Sound and wave interactions
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Sound and Wave Interactions. Sound “If a tree falls in a forest …?”. What is sound? Longitudinal wave, particles transfer energy Mechanical wave, must have a medium Bell in a vacuum. Direction of wave travel. Sound and Amplitude. Amplitude: effects the loudness (volume) of sound

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Sound and Wave Interactions

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Sound and wave interactions

Sound and Wave Interactions


Sound if a tree falls in a forest

Sound“If a tree falls in a forest …?”

  • What is sound?

    • Longitudinal wave, particles transfer energy

    • Mechanical wave, must have a medium

      • Bell in a vacuum


Sound and amplitude

Direction of wave travel

Sound and Amplitude

  • Amplitude: effects the loudness (volume) of sound

    • Decibel (db) measures volume


Sound and frequency

Sound and frequency

  • Frequency: determines “pitch” you hear

    • How “high” or “low” the sound seems

    • Gizmo on frequency

    • Ultrasound: above human hearing

      • Dog whistles

    • Infrasound: below human hearing

      • whales


Sound and frequency1

Sound and Frequency

  • Resonance: natural frequency of an object causes it to vibrate

    • Glass of water

    • Speaker/strobe

    • Bridge Collapse

  • Doppler Effect: sound waves change pitch as they move

    • Sound waves pushed together in front of moving object (higher frequency)

  • sound of Doppler

    • Doppler Radar

  • Wave interactions video


  • Speed of sound

    Speed of Sound

    • The speed of sound depends on 3 things

      • Elasticity: ability for medium to “bounce back”

        • More elastic means faster sounds

          • Solids are most elastic, liquids less, and gases not very elastic at all

      • Density: how many particles are in a given space

        • [HOWEVER, more density means slower sounds within the same phase of matter (more dense solids will be slower than less dense solids, etc.)]

      • Temperature: higher kinetic energy (higher temps) = faster sound travel.

      • Speed of Sound video


    What happens when waves meet

    Reflections

    The bouncing back of wave as it hits another object

    Law of reflection: “angle in = angle out”

    Echoes

    Echolocation

    Sonar DVD

    What happens when waves meet?


    Sound and wave interactions

    • Diffraction

      • Waves bend and spread out around an object

        • Example: sound carries around a corner or over a hill (see diagram) from where it was made


    Interference

    Interference

    • When two waves meet:

      • Constructive interference: a bigger wave is produced as the crests meet

      • Destructive interference: waves of equal amplitude meet with the crest of one and the trough of the other to cancel each other out

        • Active art on interference

    • Gizmo on Sound Interference


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