Aluminium Extra
‘Window
and Facade
Acoustics’
by Wojciech Brozyna - MD of Aluprof UK
» MOST OF US WILL BE WORKING
from home at this time and communicating
through meeting apps in order to progress
what business we can. It is at these times we
notice the sensitivities of the microphones
on our devises and hear the sounds that we
filter out during our normal home life. When
specifiers design facades for new or refurbished
properties in our towns and cities, there are a
number of factors to put into the design mix
and acoustics are becoming crucial both in
workplace and residential properties.
Different types of noise can raise stress levels
in the body, releasing a number of different
stress hormones and, as the amount of stress
hormones in the body increases, the heart rate,
blood pressure and blood sugar levels increase.
Excessive levels of these stress hormones in
the body are harmful, and should the noise
be sustained, or repeated day after day, this
exposure will be seriously affecting health and
wellbeing of building occupants.
Cities are becoming noisier with increasing
traffic and in many building locations close
to railway lines, noisy pubs, clubs, noisy
neighbours and/or flight paths. There are street
designs which include special street furniture
and planting to help reduce airborne noise
but eventually, the noise will try to penetrate
the building structure through the building
facade.
Windows or areas of glazing are the most
susceptible parts of the facade as they are
generally the ‘lightest’ of materials used.
Sound attenuation is best achieved by utilising
unbroken ‘mass’ of material, such as a brick
wall. The greater the mass, the greater the
sound attenuation.
Depending on the time of day, noise levels
of road traffic can vary between 45-70+
decibels and this is just over the sound level
that is seen to be ‘healthy’.
Old, draughty single glazed windows with
poor or non-existent weather seals are the
poorest performing windows when it comes to
sound attenuation. Even the smallest of gaps
which allows a flow of air through the window
will allow noise to penetrate the facade. So,
the more airtight the window, the greater the
sound reduction. Typically, a well-sealed single
glazed window will offer a -30dB reduction
in sound transmission, or what is known as
‘attenuation’. In busy built up areas single
glazing is now seen as inadequate.
For every 10dB reduction in the noise level
achieved, the human ear perceives this as
halving the volume.
Glazing plays the biggest part in sound
attenuation, double glazing helps, especially
if the glass used is of differing thickness. Most
materials at a given thickness will ‘resonate’
at certain frequencies and allow some of
those frequencies through, using a different
thickness ensures what passes through one will
not pass through the other. A well-designed
triple glazed unit with differing air spaces
and glass thickness, will perform even better.
Acoustic laminates used in laminated glass
are specially designed to minimise sound
transmission and a well-designed unit can
achieve up to -45dB sound attenuation.
The use of triple seals further improves
sound reduction and high thermal
performance systems with wide high
performance centre seals with further
attenuate sound around a high performance
glazed unit.
Regarding specification, Building
Regulations, Part E, ‘Resistance to the passage
of sound’ should be consulted as well as a
number of standards that are currently in
place. Depending on the building there are
also specific and differing requirements laid
down for the likes of schools, hospitals and
offices, to name a few. Some company chains,
such as Premier Inn, have their own acoustic
requirements. When specifying BREEAM
rated projects, there are points than can
also be awarded for compliance in certain
circumstances.
Sound attenuation is also a little more
complex in application and specifiers need
to be aware that a change in window size can
36 » AUG 2020 » CLEARVIEW-UK.COM