sound travels through liquids more quickly than through gases
humans have a hearing range of 20Hz to 20kHz (this range diminishes with age)
sound with a frequency of greater than 20kHz is called ULTRASOUND
Amplitude - loudness
Wavelength - length of wave
Frequency - waves per second - 1/time period
use of ultrasound #1 - medical scanning
an ultrasound probe emits ultrasound waves and listens for their echoes
the computer that the probe is connected to does millions of distance = speed x time calculations
in order to work out where the baby is positioned
the computer draws a picture of the baby (either as a 2D or a 3D image)
use of ultrasound #2 - cleaning delicate items
sound can make objects resonate - this happens if a forcing signal has a frequency that matches the natural frequency of the object
if jewellery is placed in an ultrasonic cleaner, the dirt particles are literally shaken off the jewellery by the vibrations of the ultrasound
use of ultrasound #3 - destroying kidney stones
even kidney stones have a natural frequency
an ultrasonic probe can be used to vibrate stones at their natural frequency causing then to shatter
they then pass out of the body via the bladder instead of needing surgery
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