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What is Sound What is Sound and and
How is it Produced?How is it Produced?
B. Davis and L. BlackburnB. Davis and L. BlackburnMathScience Innovation CenterMathScience Innovation Center
Sound is vibrating matter.Sound is vibrating matter.
If matter vibrates between If matter vibrates between
20 and 20,000 times in a second20 and 20,000 times in a second
humans hear ithumans hear it
Vibrating matterVibrating matter
Frequency is…Frequency is…
Number of times the vibrations complete a Number of times the vibrations complete a full cyclefull cycle in one second in one second
1 cycle per second= 1 hertz = 1 hz1 cycle per second= 1 hertz = 1 hz
Remember: Humans can hear 20-20,000 hz
Page 30 in notebook
Full cycleFull cycle
Full Full toto and and frofro movement movement There and backThere and back Complete vibrationComplete vibration
If this lasts 6 seconds, find the If this lasts 6 seconds, find the frequency.frequency.
2 cycles in 6 seconds =
2/6 cycle per second
or 1/3 hertz (.33 hz)
Could a human hear this?
Sound is vibrating matter.Sound is vibrating matter.
If it vibrates between If it vibrates between
20 and 20,000 times in a second20 and 20,000 times in a second
humans hear ithumans hear it ListenListen
SpeciesApproximate Range (Hz)
human 64-23,000
dog 67-45,000
cat 45-64,000
cow 23-35,000
horse 55-33,500
sheep 100-30,000
rabbit 360-42,000
rat 200-76,000
mouse 1,000-91,000
gerbil 100-60,000
guinea pig 54-50,000
hedgehog 250-45,000
raccoon 100-40,000
ferret 16-44,000
opossum 500-64,000
chinchilla 90-22,800
bat 2,000-110,000
beluga whale 1,000-123,000
elephant 16-12,000
porpoise 75-150,000
goldfish 20-3,000
catfish 50-4,000
tuna 50-1,100
bullfrog 100-3,000
tree frog 50-4,000
canary 250-8,000
parakeet 200-8,500
cockatiel 250-8,000
owl 200-12,000
chicken 125-2,000 Data source: http://www.lsu.edu/deafness/HearingRange.html
Period is...Period is...
If these 2 cycles occur in 6 seconds
What is the period? 3 seconds
time to complete one full cycle.time to complete one full cycle.
PeriodPeriod - - time for one complete cycle.Frequency-Frequency- number of cycles per
second.What is the relationship between What is the relationship between
period and frequency ?period and frequency ?
Frequency =1/3 and period =3
What is the relationship between What is the relationship between period and frequency ?period and frequency ?
1/3 and 3
Period and frequencyPeriod and frequency are reciprocals.are reciprocals.
Period is how long Period is how long one season lasts one season lasts
Frequency is how Frequency is how often they occur often they occur
Period is ¼ of a year
Frequency is 4 times per year
Find the frequency and periodFind the frequency and period
1/6 sec
Example: 60 vibrations are observed in 10 seconds.
6 hz
Could a human hear this?
Frequency is PitchFrequency is Pitch
How can you make the sound How can you make the sound pitch higher:pitch higher:
On string?On string? On percussion?On percussion? On wind instrument?On wind instrument?
low
HIGH
Loudness is VolumeLoudness is Volume
How can you make the sound How can you make the sound louder:louder:
On string?On string? On percussion?On percussion? On wind instrument?On wind instrument?
soft LOUD
•measured in Decibels
•1 Bel = named after Alexander Graham Bell
•Decibel is 1/10 of a Bel
•Logarithmic Scale ( like earthquakes)
•A 30 dB sound is ten times louder than a 20 dB sound
•A 40 dB sound is one hundred times louder than a 20 dB sound
LoudnessLoudness
SourceIntensity Level
Threshold of Hearing 0 dB
Rustling Leaves 10 dB
Whisper 20 dB
Normal Conversation 60 dB
Busy Street Traffic 70 dB
Vacuum Cleaner 80 dB
Large Orchestra 98 dB
Walkman at Maximum Level 100 dB
Front Rows of Rock Concert 110 dB
Threshold of Pain 130 dB
Military Jet Takeoff 140 dB
Instant Perforation of Eardrum 160 dB
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Recap:Recap:
Sound is caused by _________________ Sound is caused by _________________ of matterof matter
vibrations
The faster the vibration the higher the _________________________.Frequency or pitch
Frequency is measured in _________________________.Cycles per second
or hertz (hz)