Acoustic tests with the new sound-absorbing curtain in a normal living room: measuring the reverberation time with a loudspeaker and microphone. |
Researchers
at Empa, in cooperation with textile designer Annette Douglas and silk
weavers Weisbrod-Zürrer AG, have developed lightweight, translucent
curtain materials, which are excellent at absorbing sound. This is a
combination that has been lacking until now in modern interior design.
And the new “noise-quenching” curtains have just gone onto the market.
Noise
is annoying. It interrupts communication, reduces productivity and
tires people out – in extreme cases it can even make them ill. Sound
absorbing surfaces are therefore needed in rooms where people work, talk
to each other or are trying to relax. These decrease reverberation and
so make rooms quieter. However, so called acoustically “hard” materials
such as glass and concrete, which are commonly used in interior design,
scarcely absorb sound at all. Heavy curtains made of material such as
velvet are often used to absorb sound. On the other hand, lightweight
and transparent curtains are acoustically almost useless. At least they
were until now.
Together
with industrial partner Weisbrod-Zürrer AG, a silk weaving company, and
the textile designer Annette Douglas, Empa researchers have developed a
new curtain fabric that is lightweight but still absorbs sound.
“Acousticians
are pretty astonished when they see the readings we are achieving with
the new curtains in the reverberation room. The weighted sound
absorption coefficient is between 0.5 and 0.6”, commented Kurt
Eggenschwiler, Head of Empa’s Acoustics/Noise Control Division. In other
words, the new textiles “quench” five times more sound than
conventional translucent curtains. Eggenschwiler continued: “The new
curtain genuinely absorbs sound, noticeably improving the room acoustics
– and its design is also very high quality.”
A real gap in the market
Another
advantage is that because the new curtains are translucent, they can be
used in a variety of places such as offices, living rooms, restaurants,
hotel lobbies, seminar rooms and even multi-purpose auditoriums. They
are often the deciding factor in satisfying the acoustic requirements
and regulations that apply to these rooms. Just shortly after their
launch it became apparent that the new textiles are really filling a gap
in the market, as interest in them is “massive” according to
Eggenschwiler.
The
idea of a curtain that absorbs noise while, at the same time, being
lightweight and translucent, came from the textile designer Annette
Douglas, who has worked with the interaction between sound and textiles
for many years and received the Swiss Textile Design Award in 2005 for
the project “Acoustic walls for open plan offices”. In cooperation with
researchers from Empa’s Acoustics/Noise Control Division and silk
weavers Weisbrod Zürrer AG, and with support from researchers from
Empa’s “Advanced Fibres” Division, she submitted an associated project
to the Commission for Technology and Innovation (CTI) in 2010. Not a
simple task, because thin and, therefore, translucent fabrics are
normally poor sound absorbers.
Together with industrial partner Weisbrod-Zürrer AG, a silk weaving company, and the textile designer Annette Douglas, Empa researchers have developed a new curtain fabric that is lightweight but still absorbs sound. |
Successful combination of computer modeling, acoustic measurement and specialized textile knowledge
The
first acoustically optimised lightweight textile came into being on a
computer. The Empa acousticians wanted to use the characteristics of
this virtual textile in order to prepare a kind of “recipe” for material
experts, which would enable them to specifically manufacture a fabric
that could absorb sound. In addition, they first developed a
mathematical model to illustrate both the microscopic structure of the
fabric as well as its macroscopic composition. On the basis of numerous
acoustic measurements made on various samples, specifically woven by
Weisbrod-Zürrer, they were able to gradually optimise the acoustic
properties of the fabric. Annette Douglas then succeeded in translating
the new findings into weaving techniques. She chose yarns that gave the
materials the necessary characteristics in terms of flammability and
translucence and determined the weave structure, i.e. how the threads
should be woven in and out of each other. Weisbrod-Zürrer then adjusted
the sophisticated manufacturing process so that the industrially-made
curtains actually displayed the required acoustic characteristics.
Sound absorption measurements in Empa’s reverberation room. With a gap of 15 cm between curtain and wall, the new developed curtain – depending on the frequency – absorbs up to five times more sound than typical lightweight curtains. |
