Page 346 - NS-2 Textbook

PHYSICAL SCIENCE 341

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B. ·What pressure in ne"\vtons/ln does this corre- 10. What are two modes of operation of shipboard sonar
spond to? systems?
4. What is the audible frequency range? 11. Why do submarines rarely use active sonar?
5. In "\That lmits is relative intensity or noise level 12. How do helicopters use sonar to detect submarines?
measured?
6. Why should people be careful to protect their
eardrwns against loud sotmds?
Vocabulary
7. A. What is the apparent frequency shift of a passing
whistle or horn called? medium (sound) fathometer
B. What causes this shift? sowld intensity Doppler effect
8. What three factors affect the speed of sound in water? eardrum active sonar
9. What does the Doppler effect enable a sonar teclmi- ear canal passive sonar
dan to do when analyzing returning SOl1al' echoes inner ear hydrophone
frmn a submarine? auditory nerve sonobuoy