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Unit 2 Sound

Unit 2 Sound. Physical Science Mrs. Lewis. How sounds are made. Produced when matter vibrates Travel as longitudinal wave and mechanical wave. Frequency = Pitch. Pitch is a description of how high or low a sound is Depends on the frequency/wavelength High frequency is high pitch

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Unit 2 Sound

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  1. Unit 2Sound Physical Science Mrs. Lewis

  2. How sounds are made • Produced when matter vibrates • Travel as longitudinal wave and mechanical wave

  3. Frequency = Pitch • Pitch is a description of how high or low a sound is • Depends on the frequency/wavelength • High frequency is high pitch • Normal human hearing range is 20-20,000 Hz • Ultrasonic is higher than 20,000 Hz • Infrasonic is lower than 20 Hz

  4. Loudness • Loudness is measure of how well a sound can be heard • Indicated by amplitude of a wave • Unit of volume is decibel (dB) • Sounds > 120 dB are painful

  5. Doppler Effect • Definition is change in observed frequency of a wave when the sound source, the observer, or both are moving • Apparent increase in pitch as movement is towards sound, decrease in pitch when movement is away

  6. Speed of Sound – Depends on Medium • Phase • Fastest through solids, slower through liquids, slowest through gases • Temperature • Lower temp = slower speed/Higher temp = faster speed • Because molecules move slower/faster

  7. Interaction of Matter & Sound • Reflection • Bouncing back of a wave when the wave hits a barrier (echo) • Sound waves reflect best off smooth hard surfaces • Absorption • Rough wall absorbs sound better

  8. Sonar • Stands for Sound Navigation and Ranging

  9. Uses for SONAR • Commercial fishing • Mapping ocean floor • Camera that focuses automatically • Bats/dolphins • Cars

  10. Ultrasound • Ultrasonic Cleaning (15-400 kHz) • Jewellery, lenses, coins, watches, dental and surgical instruments, fountain pens, industrial parts, electronic equipment, cellular phone repair • Industrial ultrasonic cleaners are used in the automotive, sporting, printing, marine, medical, pharmaceutical, electroplating, engineering and weapons industries

  11. Medical Uses • Unborn baby • Allow doctors to see inside body • Destroy unwanted tissues • Physical therapy to heat injured muscles

  12. Ultrasound of baby

  13. Interactions of Sound Waves • Interference – when two or more waves overlap and combine to form one wave • Constructive interference • Waves combine to form a wave with a larger amplitude (sonic booms) • Destructive interference • Waves combine to form a wave with a smaller amplitude (noise canceling headphones)

  14. Resonance • Happens when a sound wave matches the natural frequency of an object and causes the object to vibrate • Natural frequency – all objects have a frequency (or set of) that it vibrates at

  15. Resonance • Musical Instruments • Air into mouthpiece cause vibration • Vibrations form standing wave & get louder • Standing wave is pattern of vibration that looks like a wave is standing still • Resonance occurs when standing wave is formed

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