There are roughly two ways to make high notes with the vocal cords, one is to sing thick high notes with a strong voice, which is more difficult to sing, and you won't be able to sing very high. The other is to shorten the vocal cords and sing a sharp, thin high note that can be sung very high, similar to a woman.

The former, if trained and with the method, holds up an octave higher than before.

The latter should hold up to e4 if it's not overtones

E4 is much higher than the so-called dolphin sound in LOVEING YOU