(click on the capital letter for your answer)

1. The absorptive capability of a material is frequency dependent and may be measured in sabins. T or F

2. The absorption coefficient is the fraction of acoustic energy which is ________ at a surface.

A. absorbed
B. reflected
C. transmitted
D. incident

3. Which process does NOT depend on the reflection of sound waves?

A. reverberation
B. diffusion
C. echo
D. refraction

4. Under conditions of temperature inversion (a warm air mass lying over a cold air mass) a sound wave is refracted upwards and away from the ground and therefore will NOT carry far. T or F

5. The phenomenon of sound shadow is the result of the inability of a sound wave to ___________ around an obstacle.

A. reflect
B. refract C. diffract
D. diffuse

6. Atmospheric absorption of sound energy varies according to __________.

A. frequency
B. temperature C. humidity
D. all of the above

7. Atmospheric absorption is high for low humidity situations with hot temperatures. T or F

8. Ground absorption is generally greater for high frequencies. T or F

9. Multiple reflections from parallel surfaces or buildings is called ___________.

A. echo
B. ground effect
C. canyon effect
D. diffusion

10. Ground effect refers to ___________ between the direct and reflected wave when the source and receiver are close to the ground.

A. absorption
B. attenuation
C. constructive interference
D. destructive interference

11. A barrier that fails to obscure "line of sight" propagation from a source may increase sound levels rather than lower them. T or F

12. A barrier such as a six-foot wall is most effective for attenuating ________ frequencies.

A. all
B. high
C. low
D. mid-range

13. The wavelengths for frequencies between 100 and 1000 Hz are in the range __________.

A. 10 - 100 ft / 3 - 30 m
B. 1 - 10 ft / .3 - 3 m
C. 0.1 - 1 ft / 3 - 30 cm
D. 0.01 - 0.1 ft / .3 - 3 cm

14. The fixed pattern of nodes in a standing wave are experienced as _________.

A. beats
B. combination tones
C. phasing
D. dead spots

15. Standing waves contribute to good diffusion of a sound wave. T or F

16. The fundamental resonance modes of a room are called __________.

A. dead spots
B. eigentones
C. harmonics
D. formants

17. For an echo to be perceived as such, i.e. as a separate event, it must occur at least _________ afterwards without being masked by the original sound.

A. 1 ms
B. 20 ms
C. 50 ms
D. 200 ms

18. Reverberation time is the time required for the sound energy to fall to ________ its original strength after its cessation.

A. one-half
B. one-tenth
C. -30 dB below
D. -60 dB below

19. Reverberation time increases with room size and decreases with higher absorption coefficients. T or F

20. Speech comprehension decreases with reverberation times great than a second due to the __________ of speech transients.

A. masking
B. absorption
C. attenuation
D. interference

21. The ratio of direct to indirect sound in an enclosed space falls off with increasing distance from the source, with a greater percentage of the sound energy being reflected sound. T or F

22. Due to their ability to diffract around obstacles, low frequency sound waves are difficult to localize. T or F

23. Uniform distribution of sound in a space is called ________.

A. a free field
B. a diffuse sound field
C. anechoic conditions
D. standing waves

24. The perceived pitch of a sound, moving at constant speed, changes as it approaches and leaves an observer. Compare to the pitch of the source at rest, the perceived pitch is _________ as it approaches.

A. constantly descending
B. higher by a constant amount
C. constantly ascending
D. lower by a constant amount