======Measuring the Speed of Sound with a Drum======


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**Alternative titles:** Drum Beat Time Lag Method
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====Summary====                   
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====Procedure====  
  - Choose an open, quiet area with clear line of sight (e.g. school oval). Assign one drummer and at least two observers with a tape or measuring wheel.
  - Set a steady beat rate (e.g., 2 beats per second, so the period T = 0.5 s) with a drum (e.g. snare drum) that can be heard crisply from far away.
  - Observers walk straight away from the drummer, watching the stick strike while listening to the sound.
  - Stop when the observers see a strike at the exact moment they hear the previous beat (the sound is one beat behind).
  - Measure the straight-line distance d from drummer to observers.
  - Compute speed of sound v = d / T, where T is the beat period. Repeat and average.



====Links==== 
  * None found

====Variations====
  * Repeat with different beat rates (e.g., 1 Hz, 1.5 Hz, 2.5 Hz) and compare v from each trial.
  * Try early morning vs midday to discuss temperature effects on sound speed.



====Safety Precautions====
  * Conduct the activity in a safe, traffic-free area with clear footing.
  * Keep volume moderate and consider hearing protection for repeated loud hits.
  * Maintain clear communication so no one backs into obstacles while moving away.
  * Do not perform near roads or reflective walls that could cause confusing echoes.




====Questions to Consider====
  * Why does the method use the moment when the sound is one beat behind what you see? (Because the sound delay equals one full period T of the beats, so v ≈ distance/period.)
  * If T = 0.5 s and the distance measured is 170 m, what speed do you get? (v ≈ 170 / 0.5 = 340 m/s, close to the typical value at room temperature.)
  * How would temperature changes affect your result? (Warmer air increases sound speed; cooler air decreases it, so trials at different times may shift v.)
  * What systematic errors might make v too high or too low? (Imprecise alignment, slanted distance, uneven beat timing, wind, or echoes can bias the measurement.)
  * How could you improve precision without changing the basic idea? (Use a metronome, longer distances, multiple trials, and average results.)