Lol.

Wiki because no one believes a human but wiki is the bible.........

Oh and The whistle register (also called the flageolet or flute register or whistle tone) is the highest register of the human voice lying above the MODEL register and falsetto register. This register has a specific physiological production that is DIFFERENT from the other registers, and is so called because the TIMBRE OF THE NOTES that are produced from this register are similar to that of a whistle.
In some sopranos the modal register vocal production may extend into what is usually thought of as the whistle register. With proper vocal training, it is possible for WOMEN WITHIN ALL VOICE types to develop this part of the voice. However, some women are unable to phonate or comfortably produce sound in this register. Children can also phonate in the whistle register and men can as well in very rare instances.

So whistle register is not a specific note but a texture change or timbre change that is different from the rest of the voice lying at the top of the voice. The ear can easily hear a women shift into head register but most have no idea about timbre change into the whistle register.... the normal person just things 'OH ITS NOT HIGH ENOUGH' to be whistle register...... DEAD WRONG.