This is annoying but also normal. The magnetic fields cause some parts to vibrate. I know it sounds like BS but google it. You'll see.

As bad as that sound the solution sounds even more far fetched. You got to hit it with a mallet or hammer, a whole bunch of times, until the hum goes away.

I did it to a target alpha with the power off. And turned it back on every 10 hits. Took about 50 to make the hum lower volume that the machine.

I left it in place