Measuring the Speed of Sound: Time-of-Flight
Description
This interactive simulation recreates the time-of-flight method for measuring the speed of sound in air. A hammer strikes an iron anvil to produce a single sharp pulse, and two microphones mounted on a graduated rail feed a time interval counter that measures the moment separating their signals. Because both microphones detect the same pulse, the measurement depends only on the distance between them – the arrangement used in a real acoustics laboratory.
Components
The simulation includes:
- A rail carrying two microphones on sliding stands, each freely positioned
- A hammer-and-anvil source that emits one sharp acoustic pulse per strike
- A time interval counter with SIGNAL 1 and SIGNAL 2 inputs, power switch, and reset, reading in milliseconds
- An air temperature control covering 0–40 °C
- Draggable measurement markers with a distance readout
- A built-in guided tutorial accessible at any time
How to Use
- Switch on the time interval counter
- Slide the two microphones to the separation you want to investigate
- Press Strike – the counter captures the interval at the instant of impact
- Show the measurement markers and place one on each microphone to read their separation
- Change the air temperature and strike again; the previous reading stays on the display for comparison
Learning Outcomes
Students obtain the speed of sound from two quantities they measure themselves – a distance and a time interval – rather than from a value supplied to them. Repeating the measurement at different separations and different air temperatures opens the way to investigating how the speed of sound depends on temperature, and to examining the precision of each instrument and its effect on the result. The simulation assumes dry air, which makes it a useful starting point for discussing why values measured in a real laboratory may differ.
Also on Physics-Zone
The speed of sound can also be measured by comparing the signals of two microphones on an oscilloscope rather than timing them directly – explore Phase Difference Between Sound Waves Simulation.