The Soundcard Oscilloscope receives its data from the Soundcard with 44.1kHz and 16 Bit resolution. The data source can be selected in the Windows mixer (Microphone, Line-In or Wave). The frequency range depends on the sound card, but 20-20000Hz should be possible with all modern cards.

Soundcard Oscilloscope by Christian Zeitnitz

The oscilloscope contains in addition a signal generator for 2 channels for Sine, Square, Triangular and Sawtooth wave forms in the
frequency range from 0 to 20kHz. These signals are available at the speaker output of the sound card. These can be fed back to the
oscillocope in order to generate Lissajous figures in the x-y mode.

These is another good tool for students to learn measurement on the PC.  – delabs