ᐅ Reducing Sound Transmission Through a Chimney

A question regarding sound insulation. A chimney runs through the living areas of a newly constructed multi-family house. Unfortunately, every noise and conversation can be heard above it, especially the sound transferring from the lower to the upper apartment. The construction work is actually already completed, meaning the walls are plastered and the floor with underfloor heating is installed.

Which structural measures can still be taken to reduce sound transmission?

In my opinion, something is not right; there should not be openings from two apartments into the same shaft. Have this checked by the responsible chimney sweep or specialist.

Otherwise, flaps or dampers should of course be installed in the chimneys.