Keun Young, ParkAdvanced history of building technologySpring 2011

Church Acoustics What do we need to hear?

Chapel of St. Benedict

Architect: Peter Zumthor (Swiss architect)Location: San Bennedetg, SwitzerlandDate: 1987Building Type: Chapel Structure: Timber

The padre pio pilgrimage church

Architect: Renzo Piano Building Workshop Engineers: Ove Arup EngineersLocation: San Giovanni Rotondo, ItalyDate: July 2004Building Type: Pilgrimage ChurchStructure: Composite: Masonry, Timber,Steel

Acoustics

Sound

Sound is produced by a vibrating object or surface. In order for sound to be transmitted, it requires an elastic medium. The most common medium is the air and is called “air-borne sound.”However, sound can also be easily transmitted through common building materials such as steel, concrete, wood, and gyp-bum board and is called “structure-borne sound”.

Noise is unwanted sound.

dB

A logarithmic scale based on 10 times the logarithm of a ratio of sound pressures. The decibel levels of two noise sources can not be added directly; For example, 90dB + 20dB = 90dB 60dB + 60dB = 63dB

Decibel scale: Based on human ears

0 dB: Quietest sound a human can hear 3dB: Barely perceptible 5dB: clearly noticeable 20dB: whisper 60 dB: Normal conversation 40dB: Privateoffice,quiethome 100dB: subway, loud street noise, power launmower.

Acoustics in sacred buildings

Sound distribution of a traditional church.

Acoustics in sacred buildings

Sound distribution of dome.

Angles for reflection control:

-Acute angle: reflections are trapped.

-Right angle: reflections are transmitted evenly.

-Obtuse angle: reflections gather along the wall.

Convex and concave

Convex disperse sounds.Concave concentrate sounds on a focal point - after passing the focal point, the waves then disperse.

Reflections of different frequencies on a scattering structure

Low frequencies: the surface reflects as if it were smooth.Medium frequencies: it scatters diffusely.High frequencies: act like many small reflectors.

Church AcousticsWhat do we need to hear?

The conflict between resonance and clarity

Church acoustics - especially recent designs - are often disappointing. Because acoustics is rarely considered a fundamental aspect of design, but rather something to be tacked on later, perhaps after construction.

4 items comprise the foundations for the acoustics of a church sanctuary and must be considered during the earliest stages of design: -room shaping -isolation from noise -sturdy construction -integration of sound-system design into the room

Why is it so difficult to achieve excellent acoustics in churches? In such spaces both music and speech are important, yet their acoustical requirements conflict. Church music sounds wonderful in very “live” or reverberant acoustics - the more reverberant, the better. Speech, on the other hand, can be quite difficult to understand in such reverberant acoustics - though not necessarily.

In some churches, the contemporary service with electronically amplified music has replaced the traditional organ and choir. In a traditional church, the reverberant acoustics serve to amplify the music - a function taken over by electornic systems in the contemporary service. These electronic systems do not get along very well with the natural amplification of a “live” room. They work best in “dead” rooms.

Thus, there are two approaches to the acoustics of a church: the “live” and “dead” room approach. Older catholic churches tend to be very “live” rooms; modern evangelical churches tend to be acoustically “dead”. The traditional Protestant church falls somewhere in between. Each approach has its advantages and disadvantages. The “dead”room approach is surely the more con-venient of the two. The main disadvantage to the “live”approach is difficulty with understanding speech. Many sound sys-tem designers consider “live”acoustics to be bad acoustics. The result is often too loud, too “boomy,” veryartificialsoundingspeechamplification.But the “live” acoustics are part of the worship experience. The celestial sound of the organ in the tradi-tional church fills the space; one feels as if surrounded by sound. When the congregation sings, the voices blend into one voice. Sinceh the sound comes from many different directions and kinds of sources - organ pipies, vocal cords and mouths of all shapes and sizes - the sound has a natural richness and warmth that cannot be duplicated electronically. At its best, the experience of sound in such a space is heavenly.

Church Acoustics: How does one make speech intelligible in a reverberant space?

- Strict noise control is a big part of the solution. Suppress background noise.

- Once background noise is taken care of, sound reflectionsmustbemanagedsothatsufficientsoundenergyarrivesattheearearlyenoughtosupporttratherthanobscurespeech.Thiscanbedonebycarefuldesignofsoundreflectingsurfacestoreflectsoundveryquicklytothelistener’sears.

- A modest-sized sanctuary makesitmucheasiertobalancetherequirementsofspeechandmusic.A porperly designed sanctuary seating 300 shouldbeabletoprovidesupportforsingingandsmallorgan,withnodifficultyhearingunamplifiedspeech.A2,000-seatsanctuaryisamuchmoredifficultproblem.

- Another issue, rarely addressed, is that speak clearly and distinctly from the pulpit to the congregation rather than expecting the sound system to do it all.

Church Acoustics : Room shape

Theformofaspacedeterminesthenatureofthesoundfieldwithin.A 20’ high ceiling limits the reverberation necessary for organ or choir.

A circular or conical chape will create focusing, echoes, and other entertaining acoustical effects. Barrel-shaped ceilings can produce odd whispering gallery effects and flutter echo.

A few panels on the walls will not compensate for a poorly shaped room.

Interesting, curvilinear shapes can cause problems if their acoustical effects is not planned.

Recently, it has become fashionable to orient sanctuaries so that they are wider than they are long. This fad is in the face of the experience of centuries of worhip space design. It brings peoople closer and makes the concregation feel more intimate...Nonsense. First of all, when there are not enough people to fill a sanctuary, the empty seats are inevitable in the front. Amplifi-cation makes sitting up front even less necessary.

Church Acoustics : Noise control

The single most important aspect of the acoustics of a church sanctuary.

An air-handling unit on the roof of the sanctuary or mechanical room adjacent to the sanctuary produces a haze of a noise and vibration that masks speech and dulls music.

Methods are availible for nearby noisemaskers, placing the mechanical equipment sothatitissufficientlydistantandstructurallyisolated from the sanctuary makes the essential tak of noise control much more tractable.

A church constructed in the same manner as a shopping mall will never have the rich acoustics necessary for sacred music. Gypsum-board walls absorb low frequencies, making for weak organ sound. Flimsy consturcion also allows noise from the outside to enter the church, combining with the noise from the lights and the mechanical systems. This creates a fog of noise through which nothing can be heard with clarity.

The appropriate acoustical approach depends on the congregation:

Whereby both music and speech are important for all churches, some congregations feel that speech is so important that unam-biguous speech clarity is worth sacrificing the sounhd of the organ, choir and congregation.

Furthermore,churchesthatrelyheavilyonelectornicamplificationdosobecausethecongregationprefersthatkindofsound.Forthese, the “dead” room approach is clearly the way to go.

Clients want their churches to have excellt acoustics. Yet precious few churches do. This is an opp[ortunity for architects to really distinguish themselves from the pack. (Brooks,2003)

St. Benedict Chapel

Architect: Peter ZumthorLocation: San Bennedetg, SwitzerlandStructure: Timber

A leaf motive.

The altar is situated at the focal point. This is ideal.

Due to the small sizeofthechuch,thereflectionsflowrapidly,producing a good reinforcement of the sound.

Altar

Entrance

Metal could reflect sounds. It depends on the surface treatement.

Double-wall construction (void spaces contain-ing air) , and wood ceiling and floor absorb sound. Unpleasant low frequencies are absorbed, medium and hight frequencies are scattered favourably.

St. Benedict Chapel: Sound distribution

Side: Reflected sound bounces.

Rear: Second and third order reflected sound concentrate.

Center: the direct sound is reinforced by the first order reflections.

Conclusion

The tonal quality of the space is determined by the shape of the space and its dimensions , as well as by the strong reso-nance of its materials.

Visitors recount that the resonance of the hollow floor is immediately apparent on entring the room.

In theory, the shape of the oval is problematic (acoustic focal point and a risk of echoing) as the acute angle of the point(sound concentration).

However, in combination with the shape of the shallow pitched roof and its slightly arching ridge, the choice of materials and the strongly structured interior within the small space, a room of particular acoustic intensity has been created.

The padre pio pilgrimage church

Architect: Renzo Piano Location: San Giovanni Rotondo, ItalyFunction: Catholic pilgrimage churchYear: 2004

One of the most-visited Catholic pilgrimage destinations in Italy

10 years of work.

Spiral shaped church.

6500 seatsPiazza for 30,000

A complex space where the external and internal parts merge together.

Organized accordign to a spiral movement focussed on the chancel area from which a series of stone arches of decreasing height radiate to hold the curved roof.

Finishes

Floor: Stone Walls: Rough plasterCeiling: WoodenstructurefinishedwithpaintedgypbumpanelsSeating: Thick wooden pewsWindows: Thick glazed wall

The padre pio pilgrimage church: Stone arch

22 local limestone arches crowned by the vaulted ceiling.

The design was developed to take advantages of new stonecutting manufacturing techniques.

A slightly sloped floor with the raised chancel allows good sightlines.

The architect studied acoustics carefully.

The sheer magnitude and unique architecture demanded an optimization of the acoustics. It was possible, with the assistance of absorbers and electroacoustic techniques.

The radial distribution of the pews allows the church to hold 3500 faithful relatively close to the altar, with a maximum distance of about 150ft (45m), which corresponds to an average sized chuch.

The thin gypsum ceiling panels absorb low frequency.

The crypt acts as a sounding-box; the benches are designed to provide the correct reverberation time.

PLAN

SECTION

Conclusion

Generally, a large church sounds different from a small church because the larger room is more reverberant.Despite the large dimensions the mid-frequency reverberation time is relatively low.

Strengthandclaritydecreaseregularlywithlargerfluctuationforclaritymostlyduetodirectsoundmaskingduetothearches.

Both LF and I-IACC show low average values determined by the substantial lack of side walls.However, the arches contribute in some way to increasing binaural dissimilarity.

Work Cited

Stegers, 2008, Birkhauser, A design manual Sacred Buildings p. 54-60

Brooks, 2003, McFarland & Company, Inc., Architectural acoustics

Stein, Reynolds, Grondzik, Kwork, 2006,Wiley, Mechanical and electrical equipment for buildings.

http://mjobrien.com/

greatbuildings.http://www.greatbuildings.com/buildings/San_Lorenzo_Turin.html

Video of the padre pio pilgrimage churchhttp://www.youtube.com/watch?v=-8tJHRI6T2E

padre pio pilgrimage church www.kfmtechnologies.com/pp.htmlhttp://www.architravel.com/architravel/building/1321

The Royal Church of San Lorenzo in Turin: Guarino Guarini and the Baroque architectural acousticshttp://intellagence.eu.com/acoustics2008/acoustics2008/cd1/data/articles/001344.pdf

Padre Pio Pilgrimage Churchhttp://www.architetturadipietra.it/wp/?p=2920

Structure of Padre Pio Pilgrimage Churchhttp://www.floornature.com/progetto.php?id=4446&sez=30