Core Practical 6: Speed of Sound

Question 1

CP6 Equipment List

Answer 1

• Signal generator with loudspeaker
• Oscilloscope
• Microphone
• Leads
• Metre ruler

Question 2

CP6 Method

Answer 2

1. Oscilloscope will show signal in loudspeaker and signal received by microphone
2. Move microphone away from loudspeaker until waves are in-phase
3. Record distance between microphone and loudspeaker
4. Repeat as much times as possible with available space
5. Calculate mean λ
6. Use oscilloscope trace to find frequency of sound
7. Repeat at different frequencies
8. Calculate speed at each freq, determine mean speed of sound

Question 3

CP6 Analysis

Answer 3

Frequency calculated f=1/T using time base from oscilloscope
Speed calculated with v=fλ

Question 4

CP6 Safety

Answer 4

Sound not too loud
- Avoid ear damage
Protection for ears
- High frequency sound can be painful to listen to for long periods of times

Question 5

How to decrease uncertainty for CP6?

Answer 5

Adjust time base on oscilloscope
- Lower base, higher resolution time period
**Use fixed ruler and set square*
Measure distance between microphones in more in-phase positions
- Determine multiple wavelengths, reduce uncertainty in value for d