A typical single-layer drywall assembly rates around STC 34. That lets loud speech through, so it is often worth upgrading between bedrooms, offices and meeting rooms.
Most effective upgrade
Add a second layer of 5/8 in drywall on resilient channel, fill the cavity with mineral wool and seal the perimeter.
Acoustic panels on the surface add only 1–3 STC points. They are for the sound inside the room. See STC vs NRC and flanking paths.