Here is the Original Acoustics Engineer, Earl Mullins, PE, recommendations:

A series of Reverberation Time (RT) calculations were performed, to determine the optimum amount and best placement of sound absorbing materials in the room.  RT is the time that it takes for steady-state sound to decay, and is the most commonly used measure of "liveness" in a room.  RT values for a church should be less than 2.0 seconds in the speech content frequencies, for good speech intelligibility. 

When analyzing the acoustical properties of this room, we must also look at the extremes of use - nearly empty and nearly full.  People contribute absorption too, and a room with a capacity crowd is considerably less reverberant than an empty room.

Several different options were analyzed:

"No treatment" refers to all gypsum board finishes and a concrete floor, with no supplemental acoustical treatment on the walls or ceiling.  The only absorption is provided by the padded seating and the audience.  As can be seen, the space will be unacceptably reverberant.

Each of the following additional treatment options builds on the last one -  the new treatment is added to all previous treatments to achieve the overall benefit.

    -   Carpet is not terribly efficient at sound absorption, but the large surface area helps make up the deficiency.  In this case, we assume that 80% of the Nave floor area is carpeted, without padding.

    -   Ceiling treatment means covering the flat areas and the ceiling on the longitudinal gable using with 1" thick fiber glass panels.  Acceptable materials include Armstrong Nubby or Optima, or Wall Technologies New Dimensions.  Even with this level of treatment, the RT values are still above three seconds in the most important speech frequencies.

    -   The rear wall should be covered with 1" thick fabric wrapped wall panels, as much as possible, and between 2-10 feet in elevation minimum.  When we include the effect of the audience, the RT values start to becomes reasonable, if somewhat higher than desired.

    -   Side wall treatment covers the area below about 16 feet in elevation and between columns 2.5 and 6.5.  With this extensive degree of coverage (carpet, partial ceiling, rear wall, side walls) we finally see RT values approaching the desired values, at least in the frequencies most important to speech clarity.

Based on this analysis of the Nave, I have the following recommendations:

1.      Cover the flat portions and 80% of the high peaked ceiling in the longitudinal gable with Nubby fiber glass board (or equal). 

        Nubby is a 1" thick fiberglass board with a white coated fabric facing, and looks like standard acoustical tile.  Nubby is quite absorptive and also cost effective.  Nubby is a semi-generic name for a fiber glass ceiling board;  this product is available from all of the major ceiling manufacturers, including Armstrong, Conwed, USG, Capaul, etc.   A nicer looking (but somewhat more expensive) option is Wall Technologies New Dimensions.

2.      Padded pews will also contribute to the total absorption inside the room.  Use seats with the thickest practical padding.  If the pads get deleted later in the design, their absorption will need to be replaced with wall panels or additional ceiling coverage.

3.      Consider carpeting most of the floor surface in the Nave.

The rear wall is an area of concern because most of the area is glass, which is quite reflective.  There is a strong potential for audible reflections coming back at the altar and the front seating areas.  Further, there is very little room available for adding acoustical wall panels.

4.      Cover the rear wall as much as possible with a sound absorbing panel.  Fabric wrapped walls panels should cover all non-glass areas, and extend upward to roughly 12 feet above the floor.

        The rear window walls of the Nave should not be parallel to the front wall.  They should be canted in plan view at least 1:15, with the angle set to prevent reflections back toward the altar.

        Glass portions of the rear wall should either be angled or bevelled, creating a gentle sawtooth pattern in plan view.  This type of surface will tend to scatter sound, rather than reflect it back at the altar.

        A sawtooth or bevel should also apply to the central pairs of entry doors.  Set the doors to avoid reflections back at the Sanctuary.

The side walls are typically an important space for treatment, to prevent lateral reflections across the width of the room.  This is particularly important here, since the room is wide enough so that reflections would be perceptible as echoes.  Further, the primary side wall surface is glass, which is completely reflective.

5.      The stepped walls on both sides (forming niches) should be treated with sound absorbing fiber glass wall panels.  Panels should be installed between roughly 2-12 feet in elevation, to concentrate the absorptive material where the listeners are located.

        The large interior windows (Saint Andrew's cross) in these alcoves should have the interior surface angled in a gentle sawtooth pattern.  This avoids creating a large flat reflective surface across the Nave.  A slope of roughly 1:12 or 1:15 should be adequate to prevent these lateral reflections.  It is not necessary to change the angle of the exterior window surface.

6.      The window walls at the Mother of God Chapel are fairly convoluted, which is good.  The center window section will tend to reflect sound back toward the seating on the side of the altar.  These central windows should ideally be sawtoothed too, so that the center stile is projecting out into the main space.  This will create a diffusive surface that will tend to scatter sound, rather than reflect it across the diagonal of the space.

        Admittedly, this is a minor problem, which may not actually manifest as a perceptible echo.  If it is too difficult or expensive to implement the window angle, this recommendation can be omitted.

7.      The choir area has already some acoustical features that will maximize their projection into the congregation.  In essence, the sloped ceiling creates a band shell configuration.  The ceiling should remain painted gypsum board, which is acoustically "hard" or reflective.  Do not use sound absorbing panels on the ceiling or walls surrounding the choir.

8.      The Narthex also needs sound absorption.  While it is not as acoustically critical as the Nave, it will also be used as overflow space for large services.  (Similar spaces in other local churches have little or no acoustical treatment, and tend to be remarkably reverberant).  Cover at least 60% of the ceiling with 1" thick fiber glass board, such as Nubby or New Dimensions.

9.      The Mother of God Chapel is a relatively small, but symmetrical.  Small rooms are much less critical acoustically, but the symmetry has some potential to cause minor problems.  This room would benefit from carpet, padded seats, and as much absorptive ceiling treatment (1" thick Nubby board, surface applied) as is practical. 

10.    The Founders Chapel should have an absorptive rear wall (fabric wrapped panels), and an absorptive ceiling (Nubby or equal).

11.    The Parish Hall should have a suspended acoustical tile ceiling throughout.  Since this space will probably not be carpeted, a fiber glass ceiling tile such as Nubby would provide extra absorption (compared to mineral fiber acoustical tile).

        When the operable partitions are fully opened in the Parish Hall, one end wall should have sound absorbing panels covering at least 70% of the wall surface.

12.    Typical classrooms will have suspended mineral fiber acoustical tile ceilings and carpet.  There is usually no need for additional absorptive treatments.

13.    The Music Room should have a suspended tile ceiling throughout.  Carpet is preferred, but not mandatory.  One end wall should be substantially covered with fabric wrapped wall panels.

14.    Conference B111 should have a highly sound absorbing ceiling due to the circular shape.  Use 100% coverage of Nubby, either is a suspended grid or surface applied to a hard lid.

Sound Isolation

Certain areas requires an appropriate degree of sound isolation, to both separate differing activities and to provide confidentiality and solitude.

Batt insulation is standard for any sound rated partition.  All penetrations and perimeter conditions must be caulked airtight using acoustical sealant.  Junction boxes in sound rated walls should be covered with Lowry's pads or STI Putty Pads. 

If wood studs or structural steel studs are used, then resilient channels are needed on one side of the wall only.  For lightweight metal studs, RC channels are not needed.

15.    The wall between the Reconciliation Room A112 and the choir area should be type D (shown on the attached sketch) consisting of two layers of gypsum board on each side, with batt insulation. 

16.    The wall at Reconciliation Room A110 can be type C, with two layers on one side and one layer of GWB on the other.  Batt insulation is standard for any sound rated wall.

17.    Doors to rooms having sound rated walls (type C, D, E) should be fully gasketed, including the door bottoms, for best privacy.  Use Pemko type S-88 or type 315.  Bottom gaskets must contact a hard surface for best results.  An adequate seal cannot be made against carpet.

18.    Windows in the Mother of God Chapel should be dual glazed with mismatched panes.  One option would be 1/8" glass - 5/8" airspace - 1/4" glass.  This will provide a rating of STC 33, and provide reasonable sound separation between the spaces.  [If the chapel and Nave will never be used simultaneously for different functions, then disregard this recommendation].

19.    Mother's Room A115 should use wall type C at the Nave.

20.    Typical classroom walls should be type C at adjoining classrooms.  Wall type B can be used at corridors.

21.    Conference Room B111 should use type B wall as a minimum, with a type C wall preferred.

22.    Important offices (those requiring confidential speech privacy) should use a type C wall at adjoining offices.  The corridor wall can be type B. 

23.    Standard offices can use the type B wall for separation.

24.    Counseling rooms should use the type C wall all around, and must have gasketed solid-core doors.

25.    Boiler Room B131 should have double stud type E wall all around, with two layers of GWB on each side.  It is important that vibrating equipment and non-isolated piping not be attached to the walls common with classrooms.

        If possible, consider swapping classroom B128 with the current position of Boiler B131.  This would place the boiler room next to the kitchen and storage, where equipment noise will be less of an issue.

26.    The kitchen walls should be type D, to provide adequate separation from the adjoining classrooms.

27.    The wall between Vesting Sacristy B135 and adjoining music space should be type D as a minimum, or type E if simultaneous uses are expected.

Operable partitions are a major issue for sound separation.  Many operable partitions do not perform all that well when installed, usually becasue of inferior surrounding conditions.  It does little good to choose an expensive sound rated operable partition, then have an acoustically weak open ceiling plenum spanning across the top of the wall.  The surrounding conditions must be at least acoustically equal to the partition in order to achieve adequate separation.

28.    Since most of the divided space will be used as classrooms, the operable partitions should be rated at STC 48 minimum, which will normally yield about NIC 40 when field tested.  Anything less will allow conversation to be understood in the next room, across the partition. 

            -.. An open ceiling plenum above these partitions is not permissible.  There must be a plenum barrier, consisting of at least one layer gypsum board on each side of the support beam/ header assembly, but not touching the beam. 

            -.. The operable partition bottom seals must contact a hard surface;  gaskets cannot make an adequate seal against carpet to meet NIC 40 in a field test.

            -.. Avoid ventilation openings over the partitions and take return air over the corridor walls, rather than across the partition headers.  If unavoidable, use a silencer (IAC 3ML or equal) or an internally lined acoustical "boot" (12" of duct, rectangular elbow, four feet of duct, rectangular elbow, 12" of duct).  Any single boot should be less than roughly two square feet in cross sectional area. 

Audio Systems

It is common to use two large speakers on the front wall, or a centrally located speaker cluster, to provide audio coverage for the whole room.  This is generally a poor configuration for amplified speech, especially in an acoustically "live" space.  When turned up loud enough to reach the back of the room, the sound system excites strong reflections from the room's surfaces.  The listener then hears a jumble of direct and reflected signals, all at similar loudness but arriving at slightly different times.  This destroys speech intelligibility.

It is often better to have numerous loudspeakers, each generating lower sound levels.  Then place the loudspeakers reasonably close to the listeners.  This maximizes the ratio of direct and reflected energy - direct signals are much louder than reflections from walls and other surfaces.  The idea is to get evenly diffused coverage, not unlike lighting.

However, the shape and dimensions of the Nave may preclude a distributed system.  The very high peaked ceilings and wide spaces may require a cluster arrangement with aimed elements.  A central cluster CAN work, if it is carefully designed and installed.  To the degree possible, it would be prudent to use supplemental distributed speakers around the edges of the room where the dimensions permit.

There are a few key parameters that the audio designer should consider:

29.    There should be no speaker coverage over the altar area, and possibly the first 2-4 rows of seating, to help reduce feedback.  There really should be no need for speakers forward of column line 3, except in the front corners of the space.

30.    Speakers over the choir area (if used) should be tapped down to a lower volume setting than the rest of the room, to avoid feedback through hanging choir microphones.

31.    The choir area should use no more than three hanging mics.  Mic placement should generally be just at or behind the first row of singers.  Too many mics picking up the same source will tend to create audio clarity problems (known as "comb filtering").

        Each mic should be a slightly different distance from the nearest wall(s).  Try to avoid symmetry in mic placement.  This will avoid having reflections from these surfaces arriving at different mics at the same time.

                 ................         *                        *                        *                        *

As the design progresses further I will look at HVAC duct locations, equipment noise and vibration, and other issues related to the mechanical and electrical equipment.

Call if there are any questions. 

Sincerely,

Earl Mullins, PE

Additional information provided by Mr. Mullins:

“In general, anything that you do right now will make a noticeable difference, because you are starting from virtually no absorption.  Anywhere you can add few square feet of absorption will help.  It is not critical whether it is wall or ceiling panels, just that it is in the room somewhere.  In order of priority, I would:

1.  Do the rear and side walls.  Although the amount of coverage is limited because of the door and glass areas, this is the easiest area to tackle, since it can be done internally with church membership help.  Go up as high as is practical, ideally to the top of the wall with the arched windows (roughly 15 feet above the floor level).   Start at the center rear and work outward until you get to the high bays with the large side windows.  You should also consider doing the side walls forward of the high window bays too, such as over the choir.

2.  Add padding to the pews.  Easy to do and should not be terribly expensive.

3.  Add additional speakers to the sound system.  The distributed layout achieved by placing small speakers on columns down near the listeners will help with speech intelligibility.  Turn down the main overhead speakers as much as possible.

4. Cover most of the ceiling surface and upper wall areas.  While this gets you the most treated area, and therefore the most potential improvement, it needs to be hired out to a contractor who can work up high.  Expect it to cost $4 per square foot, or even a bit more.  Use Armstrong Optima, Regular, or Painted Nubby fiberglass
5. They may suggest something other than Armstrong Nubby or Optima.  You are looking for 1" thick fiberglass boards with values of NRC 0.85 or higher.  Resist the temptation to go with 3/4" thick board.  It will be cheaper, but it will also be less effective.”

ACOUSTICS AND AUDIO NARRATIVE

(based on design meetings with church committees and the project architeGTS)

The acoustical properties of large rooms such as the Nave and Narthex are important to the comfortable use of the space, the quality of music, and the clarity of speech.

The existing space is quite "live", with very little natural absorption.  There are perceptible echoes and reflections throughout the room.

Catholic services tend toward the heavy use of spoken word.  The acoustical design approach is to make the space tend toward slightly "dead" or absorptive.  This will preserve the clarity of speech, and music can be sweetened by adding back reverberation electronically through the audio system.  Music is enhanced by very "live" spaces (for fullness and blending) but speech intelligibility suffers.  The acoustical properties of any room is a compromise between the two uses.

The shape and orientation of the major surfaces can significantly reduce the amount of sound absorbing materials that are needed.  Large parallel reflecting surfaces create the main problem, promoting reflections of sound (echoes) across the main dimensions of the room.  For example, slight changes in the slope of the rear wall (in either plan view or elevation view) can prevent reflections back to the altar.  Aiming the reflection is one way;  adding absorption to reduce the energy remaining in the reflection in another method.

Discussions with the music committee yielded some broad statements of purpose and priority:

    -   Music serves to encourage the congregation to participate in the service.  Music performance is not intended to be a feature - this is not a concert.

    -   In terms of importance, clarity of speech is 70% and high quality music listening environment is 30%.

    -   As musicians, they strongly favor acoustic support and natural audibility between themselves and for the congregation, rather than an elaborate audio system with multiple stage monitors.

The music during services and events will vary widely, from a minimal 4-5 piece ensemble up to a 50 person choir with instrumental backup.  There will be an electronic organ.  If funding permits, the music department would strongly prefer an acoustic grand piano.  The instruments used can include 2 guitars, bass guitar, 2-4 woodwinds, 2-4 brass, 2 violins, and a percussionist -  or nearly any combination.  Some instruments need amplifiers, and others need to a microphone.

The existing audio system is minimal, consisting of one hanging mic over the choir area, a mic for the priest, a podium mic for the cantor.  There is a cluster of speakers on the rear wall, and an ADA assisted hearing system.  Equipment is built around a 16 channel mixer in the equipment rack.  Fewer than eight channels are currently used, so this equipment should be adequate for the new space.

The new audio system should have a distributed loudspeaker layout, with speakers located appropriately around the rear 1/2 or 2/3 of the room.  (A central cluster system requires very careful design to work with any degree of success). 

There should be 3-4 hanging mics over the choir area.  Presenters will use individual mics, with the priest probably using a wireless lavaliere (lapel) mic, and the cantor using either a podium mounted gooseneck mic or a tabletop PZM mic.