>I am using Google Chrome Version 57.0.2987.133
>
>I didn't get any notification about your reply. I think it applies to everything when it's not working.
>
>I'll try closing this tab and re-opening LE. Try to reply in ~10 min.
>
>UPDATE. I closed LE tab and re-opened the site. Someone please reply to this message to test the sound.

I have tested that in a local environment. I used two browsers with two accounts. I replied between each others. I was able to get vocal notification each time.

But, there is something somewhere. I just need to find this simulation pattern as if you experience that, there is probably a specific condition that makes it happen.