Acoustics in buildings with mass timber floor/ceiling assemblies: theory, practice and acoustical solutions.

There has been much information previously published regarding the sound isolation performance of cross laminated timber (CLT) construction, particularly relating to sound transmission (airborne and impact) through different types of bare panels, and panels in combination with supplemental construction elements (or ‘linings’) and the influence of construction detailing on sound flanking. This paper focusses on some ‘secondary’ acoustical design challenges when using typical acoustical (non-CLT) materials within a CLT building structure, such as maintaining appropriate levels of room-to- room sound isolation, given the irregularly sized gaps that sometimes occur between CLT panels at the underside of mass timber floor/ceiling assemblies. Other challenges lie in the accurate prediction of the influence of sound flanking paths on room-to-room sound isolation in such structures and in finding methods for adding acoustically absorbent finishes to a space, where functionally required, when the project stakeholders wish to see timber left visually exposed. This paper reviews some of our company’s acoustical design experience for projects constructed within buildings utilizing CLT construction. These projects located in Canada and the USA, include residential, office buildings and even sound studio projects. Strategies are reviewed that have been used successfully to address potential acoustical challenges.