What kind of voice is "滄桑的聲音" describing?
To be exact, 沧桑 doesn't just mean aged/old.

沧桑 comes from the idiom 沧海桑田, as you understand, it means huge changes (in a long time). And 沧桑的声音 means a kind of voice, which can make you feel that he/she has experienced many things changed, e.g. many vicissitudes of life.