This program generates signals to test loudspeakers (or any other periodically vibrating device) with the help of a synchronised stroboscope. Traditionally these tests are done with dedicated hardware devices costing several thousand dollars or Euros. The only external hardware needed is a two channel amplifier and an LED flashlight.

A typical hardware configuration looks like this:
The computer sound card supplies the two signals to the two channel amplifier. The speaker signal (sine wave on the left channel) is amplified and sent to the loudspeaker under test.
The other signal is the light trigger pulse on the right channel. It is sent to the external trigger input of a stroboscope or it can also be amplified and sent directly to LEDs.
I have used a standard LED flashlight (British English: torch) as a stroboscope.

This is how the loudspeaker is connected for the test: