Higher tier: using microphones and data logger
A data logger can measure and record the time taken for sound to reach two microphones. Unlike the clap-echo method, these can be quite close together.
Using a data logger and microphones to measure the speed of sound
For example, two microphones are 3.4 m apart.
The data logger switches on when the sound from the bell reaches the first microphone, and off again when the sound reaches the second microphone.
The data logger recorded a time of 0.01 s for the sound to travel between the microphones.
Speed = \(\frac{\text{distance}}{\text{time}}\)
Speed = \(\frac{3.4}{0.001}\)
Speed of sound = 340 m/s.
This method works because there is no human reaction time involved starting and stopping the clock and because the microphones are more sensitive than human ears.