Chimney Vent Grill vs. Soundproofing

Good evening,

we are planning a fireplace for our new building.
It was actually clear to me that a "shaft" from this would go to the hallway behind the fireplace to allow the warm air to also flow through the hallway into the upper floor.
Now the fireplace builder said I should consider that this would also cause sound transmission from the hallway to the living room.
Does anyone have experience with this?
Maybe I would now simply omit the ventilation grille to the hallway and leave the door open if necessary, so that the warm air can get into the hallway.

Regards
Denz

Somehow it is not quite clear what exactly you intend to do.

Do you want to install a so-called "tunnel," that is, a fireplace to look through, which then has a glass pane both on the living room side and in the hallway? Or do you want to knock a stone out of the wall somewhere between the living room and the hallway and replace it with a ventilation grille?

Neither is likely to be great in terms of soundproofing; grilles even less so than glass.

And generally: I would think twice about installing a fireplace in a new building that would be capable of heating the whole place. Unless you are an enthusiastic woodcutter and actually intend to heat mostly that way (i.e., turn off the regular heating), you will probably curse the additional 10KW fire sooner rather than later. With a central ventilation system and open-plan design, that might be an option for the transitional period, but that does not seem to be the case for you.

Oh ok. No tunnel.

The fireplace is to be placed with the back side against the living room/hall wall. Above the heating insert there is still a walled-up cavity. I don’t know the technical term for it. And from this, the warm air should on the one hand reach the living room (through a ventilation grille on the top side of the fireplace) and on the other hand the warm air should reach the hallway through a grille in the living room/hall wall. Basically on the back side of the fireplace.

Of course, it is not about heating the whole house. Rather, it is about using the heating output generated by the cozy fire also for the other rooms and at the same time counteracting the overheating of the living room.

As written: Soundproofing of the wall would probably be massively reduced here. Whether you want that is up to you to decide.