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Important Terms Chapter 26

Important Terms Chapter 26. April 21, 2014. Important Concepts. Sound Transmission (What is Needed?) A source of vibration A Medium to transport the energy via compression and rarefaction (expansion) Types of Mediums: Solid, Liquid, Gas Solids: Metals, Wood, Rock (Steel, Iron, Brass)

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Important Terms Chapter 26

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  1. Important TermsChapter 26 April 21, 2014

  2. Important Concepts • Sound Transmission (What is Needed?) • A source of vibration • A Medium to transport the energy via compression and rarefaction (expansion) • Types of Mediums: Solid, Liquid, Gas • Solids: Metals, Wood, Rock (Steel, Iron, Brass) • Liquids: Water, Oil, Milk • Gases: Air, Nitrogen, Helium

  3. Definitions • Compression: A pulse of compressed air (air particles squeezed together) or other matter. The opposite of rarefaction. • Rarefaction: A disturbance in the air (or matter) in which the pressure is lowered. The opposite of compression. http://www.youtube.com/watch?v=zKwpv8mZHRM http://www.youtube.com/watch?v=GkNJvZINSEY http://www.youtube.com/watch?v=L4F4zaRqQdk http://www.youtube.com/watch?v=qgdqp-oPb1Q

  4. Definitions • Vibration: An oscillation, a repeating back and forth motion about an equilibrium. • Frequency: The number of events (cycles, vibrations, oscillations or any repeated event) per unit time measured in Hertz (or events per unit time) • Hertz: The SI unit of frequency, One hertz (Hz) ids one vibration (cycle) per second. • Pitch: The term that refers to how high or low in FREQUENCY a sound wave is.

  5. Definitions • Sonic: Sound waves that are between 20 Hz and 20,00 Hz or the normal range of frequencies that the human ear can detect. • Infrasonic: Sound waves that are BELOW 20 Hz. • Ultrasonic: Sound waves that are ABOVE20,000 Hz. • Most people cannot hear sound below 20 Hz nor above 20,000 Hz but many animals can hear above 20 KHz.

  6. Definitions • Amplitude: The distance from the midpoint to the maximum (Crest or peak) of a wave or equivalently , from the midpoint to the minimum (trough or valley). • Loud or Soft: The terms that refer to the magnitude of the amplitude of a sound wave. • Sound Intensity: Proportional to the square of a sound’s amplitude

  7. Definitions • Forced Vibration: The act of deliberately causing an object to vibrate using the vibrations of another vibrating object as the stimulus. An instrument sounding board is an example. • Natural Frequency: A frequency at which an elastic object, once energized, will vibrate. Minimum energy is required to continue vibration at this frequency. It is also known as the Resonant Frequency

  8. Definitions • Resonance: The phenomenon when the frequency of a forced vibration on an object (excitation frequency) matches the object’s natural frequency resulting in a dramatic increase in wave amplitude. • Why? What is occurring? • Two waves are adding in-phase thereby adding constructively

  9. Definitions • Beats: A throbbing variation in the loudness of sound caused by interference when two tones of slightly different frequencies are sounded together. • The perceived frequency of the “throbbing” is known as the Beat Frequency. • http://www.youtube.com/watch?v=oAfxkCAyFhw • http://www.youtube.com/watch?v=sTNwjTZJ-sc • http://www.youtube.com/watch?v=4Tno4L-6vP4

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