Sound

Sound

1. Sound is caused by vibrations.

2. Amplitude and Frequency

   • Loud sounds are made by large amplitude vibrations.
   • Quiet sounds are made by amplitude vibrations.
   • A high pitch is made by a high (fast) frequency.
   • Low pitched sounds are made by low frequency (slow) vibration.
   • We can observe amplitude and frequency of sound waves using an oscilloscope. Frequency is measured in hertz.

3. Loudness

   • Loudness is measured in decibels.
   • Loud sounds can cause deafness.
   • Loud sounds are sometimes called noise pollution.

4. How Sound Travels

   • Sound cannot travel in a vacuum because there are no particles.
   • Sound travels fast in gases like air.
   • Sound travels faster in liquids like water.
   • Sound travels even faster in solids like steel.
   • But light travels a million times faster than sound.

5. Sound Range

   • Sound is heard by ears.
   • Vibrations of the eardrum are converted into electrical signals, which travel to the brain.
   • Most people can hear sounds between 20Hz and 20000Hz.
   • Older people cannot hear some high pitched sounds.