Any solutions for 5577?
I haven't seen one for the Inspiron 5577. An owner of an Inspiron 5567 said he resolved the crackling by switching from the Realtek audio driver (Realtek High Definition Audio) to the Windows native audio driver (High Definition Audio Device). However doing so could result in lower uality sound overall.
See the Recent Issues FAQ for all of the owners' tips.
Do you have a Bluetooth or USB playback device you could try? If you think it is the speakers, use a Headset to test.
Does audio/video come from your system or streaming from another local source or online?
Your description of the sound could mean several different things. Any chance of getting a recording?