortably -- some people can sing that entire range and beyond, so they can call themselves whatever they want. I'd call Mariah Carey a soprano, while someone like Shakira is an alto -- they can both go higher, but the range they normally sing separate them into parts (and Mariah can make sounds that even dolphins can't hear, so...).

Answer 2

if you question then you are probably a second soprano but will do better as an alto.

Answer 3

Get a professional singer to listen to you?

Answer 4

measure your range. or better, get someone knowledgeable to measure for you.