Lamp resistance is low when cold. This will cause an initial current inrush causing the noise (my theory).
Simple to verify this low resistance issue with a meter, a 14 volt source and TS lamps.
1- Measure the total cold resistance of the lamps.
2- calculate the watts @ 14 volts using OHMS law.
3- Then power the lamps at 14 volts and measure the current.
4- Calculate the watts using EI=W.
5- Then compare the TWO results.