The NOISE module generates.. yes... noise ;-)
There are two types of noise:
- the A output generates analog noise (technically, a fluctuating voltage between about 1...4V)
- the D output generates digital noise, which is a random changing 0V / 5V
The RATE knob controls the color of the noise, which goes from almost white noise on A output and knob fully clockwise to a rather harsh and digital sound on D output and RATE counter-clockwise.