How was it wired and are the lightbar wires close to any audio equipment or signal wires?
My guess its probably because the circuit / led driver which regulates the current to the LED is PWM (Pulse Width Modulation)
Most LEDs are driven with some type of PWM circuit because its cheap, the more expensive ones are actually DC-DC current limiting but you will almost never find that in some low dollar Chinese light. Luck of the draw, you might have got one that is overly noisy...
PWM control output by turning on/off quickly at home rate like 60, 120, 500 hertz to change the duty cycle... faster the better...
Luckily I haven't experienced this with my lighter either... but I do have some flashlight that you can actually audibly hear the PWN with your ear to the light.