What specific Dell XPS model?

Identify the media application i.e. VLC, Windows Media Player etc.
Determine if the issue occurs in only one application. If using VLC, refer for Further Instructions.
Search Dell’s Knowledge Base or the software producers website for additional information
Connect external speaker/headphone and check for sound.
If the audio distortion persists.
Run Online Diagnostics on Sound card .
Update Audio Drivers or BIOS.
Perform Windows Updates.
If the issue continues after troubleshooting consider Reinstalling the Operating System. This method would result in data loss; Ensure you backup data before proceeding.
Run ePSA on Sound Card.
If audio distortion is not seen on external speaker/headphone