Sound muted when too low


I have been using kodi on my PI2 for quite a long time.
But about few month ago, I got a new problem occuring sometime.

When the volume is very low, it’s automatically muted, and it’s back when it raise again.

I would like to know if you have any idea on what could cause that, and if there was a way to correct it.

I’m using the HDMI output to transfert the sound to my monitor and then to my speaker through analog cable.