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Sound and Wave Interactions

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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  1. Sound and Wave Interactions

  2. 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

  3. Direction of wave travel Sound and Amplitude • Amplitude: effects the loudness (volume) of sound • Decibel (db) measures volume

  4. 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

  5. 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

  6. 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

  7. 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?

  8. 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

  9. 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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