Labs / Physics
Sound Beats
Two pure tones that are close in pitch don't just blur together — their waves drift in and out of step, so the combined sound swells and fades. Slide the two frequencies and watch the throb of the waveform, and the loudness meter, speed up as the tones separate and freeze when they lock into unison.
fA 220.0 HzfB 223.0 Hzbeat 3.0 Hzloud 100%
What to try
- Slide Tone B toward Tone A. What happens to the throb as the two pitches meet?
- The beat readout says 3 Hz — how many loudness pulses do you count each second?
- What frequency difference makes the beat too fast to hear as a throb, and starts to sound rough instead?
- Turn Amp A and Amp B to equal values. Does the sound ever fade to complete silence between beats?
- If the beat rate is always the difference of the two frequencies, does it matter whether you move Tone A up or Tone B down by the same amount?