Appendix 5: External Studies and Recommendations
5A: Recommendations from Rein Pirn, Acentech (30 November 1999)
Ms. Beth Norton
Director of Music
First Parish in Concord
20 Lexington Road
Concord, MA 01742
Subject:
Acoustical Observations and Recommendations
First Parish Church in Concord
Acentech Project No. 614211
Dear Beth:
It was a pleasure to visit your church and to get acquainted with your committee who so kindly gave their time to
apprise me of your acoustical problems. The main issue, as I understand it, is insufficient and uneven projection-from the organ as well as the choir--to the congregation on the floor below. I understand there are also other
problems, such as a lack of expression from the organ, which, however, is independent of the room and its acoustics
and therefore beyond my expertise.
Observations
With a volume of roughly 120,000 cubic feet and a capacity of about 400, the volume/seat ratio is in the
neighborhood of 300 cubic feet. This suggests that even if everything (except the 400 occupants) were acoustically
reflective, reverberation time would be none too long--at best 1.7 seconds, which is less than preferred by most
organists. With all the carpet, the pew cushions, and other absorbers that are now present in the sanctuary, RT is, in
my estimation, barely over 1 second. The reason I am mentioning these numbers is not that they, in themselves, are
very important, but to establish a basis for estimating the effect of the suggested changes.
Next to a lack of reverberation, which among other things translates into reduced sound propagation to the underbalcony areas, the problem is exacerbated by the not insignificant depth of the balconies. As it is, from many of the
main-level pews there is no line of sight to - and therefore no direct sound path from - the organ and choir.
Whatever a person seated in these pews hears is either diffracted or reflected. The change, as one moves from out in
the open under a balcony, is quite dramatic. With Bernie Schlager playing the organ, I was able to experience it by
slowly walking from where I could see the organ to where I was shielded from it by the balcony. The loss of the
highs, which tend to travel in a straight line, was particularly noticeable.
I also had an opportunity to inspect the organ chamber. However, I will defer judgement on its design and layout to
a qualified organ consultant. I would assume the instrument was built and laid out to take best advantage of the
available space.
Recommendations
1.
2.
Replace the carpet with any hard material of your choice. One possibility, assuming this is practical, would be
to refinish the wood floor. Other possibilities include stone, tile, even linoleum. The only exceptions are the
steps or platform by the pulpit, which, if you prefer, may remain carpeted, and the two aisles. To cushion
footfall noise, you may want to cover' the aisles with thin carpet runners. Removing the carpet will change
over 1000 square feet of floor (not counting the floor under the pews, which is subject to the same
recommendation) from moderately absorptive to reflective and increase the reverberation time by about onequarter second--a perceptible, if not dramatic, change for the better.
To the extent possible, also remove other absorbers of sound, or alter them so they reflect more. These include
the modesty curtain on the railing by the organ and the porous, cloth-covered padding on the bell choir tables.
Appendix 5 – page 1
3.
4.
The latter appears to be just as absorptive as the pew cushions. One way to make it less absorptive would be to
cover the padding with an impervious (airtight) membrane--if this does not adversely affect its intended use.
Keep the pew cushions. Do not discard them. They do absorb sound, of course, but when covered by seated
people their effect on the acoustics is much reduced. As they are loose, you can always remove them. Once the
carpet is gone, I suggest you try it. With no or few occupants, I would be not at all surprised if the
reverberation time, without much carpet and without the cushions, were to approach 2.5 seconds. (While such
reverberance may delight an organist, it could seriously hurt speech intelligibility.)
When replacing the choir seats, feel free to get padded chairs. Although this may seem to contradict the other
recommendations, I look upon this as a comfort issue. The acoustical consequences of 40 thinly-padded
chairs, especially when occupied, would be minimal.
Some Additional Thoughts
We also discussed more radical measures, such as removing the ceiling and exposing the space beyond, which
might increase the room volume by up to 40,000 cubic feet and the reverberation time by up to 25 percent. Possible,
I suppose, but, in my opinion, not at all cost effective. The same holds for removing or altering the balconies to
reduce shielding.
Another thought that we touched upon was to move the organ forward, Or to revise the chamber, to improve
propagation. Again, I question the value of doing this now. However, you should certainly consider it if and when
you replace the organ with a new one.
An acoustically still better idea would be to relocate the organ to the front of the room where it can be seen by the
whole congregation. We did not review this in any greater detail than to establish that the wall on either side of the
pulpit cannot be moved, which means the organ would have to be forward of the wall, off to one side, with the choir
on the opposite side of the pulpit. Besides better localization for those who prefer a frontal source, this would yield
more clarity and better uniformity, and would make it easier for the congregation to keep up with the choir.
Summary
The sanctuary, as now finished, is none too live. To make it more live and thus more suitable for church music, I
suggest you remove most of the carpet and, if practical, modify the padding on the bell tables. Keep the pew
cushions; they help stabilize the acoustics, which otherwise would be highly dependent on occupancy (as they are
loose, you may remove the cushions on a trial basis). The alternative of increasing the volume--e.g., by raising the
ceiling--would, in my opinion, not be cost effective.
By making the sanctuary more live, you will reduce, but not eliminate, acoustical shielding by the balconies. Unless
the sources were to be relocated to where they can be seen by all, audibility under the balconies will remain less
than optimum. Consider relocation - if not to the front of the room, then farther forward in the balcony - if and when
you are ready to invest in a new organ.
Livening the room and exposing the organ and choir are two separate things. They are not interchangeable. Over
time, I hope you can do both. Bear in mind that small changes, like removing some of the carpet while leaving most
of it in place, will not significantly alter the acoustics, and that any increase in reverberance will mean some loss of
intelligibility.
This letter may not replicate everything that I said last Wednesday. However, it does cover the main points. If there
is anything that I missed or if you have any other questions, please do not hesitate to call.
Sincerely,
Rein Pirn
ACENTECH INCORPORATED
Appendix 5 – page 2
5B: Recommendations from G. Paul Music Co. & Bose Corp (30 Oct and 18 Nov, 2002)
First Parish Sound System Improvements - Part 1
Meeting with Dan Parcell (G.Paul Music Co.) and Elliot Baskas (Bose Corp.) at the First Parish Church
on October 30, 2002. with Dave Kelch.
Purpose of meeting was to assess the acoustic characteristics in the sanctuary and parish hall for the
purpose of making recommendations on improvements to the sound amplification systems.
Sanctuary:
Dan and Elliot set up and measured the "T-60" reverberation times in the sanctuary. They injected pink
noise (sounded like hissing air) into the room at various frequency bands from 125Hz to 5KHz via our
audio system. Their equipment measured the reverberation times at these frequencies which were in the
range of 1.1 to 1.5 seconds. Elliot commented that this room was very good for the speaking voice.
I described the problem that people sitting in the front rows of the sanctuary were distracted by hearing
both the direct voice from the minister at the podium and also the amplified voice from the loudspeakers
which doesn't arrive at the listener's ears at the same time.
They had three suggestions:
Solution 1. Hang two small Bose 402 speakers centered near the ceiling about eight feet out from the
front wall angled down and out to cover the audience. This will tend to equalize the distance from the
speakers to all of the audience. Since the sound will be coming from the center of the room, above the
minister, the sound from the loudspeakers will be on center and not on either side. Also, if a listener does
hear the minister's voice, it will be ahead of the loudspeaker sound. Our brains lock onto the first sound
we hear - if it' s followed by the same sound a few milliseconds later, we're not distracted.
Advantage: Probably best sounding solution. The acoustic theory says this is the best answer.
Problems:
A. Aesthetics. Parishioners probably would object to speakers hanging in the center of the room.
However, the speakers are small and can be painted to match the ceiling or walls. It might be worth a look
at a church that has an installation like this. Evidently, many churches use this arrangement.
B. The first floor audience under the balcony would be in a "sound shadow". This could be fixed by
adding a speaker or two under the balcony on a time delay. (We already have one pair on a time delay
under the balcony.)
Solution 2. Mount four line array speakers vertically on the wall approximately above and below where
our present speakers are mounted. The arrays are four feet tall by about four inches wide. The lower array
would be mounted with its bottom about three feet above the floor. The upper would be mounted centered
about chest level with the balcony audience. Again they could be painted as needed and aesthetically
they'd be about the same as the present speakers.
Appendix 5 – page 3
These speakers have a flat, pancake sound pattern and would result in better coverage of the audience
seated in the front rows perhaps overpowering the minister's direct voice to most of the audience, so that
the loudspeaker sound would predominate.
Advantage: Appearance is about the same as our current system.
Problems:
A. When the piano lid in the right corner is raised, it would obstruct the sound from that loudspeaker.
B. I'm not completely convinced that this would fix the problem.
Solution 3: Replace our two current speakers with Bose speakers of about the same size mounted in the
same place. The Bose speakers are more accurate. Some of the distraction problem in the front pews may
be due to the fact that the loudspeaker sound is enough different in quality from the minister's voice so
that it causes distraction.
Advantage: This would be fairly easy to check out (If they'd loan us the speakers.)
Disadvantage: None. If it works, it'd be great. I have my doubts.
Parish Hall:
This room is extremely reverberant! It's probably fine for music performance, but for voice it's not very
good.
Solution: Their recommendation was to use the linear array speakers -- eight feet high by four inches
wide. These speakers have an extremely flat (pancake) shaped sound pattern which does not bounce
sound off the floor or ceiling, which drastically reduces echoes and extraneous sound to the listeners.
They set up a demonstration system which was very impressive compared to our existing system. The
Bose was very intelligible all over the room and had very little tendency to feedback.
Advantage: Sounds great.
Disadvantage: Cost/benefit. How many times do we have people speaking to groups in the Parish Hall?
We need to tell G. Paul where we want to go next.
Possibilities:
1. Borrow 402's and replace current speakers for a trial in Sanctuary.
2. Ask for quote on hanging 402's and adding delay channel to correct acoustic shadow under balcony.
3. Ask for their advice if we removed carpet and made room more reverberant. What would need to be
done to make the room acceptable for spoken voice?
4. Bose can do a detailed computer model of the room and can show the effect of changing the room
materials (removing carpet, cushions, adding people etc.) and then placing the listener at any location in
the room via computer and actually demonstrating the quality of the sound. Might be expensive but it
could be worth it if major changes are seriously contemplated.
First Parish Sound System Improvements - Part 2
Appendix 5 – page 4
Nov. 18, 2002
I had a further conversation with Dan Parcell from G. Paul Music Co. We discussed three topics.
1. The exact measurements of the reverberation times in the sanctuary were as follows. They were made
using the T-60 protocol - the time it takes sound to decay to l/60th [should be 60dB] of its original level.
Frequency (Hz)
RT60 at center of
sanct. 32' from pulpit
(seconds)
125
250
500
1000
2000
4000
8000
1.0
1.3
1.16
1.2
1.25
0.9
0.4
RT60 at right side of
sanct. 38' from
pulpit under balcony
(seconds)
1.1
1.1
1.1
1.2
1.2
0.9
0.6
The average is about 1.2 seconds. Dan commented that this is a very well-behaved room with no uneven
peaks or reflections and is just about ideal for speech.
2 If we contemplate making changes to the reverberation characteristics of the room, he suggested hiring
an acoustic consultant to make recommendations. Also, Bose can do a detailed acoustical model on
their computer system that will accurately recreate the speech sound characteristics of the room with
various reverberation times and audio amplification systems. They will actually set up the room on their
computer and one can hear the speech results in a specially constructed studio at Bose in Framingham.
The cost of doing this modeling is $65/hr and typically costs $1500 to $2000. They can't demonstrate
how the organ would sound in the room, however.
3. Dan also raised another interesting idea. That is using a digital system to add more voices to our organ
and also to enhance the apparent liveliness of the room. Our existing organ would stay in place. He says
they have done this for other churches with excellent results. Evidently, an organ specialist from G. Paul
has talked to Hugo Logemann in the past about this idea.
Dave Kelch
November 18, 2002
5C: Bose Comments on RT60 Reverberation Time and Acoustic Modeling
(from Dave Kelch, 19 July 2003)
I spoke with Elliot Baskas from Bose Corporation on July 18th. Elliot is the engineer from Bose
who did the sound measurements in the First Parish in November 2002.
The sound measurements he made were done to give him a quick, approximate understanding of
the sanctuary’s acoustical properties. Introducing the test sounds through the existing sound
system was not ideal because of the speakers’ sound pattern and frequency response which is
tailored for speech reproduction. However, based on his experience, the measurements he made
are probably within ten or twenty percent of the actual RT60 of the room.
He does do accurate measurements of RT60 routinely. He brings in special speakers and
equipment and it takes three or four hours at $150/hour. He needs to have the room as quiet as
possible while the measurements are made.
Appendix 5 – page 5
We also discussed the Bose Auditioner system which models the room’s acoustical
characteristics based on absorption characteristics of the surfaces and room geometry. In
essence, they can accurately predict the characteristics of a room before it’s constructed or
predict the affect of modifications before they’re made. Their emphasis is on maximizing
intelligibility of the sound reinforcement system. One can actually hear what the sound in the
room will be like at any chosen point.
The auditioner system also has the feature of simulating how unamplified sounds are heard. They
can simulate a person speaking or singing or playing an instrument or groups singing from a
defined place in the room without microphones or amplification and hear what they sound like at
any other place in the room.
These are ideas that are worth considering if the First Parish were to make significant changes to
the acoustical properties of the sanctuary. A more highly engineered sound system would
probably allow us to maintain and possibly even improve the overall intelligibility.
5D: Comments by Allen Hill on Acoustics re FP Organ
[The following e-mail was received by Pat Everett on 21 July 2003 from Allen Hill of FoleyBaker, Inc in response to his receiving a draft of Appendix 9]
Eric Huenneke copied me the ATF appendix draft for comment as the church's organ service
firm and I read it with great interest. Since I am not an engineer and do not pretend to understand
the criterion and logic of the enclosed analysis, I will defer to putting my thoughts into the
following analogy.
The matter of the organ's sound, the choir's singing, the congregation's sung and spoken
responses, as well as the various readers' and speakers' oratory on a given Sunday, may be
considered as the 'clappers' of a hand bell, i.e. they are all a facet of energy to create sound
within the walled space of First Parish. The room itself then, with all of its interior treatments
and appointments is the bell housing surrounding the sources of sound energy produced by the
various 'clappers' creating their sound. It is the reflective and resonating capacity of the room
(the bell housing itself) which creates, enhances, blossoms and sustains the mixture sound
(harmonics) within it until it is dampened. Dampen a bell immediately and its tone becomes a
short pitched thunk. Allow the bell to ring, and it decays naturally over what seems like an
almost infinite amount of time. Slowly dampen its decay and the ringer can control its musical
cut off.
The same is true of the room. Allow the room its natural acoustic quality (natural wood and
plaster surfaces) and it will ring with a natural decay. Treat the room acoustically
and accordingly to maximize and yet balance the decay and all sound will blossom toward and
be heard clearly, by the listener.
Tiling or otherwise modifying, the organ chamber would only attempt to affect the quality of one
of the various energy creating 'clappers' within the room in a given service event. It is the
resonating quality of the organ's own natural wood that not only reflects the sound toward the
listener, but also transmits and carries the organ's frequencies (especially bass tone) right into the
structure of the church. If tiling chambers worked as a viable and cost effective organ
building method, builders would have done it centuries ago.
Appendix 5 – page 6
For sure, any extraneous clutter in an organ chamber should to be removed and discarded;
however, I am unsure that it would have a more than just a glancing effect on the overall sound.
More specifically, cleaning the pipes, the chamber walls and re-shellacking (original finish)
them, would produce a satisfying and noticeable improvement for the organ's tonal egress into
the church; however, the congregation may only perceive it as being louder, with no enhanced
blossoming effect that only the reflective quality of the room (the bell housing itself), can
provide. Louder sounds in dampened rooms usually are condemned to being called shrill or
abrasive. I see the goal as being the need to maximize the resonating qualities of the room to
greatest benefit of the sound producing entities within it, the people, speakers, organ and
handbells. Energize the treatment of the room and less energy will be required to create the
desirable worship everyone will appreciate as being natural.
Thank you for your time.
Appendix 5 – page 7