1 / 15

Vibrations through a medium

http://www.youtube.com/watch?v=wvJAgrUBF4w http://www.youtube.com/watch?v=7v0c0Al5X0g 2:00. SOUND. Vibrations through a medium. Sound. All sounds are produced by the vibrations of material objects. PITCH = The impression about the frequency of a sound

tcathey
Télécharger la présentation

Vibrations through a medium

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. http://www.youtube.com/watch?v=wvJAgrUBF4w http://www.youtube.com/watch?v=7v0c0Al5X0g 2:00 SOUND Vibrations through a medium

  2. Sound • All sounds are produced by the vibrations of material objects. • PITCH = The impression about the frequency of a sound • high pitched–high frequency (ex: piccolo) • low pitched– low frequency (ex: fog horn)

  3. Frequency • The average frequency range for normal human hearing is between 20 Hz and 20,000 Hz (for younger people; older people lose the higher frequencies). • Infrasonic or subsonic = Sounds below 20 Hz • Ultrasonic = frequencies above 20,000 Hz http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/ https://www.youtube.com/watch?v=jSkH45nGuM8

  4. Sound in Air • Longitudinal or Compression wavestravel through air or along springs. These waves travel with areas ofcompressionandrarefaction The medium does not travel from one place to another, but the pulse/energy travels.

  5. Speed of Sound • The speed of sound in dry air at 0C is about 330 m/s. • For each degree above 0C the speed of sound increases by 0.60 meters per second. • Sound travels 15 times faster in steel than air and about 4 times faster in water than air. • Any matter will transmit sound, whether it is a solid, liquid or a gas. • Sound cannot travel through a vacuum (it is a mechanical wave)

  6. Intensity • Intensity is the rate of energy flow through an area. • The unit of intensity for sound in the decibel (dB). • Sound intensity is objective and is measured by instruments such as an oscilloscope. • Loudness is a physiological sensation sensed by the brain. It is subjective but related to sound intensity.

  7. Common Levels of Sound SOURCE OF SOUND LEVEL (dB) Jet Engine, at 30 m 140 Threshold of pain 120 Loud rock music 115 Old subway train 100 Average factory 90 Busy street traffic 70 Normal speech 60 Library 40 Close Whisper 20 Normal breathing 10 Hearing threshold 0

  8. Forced Vibration • The vibration of one object cause another object to vibrate. • Sounding boards are used to increase the volume (amplitude) of a vibrating object (like a string). STRINGS SOUNDING BOARD

  9. Natural Frequency • Everything vibrates, from planets and stars to atoms and almost everything in between. • A NATURAL FREQUENCY is one at which minimum energy is required to produce forced vibrations • also requires the least amount of energy to continue this vibration

  10. Resonance http://www.youtube.com/watch?v=bDeswHjH1-U Resonance – when the frequency of a forced vibration on an object matches the object’s natural frequency, a dramatic increase in amplitude of the vibrations occurs. • For example, a swing, or the hollow box parts of musical instruments are designed to work best with resonance. • In order to resonate, an object must be elastic enough to return to its original position and have enough force applied to keep it moving (vibrating) http://www.youtube.com/watch?v=urYWaHfel6g

  11. Interference • Sound waves interfere with each other in the same way as all waves. • Constructive interference - augmentation • Destructive interference - cancellation

  12. The Doppler Effect: Waves from a Moving Source v=f l so a smaller wavelength means a higher frequency. Animation courtesy Dan Russell, Kettering University

  13. The Doppler Effect Motion of either the source or the observer of a wave causes the frequency to shift. If the relative motion results in more wave crests reaching the observer per second, the frequency is increased. If the relative motion results in fewer wave crests reaching the observer per second, the frequency is decreased.

  14. The Doppler Effect http://www.youtube.com/watch?v=h4OnBYrbCjY

  15. Levitation with sound waves • http://www.youtube.com/watch?v=odJxJRAxdFU • Paint • http://www.youtube.com/watch?v=5WKU7gG_ApU • Pyro board • http://www.youtube.com/watch?v=2awbKQ2DLRE • Water standing waves • http://www.youtube.com/watch?v=uENITui5_jU • Julius • https://www.youtube.com/watch?v=pZNNWrA9MZQ • https://www.youtube.com/watch?v=OQ9rvkVLlDU

More Related