Q3oItpVa9fs Cymatics httpsyoutube WMnRxFDVw0g Julius Sumner Miller and Sound Waves Review Frequency describes the number of cycles in one second Period describes the number of seconds for one cycle ID: 538487
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Slide1
https://youtu.be/
Q3oItpVa9fs
CymaticsSlide2
https://youtu.be/
WMnRxFDVw0g
Julius Sumner Miller and SoundSlide3
Waves Review
Frequency describes the number of cycles in one second.Period describes the number of seconds for one cycle.(Period and frequency are inverses of each other.)Slide4
Waves Review
The speed of a wave depends only on the medium and can be calculated by multiplying the wavelength (distance between repeated points) by the frequency of the cycles.If the frequency of a wave increases, what must happen to the wavelength? What about the wave speed?Slide5
Sound Waves
As a source of sound vibrates, a series of compressions and rarefactions travels outward from the source.
Sound waves can travel in solids, liquids, and gases.
A young person can normally hear pitches with frequencies from about 20 to 20,000 Hz.
Sound waves visualized:
https
://youtu.be/
px3oVGXr4mo
http://www.physicsclassroom.com/Physics-Interactives/Waves-and-Sound/Simple-Wave-Simulator/Simple-Wave-Simulator-
Interactive
http://plasticity.szynalski.com/tone-
generator.htmSlide6
Fundamental Frequency
First Harmonic (n=1)
L = 1/2
λ
Second
Harmonic (n=2)
L = 2/2
λ
Third
Harmonic (n=3)
L = 3/2
λ
Harmonic Frequencies on a StringSlide7
Harmonic Frequencies on a StringSlide8
Harmonic Frequencies on a String
The
frequency
of the
nth
harmonic.Slide9
Harmonic Frequencies on a String
The
frequency
of the
nth
harmonic.
Harmonic NumberSlide10
Harmonic Frequencies on a String
The
frequency
of the
nth
harmonic.
The
speed
of the wave on the string.
Harmonic NumberSlide11
Harmonic Frequencies on a String
The
frequency
of the
nth
harmonic.
The
speed
of the wave on the string.
Harmonic Number
The speed only depends on the medium that the wave travels through.Slide12
Harmonic Frequencies on a String
The
frequency
of the
nth
harmonic.
The
speed
of the wave on the string.
The
length
of the string
Harmonic NumberSlide13
Sound from a pipe
Standing waves in open and closed pipesSlide14
Open Pipes
Standing waves can also form in columns of air.
Because
the air particles
can move freely at the open end of a pipe,
each end of the pipe must be an
antinode
.Slide15
Open Pipes
Standing waves can also form in columns of air.
Because the air particles can move freely at the open end of a pipe, each end of the pipe must be an
antinode
.Slide16Slide17
First Harmonic
L = 1/2
λ
Second Harmonic
L = 2/2
λ
Third Harmonic
L = 3/2
λSlide18
n = 1
n = 2
n = 3
First Harmonic
L = 1/2
λ
Second Harmonic
L = 2/2
λ
Third Harmonic
L = 3/2
λ
n
= 1, 2, 3, …Slide19
n = 1
n = 2
n = 3
First Harmonic
L = 1/2
λ
Second Harmonic
L = 2/2
λ
Third Harmonic
L = 3/2
λ
Harmonic Frequencies For An Open Pipe
n
= 1, 2, 3, …Slide20
Example (#12 on Standing Waves Practice)
The range of human hearing is roughly 20 Hz to 20,000
Hz. Based on these limits, what are the lengths of the longest and shortest pipes (open at both ends) you would expect to find on a pipe organ?Slide21
Closed Pipes
For a pipe that is closed at one end, the air molecules at the
closed end of
the pipe
cannot move, forming a
node
.
A new
set of waves is possible.
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.htmlSlide22
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.html
Closed Pipes
For a pipe that is closed at one end, the air molecules at the closed end of the pipe cannot move, forming a
node
.
A new set of waves is possible.Slide23
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.htmlSlide24
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.htmlSlide25
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.htmlSlide26
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.html
Closed PipeSlide27
http://www.acs.psu.edu/drussell/Demos/StandingWaves/
StandingWaves.html
Harmonic Frequencies For A Closed Pipe
Closed PipeSlide28
Example (#15 from Standing Waves Practice)
Aaron blows across the opening of a partially filled 0.2-m tall soft drink bottle and finds that the air vibrates with a fundamental frequency of 472 Hz. How high is the liquid in the bottle?Slide29
Open Pipe
Closed Pipe
String
(Fixed
at Both Ends)
n
= 1, 2, 3, …
n
= 1, 2, 3, …Slide30
When you play any instrument, any single note is actually a combination of harmonics, where the loudest note is the fundamental frequency.
The additional harmonics combine with the fundamental frequency to produce a sound that is unique for that instrument.
https://youtu.be/VRAXK4QKJ1Q?t=
19sSlide31
Measuring the Speed of SoundSlide32
standing Waves in a Closed Pipe (from cymatics
)http://youtu.be/sIopZnMLeQo