Investigation 16C: How sound carries information

Essential questionsHow does sound carry information, such as words?
The identity of a song, the meaning of words, and even a person’s identity are information that we immediately decode from sound. Sound carries an extraordinary amount of information through the interference of many thousands of frequencies, each of which varies in phase and amplitude over time.

Part 1: Multifrequency sound and the spectrum

How to use the multifrequency sound wave generator
  1. The electronic resource shows a waveform graph (by default). Set a frequency of 300 Hz and adjust the volume. Set the time axis to display 0.02 s.
  2. Add a 400 Hz sound, then a 450 Hz sound. Listen to the frequencies separately and together and observe the waveform.
  3. Switch the graph to display a spectrum—a bar chart that shows the frequencies of the sound. Set the same three frequencies as before and observe the spectrum as you change the frequency and volume.
  4. Starting with 300 Hz, use three frequencies in the ratios 1:3:5 to create the best approximation to a square wave.


  1. Can you hear individual frequencies or do you only hear a mixture? What evidence supports your conclusion?
  2. Compare the time and frequency graphs. Which best describes the frequency content of sound? Which describes the motion of your eardrum?
  3. Research how many different and distinct frequencies the human ear can simultaneously perceive.
In this interactive sound generator, you can create up to three sound tones that will sound at the same time. You can also see a graph of the composite waveform. You can display the sound visually either as the waveform or as a spectrum.
Piano sounds

The audio attached to this paragraph will play four beeps one second apart followed by a piano selection. Piano solo
Applause sounds

The audio attached to this paragraph will play four beeps one second apart followed by the sound of applause after a performance. Applause
The sound of beach waves

The audio attached to this paragraph will play four beeps one second apart followed by the sound of waves at a beach. Waves at the beach
Classical guitar sounds

The audio attached to this paragraph will play four beeps one second apart followed by a short classical guitar solo. Guitar solo
Crash sounds

The audio attached to this paragraph will play four beeps one second apart followed by the sound of stuff crashing to the ground. Stuff crashing

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