Sound Beats and Sine Waves


Listen to and see interference patterns produced by sound waves with similar frequencies. Test your ability to distinguish and match sounds as musicians do when they tune their instruments. Calculate the number of "sound beats" you will hear based on the frequency of each sound. [Note: Headphones are recommended for this Gizmo.]

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Assessment Questions (5):

  1. Which sound has a higher frequency, Sound A (represented by the purple sine wave below) or Sound B (represented by the green sine wave)?

    Sine waves for Sound A and Sound B
  2. Based on the image below, what is the displacement of the wave for Sound A + B at 0.1025 seconds?

    Two interfering sound waves
  3. If Sound A has a frequency of 450 Hz and Sound B has a frequency of 447 Hz, how many beats will you hear when both are played together?
  4. A piano tuner strikes her tuning fork and plays a note on the piano at the same time. She hears 8 beats in 4 seconds. How much should the pitch of the string be changed?
  5. The image below shows the combined wave for Sound A + B, where Sound A has a higher frequency than Sound B. What is the frequency of Sound A?

    Sound graph produced by interference of two sounds

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