Frequency & Pitch: Speed Decides Height
Faster vibration = higher frequency = higher pitch. Frequency is measured in Hz (cycles per second).
If your vocal folds open and close 200 times per second, that is 200 Hz. The faster they open and close, the "sharper" (higher) the sound; the slower, the "duller" (lower). Human ears hear roughly 20 Hz – 20,000 Hz. When you sing, your pitch is the vibration frequency of your vocal folds — in vocal terminology, F0 (fundamental frequency).
Experiment 2 · Drag Faster or Slower, Hear the Height
Drag the slider to change frequency: the waveform becomes denser/sparser (visual) and the pitch rises/falls (audio). Note: frequency is perceived logarithmically — going from 100→200 Hz and 400→800 Hz sounds like the same leap (both double, an interval of one octave).
Frequency determines pitch. The app's "pitch" chart measures your F0 in real time. That is why female voices are usually higher than male voices — shorter, thinner vocal folds vibrate faster.