1 / 32

Chapter 20

Chapter 20. Sound. Slide - A tree in the forest. 1. ORIGIN OF SOUND. The frequency of a sound wave is the same as the. frequency of the source of the sound wave. Demo - Oscillator and speaker Video – You Tube - Hearing Test .

aldon
Download Presentation

Chapter 20

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. Chapter 20 Sound

  2. Slide - A tree in the forest.

  3. 1. ORIGIN OF SOUND • The frequency of a sound wave is the same as the frequency of the source of the sound wave. Demo - Oscillator and speaker Video – You Tube - Hearing Test

  4. The human hearing range is about 20 Hz - 20,000 Hz. Frequencies below 20 Hz are infrasonic. Frequencies above 20,000 Hz are ultrasonic.

  5. 2. NATURE OF SOUND IN AIR Video - Tuning Fork Demo - Strobed Tuning Fork Sound in air is longitudinal with Compressions (Condensations) and Rarefactions Demo - Vortex Box

  6. 3. MEDIA THAT TRANSMIT SOUND • Air is most common but is a poor conductor. • Solids and liquids are good conductors. • A medium is required. • Video - Vacuum Pump

  7. 4. SPEED OF SOUND IN AIR • Video – Lumberjack Thunder and Lightning Explosion • Much slower than light • Video– Sound Delay • Depends on wind, temperature, humidity • Slide - Wind and Snoopy • Does not depend on frequency

  8. = 750 mi/hr = 330 m/s At 0o C (dry air) v = 1090 ft/s How v varies: increases with humidity increases with temperature is faster in liquids and solids

  9. 5. REFLECTION OF SOUND • Occurs anytime waves change media. Example: Echoes • Reverberation - prolonging of sound by reflection Rumble of distant thunder (several reflections from different distances) Example:

  10. What is not reflected is transmitted and absorbed. • The study of sound properties is acoustics. Examples: San Francisco Symphony Hall Back of lecture room

  11. 6. REFRACTION OF SOUND When different parts of a wave front move at different speeds, the wave front will bend. This bending is known as refraction. It occurs when different parts of a wave front are traveling in different media. Slide - Sounds and Sleeping Dog

  12. Warm Air Cool Air

  13. Thunder and lightning Sometimes distant lightning is not heard well. Other times it is. Other Examples Submarines and Sonar Refraction due to thermal gradients can “hide” submarines. Ultrasound in medicine Ultrasound echo and dolphins

  14. 7. ENERGY IN SOUND WAVES • Energy in sound is weak when compared to the energy in light. • The human ear is a remarkable detector. 10 million people speaking at the same time produce approximately enough energy to light one flashlight.

  15. High frequencies of sound in air more easily lose their energies to thermal energy than do low frequencies. That is why low frequencies can be heard farther away.

  16. 8. FORCED VIBRATIONS • Demo - Tuning Fork Touching a Table • Sound is intensified because of the larger surface area that can vibrate the air. • The surface is forced to vibrate at the frequency of the tuning fork. (It is not a resonance phenomenon.) • Demo – Call Mobile Phone on Table Examples: Musical sounding boards

  17. 9. NATURAL FREQUENCY • Demo - Drop Different Sounding Objects • Objects have natural frequencies at which they vibrate. • The natural frequency depends on elasticity and shape. • Demo - Gravity Chimes • Demo – Boomwhackers

  18. Yankee Doodle (arranged by Anthony T.)

  19. Beethoven’s Ode to joy (arranged by Anthony T.)

  20. Christmas Boom WhackersCan CanBoomWhackers

  21. 10. RESONANCE • Resonance occurs when successive impulses are applied to a vibrating object in time with its natural frequency. • Result - increased amplitude Examples: Swinging Marching on a bridge (rout step or break step)

  22. Video - Matched Tuning Forks Tuning Fork on Guitar Breaking Glass Demo - Matched Tuning Forks Demo - Singing Glass Glass armonicaby Ben Franklin

  23. Demo - Vibrating Rod Demo - Vibrating Plate Demo - Fog Horn Note: Submultiples of the natural frequency also produce resonance. Demo - 256 & 512 Hz Tuning Forks Video - Tacoma Narrows Bridge (url)

  24. 11. INTERFERENCE • Defined in Chapter 19 • Demo - Oscillator & Two Speakers • Slide - Oscillator & Two Speakers

  25. Examples: Dead spots in theaters and music halls Anti-noise technology

  26. 12. Beats • Fluctuating loudness due to two tones of slightly different frequencies that are sounded together (tremolo) • It is an interference effect. • Beats/s = difference in frequencies • Musical instruments are tuned using beats. • Dolphins use beats and Doppler effect.

  27. Slide - Beats

  28. D D D C C C Consider two waves of slightly different frequencies traveling together. Constructive Interference Destructive Interference

  29. URL - Beats Demo - Vibrating Rods Demo - Two Oscillators & Two Speakers Demo - Guitar

  30. RADIO BROADCASTS Slide - Radio Broadcasts AM - 535 kHz to 1605 kHz FM - 88 MHz to 108 MHz

More Related