Soundwaves 100212173149-phpapp02
-
Upload
abhinav-yadav -
Category
Technology
-
view
518 -
download
0
Transcript of Soundwaves 100212173149-phpapp02
![Page 1: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/1.jpg)
. 2 0 0 7W S a u t t e r
![Page 2: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/2.jpg)
These are also calledCompressional Waves
![Page 3: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/3.jpg)
Crest
Trough
Compression Rarefaction Compression CompressionRarefaction Rarefaction
Trough
Crest
Rarefaction = low PressureCompression = high Pressure
![Page 4: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/4.jpg)
Wavelength
λ
Frequency
ν
Velocity Wavelength
λFrequency
ν Velocity
vx =
![Page 5: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/5.jpg)
Wave A
Wave A
Wave A
Wave B
Wave B
Wave B
Constructive interference
Destructive interference
Partially Constructive interference
![Page 6: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/6.jpg)
Intensity = Power / Area
SoundSource
Sound radiates out from a source as concentric spheresand follows an Inverse Square function
![Page 7: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/7.jpg)
Inverse Square means as distance from the source doubles,the intensity 1/4 the original. If distance triples, the intensity
is 1/9 the original and so on.
The surface area of a sphere is given by 4 π r2
Power is measured in watts ( 1 joule / second)
Intensity = Power / Area = watts/ 4 π r2
Or Watts / meter2
![Page 8: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/8.jpg)
dB = 10 log ( I / I0 )
I = the intensity of the sound to be evaluatedI0 = intensity of lowest sound that can be heard
(1 x 10-12 watts / meter2)
![Page 9: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/9.jpg)
•SINCE LOGS ARE POWERS OF 10 THEY ARE USED JUST LIKE THE POWERS OF 10 ASSOCIATED WITH SCIENTIFIC NUMBERS.
•WHEN LOG VALUES ARE ADDED, THE NUMBERS THEY REPRESENT ARE MULTIPLIED.
•WHEN LOG VALUES ARE SUBTRACTED, THE NUMBERS THEY REPRESENT ARE DIVIDED
•WHEN LOGS ARE MULTIPLIED, THE NUMBERS THEY REPRESENT ARE RAISED TO POWERS
•WHEN LOGS ARE DIVIDED, THE ROOTS OF NUMBERS THEY REPRESENT ARE TAKEN.
Decibels are logarithmic functions
![Page 10: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/10.jpg)
• A LOGARITHM (LOG) IS A POWER OF 10. IF A NUMBER IS WRITTEN AS 10X THEN ITS LOG IS X.
• FOR EXAMPLE 100 COULD BE WRITTEN AS 102 THEREFORE THE LOG OF 100 IS 2.
• IN PHYSICS CALCULATIONS OFTEN SMALL NUMBERS ARE USED LIKE .0001 OR 10-4. THE LOG OF .0001 IS THEREFORE –4.
• FOR NUMBERS THAT ARE NOT NICE EVEN POWERS OF 10 A CALCULATOR IS USED TO FIND THE LOG VALUE. FOR EXAMPLE THE LOG OF .00345 IS –2.46 AS DETERMINED BY THE CALCULATOR.
Decibels are logarithmic functions
![Page 11: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/11.jpg)
Whisper 20 decibels Plane 120 decibels
Conversation 60 decibels Siren 100 decibels
![Page 12: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/12.jpg)
The frequency of a string depends on the Tension (N)and string Linear Density in kilograms per meter (Kg/m).
Light strings under high tension yield high frequencies.Heavy strings under low tension yield low frequencies.
![Page 13: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/13.jpg)
V (air) = 341 m/s at 20 oC
If observer is moving towards the source, V(observer) = +If observer is moving towards the source, V (observer) = -If source is moving towards the observer, V (source) = - If source is moving towards the observer, V (source) = +
![Page 14: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/14.jpg)
Slower at low temp
Faster at high temp
![Page 15: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/15.jpg)
0C
![Page 16: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/16.jpg)
Moving Towardsource
Moving Towardobserver Observed Frequency
Is higher
![Page 17: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/17.jpg)
Moving Away from
observer
Moving Away from
sourceObserved FrequencyIs lower
![Page 18: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/18.jpg)
Moving Away from
observerObserver
At restObserved FrequencyIs lower
![Page 19: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/19.jpg)
Moving Towardobserver
ObserverAt restObserved Frequency
Is higher
![Page 20: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/20.jpg)
1/2 λ 1 λ 3/2 λ
Fundamental λ = 2 L Second Harmonic λ = L Third Harmonic λ = 2/3 L
![Page 21: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/21.jpg)
λ fundamental
λ fundamental
d = diameter of tubeL = length of tube at first resonant point
If d is small compared to L(which is often true) then:
![Page 22: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/22.jpg)
Since V = λ f
If velocity is constant thenas λ decreases, f increases
In the same ratio
Second Harmonic λ = L
Fundamental λ = 2 L
Third Harmonic λ = 2/3 L Third Harmonic λ =3 ffund
Fundamental f = ffund
Second Harmonic f = 2 ffund
![Page 23: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/23.jpg)
1/4 λ 3/4 λ 5/4 λ
Fundamental λ = 4 L Second Harmonic λ = 4/3 L Third Harmonic λ = 4/5 L
![Page 24: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/24.jpg)
λ fundamental
λ fundamental
d = diameter of tubeL = length of tube at first resonant point
If d is small compared to L(which is often true) then:
![Page 25: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/25.jpg)
Since V = λ f
If velocity is constant thenas λ decreases, f increases
In the same ratio
Second Harmonic λ = 4/3 L
Fundamental λ = 4 L
Third Harmonic λ = 4/5 L Third Harmonic λ = 5 ffund
Fundamental f = ffund
Second Harmonic f = 3 ffund
![Page 26: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/26.jpg)
Fundamental λ = 2 L
Second Harmonic λ = L
Third Harmonic λ = 2/3 L
Fourth Harmonic λ = ½ LNode
Node
VIBRATIONAL MODES
![Page 27: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/27.jpg)
Since V = λ f
If velocity is constant thenas λ decreases, f increases
In the same ratio
Second Harmonic λ = L
Fundamental λ = 2 L
Third Harmonic λ = 2/3 L Third Harmonic λ = 3 ffund
Fundamental f = ffund
Second Harmonic f = 2 ffund
![Page 28: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/28.jpg)
Waves from aDistant source = crest
= trough
Barrier withTwo slits
In phase wavesEmerge from slits
Constructive interference
Destructiveinterference
![Page 29: Soundwaves 100212173149-phpapp02](https://reader033.fdocuments.in/reader033/viewer/2022052911/559dcf141a28ab5e368b4852/html5/thumbnails/29.jpg)