Crackling sound on a mid 2012 Macbook Pro 15 in

Hi,

I am having this crackling speaker sound issue since last one week. Sound is fine from earphones which says the sound card itself is working fine.

I have tried all the common suggestions found on this forum such as:

• Tried different User Account
• Reset NVRAM
• Reset SMC
• Tried to run system diagnostics- could not because it gives an error code which I do not understand.

I am running Mojave 10.14.6 software

Any suggestions from the experts out there?

Thanks