Sound problem

I have a MacBook Pro (15 inch, 2016) with Mojave 10.14.1 installed on it.

After I have updated my computer to Mojave 10.14 I am having a serious problem with the sound.

When I use its internal speakers and the volume is over 50% the sound is somehow dull and distorted.

Using the sudo killall coreaudiod command from the terminal solves the problem for a few minutes but, if I don't lower the volume, the problem reappears.

I didn't check if this problem happens when I use my headphones as using volume over 50% is too loud for my ears...

I thought that after installing the 10.14.1 update would solve my problem but, unfortunately, this problem persists.