My boss has a bad habit of leaving his phone unmuted when on a conference call. Usually, we hear some background keyboard noise or some throat clearing noise, and somebody politely asks everyone to go on mute. Half of the time he ignores the request, probably because he's not fully listening.
Recently, it's gotten to the next level of awkward as he's started taking his headset into the bathroom with him. To give you a sense of how awkward this is, yesterday everybody on the call heard bodily functions accompanied with quiet moaning with the occasional "oh man", followed by a loud flush.
A lot of my peers find this funny, but I'm just embarrassed for my boss. I've tried leaving all sorts of hints like "Hey boss, don't forget to mute your phone!" and "I was hearing some weird noises that might be coming from your phone, do you mind muting next time when you not talking?" But he just smiles and says "thanks for the reminder!", and then forgets again.
I feel like somebody needs to have a blunt conversation with him, but I'm fearful to do so myself because I know it will be very awkward and uncomfortable. Is it my place to have this conversation with him? If so, how can I tactfully bring this up with him? (If I'm vague, I fear he won't understand what I'm saying, but I really don't want to have to tell him "everybody can hear you taking a dump").
EDIT:
So I did what some of you have suggested and confronted him again. For whatever reason, he admitted that he did it on purpose and plans to stop at the end of this week. Should I press on him to immediately stop if I do bring it up again?