Chapter 12: Terms

1. longitudinal wave: a wave in which the individual motion that makes up the wave is in the same direction as the motion of the wave (in contrast to a transverse wave in which the individual motion that makes up the wave is perpendicular to the motion of the wave).

2. audible range of frequencies: the range of frequencies that can be heard by a human ear. Typically, this is about 50 Hz to 20 kHz. As people grow older they tend to loose their ability to hear higher frequencies so the audible range may decrease to about 50 Hz to 12 kHz.

3. infrasonic: frequencies below the audible range

4. ultrasonic: frequencies above the audible range

5. supersonic: speeds greater than the speed of sound

6. speed of sound: for air, about 345 m/s (1240 km/h or 770 m/h) at ordinary room temperature (23C)

7. loudness: a description of the power carried across an area by sound; a description of the amplitude of a sound wave

8. fundamental frequency: the lowest frequency present in a sound; determines the pitch of the sound

9. pitch: how low or high a sound is; determined by the fundamental frequency of the sound

10. harmonics: additional frequencies that are present in a sound in addition to the fundamental frequency; also called overtones

11. overtones: additional frequencies that are present in a sound in addition to the fundamental frequency; also called harmonics

12. quality: distinctive characteristics that make up an individual sound; collection of fundamental and harmonics that distinguish an individual sound

13. attack: details of how a sound begins

14. decay: details of how a sound stops

15. octave: a sound with twice the frequency of another is one octave higher

16. equally tempered scale: a scale in which the frequency of each successive note is 1.06 times greater than the previous one

17. beats: the rise and fall in loudness that is heard when two sounds of nearly the same frequency are heard together

18. beat frequency: the frequency with which the loudness rises and falls as two sounds of nearly the same frequency are heard together; equal to the difference in the frequency of the two sounds causing the beats

19. Doppler effect: the change in pitch that is heard due to a moving sound source or to a moving listener

20. sonic boom: the loud noise and pressure wave caused by the buildup of sound waves as an object travels faster than the speed of sound.