Sound

1. Chapter Sound 15 In this chapter you will: • Describe sound in terms of wave properties and behavior. • Examine some of the sources of sound.

2. Section Properties and Detection of Sound 15.1 Sound Waves • _________ is an important part of existence for many living things. • From your everyday experiences, you already are familiar with several of the characteristics of sound, including volume, _____, and ______. • You can use these, and other characteristics, to categorize many of the sounds.

3. Section Properties and Detection of Sound 15.1 Sound Waves • Sound is a type of _________. • As the bell shown in the figure moves back and forth, the edge of the bell strikes particles in the air. • When the edge moves forward, air particles are driven forward; that is the _______ particles bounce off the bell with a greater ___________.

4. Section Properties and Detection of Sound 15.1 Sound Waves • When the edge moves backward, air particles bounce off the bell with a lower velocity. • The result of these velocity changes is that the forward motion of the bell produces a region where the _______________ is slightly _________ than average. • The backward motion produces slightly below-average pressure.

5. Section Properties and Detection of Sound 15.1 Sound Waves • _____________ among the air particles cause the ______________ variations to move away from the bell in all directions. • A pressure variation that is transmitted through matter is a __________________. • Sound waves move through air because a __________ source produces regular ______________, or ______________, in air pressure. • The air particles ___________, transmitting the pressure variations away from the _____________ of the sound.

6. Section Properties and Detection of Sound 15.1 Detection of Pressure Waves • The ___________ of the wave is the number of oscillations in pressure each ________. • The _____________ is the distance between successive regions of high or low pressure. • Because the motion of the air particles is parallel to the direction of motion of the wave, sound is a ________________ wave.

7. Section Properties and Detection of Sound 15.1 Sound Waves • The speed of sound in air depends on the temperature, with the speed increasing by about _______ for each ______ increase in air temperature. • At room temperature (______), soundmoves through air at sea level at a speed of _________ m/s. • The speed of sound is _________ in _________ and _____________ than in gases. • Sound _________ travel in a __________ because there are _____ particles to __________.

8. Section Properties and Detection of Sound 15.1 Sound Waves • Sound waves share the general properties of other waves. • ____________ sound waves are called ____________. • The time required for an echo to return to the source of the sound can be used to find the _____________between the source and the reflective object. • Two sound waves can interfere, causing dead spots at nodes where little sound can be heard. • The frequency and wavelength of a wave are related to the speed of the wave by the equation _________.

9. Section Properties and Detection of Sound 15.1 Detection of Pressure Waves • Sound detectors convert sound energy—the kinetic energy of the vibrating air particles—into another form of ________. • A common detector is a microphone, which _________________ waves into _________ energy. • A microphone consists of a thin disk that vibrates in response to sound waves and produces an electrical signal.

10. Section Properties and Detection of Sound 15.1 The Human Ear • The _____ detects sound waves over a wide range of frequencies and is sensitive to an enormous range of ____________. • In addition, human hearing can distinguish many different qualities of sound.

11. Section Properties and Detection of Sound 15.1 Perceiving Sound – Pitch • Marin Mersenne and Galileo first determined that the ________ we hear depends on the __________ of vibration. • Pitch can be given a name on the musical scale. For instance, the middle C note has a frequency of 262 Hz. • The ear is not equally sensitive to all frequencies.

12. Section Properties and Detection of Sound 15.1 Perceiving Sound – Frequency • Most people _________ hear sounds with frequencies below ____ Hz or above _________ Hz. • Older people are less sensitive to frequencies above 10,000 Hz than young people. • By age ____, most people cannot hear sounds with frequencies ________ 8000 Hz. • This loss affects the ability to understand speech.

13. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • Frequency and wavelength are two ____________ characteristics of sound waves. • Another physical characteristic of sound waves is amplitude. • Amplitude is the __________ of the ___________ in pressure along a wave.

14. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • In humans, sound is detected by the ear and interpreted by the brain. • The __________ of a sound, as perceived by our sense of hearing, depends primarily on the ___________ of the pressure wave. • The human ear is extremely sensitive to pressure variations in sound waves, which is the amplitude of the wave.

15. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • The sound level depends on the ratio of the pressure variation of a given sound wave to the pressure variation in the most faintly heard sound, 2×10−5 Pa. • Such an amplitude has a sound level of 0 dB. • Because humans can detect a wide range in pressure variations, these amplitudes are measured on a logarithmic scale called the ______________. • The unit of measurement for sound level is the ____________ (dB).

16. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • Most people perceive a 10-dB increase in sound level as about twice as loud as the original level. • In addition to pressure variations, power and intensity of sound waves can be described by decibel scales.

17. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • Exposure to loud sounds, in the form of noise or music, has been shown to cause the ear to ________ its _____________, especially to high frequencies. • The longer a person is exposed to loud sounds, the greater the effect. • A person can recover from short-term exposure in a period of hours, but the effects of long-term exposure can last for days or weeks. • Long exposure to _________ or greater sound levels can produce __________ damage.

18. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • Hearing loss also can result from loud music being transmitted through stereo headphones from personal radios and ______ players. • Cotton earplugs _________ the sound level only by about ____ dB. • Special ear inserts can provide a ______ reduction. • Specifically designed earmuffs and inserts as shown here in the figure can reduce the sound level by up to ____ dB.

19. Section Properties and Detection of Sound 15.1 Perceiving Sound – Loudness • Loudness, as perceived by the human ear, is not directly proportional to the pressure variations in a sound wave. • The ear’s __________ depends on both ______ and ____________. • Also, perception of _________ tones is different from perception of a mixture of tones.

20. Section Properties and Detection of Sound 15.1 The Doppler Effect

21. Section Properties and Detection of Sound 15.1 The Doppler Effect • For both a moving source and a moving observer, the frequency that the observer hears can be calculated using the equation below. • The frequency perceived by a detector is equal to the velocity of the detector relative to the velocity of the wave, divided by the velocity of the source relative to the velocity of the wave, multiplied by the wave’s frequency.

22. Section Properties and Detection of Sound 15.1 The Doppler Effect • In the Doppler effect equation, v is the velocity of the sound wave, vd is the velocity of the detector, vs is the velocity of the sound’s source, fs is the frequency of the wave emitted by the source, and fd is the frequency received by the detector. • The equation for Doppler effect applies when the source is moving, when the observer is moving, and when both are moving.

23. Section Properties and Detection of Sound 15.1 The Doppler Effect • The ________ effect occurs in all _______ motion, both mechanical and __________. • _________ detectors use the Doppler effect to measure the _________ of baseballs and automobiles. • ____________ observe light from distant galaxies and use the Doppler effect to ____________ their speeds and infer their distances. • _________ can detect the _________ of the moving heart wall in a fetus by means of the Doppler effect in ultrasound. • Bats use sound waves to navigate and locate their prey.

24. Section Section Check 15.1 Question 1 What properties does a sound wave share with other waves?

25. Section Section Check 15.1 Answer 1 Like other waves, _______ waves also _________ off ________ objects, such as the walls of a room. Reflected sound waves are called echoes. The two sound waves can __________ (like other waves), causing dead spots at nodes where little sound could be heard. The __________, speed, and _____________ are also related as v = fλ, like other waves.

26. Section Section Check 15.1 Question 2 What does loudness of sound depend upon? • Amplitude of pressure waves • Frequency of pressure waves • Wavelength of pressure waves • Period of pressure waves

27. Section Section Check 15.1 Answer 2 Answer: ____________ Reason:The loudness of sound, as perceived by our sense of hearing, depends primarily on the amplitude of pressure waves.