Germanium transistor Ql is used as a noise generator in the audio range. Ul acts as a high-gain amplifier. Ql is not
critical; most germanium transistors appear to be satisfactory. A germanium diode can also be substituted. This circuit is mainly used for sound effects and noise experiments. It is not flat over the audio range because of unpredictable effects in Ql, but it should be useful where high precision is not necessary.