Velocity of sound

Velocity of sound can be obtained by measuring the time it takes to travel a fixed distance. This can be done by a 40 KHz resonant frequency piezo electric transmitter receiver pair. The setup is shown below.

The transmitter piezo is connected to digital output D0. The receiver piezo output is amplified around 1000 times and converted into a TTL signal that is fed to digital input D0. The software sends a single 13 microsecond wide pulse to the Transmitter that generates an ultrasound wave that travels to the receiver through air. The program waits for the Digital Input signal transition and calculates the time the sound wave takes to reach from transmitter to receiver.
    To eliminate errors due to delay in electronic circuits, we measure the time for different distances and take the difference to calculate the velocity.

Method 2:

  A metallic plate or gong is connected to one of the digital inputs (D0) . When it is hit by another metal object that is connected to ground the input signal goes from HIGH to LOW. This transition is detected by software to mark the Start Time. The sound generated by the collision is captured by a microphone (It is easier to use a loudspeaker for this purpose). The output of the microphone is amplified and given to another digital input (D1) . The rising edge of this signal is used for marking the Stop Time. Dividing the distance by the time interval gives the velocity of sound. The same technique can be extended to find the speed of sound in materials other than air.

60 microseconds is subtracted from each reading.

Related Experiments:

Beats

Resonance

Spectrum analysis