Xbox One Power Brick making a revivng noise

Will probably be the fan that's inside they get covered in dust after a while and go noisy

Is it in a well ventilated area? Are the vent holes filled with dust or anything?

The power supply has a built-in cooling fan.
The fan starts automatically when you turn on your Xbox.

• The fan should make a noticeable whirring sound typical of most cooling fans.
• When your Xbox is in energy-saving mode or when it’s disconnected from its power supply, the fan is turned off.
• If your Xbox power mode is in Instant-On, the power supply and fan will remain turned on.
• The fan speed increases or decreases, along with the sound of the fan, as the power supply changes temperature.

To keep the power supply working more efficiently and safely:

• Don't block the power supply’s vents.
• Don't leave the power supply on a bed, sofa, or other soft surface.
• Make sure the power supply has good air flow. Don't put it inside a bookcase, rack, or stereo cabinet unless that space has good ventilation.
• Don't leave the power supply near heat sources such as a radiator, heat register, stove, or audio equipment.
• Don't stack electronic devices on top of the power supply.
• Position the power supply horizontally so it sits flat on its rubber pads.

Note

If noise from the power supply seems excessive, the power strip or surge protector it’s plugged into may be overloaded. Plug your Xbox power supply directly into a wall outlet instead.

If the proplem persists or other problems arise i would recommend getting a new power brick

It can also be a sign that you are overloading the power (have too much connected), or connected to a surge protector. More info on here

https://support.xbox.com/en-GB/xbox-one/accessories/about-power-supply