Thanks to Tim Escobedo for this device. The following is the text that was on the original schematic.
This is a lo-fi circuit intended to turn audio signals into the kind of sounds you’d get from a cheap pocket transistor radio. First and foremost, it cuts all the bass from the signal. The small input, output and AC shunting caps make sure of that. Second, the 500k pot/Schottky diode on the input make an adjustable tinny distorting tiny speaker simulator. Third, and difficult to show on a schematic, is the specially selected “noise enhanced” transistor used specifically for it’s noisy properties and accentuated background hiss. Just about any BJT could be used here, but I found old low hFE transistors to work best.