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Ch. 26

Ch. 26. 1. Sound waves are produced by vibrations of material objects 2. Pitch is the frequency of a sound wave 3. Average range of hearing is 20-20,000 Hz. 4. Infrasonic sounds occur at frequencies less than 20 Hz; Ultrasonic sounds occur at frequencies above 20,000 Hz. 5.

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Ch. 26

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  1. Ch. 26

  2. 1. Sound waves are produced by vibrations of material objects • 2. Pitch is the frequency of a sound wave • 3. Average range of hearing is 20-20,000 Hz. • 4. Infrasonic sounds occur at frequencies less than 20 Hz; Ultrasonic sounds occur at frequencies above 20,000 Hz.

  3. 5. • The compression is the high pressure or more dense region of the sound wave; the rarefaction is the low pressure or less dense region of the sound wave. • The original pulse pushes the matter together (compression) and when the matter moves backwards producing a low density region behind (rarefaction)

  4. 6. Sound is a mechanical wave and requires a medium to travel through. So sound waves cannot travel through a vacuum. • 7. a) 340 m/s • b) an increase in temperature will increase the speed of sound. • 8. The speed of sound in air is much slower that in water or steel. • 9. Sound travels faster in solids and liquids because the molecules are closer together and transfer energy more rapidly.

  5. 10. Intensity is objective and is a measured by instruments, loudness is relative to the sensation sensed in the brain, so it is subjective, but is related to intensity. • 11. Different objects make different sounds because each exhibit different sets of natural frequencies when vibrating. • 12. It means that differing compositions vibrate naturally in a specific characteristic way. • 13. The sounding board is forced to vibrate by the vibrating source, which causes the sound to be amplified (more air molecules are set vibrating creating a louder sound)

  6. 14. A forced vibration causes an object to vibrate at that frequency, but unless the forced vibration matches the natural frequency of the object, resonance cannot occur. • 15. A tissue is too limp to rebound and continue to vibrate • 16. Resonance occurs when the vibration from one object matches the natural frequency of another object causing the vibrations in the second object to build in amplitude over repeated vibrations.

  7. 17. The tuner on a radio station allows the receiver to resonate to the incoming signal by adjusting the natural frequency of the radio to the desired station. • 18. Yes. Sound waves can destructively interfere. • 19. If the path lengths differ by ½ wavelength, then the

  8. 20. Beats occur when sound waves of slightly differing frequencies interfere constructively and destructively, producing a regular fluctuation that sounds louder and softer. • 21. The beat frequency is 2 Hz (496 Hz -494 Hz).

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