Activity 1.3 - Make an A-scan

Learning Aims:
  • To explain how ultrasound pulses are used to measure a distance
  • To describe how an ultrasound A-scan is created
  • To interpret a simple ultrasound A-scan
Materials:
A computer, a sound sensor, data-logger and software that displays sound waveforms (e.g. CMA Coach 6), a cartoon hollow tube or plastic tube.
Suggestions for use:

In this activity students learn what an ultrasound A-scan is and how it is created.
They start with activity 1 (exploration) in which they once more analyse the experiment with the sound reflection in the cartoon tube. This time they get a recorded sound graph and they have to predict how the graph will look when a tube is 50% longer and when there is another barrier inside the tube. There is a small step from the graph of the sound signal versus time to a graph of the sound signal versus position - an A-scan.

The explanation of the A-scan concept is given in activity 2.

In activity 3, an A-scan of the human eye is presented. Let the students analyse the given A-scan. Discuss with them the scan, let students identify which eye parts generate respective ultrasound peaks.

Based on the given photo discuss how the A-scan is taken by a doctor.
Possible questions:
  • What would you assume the speed of sound in the human?
  • Which parts of the eye generate the ultrasound spikes?