Sound waves (pg 36 & 37)

• Sound waves are longitudinal waves caused by vibrating objects. The vibrations are passed through the surrounding medium as a series of compressions.
• The human ear is capable of hearing sounds with frequencies between 20 Hz and 20,000 Hz.
• The denser the medium, the faster sound travels through it, because they are caused by vibrating particles.
• Sound generally travels faster in solids than in liquids, and faster in liquids than in gases.
• Sound waves will be reflected by hard flat surfaces, while soft surfaces will absorb them.
• An oscilloscope is a device which can display the microphone signal as a trace on a screen.
• The greater the amplitude of a wave, the more energy it carries, which means the louder it will be.
• The higher the frequency the higher the pitch.
• In an oscilloscope: time is on the horizontal axis and voltage is in the vertical axis.
• Formula linking frequency and period:

  $f=$$1 / T$