1. Sound Lesson 2

2. Previously… Sound as product of vibrations Longitudinal nature of sound Medium required for transmission of sound Differing speed of sound in different mediums Loudness and amplitude Pitch and frequency CRO

3. This lesson… Audible range of sound Ultrasound and uses Production of an echo Determining speed of sound

4. Audible range of sound 20Hz – 20kHz Can you think of any examples of ‘sounds’ outside this range?

5. Ultrasound Sound pressure of frequency >20kHz Applications? ◦ Examine inside human body ◦ Detect flaws in metals ◦ Clean spectacles/jewellery ◦ Sonar

6. Production of echoes Since sound is propagated as a wave, it exhibits wave properties as well and can be reflected. Echoes are simply reflected sounds.

7. Watch this clip… http://www.youtube.com/watch?v=kIdJ6D V9iz4 http://www.youtube.com/watch?v=kIdJ6D V9iz4

8. Determining speed of sound Direct method Speed of light: 3.0 x 10 8 ms -1 Speed of Sound: 330 ms -1 v = s / t (speed = distance / time)

9. Determining speed of sound Indirect method Sound travels double the distance v = 2s / t (speed = distance travelled/time)

10. Practical Time!