I have been experience random crackling/buzzing/popping sound from my 7577 inspiron. The following are the scenario that I'm able to figure out that able to trigger the crackling/buzzing/popping sound.

The first video url is the popping sounds when i perform a full refresh (CTRL + F5) in youtube video. Whenever the video starting to play, a 'pop' noise will be heard. The second video url is buzzing sound whenever i adjust volume in youtube video. And a random crackling sound that happens randomly. 
1. https://www.dropbox.com/s/sdofx6lhcsj4uzw/IMG_5604.MOV?dl=0
2. https://www.dropbox.com/s/6dbnpaiyfbhi3gq/IMG_5622.MOV?dl=0

I tried the following solution posted in forum but none of them can solve the problem.

1. https://www.dell.com/community/Inspiron/Dell-Inspiron-7577-Windows-10-realtek-sound-driver-issue/td-p/5927018

2. https://www.dell.com/community/General/Speakers-popping-on-Inspiron-15-7567/m-p/5155487#M929649

3. https://www.dell.com/community/General/Crackling-speakers/td-p/4483294

It is fairly disappointing to get a good review laptop in such condition. Dell has just disappoint another customer.