Unit Test 4 (Sound) Flashcards
(93 cards)
1
Q
How does sound start?
A
disturbance, vibration, wave.
2
Q
Describe transverse waves.
A
The particle vibrates perpendicularly to the direction of the motion.
3
Q
Give an example of transverse.
A
An audience wave at a concert or sports game.
4
Q
What is a wavelength?
A
The length between one point on a wave to the same point on the next wave. Measured in m or cm. LAMBDA
5
Q
What is amplitude
A
The height of the crest or trough, the distance from rest position to max or min.
6
Q
What is frequency?
A
How often the waves (cycles) are occurring. Measured in cycles/sec or Hz.
7
Q
What is a period?
A
How long it takes to complete 1 cycle. Measured in seconds.
8
Q
Describe longitudinal waves.
A
A wave vibrating in the direction of propagation. Has compressions (close together) and rare factions (spread out).
9
Q
What is the universal wave equation?
A
V=fλ
V=speed of the wave in the medium (m/s)
f=frequency (Hz)
λ=wavelength (m)
10
Q
What is controlled by the medium?
A
The speed of the wave in the medium. When the particles are different spaces apart sound moves differently through them.
11
Q
What is controlled by the source?
A
The frequency (cycles/sec)
12
Q
What is sound?
A
A form of energy produced by rapidly vibrating objects detectable by sensory organs such as the ear.
13
Q
What does a medium do?
A
A medium efficiently permits the transmission of energy through vibrations. (air, water)
14
Q
What type of wave does sound travel in?
A
A longitudinal wave.
15
Q
What mediums can sound travel through?
A
solids, liquids, and gases.
16
Q
What state does sound travel fastest through? Why?
A
Solids because the particles are closer together in solids so when they transfer the vibrations more quickly. Example: line in a classroom.
17
Q
What is the speed of sound affected by in air?
A
The temperature.
18
Q
What is a crest?
A
The highest point the medium rises to.
19
Q
What is a trough?
A
The lowest point the medium sinks to.
20
Q
Formula for temperature and speed of sound:
A
Vs=332 + 0.6T
21
Q
What is mach #?
A
A number that refers to the speed of an object compared to the speed of sound.
22
Q
Formula for mach #:
A
Mach #=Vo/Vs
Vo=velocity of object
Vs=velocity sound
23
Q
What does mach # greater than one mean?
A
Faster than the speed of sound (SUPER SONIC).
24
Q
What does mach # 1 mean?
A
Speed of sound.
25
What does mach # less than one mean?
Slower than the speed of sound. (SUB SONIC)
26
What affects the pitch you hear?
Thhe frequency: high frequency gives a high pitch. Low frequency gives low pitch.
27
What is the human hearing range?
20-20 000 Hz but it decreases with age.
28
What is loudness/intensity of sound measured in?
Decibals (dB)
29
What does loudness actually describe?
The power of sound/m squared. Uses a logarithmic scale, no linear relationship.
30
What happens as sound wave moves out from a source?
Its energy is spread more thinly.
31
Threshold of hearing
0 dB
32
Average whisper at 2m
20 dB
33
Busy street traffic
70 dB
34
Instant perforation of ear drum
160 dB
35
What is the principle of superposition?
The principle of superposition may be applied to waves traveling through the same medium at the same time. The waves pass through each other without being disturbed. The net displacement of the medium is simply the sum of the individual wave displacements.
AMPLITUDES ARE ADDED. WAVES PASS THROUGH EACH OTHER UNAFFECTED.
36
What is the wave created as they pass through each other called?
The resultant wave.
37
What is constructive interference?
If the resultant wave has a larger amplitude than the original one.
38
What is it called if the resultant wave has a larger amplitude than the original one?
constructive interference.
39
What is it called if the resultant wave is smaller than the original?
Destructive interference.
40
what is destructive inference?
If the resultant wave has a smaller amplitude than the original one.
41
How many waves do tuning forks make?
Two: one originating between the tines and one on the outside.
42
What causes quiet zones in a tuning forks?
The two waves that radiate from the middle and the sides are in opposite phases. When they meet at the corners, they create quiet zones because the amplitudes add together creating destructive interference.
43
What are beats?
A periodic change in sound intensity caused by the interference between two similar waves.
44
Describe how the waves interact to form beats.
The tuning fork with a slightly lower frequency will also have a slightly LONGER wavelength. The waves interact and the superposition of the two waves sometimes add constructively and sometimes destructively because they don't line up perfectly. It creates beats with slightly different frequencies.
45
What is the beat frequency formula?
Bf=f1-f2.
46
Explain the doppler effect.
As an object moves it moves towards the wave fronts it just produced. the waves in front of it are shortened and the ones behind are lengthened. The overall effect is a change in pitch from high to low. The change depends on the original speed of sound and the speed of the object.
47
Formula for moving sound sources.
```
f=(vs/vs+-vo)fo
fo= frequency of object
f= frequency heard
vs=velocity of speed
vo= velocity of object.
```
48
Steps of doppler effect.
1. moves towards wave front
2. wavelengths decrease.
3. frequency increases.
49
What is the sound barrier?
Where vo=vs
50
Why is there a buildup of pressure when an object breaks the sound barrier?
Because the object moves at the same speed as the sound it is creating, the compressions are constantly getting more compressed resulting in high pressure.
51
Why do fast planes have needle noses?
The sharp point displaces the air creating turbulence and breaking up the pressure.
52
Why do you hear a boom after a fast plane?
Because the high pressure on air creates a disturbance which makes a BOOM! You hear it after the plane has already passed because the plane leaves the sound behind.
53
What is a sound boom?
When an object is going faster than the speed of sound, the sound is left behind creating a cone of pressurized air. This creates a BOOM when it reaches the ground.
54
What is resonance?
If an object is free to vibrate and is acted on by a force that matches its natural frequency, its AMPLITUDE OF VIBRATION WILL INCREASE. This is known as a resonance.
55
What will happen if two tuning forks have the same frequency and are close enough together?
The other will start ringing when the air compressions hit it at the exact right time. It will only work if they have the same frequency.
56
Why will the ringing of the second tuning fork only happen if they are the same frequency?
Because the air compressions have to push on the fork at the right amplitude.
57
What are standing wave patterns?
Two waves having equal amplitude and wavelength yet travelling in opposite directions. They will INTERFERE resulting in a standing wave.
58
What is a node?
A point that remains at rest (because of destructive interference). The space between two nodes is half a wave length.
59
What is a loop?
Areas with alternating double crest and double troughs (because of constructive inference).
60
The space between nodes is...
.5λ
61
What will happen to a longitudinal wave when in reflects from a fixed point?
It will reverse phase.
62
How is an acoustical standing wave formed?
If the pattern is repeated, interference between the incoming and outgoing waves occurs producing the acoustical standing wave with nodes and loops.
63
How else can an acoustical standing wave be formed?
When there is a free end reflection.
64
Where do nodes form?
At the fixed end.
65
Where do anti nodes (loops) form?
At the free end.
66
How often do nodes and antinodes alternate?
Every 1/4 λ
67
How long are loops?
.5λ long.
68
What is the only way resonance can occur in closed end air columns?
If a standing wave is set up involving the air molecules. This can occur if the length of the column is a resonant length.
69
What are the three resonant lengths for closed end air columns?
1st: .25λ
2nd: .75λ
3rd: 1.25λ
70
What are the three resonant lengths for open ended air columns?
1st: .5λ
2nd: λ
3rd: .75λ
71
What is an anvil?
A tiny bone that passes vibrations from hammer to the stapes,
72
what is a cochlea?
A spiral shaped , fluid-filled inner ear structure; it is lined with cilia that move when vibrated and cause a nerve impulse to form.
73
What is an eardrum?
A thin membrane that vibrates when sound waves reach it.
74
What is an Eustachian tube?
A tube that connects the middle ear to the back of the nose, it equalizes the pressure between the middle ear and the air outside. When you pop your ears as you change altitude you are equalizing the air pressure in your middle ear.
75
What is the hammer?
A tiny bone that passes vibrations from ear drum to the anvil.
76
What do the nerves do?
These carry electro-chemical signals from the cochlea to the brain.
77
What is the outer ear canal?
Tube through which sound travels to the ear drum.
78
What is the pinna?
The visible part of the outer ear.
79
What does the pinna do?
It collects sound and directs it into the outer ear canal.
80
What are the semicircular canals?
Three loops of fluid-filled tubes that are attached to the cochlea in the inner ear.
81
What do the semicircular canals do?
Give us sense of balance.
82
What is the stapes?
tiny, u shaped bone that passes vibrations from the stirrup to the cochlea. this is the smallest bone in the human body. (0.25-0.33cm)
83
Does the amplitude of transverse waves change as the pulse moves from one end to the other?
Yes the amplitude decreases because it is moving farther away from the energy source. Friction also contributes to the loss of energy.
84
Do two transverse pulse stay the same distance apart?
Yes, this tells us that we can't do anything to control the speed of the pulse because the medium determines that.
85
If you use a medium with more tension how is the speed of the pulses affected?
The speed of the pulses is increased. More tension=more potential elastic energy.
86
What happens to a pulse when it encounters a fixed end?
It bounces back on the opposite side and dissipates as it gets farther from the energy source.
87
Two opposite and positive longitudinal waves do what?
Pass through each other unaffected but add together to create as big wave.
88
Two opposite longitudinal waves one positive one negative do what?
Pass through each other unaffected but cancel each other out.
89
How do you create a standing wave on a slinky?
Have one fixed end and generate pulses with a constant frequency.
90
How does having a fixed or free end affect the reflected waves?
Fixed end: wave reflects on other side.
| Free end: wave reflects on same side.
91
Name two reasons why the reflected pulse has a smaller amplitude than the incoming pulse?
Friction and if the fixed end is not completely fixed.
92
What happens when an incoming pulse goes from a thin medium to a thick medium?
Thin side: opposite side comes back, same speed, smaller amplitude, longer wavelength.
thick side: slower, smaller amplitude, wavelength gets smaller, same side and same direction.
93
What happens when an incoming pulse goes from a thick medium to a thin medium?
Thick side: reflects on same side, smaller amplitude, same speed.
Thin side: same direction, higher amplitude, faster speed, smaller wavelength.
