The issue of conversations in the boardroom being heard in the adjacent corridor is likely due to inadequate sound insulation, with the hollow core door being the most probable cause. Hollow core doors do not provide significant sound blocking capabilities, allowing sound to travel through them more easily than solid doors.
This can be a common oversight in acoustic design, especially in spaces where confidentiality is important.
Addressing this issue by installing a solid core door or additional soundproofing measures would improve privacy and acoustic comfort in both the boardroom and the adjacent spaces.