Most HID ballasts make some sort of noise or “buzzing” while operating – it’s simply the sound of electricity being converted and applied to your new HID bulbs.
Some HID ballasts will have noticeable noise during startup (the first 30-60 seconds) and will quiet down a bit. Some will remain noisy for the entire duration of your headlights being on.
This is perfectly normal, not harmful in any way and is not heard during normal driving conditions.
If you have any LOUD arcing sound, this may indicate a problem. This is extremely rare though.
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