Ultrasound

Ultrasound

1. Ultrasound is a sound with a higher frequency than we can hear

2. Partial reflection

   • When a ultrasound wave hits a boundary between two mediums some is refracted, however some is also reflected this is called partial reflection

3. The time it takes for a ultrasound to return can be detected with a detector and can measure how far away a object is

4. S=V X T

   • An ultrasound machine is used to check for cracks in aluminium. The oscilloscope trace oscilloscope trace for the ultrasound is displayed below. Each square on the oscilloscope represents 20 microseconds µs). The speed at which sound travels through aluminium is 6,320 m/s.
     • Step 1: Work out the time between the pulse being emitted and detected There are six squares, so the time is 120 µs
       • Step 2: Convert µs into s 1 s = 1 000 000 µs 120 µs = 120 ÷ 1 000 000 = 0.000 12 s (1.2 × 10 -4 s)
         • Step 3: Put the values into the formula s = v x t distance = 6320 × 0.000 12 = 0.758 m
           • Step 4 Remember that the ultrasound travels to the crack and back again. Therefore the distance to the boundary is half the total distance: distance to crack = 0.758 ÷ 2 = 0.379 m