Thuds, thumps and booms: issues with Cross Laminated Timber apartment acoustics solved
17 June 2019
Housing affordability and sustainability
imperatives are fast tracking the development of
innovative construction
methodologies in high density
residential building designs. One such
innovation is the replacement of traditional concrete structures with
lightweight
Cross Laminated Timber (CLT).
CLT has a number of advantages over concrete; it is produced from
sustainable wood supplies, has high flexibility and good resistance to
seismic forces, and can be
prefabricated offsite to drastically reduce
on-site build times.
Norman Disney & Young, A
Tetra Tech Company (NDY), is part of this
lightweight revolution, providing ongoing design input and benchmark
testing on new
apartment complexes in
Auckland. NDY Acoustics Manager Tim Beresford and the team have been
carrying out airborne and impact insulation tests establishing the
performance of various systems in relation to
New Zealand and Australian
Building Code requirements. These tests
have been designed to optimise CLT constructions to provide the best
value-for-money acoustic design solutions for a given apartment
situation, whether it be a code-minimum budget housing development or a
high-end luxury apartment building.
One common complaint from occupants of lightweight-floored apartments is
that low-frequency sounds (thuds, thumps and booms) can be highly
audible and annoying; an issue which is far less prevalent in
concrete-floored apartments. Given that CLT floors fall into the
‘lightweight’ category, special design considerations need to be
employed if good low-frequency performance is to be achieved.
Unfortunately, most building codes do not mandate controls for the
low-frequency performance, and therefore this issue is often overlooked
during the design stage of most projects.
NDY has been carrying out heavy impact (low-frequency) assessments of
CLT and other apartment floor types to determine their relative
resistance to thuds, thumps and booms; a technique entirely new to the
Australian and New Zealand building industries.
The procedure for these tests utilises the ball drop methodology
outlined in Japanese Industrial Standard A 1418-2. This procedure is
better suited to determining a floor’s resistance to low-frequency
impact transmission than the “standard” impact tests (using a tapping
machine) as stipulated in the Australian and New Zealand Building Codes.
The data and analytics gathered by NDY is instrumental in
developing lightweight CLT buildings which are cost effective, energy
efficient and provide good impact and airborne sound insulation
performance.
For further information and advice, contact Tim Beresford via https://www.ndy.com/contact
--ENDS--
Source: Norman Disney & Young (NDY) - www.ndy.com
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