Ch 3 (MIDTERM)

Question 1

Speed of Sound

Answer 1

343m/s or 1100ft/s

Question 2

What is speed of sound NOT affected by?

Answer 2

Frequency, wavelength, period

Question 3

What is speed of sound affected by?

Answer 3

Medium’s density, elasticity
Temperature/altitude

Question 4

Speed of sound & Elasticity of medium

Answer 4

DIRECT relationship
If medium has high elasticity, more tightly packed, more force repelling each other when compressed, more speed since disturbance is carried onward faster

Question 5

Speed of sound & Density of medium

Answer 5

INVERSE relationship
If medium has more density, greater mass, slower vibration

Question 6

Speed of sound & Temperature of medium

Answer 6

Higher temperature, faster sound (more kinetic energy)

Lower temperature, slower sound (less kinetic energy)

Question 7

Speed of sound & Altitude

Answer 7

Higher altitude, slower sound
Lower altitude, faster sound

Think: higher altitude, colder, slower sound

Question 8

Periodic Wave

Answer 8

Each cycle takes the SAME amount of time
Pattern, symmetrical

Question 9

Aperiodic wave

Answer 9

Each cycle takes different amount of time
Asymmetrical noise

Question 10

Diffraction

Answer 10

BENDING of sound as it encounters a barrier
will either:
a.) pass around barrier
b.) go through a hole

Question 11

If sound passes around a barrier…

Answer 11

Greater wavelength than barrier, better diffraction, sound wave long enough to wrap around barrier and be heard

Lower wavelength than barrier, lower diffraction, sound wave not long enough to wrap around barrier and not be heard

Question 12

If soundwave goes through a hole…

Answer 12

Opening acts as the new origin of sound/sound speaker

Question 13

Head shadow

Answer 13

Wavelength lower than head (higher freq): cannot wrap around, bounces off (reflected)
or, it creates a head shadow where it cannot be heard in both ears because it doesn’t wrap fully around head

Wavelength higher than head (lower freq): wraps around head and can be heard in both ears

Think, whistle vs. horn

Question 14

2 cues for localization

Answer 14

Intensity
Time of arrival

Question 15

Higher frequency uses which cue?

Answer 15

Intensity cue
Lower wavelength will not full wrap around head, one ear will hear it louder, that’s where sound came from

Question 16

Lower frequency uses which cue?

Answer 16

Time of arrival cue
Higher wavelength will fully wrap around head, both ears will hear it at around the same intensity
but one ear would have heard it earlier/faster

Question 17

Anechoic chamber

Answer 17

Closest we can get to a sound proof room
Barrier with absorbing layer and reflecting layer, increasing transmission loss
Kemar (mannequin for hearing aid)

Question 18

When sound wave approaches barrier, it can either:

Answer 18

be reflected
absorbed
transmitted
diffract

Question 19

Incident wave

Answer 19

Sound wave striking object

Question 20

Coefficient of absorption

Answer 20

Ratio of sound absorbed to sound reflected
Different material are better at absorbing

Question 21

Materials better at reflecting

Answer 21

Hard, dense
smooth
i.e. window, sound tiles

Question 22

Materials better at absorbing

Answer 22

Soft, fricative
rough
i.e. carpet

Question 23

Sound proof room…

Answer 23

More sound absorption, less reflection
no reverberation
good for understanding speech because there is less overlap

Question 24

Reverberation time

Answer 24

Sound lasts longer due to incident wave reflecting off and going back into eardrum
If sound wave arrives at ear again when its still vibrating, its REVERBERATION
Small distance
Sound never stops

Question 25

Echo

Answer 25

When sound wave reflected and reaches ear again when ear drums have stopped vibrating
Substantial distance
Sound stops then is heard again

Question 26

Doppler effect

Answer 26

When something moves towards its compression wave, lower distance between each consecutive wave, higher frequency
i.e. train
as train moves closer, higher frequency
as train moves farther, lower frequency

Question 27

Sonic Boom

Answer 27

Plane’s doppler effect
As plane reaches the speed of sound, has a barrier of compressed air constantly in front of it
as plan goes faster than speed of sound, leaves behind a trail of compression waves that is heard as sonic boom on Earth

Question 28

Interference

Answer 28

Combination of waves that can either enhance or delete sound

Question 29

Constructive interference

Answer 29

Enhances sound
Amplifies it by adding up amplitudes of both waves

Question 30

Destructive interference

Answer 30

Deletes sound
Waves combine (areas of compression and rarefaction) and decreases resultant amplitude by subtracting both amplitudes

possibility of complete dampening if exact match