Can I do 'old movie noise' with the particle system?

Is there a way to adjust the noise?

I'm thinking specifically of adjusting the speed of its movement, the size of the 'particles', and perhaps even the way they're scattered...

You can probably adjust it by messing about with the shader toolkit itself, but there's thousands of lines of code & I didn't write the shader toolkit, so I couldn't say where to make changes or what lines to edit. Simon?