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Chapter 12

Chapter 12. Sound. Section 1. All sounds are caused by vibrations Sound waves formed when a vibrating object collides with air molecules, transferring energy to them Compressional waves

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Chapter 12

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  1. Chapter 12 Sound

  2. Section 1

  3. All sounds are caused by vibrations • Sound waves • formed when a vibrating object collides with air molecules, transferring energy to them • Compressional waves • have two regions, called compressions and rarefactions, which push air molecules together and then spread them apart

  4. Medium • the type of matter, whether liquid, solid, or gas; that sound waves travel through • A sound wave’s speed depends on the substance of the medium and whether the medium is solid, liquid, or gas. • Sound travels more quickly through solids and liquids because the individual molecules are closer together than the molecules in gas. • As a medium’s temperature increases, its molecules move faster and it conducts sound waves faster.

  5. Section 2

  6. Properties of Sound • Amplitude • The amount of energy a wave carries corresponds to its amplitude • which is related to the density of the particles in the compressions and rarefactions. • Intensity • the amount of energy that flows through a certain area in a specific amount of time • Loudness • human perception of sound intensity • Decibel • Each unit on a scale that measures sound intensity

  7. Pitch • how low or high a sound seems to be • Frequency • is the number of compressions or rarefactions of a sound wave that pass per second • human ears can hear frequencies from ~20 to ~20,000 Hz • Ultrasonic waves • sound frequencies over 20,000 Hz that have medical and scientific uses. • Infrasonic or subsonic waves • frequencies below 20 Hz usually can’t be heard but may feel like a rumble. • Doppler effect • change in pitch or wave frequency due to a moving wave source • either the source of the wave or the observer can be moving

  8. Section 3

  9. Music • sounds that are deliberately used in a regular pattern • Natural frequency • frequency at which the a material vibrates • Resonance • the ability of a medium to vibrate by absorbing energy at its own natural frequency • Soundquality • differences among sounds of the same pitch and loudness • Fundamental frequency • the main tone played and heard • Overtone • vibration with a frequency that is a multiple of the fundamental frequency

  10. Musical instruments • devices used to make musical sounds • Strings • instruments in which sound is produced by plucking, striking, or drawing a bow across tightly stretched strings • Brassandwoodwinds • air vibration in a resonatorwith the pitch determined by the length of the vibrating tube of air • Resonator • Hollow chamber that amplifies sound • Percussioninstruments • produce sound by being struck, shaken, rubbed, or brushed. • Beats • pulsing vibration in loudness

  11. Section 4

  12. Uses of sound • entertainment, warning signals, information • Acoustics • study of sound, which can prevent excessive reverberation and create good listening environments • Echolocation • process of locating objects by sending out sounds and interpreting the waves reflected back • Sonar • uses reflection of underwater sound waves to locate objects • Ultrasound waves • used to diagnose, monitor & treat many medical conditions • Can produce images of internal structures for detection of medical problems • Can treat medical problems such as kidney or gallstones

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