Disconnect the Alternate Current (AC) Adapter from the laptop or other device and test each part separately for any signs of noise to determine where the noise is coming from.
Try the adapter/charger in a different wall power outlet (plug straight into the outlet bypassing any surge protector or Uninterrupted Power Supply (UPS)) and check for noise.
Download and Install the latest BIOS for your laptop or device that is available from: The Dell Support site
The AC adapter is still making noise. Unplug the AC adapter from the outlet and separate the power cable from the adapter. Reseat the cable and AC Adapter. Plug the power cable back into an outlet and check for noise.
If the noise stays with the Adapter, the best course of action is to: Contact Technical Support
If the noise remains with the laptop or device, then continue to troubleshoot on the following article: