View
229
Download
10
Category
Tags:
Preview:
Citation preview
Physics 101: Lecture 22, Pg 1
Physics Sound ReviewPhysics Sound Review Review and Assessment with Clickers!
Chapeter test
Physics 101: Lecture 22, Pg 2
Speed of SoundSpeed of Sound
sound waves require a medium to travel speed of those waves depends on the density
and atomic forces (tension) in the medium:
Speed = square root(Force /density)
Speed in air is given by V= 331 + 0.6*Temp
Physics 101: Lecture 22, Pg 3
Speed of SoundSpeed of Sound
Rank these medium from fast to slow:
a. Air > water > steel
b. Steel > water > air
c. Water >air > steel
d. Trick question- all the same!
Physics 101: Lecture 22, Pg 4
Speed of SoundSpeed of Sound Rank these from medium
from fast to slow
a. Air > water > steel
b. Steel > water > air
c. Water >air > steel
d. Trick question- all the same!
Medium Speed (m/s)
Steel 5600
Water 1500
Air 344
Steel is 15x air
Water is 3x air
Physics 101: Lecture 22, Pg 5
Speed of SoundSpeed of Sound
speed in air is given by V= 330 + 0.6*Temp(where temp is always measured in celcius)
What is the speed of sound in m/s at room temperature which is about 20 C?
a. 340 b. 550
c. 343 d. 350
Physics 101: Lecture 22, Pg 6
Speed of SoundSpeed of Sound
speed in air is given by V= 330 + 0.6*Temp(where temp is always measured in celcius)
What is the speed of sound in m/s at room temperature which is about 20 C?
a. 340 b. 550
c. 343 d. 350
Physics 101: Lecture 22, Pg 7
What is a Wave?What is a Wave? Movement (wiggle & jiggle) in Space & Time Transfer Energy (Info) without transferring Mass
All waves have similar properties! Sound vibrations move along with the wave
and are called longitudinal waves Light vibrations move perpendicular to the
wave’s motion and are called transverse
Physics 101: Lecture 22, Pg 8
Transverse WavesTransverse WavesThe following video demonstrates the
motion of a Transverse Wave…
Physics 101: Lecture 22, Pg 9
Longitudinal WavesLongitudinal WavesThe following video
demonstrates the motion of a Longitudinal Wave…
Physics 101: Lecture 22, Pg 10
What type of wave is this?What type of wave is this?A. sound b. lightA. sound b. light
c. water wave d. radioc. water wave d. radio
Physics 101: Lecture 22, Pg 11
What type of wave is this?What type of wave is this?A. A. sound sound b. light b. light
c. water wave d. radioc. water wave d. radio
Physics 101: Lecture 22, Pg 12
Which statement is totally Which statement is totally true?true?
a.. sound is a longitudinal wave that does not exist at ultra sound frequencies
b. Sound is a transverse wave that exists at infrasonic and ultrasonic frequencies
c. Sound is a longitudinal wave that does not exist in outer space
d. Sound is a transverse wave that does not exist above 120 dB
Physics 101: Lecture 22, Pg 13
Which statement is totally Which statement is totally true?true?
a.. sound is a longitudinal wave that does not exist at ultra sound frequencies
b. Sound is a transverse wave that exists at infrasonic and ultrasonic frequencies
c. Sound is a longitudinal wave that does not exist in outer space
d. Sound is a transverse wave that does not exist above 120 dB
Physics 101: Lecture 22, Pg 14
Wave parts (M=10Wave parts (M=1066, , =10=10-6-6))
Crests
Troughs
Amplitude (A)
Wavelength (
Equilibrium
wavewave
Physics 101: Lecture 22, Pg 15
Wave CharacteristicsWave Characteristics
v = f
Wavelength (: Distance it takes for Wave to repeat itself (units in meters)
Period (T): Time for one complete cycle (units in seconds)
Frequency (f): Number of complete cycles per unit time (units in 1/sec or Hz)
Unit Analysis: m/s = (m)(1/s)
f = 1/T
Wave Velocity (v): Speed of wave propagation (units in m/s)
Physics 101: Lecture 22, Pg 16
What is shown What is shown here?here?
A. frequencyA. frequency b. wavelength b. wavelength
c. period c. period d. amplituded. amplitude
Physics 101: Lecture 22, Pg 17
What is shown What is shown here?here?
A. frequencyA. frequency b. wavelengthb. wavelength
c. period c. period d. amplituded. amplitude
Physics 101: Lecture 22, Pg 18
A 100 Hz wave contains 10 waves A 100 Hz wave contains 10 waves every 20 m. What is it’s speed?every 20 m. What is it’s speed?
A. 1 m/sA. 1 m/s b. 2 m/sb. 2 m/sc. 5m/sc. 5m/s d. 200 m/sd. 200 m/s
v = d/t v= f v = /T
Physics 101: Lecture 22, Pg 19
A 100 Hz wave contains 10 waves A 100 Hz wave contains 10 waves every 20 m. What is it’s speed?every 20 m. What is it’s speed?
A. 1 m/sA. 1 m/s b. 2 m/sb. 2 m/sc. 5m/sc. 5m/s d. 200 m/sd. 200 m/s
v = d/t v= f v = /T
Physics 101: Lecture 22, Pg 20
If you shake a slinky at If you shake a slinky at twice the frequency…twice the frequency…
a. amplitude doublesa. amplitude doubles b. period doubles b. period doublesc. speed doublesc. speed doubles d. no answer d. no answer
Physics 101: Lecture 22, Pg 21
If you shake a slinky at If you shake a slinky at twice the frequency…twice the frequency…
a. amplitude doublesa. amplitude doubles b. period doubles b. period doublesc. speed doublesc. speed doubles d. no answer d. no answer
Physics 101: Lecture 22, Pg 22
Physics of MusicPhysics of Music
BeatBeat is humming sound between 2 is humming sound between 2 closely matched frequenciesclosely matched frequencies
(beat frequency= f(beat frequency= f22 – f – f11))
Octave Octave = double or half frequency= double or half frequency
half stephalf step = frequency * 1.059 = frequency * 1.059 (1.059 * itself 12 times = 2(1.059 * itself 12 times = 2
since 12 notes in an octave)since 12 notes in an octave)
Physics 101: Lecture 22, Pg 23
Beats are due to interferenceBeats are due to interference
Consider two harmonic waves A and B meeting at x=0.
A(1t)
B(2t)
CONSTRUCTIVEINTERFERENCE
DESTRUCTIVEINTERFERENCE
C(t) = A(t) + B(t)
Physics 101: Lecture 22, Pg 24
A4 is middle A on a piano with a 440Hz. A4 is middle A on a piano with a 440Hz. What is the frequency of the next A What is the frequency of the next A
note 12 keys higher?note 12 keys higher?A. 441A. 441 b. 880b. 880C. 439C. 439 d. 220d. 220
Physics 101: Lecture 22, Pg 25
Your guitar string should play 256 Hz, Your guitar string should play 256 Hz, but when you play a 256Hz tuned but when you play a 256Hz tuned
piano key at the same time you hear a piano key at the same time you hear a beat frequency of 2 hz. What is the beat frequency of 2 hz. What is the
frequency of your strings?frequency of your strings?
A.A.2 2
b. 258b. 258
c. 254 or c. 254 or 258258
d. 512d. 512
Physics 101: Lecture 22, Pg 26
Intensity and LoudnessIntensity and Loudness Intensity is the power per unit area. (W/m2)
I = P / A where P = power in watts
A = area = 4*pi *d2 (d=distance away)
Threshold for hearing I0 = 10-12 W/m2
Loudness (Decibels) is the perception of intensityMeasured on log scale using decibels = (10 dB) log10 ( I / I0)
Physics 101: Lecture 22, Pg 27
Bow WavesBow Waves source of a wave moves
faster than the sound waves
Ex: Boat faster water waves
V-Shaped pattern of bow waves behind the boat.
Physics 101: Lecture 22, Pg 28
Shock WavesShock Waves
A Shock Wave = 3-D version of 2-D Bow Wave.
Except that the shock wave is shaped conically while the bow wave is a V-Shape.
Physics 101: Lecture 22, Pg 29
Sonic BoomSonic BoomPlane travels faster than soundSound waves overlap– constructive interferencesonic boom is continuously formed behind jet Mach number = speed plane / speed of sound
Mach = jet distance/sound distance
jet distance
Sound distance
Physics 101: Lecture 22, Pg 30
Sonic BoomSonic BoomWhat is the mach number of this plane?
1. 1 2. 2 3. 3 4. 4
Physics 101: Lecture 22, Pg 31
Sonic BoomSonic BoomWhat is the mach number of this plane?
Physics 101: Lecture 22, Pg 32
Intensity and LoudnessIntensity and LoudnessRules of 10 dB
10 times more people is 10x more sound
it’s 10 more dB
it’s 10x more intense
but it only sounds 2x louder to us
Compare to 1 person whispering: 0 dB , Io
10 people talking: 10 dB, I = 10x, loudness = 2x
100 people talking: 20 dB, I=100x, loudness=4x
1000 people talking: 30 dB, I=1000x, loudness=8x
Physics 101: Lecture 22, Pg 33
Intensity and LoudnessIntensity and LoudnessRules of 3 dB
2 times more people is 2x more intensity
but it only sounds 1.7x louder to us
Compare to 1 person whispering: 0 dB , Io
2 people talking: 3 dB, I = 2x,
4 people talking: 6 dB, I= 4x,
8 people talking: 9dB, I= 8x
16 people talking: 12 dB, I= 16x
Physics 101: Lecture 22, Pg 34
Intensity ACTIntensity ACT Recall Intensity = P/A. If you are standing 6 meters
from a speaker, and you walk towards it until you are 3 meters away, by what factor has the intensity of the sound increased?
1) 2 2) 4 3) 8 4) 18
Physics 101: Lecture 22, Pg 35
Intensity ACTIntensity ACT Recall Intensity = P/A. If you are standing 6 meters
from a speaker, and you walk towards it until you are 3 meters away, by what factor has the intensity of the sound increased?
1) 2 2) 4 3) 8 4) 18
Physics 101: Lecture 22, Pg 36
Decibels ACTDecibels ACT
If 1 person can shout with loudness 50 dB. How loud will it be when 100 people shout?
1) 52 dB 2) 70 dB 3) 150 dB
Physics 101: Lecture 22, Pg 37
Intense Concert PhysicsIntense Concert PhysicsSuppose at a concert you want to quadruple (4x) how loud it sounds.
Since you can’t quadruple the number of speakers w/o permission,how much closer should you get to quadruple your listening pleasure?
1. 2x close 2. 4x closer 3. 8x closer 4. 16x closer
Physics 101: Lecture 22, Pg 38
Intense Concert PhysicsIntense Concert PhysicsSuppose at a concert you want to quadruple (4x) how loud it sounds.
Since you can’t quadruple the number of speakers w/o permission,how much closer should you get to quadruple your listening pleasure?
1. 2x close 2. 4x closer 3. 8x closer 4. 16x closer
Physics 101: Lecture 22, Pg 39
Intense Concert PhysicsIntense Concert PhysicsSuppose at a concert you want to decrease how loud it sounds
By 100 times using ear plugs. How many decibels is this?
1. 0dB 2. 3 dB 3. 6 dB 4. 20 dB
Physics 101: Lecture 22, Pg 40
Intense Concert PhysicsIntense Concert PhysicsSuppose at a concert you want to decrease how loud it sounds
By 100 times using ear plugs. How many decibels is this?
1. 0dB 2. 3 dB 3. 10 dB 4. 20 dB
Physics 101: Lecture 22, Pg 41
Constructive Constructive InterferenceInterference
Constructive Interference occurs when 2 waves combine with their troughs lining up, and their crests lining up.
Once aligned, a wave “grows” between the waves, demonstrating increased size.
Physics 101: Lecture 22, Pg 42
Destructive Destructive Interference DiagramInterference Diagram
The following demonstrates Destructive Interference…
Physics 101: Lecture 22, Pg 43
Standing Waves areStanding Waves areinteger multiples of harmonicsinteger multiples of harmonics
Node…. NodeStrings, flutes
/2, , 3/2 /, …
Anti-Node…. Nodeclarinet, palm pipe
/4, 3, 5/4 , …
Physics 101: Lecture 22, Pg 44
How many waves is this How many waves is this 11stst harmonic harmonic
(fundamental)?(fundamental)?A. ¼ b. ½ c. 3/2 d. 1A. ¼ b. ½ c. 3/2 d. 1
Physics 101: Lecture 22, Pg 45
How many waves is this How many waves is this 11stst harmonic harmonic
(fundamental)?(fundamental)?A. ¼ b. ½ c. 3/2 d. 1A. ¼ b. ½ c. 3/2 d. 1
Physics 101: Lecture 22, Pg 46
Which harmonic wave is Which harmonic wave is this:this:
a. 1a. 1stst b. 2 b. 2ndnd c. 3 c. 3rdrd d. 4th d. 4th
Physics 101: Lecture 22, Pg 47
Which harmonic wave is Which harmonic wave is this:this:
a. 1a. 1stst b. 2 b. 2ndnd c. 3 c. 3rdrd d. 4th d. 4th
Physics 101: Lecture 22, Pg 48
This 3This 3rdrd harmonic forms in harmonic forms ina. guitara. guitar b. flute b. flute
c. clarinet d. organ pipec. clarinet d. organ pipe
Physics 101: Lecture 22, Pg 49
This 3This 3rdrd harmonic forms in harmonic forms ina. guitara. guitar b. flute b. flute
c. clarinet d. organ pipec. clarinet d. organ pipe
Physics 101: Lecture 22, Pg 50
Resonance ACTResonance ACT
What happens to the fundamental frequency of a pipe, if the air (v=300 m/s) is replaced by helium (v=900 m/s)?
1) Increases 2) Same 3) Decreases
Physics 101: Lecture 22, Pg 51
Resonance ACTResonance ACT
What happens to the fundamental frequency of a pipe, if the air (v=300 m/s) is replaced by helium (v=900 m/s)?
1) Increases 2) Same 3) Decreases
Physics 101: Lecture 22, Pg 52
Organ PipeOrgan Pipe
A 0.9 m organ pipe (open at both ends) is measured to have it’s first harmonic at a frequency of 382 Hz. What is the wavelength of this note?a. 1.8 m b. 0.9m c. 0.45m d. No idea and can’t draw
pictures
L=0.9 m
Physics 101: Lecture 22, Pg 53
Organ PipeOrgan Pipe
A 0.9 m organ pipe (open at both ends) is measured to have it’s first harmonic at a frequency of 382 Hz. What is the wavelength of this note?a. 1.8 m b. 0.9m c. 0.45m d. No idea and can’t draw
pictures
L=0.9 m
Physics 101: Lecture 22, Pg 54
Organ PipeOrgan Pipe
A 0.9 m organ pipe (open at both ends) has a speed of sound of 180 m/s. What is it’s frequency?
L=0.9 m
A.1.8 b. 180 c.100 d. Idk, need wavelength
Physics 101: Lecture 22, Pg 55
Organ PipeOrgan Pipe
A 0.9 m organ pipe (open at both ends) has a speed of sound of 180 m/s. What is it’s frequency?
L=0.9 m
A.1.8 b. 180 c.100 d. Idk, need wavelength
Physics 101: Lecture 22, Pg 56
DopplerDoppler Effect Effect When source is moving toward you:
Distance between waves decreasesFrequency increasesVelocity of sound is still same (same medium)
When source is moving away from you:Distance between waves increasesFrequency decreasesVelocity of sound is same (same air,same temp)
Physics 101: Lecture 22, Pg 57
Preflight 5Preflight 5 As a police car passes you with its siren
on, the frequency of the sound you hear from its siren
1) Increases 2) Decreases 3) Same
Doppler Example Audio
Doppler Example Visual
Physics 101: Lecture 22, Pg 58
Preflight 5Preflight 5 As a police car passes you with its siren
on, the frequency of the sound you hear from its siren
1) Increases 2) Decreases 3) Same
Doppler Example Audio
Doppler Example Visual
Physics 101: Lecture 22, Pg 59
Doppler ACTDoppler ACTA: You are driving along the highway at 65 mph, and behind you a police car, also traveling at 65 mph, has its siren turned on.
B: You have both pulled over to the side of the road, and a police car turns on a siren and travels past you as they chase after someone else
In which case does the frequency of the siren seem higher to you?
1. Case A 2. Case B 3. both 4. neither
vs
f
vo
f’v
Physics 101: Lecture 22, Pg 60
Doppler ACTDoppler ACTA: You are driving along the highway at 65 mph, and behind you a police car, also traveling at 65 mph, has its siren turned on.
B: You have both pulled over to the side of the road, and a police car turns on a siren and travels past you as they chase after someone else
In which case does the frequency of the siren seem higher to you?
1. Case A 2. Case B 3. both 4. neither
vs
f
vo
f’v
Physics 101: Lecture 22, Pg 61
SummarySummarySound travels as fast as the medium allows
it’s measured by wavelength and frequency
Two sounds close but not perfect make beats
You hear a higher or lower pitch when sound moves closer or further away
Resonance is the resounding of natural frequencies or harmonics creating timbre
Physics 101: Lecture 22, Pg 62
That’s all folks!That’s all folks!
Recommended