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Published byPhoebe Bond Modified over 9 years ago
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What is a sound wave? Mechanical wave – longitudinal *A vibration *Particles of medium are disturbed *Causes a wave causes Most common medium is air Can travel through solids and liquids
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Sound Interactions Reflection – Echo - when a sound wave reflects off a surface. Harder and smoother the surface the stronger the reflection. Diffraction – Through openings (doorways) – Around corners Interference – Can be: Destructive – sound will be fainter Constructive – sound will be louder
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Speed of Sound (SOS) 343 m/s – at room temperature through air Depends on medium sound is traveling through – 3 characteristics of the medium affect SOS: 1. Elasticity 2. Density 3. Temperature
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Elasticity The ability of a medium to bounce back after being disturbed. More elastic medium – the particles bounce back faster – sound travels faster. Less elastic medium – the particles bounce back slowly – sound travels slower. From faster to slower: solids > liquids > gases
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Density Sound travels more slowly in denser mediums Due to particles not moving as quickly back to rest position in denser materials (too crowded).
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Temperature Sound travels more slowly at lower temperatures than higher temperatures. Because particles move slower in lower temperatures.
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SOS final thoughts The faster the particles of the medium can return to rest position – the faster sound will move through medium. – More elastic – faster (bounce back quicker) – Less dense – faster (not as crowded) – Higher temp – faster (particles naturally move faster) First person to break sound barrier (go faster than sound) – Chuck Yeager – Flew at higher altitude b/c lower temp = lower SOS
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Properties of sound Loudness – depends on amount of energy used to create sound (amplitude of wave). Pitch – depends on frequency of wave.
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Loudness Depends on 2 things: – The amount of energy it takes to make the sound. – The distance from the source of the sound. Decibel (dB) – unit for loudness of sound Intensity – The amount of energy a sound wave carries over a certain amount time in a particular area.
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Pitch How high or low the sound seems High pitch – high frequency Low pitch – low frequency Ultrasound – sound waves with freq. above normal human hearing. (Usually above 20,000 Hz) Infrasound – Below human range of hearing (usually under 20 Hz)
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The Doppler Effect The change in frequency (pitch) as a source of sound MOVES in relation to the observer. – Pitch increases as source moves toward observer. – Pitch decreases as source moves away. Think of a siren approaching then passing by. It sounds different. Can happen with light waves also.
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