Get an electrician to check the circuits on the
wall. They are probably on the same phase in
the breaker panel as the lights. If that is the
case have him move the outlet circuit to a
different phase.
Now before the people that don't readwell
start tearing apart my answer. I said on the
same phase not the same circuit.
In an electricial panel there are either 2 or 3
phases. Going down the circuit breakers the
phases for a 3 phase panel are 123 123 123.
So if you have anoisy circuit on 1. The noise is
transfered to every breaker on the 1 phase.
Same on a 2 phase panel. 12 12 12.
The electrician can discuss options if this is
not possible.
Motors, fluorecent lights, dimmers, ect will
cause these type of problems.
Good Luck Lee