Inducing noise for testing AC line filters
Brush type AC / DC motors produce a lot of low-band RF and audio noise. The best I have found is a Dremel tool motor running at full speed with no load. Isolate it from the AC line with heavy LC filters and tap noise from the motor with 1 uF 630 VDC polypropylene capacitors. If you need more isolation insert a 1" to 2" diameter ferrite toroid, N30 material. Use 30 turns 22-24 awg on both primary and secondary.

Not sure what your bottom roll-off frequency is but the capacitors will remove much 50/60 Hz content and the added transformer should remove noise below 2 KHZ. Add more turns for more LF content, but N30 cores saturate easily.

If isolation not needed a 100 uH inductor could remove LF content, else you will get all the noise the brushes put out. Note that the capacitors will NOT prevent a shock hazard if power source is a AC outlet. If you need noise in the low MHZ range a spark-gap device or Jacobs ladder may work just fine.