To troubleshoot noise coming from the AC adapter, disconnect the adapter from the laptop. Test each part of the adapter separately to determine where the noise is coming from. Plug the adapter into a different wall outlet and make sure not to use a surge protector. Check if the issue reoccurs. If the problem persists, let's manually update BIOS. Open a web browser and go to dell.com/support. Type in your Service Tag to identify your system. Click on Drivers and Downloads and then click on Find Specific Drivers. Choose your operating system and set the category to BIOS. Scroll down, select the BIOS file and click on Selected for download. Click the driver link to open the details page, then scroll down and click Download. Open the file when it finishes downloading. In the User Account Control prompt, click on Yes to accept the changes to your system. In the Bios Update Utility, check the box to Suspend BitLocker Drive Encryption. Click on Update and wait for the computer to complete the process. A restart may be required. If you're still having issues after updating BIOS, unplug the adapter from the outlet and separate the power cable from the adapter. Reseat the cable and AC adapter. Plug the power cable back into the outlet and check for noise.
