STUDENT INFORMATION

Experiment 9.2: Speed of Sound

How fast does sound travel?

In this experiment, you'll measure the speed of sound in air by timing how long it takes for a sound to travel a known distance. Because the travel time is often less than 1 second, you will use a phone recording (video or audio) to measure the delay more accurately than a handheld stopwatch.

Materials Needed:

Affects sound speed: 343 m/s
Negative = headwind, Positive = tailwind

Measurements:

Distance: 250 meters

Time: 0.000 seconds

Speed: 0 m/s

Effective Speed: 0 m/s

Environmental Effects:
  • Base speed of sound: 343 m/s
  • Temperature effect: +0 m/s
  • Wind effect: +0 m/s
  • Humidity effect: minimal
Record your observations:

Procedure:

  1. Setup

    Find an open area outdoors. Measure and mark a distance of 250 meters (a longer distance gives a larger time delay and is easier to measure).

    Safety Note: Wear safety goggles to protect your eyes from any metal particles when striking the pots.

  2. Position

    Have your partner stand at one end with one pot and the metal spoon. You stand at the other end with the second pot and the stopwatch.

  3. Measurement

    Your partner will raise the spoon high enough for you to see, then strike their pot. Instead of using a handheld stopwatch (reaction time is too slow for small delays), record the event using your phone:

    • Video method: Record video (60 fps or higher if available). Start counting frames at the moment you see the strike and stop at the first moment you hear the sound in the recording. Convert frames to time.
    • Audio method: Record audio. You should see two distinct spikes (the strike/impact sound at the source and the sound arriving at your location). Use the timestamp difference.

  4. Calculate

    Record the time in seconds. Calculate the speed of sound using the formula: Speed = Distance ÷ Time

  5. Repeat

    Repeat the measurement 5 times and calculate the average speed.

Data Collection:

Trial Distance (m) Time (s) Speed (m/s)
1 0
2 0
3 0
4 0
5 0
Average Speed: 0

Analysis:

Based on your measurements, answer these questions:

  1. How close was your measured speed to the actual speed of sound (approximately 343 m/s at room temperature)?
  2. What factors might have affected your measurements?
  3. Why is it important to see the spoon hit before starting the timer?
  4. How might temperature affect the speed of sound?