June 10, 2008
June 8, 2008
A440 is the 440 Hz tone that serves as the standard for musical pitch. A440 is the musical note A above middle C (A4).
Every time you double the frequency, the pitch goes one octave up. Starting from the note A at 440Hz, doubling the frequency six times, you hear five different As until the sound becomes ultrasonic and inaudible. Another 36 octaves up and the frequency is the same as that of visible light, in our case from A440 you get a frequency of 484THz, which is a wavelength of 619nm, which is red.
The frequency spectrum of visible light is a bit less than one octave. This can actually be seen, in that on one end of the spectrum is red and the other end is moving back from blue to red, giving violet.