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The following article was first written by
Joseph De Buglio in 1988 and published in
1991 for Your Church Magazine. It has been
Updated Jan. 1996.
TROUBLE SHOOTING CHURCH ACOUSTICS,
THE PRO'S AND CON'S.
From the JdB Church Sound Series
Why Band Aids Don't Work well in Open Heart
© By Joseph De Buglio 1996
For the latest Article on Room Acoustics 2021
JdB Sound Acoustics answers to secrets
Since most churches have a problem or would
wish to avoid a problem, here are some after
the fact solutions.
In old cathedrals of Europe and in a few
churches in North America, pillars were used
to tune the church. Slots or holes in the
back of a pillar were cut to select the offending
frequencies. By adding sand, or as done recently
in Chicoutimi, Quebec, adding blown insulation,
you can tune the pillars. If a mistake is
made, the sand can be removed from a hole
at the base of the pillar. The pillars greatest
effect is on the sound quality of the Pipe
Organ and congregational singing. Pillars
tuning is still being done today and it is
possible to retrofit an existing church with
Ash pots were first used by the Greeks, then
the Romans and later in Northern Europe.
The technique is very simple and effective.
Where ever there was a known or planned acoustical
problem, clay pots of various sizes would
be built into the walls of the church or
theatre. The most common walls were the back
walls and rear corners. After many trial
and error tests, an employee of the church
would fill or empty the pots with ash for
various function. Today this same technique
could be used. You can replace the ash with
fiberglass insulation which is reusable.
Us a silicone spray on the fiberglass and
it will reduce the dust and keep the fibers
from falling apart. A better alternative
would be an adjustable Helmholtz Resonator.
Please read the book Architectural Acoustics, David M Egan, published by McGraw Hill,
1988 or "The Masters Handbook of Acoustics" Second Edition F. Alton Evert, Tab Books
1989 for further details.
Slotted blocks have been around for a long
time. Slotted blocks were often combined
with the clay pot system. Today, the slotted
block is a very attractive system that stands
on it's own. The principal is simple. Take
a standard 8 x 8 x 16 inch block. Cut a slot
from top to bottom of the block to a certain
width for the frequency you want to control.
Add some fiberglass inside of the block.
When finished, you can paint or wax the block
or cover with curtain or cloth. The block
companies that manufacture these blocks also
make different size chambers within the block
and the have different surface finishes that
don't need to be painted. These blocks work
well for mid and low frequency control and
they are generally interior blocks.
Depending on who the manufacturer is, this
system has many names. The most common appearance
of the system is 12" x 18" x 3"
flat panel. Usually the back of each unit
has a mounting deck that raises the units
about an inch from the wall. These units
are effective for mid and high frequency
control. Although the manufacturer claims
are accurate, they are very misleading. If
you have a room with an internal volume 50,000
cubic feet, the literature will say that
all you need is 1 or 1.5% of material to
treat the room or 750 units. What they are
not saying is that 3 of the walls have to
be cover from floor to ceiling to get the
desired results. Using these products requires
more than a siding scale to figure out.
Split Face Blocks.
A split faced block is nothing more than
a block with an exposed shape. There are
many patterns and styles. Usually the exposed
shape is 2 inches deep or less. These blocks
are also often called Architectural blocks
and they are treated a decorative block.
The Acoustical properties of these blocks
are very limited. Some times you will see
a 6 or 8 foot ring of these blocks in the
upper half of a school gyms. Although an
Architect will state that he chose those
blocks for their acoustical properties and
smile for his wise choice, an acoustical
expert will notice right away that two of
the walls should have had the spit face block
from the floor to the ceiling and an eight
foot ring in the other two walls. The spilt
face block is not very efficient in distributing
or absorb sounds. The split faced blocks
combined with other systems can be very attractive.
ASC Tube Traps
A functional Bass trap, high frequency diffuser
and mid range absorber makes this product
the most effective. Although they cost a
few dollars more, you need far fewer of them
when compared to other sound control objects.
ASC tube traps were designed originally as
a recording studio product. When this product
was unleashed to the church community, it
has literally performed miracles as some
minister would express its. The beauty of
the product is three fold. First is being
able to trap a lot of bass sounds in room
corners in a small package. Almost all churches
have corners including domed churches. Bass
always builds up in the corners. ASC Tube
Traps traps the bass without reducing the
high frequency range noticeably. Secondly
it absorbing mid range sound. By spacing
the traps at difference widths, you can change
the amount of mid range absorption. The third
effect is diffusion. The diffusion occurs
from 500 hertz and up. Usually you don't
want to absorb high frequency in a church.
The Tube Trap can maintain the singing quality
of a church while fixing the low frequency
problem areas. As a side benefit, in every
installation of ASC Tube Trap that I have
visited, the organist always make comments
like, "there is more bass coming out
of the organ" or "the music is
easier to follow and play. I didn't realize
how much poor acoustics were restricting
our ability to perform" (Scott Tyler,
St. Paul's United Church, Bowmanville, Ontario,
Can.) ASC products can be used on their own
or be used with other products.
RPG Diffusors. (Reflection Phase Grating)
Diffusion is often used to solve acoustical
problems. For years, the acoustical community
was looking for a diffusive surface that
gave a uniform diffusion of sound energy.
Such a system was invented by Manfred R.
Schroeder, a professor at the University
of Gottingen, Germany and at AT & T bell
Laboratories at Murry Hill, New Jersey. The
panels have many different sizes and shapes
to accommodate almost any acoustical condition.
The panels have long wells which are cut
to different 1/4 wave lengths deep. The well
depths have a very specific pattern. Each
panel is based on the "Maximum Length
Sequence Code". Today the general term
is Diffraction Grating and many acoustical
engineers design their Diffraction Grating
The RPG diffusors is trademark of a ready
made, of the shelf, effective system of,
non-patented panels which are primarily made
of wood. The Following is a Quote from the
book, The Master Handbook of Acoustics, Second
Edition, by F Alton Everest (TAB Books)
"In churches, there is always conflict
between the intelligibility of the spoken
work and conditions for full enjoyment of
the music. The rear wall is often the source
of reflections which create disturbing echoes.
To make this wall absorbent is often detrimental
to music conditions. Making the rear wall
diffusive, however, minimizes the echo problem
while at the same time conserving precious
music and speech energy. Music directors
or often faced with the problem of singers
or instrument players not hearing each other
well.... Surrounding the music group with
an array of reflection phase grating diffusors
both conserves music energy and spreads it
around to achieve ensemble between musicians."
The combination of RPG products and ASC Tube
Traps offers the most versatile and complete
solution to any church with acoustical problems.
Tectum (Spaghetti Board)
Tectum is one of those products that you
love to hate. When used properly, Tectum
tiles an panels work great. However, because
they are so cheap to buy and every Architect
has a "Guide Book" from the manufacturer,
Tectum usually gets installed in a broad
and indiscriminate way. As a result, Tectum
gets installed in such a way that it solves
one problem very well, but it creates other
problems. In a Gym or a Cafeteria, the latitude
in using Tectum is quite broad, but in a
church, there is a fine line between how
much you use, how it is installed and which
surfaces it is installed on.
Tectum is an inert fiber board that comes
in thickness from 1 to 4 inches. When exposed,
the panels look like compressed spaghetti.
Although it is paintable, the Guilford Cloth
covered products are better in a church.
When painted, the Tectum will shift in frequency.
Sonex is a patented foam system. In comes
in square panels from 1 to 4 inches thick.
These panels are very efficient high frequency
absorbers. Their best use is for attenuating
high frequency in a church. A very effective
application of Sonex is under balconies and
around entrance areas where you don't want
sound from the foyer disturbing people in
the sanctuary. If you have a high frequency
problem and you need to cut down about 3
seconds at 4000 hertz, you will not need
very many traps to do the repair.
Carpets and Curtains
Once upon a time, a church used a little
bit of carpet to solve a problem. Today,
most church have a problem because of carpets
and or curtains. Carpets in the church are
often installed without any consideration
of the consequences. What most "Experts"
and builders often do is lump carpet and
Padded pews together. A church that has padded
pews is just trying to keep the same Reverberation
Time (RT60) for when the church is full or
empty. Carpet is a surface treatment. It
has short fibers that absorb high frequency
sounds very well but! reflect low frequency sound energy back
into the room. There is a big difference
between padded pews with carpet and without.
The rules for carpet are as follows.
For example, If your church installs
sq. ft. of carpet, you would need 500
of ASC 16" half rounds at 24"
This will give the church a flat frequency
response. The skill is knowing where
When the internal volume of the room greater
than 20 times the floor space, you can use
carpet in the isles.
When the internal volume of the room greater
than 30 times the floor space, you can use
carpet in the isles and pew areas.
For every square foot of carpet installed,
you have to install a 150 to 500 hertz mid
range bass absorber that has equal or greater
efficiency in absorption.
Electronic Reverberation Systems
The newest and most exciting system of solving
a whole array of acoustical problems is the
Electronic Reverb Systems. There are several
systems available and some custom systems
as well. It is a system that consists of
microphones, speakers, amplifiers, electronic
digital reverberation and a complex matrix
system. When adjusted properly, these system
can often make up for poor acoustics and
also shape the reverb time to be natural.
However, it can not correct acoustical problems
such as bass build up or standing waves,
but, you can often hide echoes and in some
cases improve intelligibility.
The plan is to make the house of worship
sound like a recording studio. Make the room
quiet, free of obvious acoustical problems
and use the reverb system to restore the
desired acoustics as needed.
In Europe, there is a successful system called
the ACS or Acoustical Control System from
Holland. Although North American installations
of such systems are limited, these systems
offer the widest solution a church can ask
for. From personal experience in installing
and using an ACS system, it gives the best
performance for everyone to experience. In
the United Church installation which sat
600 people, the Organist or Soundman were
able to switch the acoustical performance
to match the event during the service.
There were four preset position. Position
one was for Organ, acoustical instrumental
and Singing solo performances. The reverb
time in this position was at it's longest.
Position two was for choir performances.
In this position, the reverb time was slightly
shorter and the microphones nearest the choir
were turned up higher to assist the choir.
This helped the Organist to balance to the
choir. The third and perhaps the most important
setting was setting three. In this position,
the reverb system was adjusted of optimum
congregational singing. The audience mics
were turned up while the mics near the organ
and choir where turned down. Setting four
was for speaking, although a proper sound
reinforcement system was used as well, the
reverb system was adjusted with a short reverb
time above the balcony while under the balcony,
the speakers were turn up with a little more
delay time. As a result, a separate delayed
system under the balcony was not needed.
One neat effect was when moving from the
main part of the sanctuary to under the balcony,
- you didn't notice the roof over you head
until you looked up.
An Electronic Reverberation Systems can have
many more presets and are a great partial
or complete problem solver, and, they do
represent the latest in modern technology
for meeting today's needs of a multi purpose
In church acoustics, these are just some
of the most common techniques seen. The cost
of a good acoustical system that solves most
of your real major problems can vary. Please
note the words "solve most of your problems".
This is due to the fact that some building
shapes are so poor, that rebuilding the church
would be cheaper that trying to solve a problem
until it is reasonable. However, there are
some compromises you can live with. Accepting
minor compromises will keep acoustic solution
costs down. From experience, the average
one time cost of an acoustical solution works
out to be from $30 to $55 per seating position
in the house of worship. Therefore a church
that seats 400 people including choir loft
seating should spend no less that $12,000
for a meaningful solution than will satisfy
most church members and no higher than $22,000
for extreme cases. If you get a second opinion
that is over $55 per seat, it is time to
consider condemning you church sanctuary
and build a new house of worship. These same
figures are of 2 or 3 times higher than the
cost for planning and doing the acoustics
in a new church building. If your church
is considering an electronic solution, be
prepared to make a one time investment between
$70 to $130 per seat plus correcting any
existing major acoustical problems.
OK, now that you have just received some
of the best knowledge on church acoustics
available, now you can get the technical
books on acoustics design your church acoustics
right! Wrong!!! Just because the church down
the street did it or you read of a solution
in a book, it does not mean that their solution
is right for your church. You might have
a one of a kind problem (which happens not
too often). Although many consider me as
a doctor (an expert), the truth is, I have
all of my work check out by other experts
before a recommendation is made. There are
just to many variables that can be easily
over looked. One wrong number in a calculation
can cost a church thousands of dollars. I
have never yet met a church that had an unlimited
budget like some government projects seem
to have. Churches can't afford experiments.
Churches need solutions.
Church acoustics is 40% science, 10% art,
40% skill from experience and 10% inspiration.
Judging from the many churches that I have
visited over the past 15 years, all you see
is 100% perspiration, 100% desperation, no
art, no skill and no science. Isn't it time
for the church communities to define their
needs and use science, art and skill to set
acoustical standard? Lets stop using a Band-Aid
approach to church audio and acoustics. If
you want to see perspiration, be a surgeon
- half way through open heart surgery, be
told that there are no more sutures or stitches
left in the hospital. All you have to work
with are Band-Aids. What do you think the
patient will say when he wakes up? - Sorry,
I was not implying that churches are asleep!
Some statements and Specs have been blanked
out under the understanding that it is part
of the "intellectual Knowledge"
guidelines and were not part of the original
article. Such knowledge has value and can
be purchased through investing in the book
Back to THE LEARNING CENTER Blog
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Copyright (c) 1996 JdB Sound, Acoustic Lab.