Grishka is in fact correct, and I for one was mistaken.

I had always assumed that the note at the third fret on the fifth string of the guitar was middle C, but it isn't ... middle C, in equal temperament, is 262Hz, and that is the note on the B string at the first fret. The note on the fifth (A ) string, 3rd fret, is 131Hz. I just now tested this with my Peterson tuner.

So the high notes are in fact the ones directly above middle C, and not the ones an "octave+interval" above, (which would be unattainable by any normal male voice).