Blocking Mass For Architectural Vibration Attenuation – A Case Study

Résumé

With many cities facing the challenges of urban infill, a large number of older buildings are being altered to host activities which are not necessarily compatible with the original intent of the building design. As such, noise-sensitive operations are sometimes forced into close quarters with inherently noisy neighbouring tenants/owners. This case study reports the acoustic, noise and vibration challenges associated with the retrofitting of an old theatre which was repurposed and split into two adjacent properties: a large music venue on one side, and an off-track betting facility on the other. Specifically, this paper addresses the continuous metal roof deck between both operations, which constitutes one of the primary noise flanking paths. Noise energy from the music venue excites the common roof deck, allowing vibration to travel across the demising partition and into the off-track betting facility, where it is re-radiated as structure-borne noise at the point of reception. In order to help mitigate this issue, a blocking mass was designed to reflect roof deck vibrations back towards the music venue. While these blocking masses are typically installed on top of the roof deck, design constraints resulted in the suspension of the blocking mass from the underside of the roof deck. The predicted vibration attenuation is discussed, along with the proposed design which combines the blocking mass with the demising partition, effectively blending these two sound attenuating elements together.