You could implement a basic one-pole filter as follows (I just took this from the OnePole help file). Adjust the coefficient closer to 1 for more feedback==more smoothing.

(
var coef = 0.5, last = 0;
n = Signal.periodicPLNoise(1024);
m = n.collect{|item, i|
var val = ((1 - abs(coef)) * item) + (coef * last);
last = val;
};
[n, m].plot
)