Ultrasound

Ultrasound

Ultrasound - sound with a frequency higher than we can hear

On the screen, CRO traces of ultrasound can just look like CRO traces for normal pitched sounds, to show ultrasound the CRO is set so each square corresponds to a very short amount of time e.g. 1 us (0.000001secs), letting you see each peak and trough.

Ultrasound waves get partially reflected as boundaries between media...

• When a wave passes from one medium to another, some of the wave is reflected off the boundary, some is transmitted and some is refracted - partial reflection
• This means that you can point a pulse of ultrasound at an object and wherever there are boundaries between media, some of the ultrasound gets reflected back
• The time it takes for the reflections to reach a detector can be used to measure how far away the boundary is
• This is how ultrasound imaging works

You can use oscilloscope traces to find boundaries...

• Given the seconds per division setting of the CRO, you can work out the time between the pulses by measuring on the screen
• Given the speed of sound in that medium you can work out…