II. Sound Waves 

   A. General properties of waves

       1. Waves transfer energy by oscillation without transferring matter; matter disturbed by a wave returns to its original place.

       2. Wave properties: wavelength, frequency, speed, crest, trough, amplitude.

       3. Two kinds of waves: transverse (for example, light) and longitudinal (for example, sound).

       4. Common features of both waves:

           a. Speed and frequency of wave determine wavelength.

           b. Wave interference occurs in both sound and light.

           c. Doppler effect occurs in both light and sound.

   B. Sound waves: longitudinal, compression waves, made by vibrating matter, for example, strains, wood, air.

      1. While light and radio waves can travel through a vacuum, sound cannot. Sound waves need a medium through which to travel.

      2. Speed

          a. Sound goes faster through denser mediums, that is, faster through solids and liquids than through air (gases).

          b. At room temperature, sound travels through air at about 340 meters per second (1,130 feet per second).

          c. Speed of sound= Mach number

          d. Sonic booms; breaking the sound barrier.

     3. Frequency

         a. Frequency of sound waves measured in "cycles per second" or Hertz (Hz). 

         b. Audible frequencies roughly between 20 and 20,000 Hz

         c. The higher the frequency, the higher the subjective "pitch".

     4. Amplitude

         a. Amplitude or loudness is measured in decibels (dB).

         b. Very loud sounds can impair hearing or cause deafness.

         c. Resonance, for example, the sound board of the piano, or plates of a violin.