Eighth octave C

The musical note C8 is the C two full octaves above soprano high C. The note is one octave above the top of common piano keyboards. The pitch vibrates at 4,186 Hz (the A note below middle C vibrates at 220 Hz in comparision).

For a vocalist to hit a note of this pitch, their vocal chords must vibrate at over 4,000 times per second. This is nearly impossible because of the muscular control required in adducting the vocal cords that high. Minnie Riperton and Mariah Carey are rumored exceptions. Because every octave jump doubles the rate of vibration (ie. C5 vibrates twice as fast as middle C (C4) and soprano C two octaves higher vibrates four times as fast), this helps explain why rumors of Mariah Carey being able to vocalize pitch beyond the human range of hearing are highly improbable. (Her vocal cords would have to vibrate about 20,000 times per second.) The Guinness Book record is held by Mariah Carey's G#7, still two and a half notes below C8.