What is Sound and How is it Produced? B. Davis and L. Blackburn MathScience Innovation Center

Sound is vibrating matter. If matter vibrates between 20 and 20,000 times in a second humans hear it Vibrating matter

Page 30 in notebook Frequency is… Number of times the vibrations complete a full cycle in one second 1 cycle per second= 1 hertz = 1 hz Remember: Humans can hear 20-20,000 hz

Full cycle Full to and fro movement There and back Complete vibration

How many full cycles? 2 cycles

If this lasts 6 seconds, find the 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. If it vibrates between 20 and 20,000 times in a second humans hear it Listen

Approximate Range (Hz) Species Approximate 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 canary  250-8,000  parakeet  200-8,500  cockatiel owl  200-12,000  chicken  125-2,000  Data source: http://www.lsu.edu/deafness/HearingRange.html

Graph source: http://encarta. msn

time to complete one full cycle. Period is... time to complete one full cycle. If these 2 cycles occur in 6 seconds What is the period? 3 seconds

Frequency =1/3 and period =3 Period - time for one complete cycle. Frequency- number of cycles per second. What is the relationship between period and frequency ? Frequency =1/3 and period =3

What is the relationship between period and frequency ? are reciprocals. 1/3 and 3

Period is how long one season lasts Frequency is how often they occur Period is ¼ of a year Frequency is 4 times per year

Find the frequency and period Example: 60 vibrations are observed in 10 seconds. Find the frequency and period 6 hz 1/6 sec Could a human hear this?

Frequency is Pitch How can you make the sound pitch higher: On string? On percussion? On wind instrument? HIGH low

Frequency is Pitch Listen to musical scale HIGH low

Loudness is Volume How can you make the sound louder: On string? On percussion? On wind instrument? soft LOUD

Loudness 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

Walkman at Maximum Level 100 dB Front Rows of Rock Concert 110 dB Source Intensity 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 Fact source: http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l2b.html

Sound is caused by _________________ of matter Recap: vibrations Sound is caused by _________________ of matter The faster the vibration the higher the _________________________. Frequency or pitch Frequency is measured in _________________________. Cycles per second or hertz (hz)

Recap: louder decibels (db) The bigger the vibration the __________ the sound. Loudness is measured in _________________________. decibels (db)