Similar to LFNoise2 , it generates polynomially interpolated random values at a rate given by the freq argument, with 3 differences:
If you don't need very high or very low freqs, or use fixed freqs, LFNoise2 is more efficient.
| freq | Approximate rate at which to generate random values. | 
| mul | Output will be multiplied by this value. | 
| add | This value will be added to the output. |