sound
sound production
sound is produced by vibrating sources. vibrations of the source create pressure waves in the medium around it.
longitudinal waves
sound waves are longitudinal waves. direction of vibration (compression and rarefaction) is parallel to direction of wave propagation.
audible frequency range
approximate range of frequencies audible to humans is 20 Hz to 20,000 Hz (20 kHz). frequencies below 20 Hz are infrasound; frequencies above 20 kHz are ultrasound.
mediums
sound waves require a medium (solid, liquid, or gas) to travel. sound cannot travel through a vacuum because there are no particles to vibrate and transmit the wave.
properties of sound
mechanical wave requiring a medium to travel. cannot travel through a vacuum. travels at different speeds depending on medium: approximately 330 m/s in air, faster in liquids and solids.
frequency and pitch
frequency measured in hertz (hz). higher frequency means higher pitch. human ear typically hears 20 hz to 20,000 hz.
amplitude and loudness
amplitude determines loudness. greater amplitude means louder sound.
wave properties
longitudinal waves with compressions and rarefactions. reflects off surfaces (echo). absorbed by materials.
ultrasound
frequencies above 20,000 hz. used for medical imaging, cleaning, and pest control.
infrasound
frequencies below 20 hz. produced by earthquakes and large animals.
sound transmission
sound can be transmitted as digital or analogue signal. digital transmission offers better quality and longer range than analogue transmission due to signal regeneration capabilities.
echo
speed of echo defined by the equation v = 2d/t, where d is the distance from the source to the reflecting surface and t is the time taken for the echo to go to the surface and back.