Arduino Leonardo makes noises?

I got an Arduino Leonardo that works fine. Today I powered it using a 9v battery (the little brick) though the barrel jack. I have done this many times before without any problems. Today I swapped the battery with a new one and it suddenly makes noises. I swapped it with a new battery from another brand and the same noise happened. I tried switching back to the old battery that I have been using so many times before. No noise.

The noise is like a long biiiiiiiiiiiiiiiiiiiip that lasts until the power is unplugged again.

Whats happening? Is the voltage regulator broken?

Do you know what is making the noise ? There is nothing on the board that is able to make noise (I think). Or a leaking capacitor ? Something shortcutting ? That is all very unlikely.

You don't want a bad capacitor to blow into your eye. Do you have a mic or headset you can connect to a computer, try to find the location.

A 9V battery is very weak. A few leds can already be to much. Is something connected to the board ? Can you measure the voltages on the Arduino board (VIn, 5V) with different batteries.