| Project 1.
sound absorbent walls
The projects described
on this site relate to the specific situation concerned,
and may require adaptation to suit other situations.
The information does not necessarily include all relevant
Health and Safety information and guidance. No responsibility
is accepted by the author(s) or by PAforMusic for any
consequence arising directly or indirectly as a result
of information provided or omitted.
The project information presented on this page has been
kindly submitted by Mike Holt and Martin Mason of Elim Church,
Coventry, England. Any queries should be addressed to them
(contact information is provided at the bottom of the page).
Take great care when working at height. Follow the Health
and Safety Regulations and Guidance and, where relevant,
the Building Regulations, that are applicable in your country
Solving Church Acoustics
Demands on Church acoustics have changed radically
in the last two decades. The church has moved from no
sound reinforcement and the use of purely acoustic
instruments with modest sound levels to a situation
where a great variety of instruments and voices are used,
all amplified sometimes up to levels peaking at
100 dB C.
The church environment is becoming more akin to a
theatre rather than the traditional concept. This
increase in sound levels and complexity together with
a requirement for higher standards, and of course the
Church is more concerned with clarity and intelligibility
than the normal music venue, has brought with it
excessive demands on the sound engineering.
This is the situation that the Elim Pentecostal Church,
Coventry found itself in recently, ahead of a major
refurbishment of the worship area and hence the
opportunity to address these issues. The specific
problems at the church are unpleasant room resonance
in the upper bass area, a thickening of sound textures
and a general lack of clarity. This was particularly
bad in specific congregational positions such as
adjacent to side walls and other locations dependent
on resonant frequency being produced.
The main Church built in 1980 and therefore of a modern
design, is essentially square in plan view with a
vaulted roof. The worship area where the platform of
musicians and singers are is set into one of the corners
of the square. The roof, being multi-faceted, was good
from an acoustic point of view, but the square section
plan of the congregational area was the worst possible
proportions. Two side areas are provided so that the
seating area can be extended from 270 to 350, which
turns the shape of the building into a rectangle,
which improves the acoustics slightly. The construction
of the church is that all of the walls are plain brick,
with wood cladding on the roof plus some large expanses
of glass. This was a very pleasing modern design but
introduced some inherent acoustic problems. The floor
was wood block except the platform area, which was
carpeted. However the Church was not known as being
'poor' acoustically on the contrary, but increasing
demands were producing problems that could not be
solved with conventional sound engineering available
to a small church.
The music was produced by a worship band comprising
electric piano, electric guitar, bass guitar, drums,
alto sax, flute plus vocals of worship leader and up
to three backing vocals. All musicians were connected
to the sound system with three microphones on the
drums. No digital sound processing was being used.
This picture shows the bare platform area prior to
The problems were isolated to the 'direct' sound from
the musicians located in a recessed corner of the building
as the main problem and also, as a secondary issue,
the problems associated with the main building shape.
With a 'revamp' of the worship area it was decided to
explore improvement possibilities. The aim being to
reduce the resonances and nodes being set up in the
This picture shows church being used for a Youth event.
Part of the refurbishment project was for the
platform area to have the walls changed visually
from brick to a white plaster surface so that wall
washers could be introduced and so enable changeable
colours to be used to improve the visual aspects.
The idea actually adopted was for all the 'wall'
area on the platform to be transformed into a sound
absorbing area, so that only direct sound emanated
from the platform. The 'muddying' of the reverberant
sound from the walls would be nullified by being
absorbed thereby reducing resonances from the sound
The final design comprised a white canvas outer skin
onto which the coloured light from the wall washers
could be projected, under which were 2 layers of
45 mm of 100 Kg/m3 sound-absorbing
felt mounted within studding to maintain its position.
Sound would therefore have to travel through 180 mm
of absorbing material if it was to reverberate into
The sound quality has been transformed by the
implementation of the above design. The musicians
have been very complimentary about the changes,
as have the congregational members. In other words
not only can the congregation hear the music better
and more clearly but so can the musicians hear each
other better on the platform. Foldback levels have
been reduced. The resonant frequency aberrations have
been eliminated much to the appreciation of congregational
members. Acoustic improvements have occurred in all
areas and the solution was far more cost effective than
any other solution to the problem.
The issue of a canvas wall being vulnerable to misuse
has not materialised as a problem. The kick-board trough
has accomplished its function of keeping people and
damaging objects away and no serious damage has occurred
in the initial years of use. The area does not
experience traffic from the general public and the area
is restricted. Damage could occur in an area more
accessible to the public. The construction has remained
taut and provided the function excellently. No drawbacks
have been discovered beyond the obvious. For others
experiencing problems such as those described above,
this would appear to be an excellent solution.
Construction of the Sound Absorbent Walls
It has been suggested that I place on the Web some
recent practical experience of covering a brick wall with
sound absorbent material finishing with a flat finish
suitable for lighting effects.
The wall lit in pink was standard brickwork, as can be
seen on either side. It measures 11 metres wide by 6 metres
high at its highest point and consists of 90 mm of
sound absorbent wadding supported by a wooden frame attached
to the wall, and finished in heavy duty canvas,
as used in stage scenery.
This picture shows the start of the operation
with some framing in place. The framing consists of
50 x 50 mm sawn softwood battens screwed
directly to the wall using 125 mm frame fixings.
To each of these is screwed another 50 x 50 mm
batten using 90 mm x 10 screws.
This should give a top surface to each batten 100 mm
from the wall surface. [Should the timber size be marginally
under 100 mm it is suggested that 12 mm slats
are nailed on top to make sure the surface of the wadding
doesn't touch the canvas when taut.]
This photo shows the framing packed with 90 mm wadding.
Please note that a tough plastic netting, as is sold in most
garden centres, is stretched tightly across the timber
battens and frequently stapled to ensure that the wadding
is unlikely to fall forward and spoil the flat surface of
the taut canvas.
This shows the heavy duty, un-shrunk canvas being fixed.
It is fixed temporarily with nails at the top, and then
pulled in each direction to remove wrinkles and
frequently stapled [e.g. every 150 mm.],
but only around the edges of the canvas.
Do not attempt to stretch the canvas by hand, but
ensure any loose canvas is flattened by merely pulling
out the wrinkles, so that the final surface
is as flat as possible.
Following this a coat of fireproofing spray is applied,
which itself begins the process of tightening, followed,
when dry, by a liberal coat of PVA adhesive mixed
1:1 with water.
This should produce a completely flat, taut surface,
if the wadding has been so fixed that it does not fall
against the canvas.
Finish the edges with 50 mm rounded
architrave [to avoid shadows] and paint with 2 coats
For lighting purposes a stone coloured matt emulsion
This produces a finish which responds well to lighting
effects but is also effective in allowing sound to pass
through into the wadding.
This photo shows an option for dealing with the bottom
of the wall.
In the instance photographed, the framing for the canvas
finished 300 mm above the floor so a kickboard
450 mm high was used for the whole 11 metre width.
Apart from providing a good place for loose cables
it keeps people away from the canvas, which is remarkably
resilient but it is best to minimise human contact.
Any queries on the above should be directed to:
Mike Holt at
Martin Mason at
or to the following address:
c/o Elim Church, The Butts,
Coventry CV1 3GR
UK Tel. 024 7622 6493
International Tel. (+44) 24 7622 6493
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This page last updated 04-Feb-2016.