9. Sounds are how we perceive pressure waves in the air. The note F-sharp, directly below the note 'middle 0', is a sound wave with an ordinary frequency'r f = 220 Hertz or cycles/sec. If you need to use the symbol 71'. type "pi". Model this note with the sine function. assuming that the amplitude is 1 and the phase shift is 0. Write the function in terms of x. 9(a) = v: *This frequency is based on thejust-intonation scale. The frequency based on the equal tempered scale would be f = 220