I've read some suggestions for dampening down the whine. But even if you could do it, EL material is a highly expensive solution for something you can usually do much more cheaply and more easily with a few common lights.
The only times I've used EL sheet and wire is in 2004 on a film set that required them (the control panels needed to be practical and appear to float in the air, which meant they needed to be no more than 1/8" thick).
Test shot on the set (most of the screens without the control panel art)...
Another angle (with art in all the panels)
(The screens on the wall to screen right are lit with an artist's lightbox, and you can see how that's not as even as the EL sheet. The screens on the lower front console are LCD computer monitors running animations done in a style to match the art on the floating panels.)
With no damned actor in the way...
Finally, during a sound check, and the "house lights" brought up, you can see the EL material turned off...it's pinkish: