Ballast makes a Buzzzzzzzzz

Bought a 400w HPS light this past weekend. Got a great deal, 50 bucks off of Craigslist. It is a light with a large metal dome that you see hanging in warehouses. I took it apart wanting to make the ballast a remote one. No problems in doing that. Put the ballast and all the workings in an old ammo can. Drilled many holes along the side so it will stay cool. I works great. Light is bright as hell. The problem that I have it that it is making a buzzing sound from my ammo box. The sound doesn't bother me but was hoping someone would know how to make it mo so noisey. I had planned on building a cabinet to grow in the house, but with the buzz sound, I will have to grow in the barn. Any suggestions would be greatly appreciated.

Baremeat
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well every ballast I ever had buzzed and not just grow light ballasts that is just the way the coil works, also the possibility of sloppy mechanical construction which lets something vibrate from the magnetic field could happen too.