1. Reviewing Main Ideas The Nature of Sound
Sound is a longitudinal wave created by something that is vibrating.
Sound travels fastest through solids and slowest through gases. You see the flash of lightning before you hear the clap of thunder because light travels faster than sound.

2. Reviewing Main Ideas The Nature of Sound
The human ear can be divided into three sectionsthe outer ear, the middle ear, and the inner ear. Each section plays a specific role in hearing.
Hearing involves four stages: gathering sound waves, amplifying them, converting them to nerve impulses, and interpreting the signals in the brain.

3. Reviewing Main Ideas Properties of Sound
Intensity is a measure of how much energy a wave carries. Humans interpret the intensity of sound waves as loudness.
The pitch of a sound becomes higher as the frequency increases.

4. Reviewing Main Ideas Music
Music is made of sounds used deliberately in a regular pattern.
Instruments, such as a flute, use a variety of methods to produce and amplify sound waves.
When sound waves of similar frequencies overlap, they interfere with each other to form beats.

5. Reviewing Main Ideas Using Sound Acoustics is the study of sound.
Sonar uses reflected sound waves to detect objects.
Ultrasound waves can be used for imaging body tissues or treating medical conditions.

6. Chapter Review Question 1
What are the two types of regions in a longitudinal wave?

7. Chapter Review
Answer
The two regions are called compressions and rarefactions.

8. Chapter Review Question 2 What is the function of the cochlea? Answer
The cochlea converts sound waves to nerve impulses.

9. Chapter Review Question 3
What is the function of the hollow chamber of a violin?
Answer
The hollow chamber is the resonator; it amplifies the sound when air inside it vibrates.

10. Chapter Review Question 4
Which is most likely to produce wave pattern B?
A. a horse’s nay
B. didgeridoo
fingernails
scraping
chalkboard
D. steel drum

11. Chapter Review
Answer
The answer is C. Pattern A has a regularly repeating pattern; B has random patterns and pitches.

12. Chapter Review Question 5
If sound travels at 1,500 m/s in water, how long will it take a sonar pulse to travel 4.5 km?
A s
B s
C s
D s

13. Chapter Review
Answer
The answer is D. Remember that 1 km is equal to 1,000 m.

14. Standardized Test Practice
Question 1
Use the table to estimate how far a sound will travel through a steel rail in 5s.
A. 5 km
B. 10 km
C. 20 km
D. 30 km

15. Standardized Test Practice
Answer
The answer is D. Remember that distance equals speed multiplied by time.

16. Standardized Test Practice
Question 2
Which structure vibrates and transfers sound waves to the middle ear where they are amplified?
A. A
B. B
C. C
D. D

17. Standardized Test Practice
Answer
The answer is A. The vibrations of the eardrum are passed into the middle ear, where the waves are amplified.

18. Standardized Test Practice
Question 3
__________ is the human perception of sound volume and depends primarily on sound intensity.
A. decibel
B. frequency
C. loudness
D. pitch

19. Standardized Test Practice
Answer
The answer is C. The decibel is the unit on the scale for sound intensity; loudness is the human perception for sound volume and depends primarily on sound intensity.

20. Standardized Test Practice
Question 4
Sonar is used to locate an underwater object. At approximately what depth would you expect to find the object if the speed of sound in water is 1,439 m/s and the total time taken for the sonar pulse was 1.6 s?

21. Standardized Test Practice
A m
1,200 m
C. 1,800 m
D. 2,400 m

22. Standardized Test Practice
Answer
The answer is B. Remember that the time it takes for the sonar pulse to reach the bottom of the ocean is half the total time.