Mac book pro speaker make crackling/static sound?

When i try to play a video or music thru the internal speaker s or headphone all I Get is a cracking sound. Here's what I have tried to to no avail remedy this problem:

1.   Restarted in primary account

2.   Restarted in “safe” mode

a.   In safe mode, No crackling or sound of any kind when playing Youtube video or track in iTunes. System sound preference panel shows no sound input

3.   Reset NVRAM

4.   Ran “sudo kill -9 ps ax|grep 'coreaudio[a-z]' | awk '{print $1}'“ in terminal mode

5.   Reproduced problem in old test account when trying to play Youtube video following normal log in

6.   Reproduced problem when trying to play Youtube video in new test account following normal log in

Suggestion on the problem and remedy?