Sound-Environment Interaction

Question 1

The absorptive capability of a material is ________ and may be measured in ________

Answer 1

Frequency dependent, Sabins

Question 2

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

Answer 2

Absorbed

Question 3

________ refers to a bending of the sound wave because of differences in the speed of the sound wave caused by temperature gradients

Answer 3

Refraction

Question 4

A sound shadow is the result of the inability of a sound wave to ___________ around an obstacle

Answer 4

Diffract

Question 5

Atmospheric absorption of sound energy varies according to __________

Answer 5

Frequency, temperature and humidity

Question 6

Atmospheric absorption is __________ for low humidity situations with hot temperatures

Answer 6

High

Question 7

Ground absorption is generally __________ for high frequencies

Answer 7

Greater

Question 8

______ is a singular reflection off a surface

Answer 8

Echo

Question 9

Multiple reflections from parallel surfaces or buildings is called ___________

Answer 9

Canyon Effect

Question 10

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

Answer 10

destructive interference

Question 11

A barrier that fails to obscure “line of sight” propagation from a source may ______ sound levels

Answer 11

Increase

Question 12

A six-foot barrier will be most effective for reducing ______frequencies, and completely ineffective for reducing ______ frequencies

Answer 12

High, Low

Question 13

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

Answer 13

dead spots

Question 14

The fundamental resonance modes of a room are called __________

Answer 14

eigentones

Question 15

A delayed sound, as with an echo, must occur at least ______ after the event without being masked by the original sound

Answer 15

50 ms

Question 16

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

Answer 16

-60 dB below

Question 17

Reverberation time ________ with room size and _______ with higher absorption coefficients

Answer 17

Increases, decreases

Question 18

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

Answer 18

masking

Question 19

The ratio of direct to indirect sound in an enclosed space falls off with _________ distance from the source, with a greater percentage of the sound energy being reflected sound

Answer 19

Increasing

Question 20

Due to their ability to _________ around obstacles, low frequency sound waves are difficult to localize

Answer 20

diffract

Question 21

Uniform distribution of sound in a space is called ________

Answer 21

a diffuse sound field

Question 22

A ________ is an environment with anechoic conditions because the sound energy falls off according to the square of the distance

Answer 22

free field

Question 23

The phenomenon of ________ occurs when a moving sound source approaches and recedes from a listener

Answer 23

Doppler effect

Question 24

According to the Doppler effect, when the speed is constant, the effect is a ________ when the source approaches and a ________ when it recedes

Answer 24

higher pitch, lower pitch