Here are some things you can do to try to fix it yourself:
1. Update all sound drivers (As well as video drivers, because sometimes outdated video card drivers can cause some funky issues.)
2. If that doesn't work, try going into the audio settings on your OS and see if your speakers are recognized. If they are, make sure that it is set to the default sound output. Then scan through all the settings and make sure that everything is turned on or off that's supposed to be.
3. If your speakers aren't recognized in your audio settings, check your device manager. If it's not in there either, you may have a hardware problem, and you should contact Dell Support. HERE IS THEIR CHAT SERVICE
They are usually pretty good about helping, so you may figure it all out there.
Try the first two yourself, and if you can't figure it out, Dell Support definitely can. If they can't, I'm sure you can send it in free of charge and they'll take care of it for you. You may even get a technician to come to you instead if you're lucky.