What is sound?

  • Sound is a form of energy produced by vibrating matter

  • Sound waves travel through air, water, and solid objects

  • When they reach our ears, these waves make the skin of our eardrums vibrate

  • Sound waves are compression/longitudinal waves

  • When compression/longitudinal waves move through matter (solid, liquid, or a gas), the molecules of the matter move backward and forward

  • Examples of longitudinal waves include sound waves, earthquakes and ocean currents

As sound waves travel, molecules are pressed together in some parts (compression) and spread out in others (rarefaction)

Longitudinal waves are sound waves (particle motion parallel to wave motion), while transverse waves are light waves (particle motion perpendicular to wave motion)

  • What is a medium?

    • When we talk, sound waves travel in the air.

    • Sound also travels in liquids and solids.

    • Sound waves must have a medium through which to travel.

    • In a vacuum, sound cannot travel because there is no matter for it to move through.

    • Sound travels more quickly through solids than through liquids and gases because the molecules of a solid are closer together. Sound travels the slowest through gases because the molecules of a gas are farthest apart.

The frequency of sound is the number of wavelengths in a given unit of time

  • The wavelength of sound is the distance between two compressions or between two rarefactions

  • It can be measured from any point on a wave as long as it is measured to the same point on the next wave

  • Pitch is determined by the frequency of a vibrating object

    1. Objects vibrating faster have a higher pitch than objects vibrating slower

    2. A change in frequency of sound waves causes a difference in pitch

  • Amplitude is the amount of energy in a compression (longitudinal) wave and is related to intensity and volume

Applications of Sound Waves:

    • Musical instruments (vibrate to produce sound, but different musical instruments cause vibrations in different ways)

    • Medicine (ultrasound -- sound waves with frequencies higher than the limit of human hearing, kidney stones)

    • Cleaning, mixing, accelerating chemical processes

    • Telephones

    • Recorded Sound (music, audio tapes, CDs) - sound has been turned into electrical signals stored on the tape as magnetic information

    • SONAR

      1. Uses ultrasonic waves in a system called SOund Navigation And Ranging (determines distance by the time it takes sound to bounce back)

      2. Uses: map the ocean floor, militar

After you try the quiz, check your answers!

Quiz answers:

  1. A

  2. A

  3. E

  4. C

  5. B

  6. A

  7. A