Section 2 review
Sound waves are invisible. Sensors and electronic devices are useful for displaying how the pressure of a sound wave varies with time on a waveform graph. Ordinary sound contains many simultaneous frequencies. The frequency spectrum shows amplitude versus frequency. The information content in sound is encoded in the patterns of how amplitude changes over time across many frequencies. Read the text aloud
microphone, frequency spectrum, Fourier’s theorem, spectrogram

Review problems and questions

Three amplitude versus time graphs for sound waves
  1. One of the three graphs shows a sound that contains two different frequencies.
    1. Which graph is it and how do you know?
    2. What is the lower frequency in this sound?
    3. What is the higher frequency in the sound? Read the text aloud Show
Match the waveforms with the spectra
  1. Match each waveform from the left-hand column with one spectrum from the right-hand column. Assume that the y-axis of each graph is amplitude. Read the text aloud Show
  1. Music can be recorded, transmitted, and stored digitally. Describe the tradeoffs between sound quality and file size in digital audio formats. Show

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