L6 and L7 Sound Intensity, Sound Level/Loudness (Decibels), The Ear.
Sound Intensity Intensity definition Changes with distance Intensity scale - decibels.
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Transcript of Sound Intensity Intensity definition Changes with distance Intensity scale - decibels.
Sound Intensity
Intensity definition Changes with distance Intensity scale - decibels
Which wave is has higher energy?
a)
b)
Sound Intensity
Higher energy = higher amplitude. In terms of sound, this means it is louder!
Higher amplitude = Higher volume
Intensity Changes with Distance
Peanut butter on bread, as you spread it out, the thickness of the peanut butter decreases, but the total amount of peanut butter does not.
Intensity Changes with Distance
The total energy of the sound wave does not change, it just spreads out.
Geometric Proof
r
R
2r = RSet up a ratio
Area of small circleArea of large circle
4r2
4R2
r2
R2=
r2
(2r)2= r2
4r2=
1
4
Main Point
Double the distanceIntensity decreases by 4 times
Inverse Square Law!
2
1
dI
Intensity = volume
Create your own analogy…
Intensity Source10,000,000,000,000 Jackhammer, gun
1,000,000,000,000 Siren, rock concert100,000,000,000
10,000,000,000 Subway, lawn mower1,000,000,000
100,000,000 Busy traffic10,000,000 Vacuum cleaner
1,000,000 100,000 Normal Conversation
10,000 Mosquito buzzing1,000 Whisper
100 10 Rustling leaves
1 Threshold of hearing
The human ear is AMAZINGThis is a huge range of
intensities. Also, it is an inconvenient
scale.
Intensity Source dB10,000,000,000,000 Jackhammer, gun 130
1,000,000,000,000 Siren, rock concert 120100,000,000,000 110
10,000,000,000 Subway, lawn mower 1001,000,000,000 90
100,000,000 Busy traffic 8010,000,000 Vacuum cleaner 70
1,000,000 60100,000 Normal Conversation 50
10,000 Mosquito buzzing 401,000 Whisper 30
100 2010 Rustling leaves 10
1 Threshold of hearing 0
Source dBJackhammer, gun 130Siren, rock concert 120
110Subway, lawn mower 100
90Busy traffic 80
Vacuum cleaner 70 60
Normal Conversation 50Mosquito buzzing 40
Whisper 30 20
Rustling leaves 10Threshold of hearing 0
Main Point
Decibel scale is used to measure sound intensity (volume)
+10 dB = 10 times the volume
+20 dB = 100 times the volume
USA Today – ipod article
Extra Credit assignment
Write a 500 word report (NO COPY PASTE!)
On hearing loss and ear bud use.
Use sources USA Today article OSHA Other?
Must cite your sources ( www.bibme.com )
The Threshold of hearing is strongly dependent on frequency
Which is the easiest frequency to hear?
~ 3300 Hz
When the sound is loud (top curve, threshold of pain) all frequencies can be heard equally well.
Frequency Response Curves