1. What we will do today: Investigate the range of human hearing. State what is meant by Ultrasound. Give one medical use of ultrasound in medicine. Give one non-medical use of ultrasound.

2. Range of Human Hearing The range of sounds is given by the frequency in which sound waves are produced. Frequency is measured in Hertz (Hz). The range of hearing in a young human is: 20 Hz – 20 000 Hz (20 kHz).

3. Ultrasounds Sound frequencies above the range of human hearing, eg above 20 000 Hz are called ‘Ultrasounds’.

4. Range of Hearing (read)

5. Medical use of ultrasound Ultrasounds are used in medicine to: 1.Examine a baby in the womb (safer than X-rays). 2.Break up kidney stones in the body (no surgery).

6. Human in the womb

7. Dog at 60 days (of 63)

8. Elephant at 19 months (of 22)

9. Dolphin at 9 months (of 12)

10. Non-Medical use of ultrasound Non-medical uses are used to tell how far away something is (SONAR): 1.Bats are blind but use ultrasound to detect objects around them. 2.Boats use ultrasound to tell how deep the water is below them. Bats on the hunt