I'm assuming the OP means fluorescent lights rather than neon.
Also, anything on a simple thyristor/triac control will cause some noise as at settings lower than 100% it will switch on when the ac waveform is part way through its positive or negative cycle.
I walked up and unplugged a neon bar sign that was directly behind the amps ( and sharing power) and everything immediately cleared up.
Things like that are always good. One of my friends would comment
"Now it's your turn to wear the smug hat".Steve.