Help!! Macbook pro speakers buzzing loudly

Dear All,

I am using MBP 13 inch Retina display early 2015 (El Capitan 10.11.16).

I had experienced my MBP speakers buzzed (very audible) while I played a music on Itunes. Next, I tried plugging external speakers and the problem still there. I tried to play some audios on youtube and the problem was still there.

Because I couldn't find another way to fix this, I tried restarting the laptop as my last resort. The problem disappear since then. I would like to ask if anybody out there ever experience the same thing with their MBP speakers.

I would appreciate any feedbacks. Thank you.