Static/crackling problem with Inspiron 15-3558

Hi--I'm new to this site, so please excuse me for being super computer illiterate. My laptop, Inspiron 15-3558, has been great until recently. About 3 weeks ago, a message came up on the screen saying that my adapter is not being recognized and is not charging my battery. Since I almost always use the computer plugged in, I didn't know about this until I looked at the battery and it was at 22% and not charging. However, the computer was running fine when plugged in, except for one strange thing. When watching a live streamed program, any speaking or loud sounds are accompanied by pretty loud static. If there is no audio going on, there is no static. Even stranger, if I open another tab, and this new page is on top of the page with the audio, the static stops. Right now, I am listening to CNN live streamed news, while typing on this window. If I click on the page with the news to bring it on top to view, the static starts up again. Also, since all this started, I noticed that when loading pages, which used to take hardly any time at all, now are very slow. I spoke with Dell support, and they want me to send it in. I wouldn't mind doing that because the laptop is still under warranty. However, I work from home, and if I don't have the computer, I won't be able to work the whole time they have it. So I want to see if there is anything I can try before I resort to sending it in. I hope that my post isn't too confusing or too long. Like I said, I can use a computer well, I know nothing about what makes it do what it does. Thanks for any help or information you can give me.