This article is part of the Continuing Education Unit of Think Wood, a U.S. industry-driven initiative which provides research and resources on the benefits of using timber in residential and commercial building applications to design and construction professionals. The Think Wood portal including its research library can be accessed here: www.thinkwood.com.
This article has been written for the North American context and follows US and Canadian legislation. Readers should be aware that certain definitions like the NRC and OITC values do not have the same relevance and/or meaning in New Zealand.
In New Zealand, Clause G6 “Airborne and Impact Sound” of the New Zealand Building Code provides the minimum requirements in terms of acoustic performance. During the design phase, inter-tenancy walls/floors and walls/ floors to common spaces are required to achieve a design Sound Transmission Class (STC) of 55 dB. Floors to other tenancies or common spaces are required to achieve a design Impact Insulation Class (IIC) of 55 dB. Field testing on-site once the building is constructed is to be within 5 points of the design rating (i.e. no less than STC 50 dB or IIC 50 dB). These values should be considered as a bare minimum and care should be taken when designing floor and wall junctions in multi-storey buildings in order to reduce noise transmission by flanking. It is recommended to seek specialist advice from an acoustic engineer when designing multi-storey timber buildings due to its lightweight nature.
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