Once considered a buzz phrase, biophilic design has become an important part of architectural and interior design, perhaps even more so recently, as many have come to appreciate the impact nature has on our mental health and well-being. Derived from the Greek words for life and love, biophilia means a love of nature. It brings the outside world inside, integrating natural elements like plants and wood into the building interior. Examples include skylights, plants, green walls, healing gardens and wood finishes. When wood is used as a structural element and there is a desire for increased amounts of exposed wood, it introduces significant acoustical challenges, particularly for secondary or indirect paths of noise transfer. Direct sound travels through floors, ceilings or walls and allows loud noises in one unit to be heard through a dividing wall. Indirect sound travels through structural elements, such as the floor, joists or shear walls, as well as ceiling cavities, pipe penetrations, junctions between floors and walls, and cracks. These secondary sound transmission paths are known as flanking paths, and wood buildings are more susceptible to noise issues due to the number of paths available for sound to travel, other than directly through the demising partition itself. Flanking is an issue in all types of structures but more so in lightweight construction. For comparison, a typical mass timber floor is about 20–25 psf and a typical concrete floor is 80–100 psf. In heavy concrete construction, flanking noise starts to show up when designing for very high STC (sound transmission class) ratings (typically 65+). STC measures how effectively a wall, floor or ceiling can reduce the transmission of airborne sound between rooms. Generally, the higher the STC number, the less sound is transmitted. An STC rating as high as 65+ would be used in a facility like a recording studio where you don’t want any sound transmission between adjacent spaces. The room within a room construction typically 46
The exposed ceiling at the Catalyst Building showcases the building’s wood structure IMAGE: Ben Benschneider
used for theatres, studios, and loud mechanical rooms is done to provide high STC ratings for these spaces and also reduce the flanking sound transmission by protecting the structural elements from noise generated in the room. In lighter weight construction, flanking issues become prevalent at lower STC ratings which is why it can be more of an issue with mass timber. High STC ratings at the demising wall alone will not guarantee a high level of sound isolation because flanking noise is unaccounted for in STC tests
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for partitions that are determined in laboratories. ASTC (apparent sound transmission class) is a more realistic measure of the actual sound level transmitted between adjacent spaces in a building since it includes noise transmitted through walls, ceilings, and floor junctions. Leaving mass timber exposed compounds the issue by adding to the flanking paths. Exposed timber structural walls and ceilings reduce the ASTC rating and complicate the sound isolation design. There are no requirements or building
