1 / 35

SOUND

SOUND. SOUND. Tiffany Rhodes Physics. Topics Covered. Source Wave Medium Frequency Amplitude Speed Mach Number. If a tree falls in the forest and nobody is around to hear it, does it make a sound?. I. EVERY SOUND IS CREATED BY A VIBRATION. Guitar string vibrates

michellewhite
Télécharger la présentation

SOUND

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SOUND SOUND Tiffany Rhodes Physics

  2. Topics Covered • Source • Wave • Medium • Frequency • Amplitude • Speed • Mach Number

  3. If a tree falls in the forest and nobody is around to hear it, does it make a sound?

  4. I. EVERY SOUND IS CREATED BY A VIBRATION • Guitar string vibrates • Reed of clarinet vibrates • Vocal cords vibrate • Table top vibrates when hit with a hammer • Brain translates vibration into sound

  5. II. SOUND IS A LONGITUDINAL WAVE • Compressions and rarefactions • AIR DENSITY CHANGES AS SOUND ENERGY TRAVELS THROUGH • Only energy is transported!!!!

  6. III. SOUND NEEDS A MEDIUM • Sound can travel through air, liquids, and solids • Sound travels faster thru solids! • Sound can NOT travel thru a vacuum

  7. Can sound travel through space? Why?

  8. IV. Frequency of Sound = PITCH • LOW PITCH = LOW FREQUENCY • HIGH PITCH = HIGH FREQUENCY • 1 Hertz = 1 vibration/second

  9. V. HUMAN HEARING • Range 20 – 20,000hz • Most sensitive at 200 to 4,000 Hz. • Normal voice range is about 500 Hz to 2000 hz Low frequencies are vowels and bass. High frequencies are consonants • Lose hearing as we age, especially at the high frequency end. • Girls usually hear higher frequencies better than boys

  10. Range of frequencies

  11. FREQUENCIES • Below 20 HZ = INFRASONIC • Above 20,000 HZ = ULTRASONIC • We can NOT hear either spectrum

  12. Range of frequencies

  13. VI. INTENSITY DEPENDS ON AMPLITUDE • Intensity can be measured by an oscilloscope • More Intense = Bigger amplitude • Less intense = smaller amplitude • Loudness is perceived intensity. Subjective http://www.youtube.com/watch?v=ydxoTPwFwjs

  14. Intensity • Unit of Intensity = Decibels (dB) • Named after Alexander Graham Bell • Zero Decibels = threshold of hearing • Increase to 10 decibels (intensity increased by a factor of 10) • Thus it is 10 times more intense • 60 dB is 100 times more intense than 40 dB http://www.youtube.com/watch?v=RyIphO4Ypoo http://www.youtube.com/watch?v=oPWucNgN8TQ

  15. VI. SPEED OF SOUND • Medium Affects Speed • 2 Properties of a medium affect speed • 1. Elastic properties • 2. Inertial property Temperature of medium also affects it. • Generally, Hotter = faster Cooler = slower • See Hand out for more information

  16. Speed of sound in Various Mediums • Carbon Dioxide 258 • Air 332 • Cork 500 • Alcohol 1241 • Fresh water 1500 • Marble 3810 • Steel 5050 • Aluminum 5104 • Earth 7000-13000

  17. Which medium would sound travel fastest through? • Air • Aluminum • Ocean water • Helium

  18. SPEED EQUATION V = (332 + 0.6T) m/s V = Speed of sound T = Temperature in Celsius

  19. What is the Speed of Sound in air at 30 C and –30 C?

  20. At 30 Celsius:V= (332 + 0.6 * 30)V = 350 m/s At –30 Celsius:V = (332 + 0.6 * -30)V = 314 m/s Hotter = Faster Cooler = Slower

  21. Mach Number • What do you already know about Mach Number? Related to sound?? Related to air planes??

  22. Mach Number • Relates speed of object with speed of sound • Usually used with aircrafts since they are our fastest means of travel • Mach Number = Speed of Object/ Speed of sound • Speed of object and sound have to have same units. They cancel out… • Mach Number has No units!

  23. What do you know about an airplane that travels at mach 1? • It is traveling at the same speed of sound What do you know about an airplane that travels at mach 2? • It is traveling double the speed of sound

  24. II. Wave Equation • Sound is a wave so therefore the wave equation still applies. • Speed of the wave = wavelength * frequency • V =  * f

  25. Questions • Mach Number problems? • Wave Equation problems?

  26. A rocket is traveling at 8643.6 km/hr. If the air temperature is 20ºC, what is the rocket’s Mach Number? Warm Up

  27. Answer • Speed of object = 8643.6 km/h • Speed of sound = 332 + 0.6* Temp = 332 + 0.6 (20) = 344 m/s Convert to km/h 344m 1 km 3600sec 1 sec 1000m 1h = 1238.4 km/h Mach # = Speed of Object/Speed of sound = 8643.6/ 1238.4 = 7

More Related