Chapter 4

Question 1

Wave fronts

Answer 1

The shape/configurations of the component compressions and rarefactions as they diffuse through a medium

Question 2

The further one is from a sound source, the (louder/softer) the sounds are

Answer 2

softer

Question 3

Diffusion

Answer 3

dissipation of sound energy or weakening of wave trains as they travel through a medium

Question 4

Sounds above 1000 Hz lose energy (faster/slower) than low frequencies

Answer 4

faster

Question 5

Sound travels (faster/slower) in warmer air

Answer 5

faster

Question 6

Concave surfaces (focus/diffuse) sound

Answer 6

focus

Question 7

Convex surfaces (focus/diffuse) sound

Answer 7

diffuse

Question 8

the angle at which a wave front hits a smooth, flat surface will be (less than/greater than/equal to) the angle of its echo or reflection

Answer 8

equal to

Question 9

Refraction

Answer 9

Bending of wave fronts as they pass through media having unequal or varying density

Question 10

A cool, dry evening will bend sound (upward/downward). Explain

Answer 10

Downward. Sound meets warmer air lying about the cool evening air

Question 11

A hot, moist afternoon will bend sound (upward, downward). Explain

Answer 11

Upward. Sound travels faster in warmer air & tend to lift away from earth

Question 12

Wind bends sound (in/against) the direction it is blowing and (toward/away) from the ground

Answer 12

in, away

Question 13

Diffraction

Answer 13

The spreading out of wave fronts into areas behind and around physical barriers

Question 14

The higher the frequency the (more/less) sound will be diffracted

Answer 14

less

Question 15

The frequency and amplitude of a sound source moving towards you will (increase/decrease)

Answer 15

increase

Question 16

Compressions and rarefactions that coincide in multiple sound sources will (increase/decrease) overall amplitude

Answer 16

increase (reinforcement)

Question 17

A compression that coexists with a rarefaction in multiple sound sources will (increase/decrease) overall amplitude

Answer 17

decrease (cancelation)

Question 18

Dead spots occur when reflected echoes (reinforce/cancel) the primary sound

Answer 18

cancel

Question 19

Beats are only perceived when the two sources are within __ Hz of each other

Answer 19

20

Question 20

Describe the combination of two tones about 20 Hz apart

Answer 20

rough and raspy

Question 21

Difference tone

Answer 21

two tones >20 Hz apart will create a third tone that is the difference between frequencies of the original tones

Question 22

Summation tones

Answer 22

Subjective tones produced by the ear that are perceived as the sum of two external frequencies

Question 23

Summation tones are heard best at the (top/middle/bottom) of the audible spectrum

Answer 23

middle

Question 24

Subjective tones

Answer 24

Tones that do not exist in the environment, but by forcing parts of the ear into non-linear vibration, are created within the ear itself

Question 25

Reverberation

Answer 25

perceived phenomenon of multiple echoes mixing with the primary sound

Question 26

Absorption

Answer 26

trapping of sound waves in fibrous or porous materials which weakens the wavefront by reflecting and diffusing sound energy

Question 27

Insulation

Answer 27

Preventing sound waves from traveling through physical barriers

Question 28

All sounds travel through a homogenous source at (same/different) rate of speed

Answer 28

same

Question 29

Friction of air molecules (increases/reduces) amplitude

Answer 29

reduces

Question 30

Doppler Effect

Answer 30

The faster the speed that the sound source and listener travel to/away from each other the greater the rise/fall in pitch

Question 31

Describe out-of-phase speakers

Answer 31

One does compression, one does rarefaction, one speaker sounds ‘ahead’ of the other