Near the top of the keyboard you'll notice a PCB and a yellow coated transformer. This is used to power the EL backlight and the blue LEDs. There is a slight hum/buzz generated when the EL is working, but it's pretty quiet and unnoticeable beyond a few inches. Seeing as how most people will have at least a foot or two between their ears and the keyboard, this shouldn't pose a problem. Newer keyboards are using LEDs for backlighting (as they're more reliable and don't require a transformer), but EL still has the advantage of being more uniform without any pockets of extreme brightness and darkness.
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