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109063Session

Architectural Acoustics

Saturday, October 24

3:30pm-5:00pm

Jack B. Evans and Chad N. Himmel

A rc hitec tural A c ous tic s and the A RE 9/16/09 1:13 PM

P OW E R: Acoustic Energy in a Source, or the rate of radiation: dB in watts P RE S S URE : Change in pressure due to sound energy relative to static pressure (without the sound wave): dB in N/m2 or dB in microbars or dB in µPascals S OUND P RE S S URE LE V E L: measure of the magnitude of sound pressure,

• 20 x log10 (Sound Pressure / Reference Pressure): dB in N/m2 or microbars or µPa DE C I B E L (dB ): metric (unitless) for describing the magnitude of sound

• Threshold of Hearing 0-10 dB, Speech 60-70 dB, Pain Threshold 120-140 dB ARCHITECTURAL ACOUSTICS:

• Room Acoustics: reverberation and reflections • Privacy / Sound Isolation: containment of sound, freedom from intrusive noise • Audio Systems: Speech Reinforcement, Sound Masking, A/V audio • Structural Vibration: feelable (floor) vibration, radiated airborne sound due to

structure borne surface vibration BUILDING SYSTEMS NOISE & VIBRATION CONTROL:

• Bldg. Systems Noise: central plant, HVAC, electrical, elevator, etc. • Bldg. Systems Vibration Isolation: equipment, piping, conduit, duct & ancillary

ENVIRONMENTAL NOISE: • Noise Crossing Property Boundaries: Sound source emissions on building site or

intrusive sound sources entering building site • Outside to Inside Sound Transmission Loss: sound intrusion through building shell

OCCUPATIONAL / WORKPLACE NOISE: • Noise related to hearing conservation, health & stress

ACOUSTICAL & NOISE CRITERIA • Room Acoustics: Reverberation Decay Time (RT60) time for 60 dB decrease • Privacy / Sound Isolation: STC (lab), ASTC or NIC (field msmnt), CAC (ceiling) • Outdoor-Indoor Transmission Class (OITC) • Continuous Bldg. System Background : Room Criteria (RC), Noise Criteria (NC) • Structural Vibration: Generic Floor Vibration Criteria (VC)

ENVIRONMENTAL NOISE CRITERIA • Day-Night Level (LD N): annualized time-weighted average with night penalty • Equivalent Level (LEQ): integrated average over measurement time; min., hour, day • Sound Pressure Level (Lp): simple level for transient or continuous sound

OCCUPATIONAL NOISE CRITERIA • Exposure: time-weighted average dBA; (half time for each 5 dBA increase) • 90 dBA TWA over 8 hours, based on monitoring trigger at 85 dBA TWA

Architectural Acoustics and the ARE 9/16/09 1:13 PM

ACOUSTICAL MATERIALS A b sor b e r : converts sound energy passing through into heat or other energy form

• Reduces reflected energy / Does not stop transmission • Fiberglass, Mineral Fiber, Carpet, Perforated Solids, Porous, Fibrous Materials • Noi se Re du c t i o n C oe ffi c i e n t (NRC ): average of 4 absorption coefficients

B a r r i e r : solid material that reflects sound energy / stops transmission • Brick, CMU, Wood, Metal, Glass, Plaster, Gypsum Board, Non-Porous Materials • S ou n d Tr a n sm i ssi on C l a ss (S TC ): airborne sound transmission loss • C e i l i n g A t t e n u a t i on C l a ss (C A C ): airborne sound transmission loss in ceiling • I m pa c t I n su l a t i on C l a ss ( I I C ): structure borne impact loss floor-ceiling assy.

Di ffu se r : articulated surface or shape causing dispersion of reflected sound • spreads out energy density, such as column, splay, 3-D or Sloped/Skewed Surface

Foc u se r : Concave surface shape that concentrates reflections Da m pe r : material that dissipates vibration energy by inhibiting free vibration to reduce the amplitude of movement or shorten time of free vibration. Also removal of echoes and reverberation by sound absorbing materials within an enclosure/room.

• Viscous Liquid, Mastic, Constrained Layers, Mass (added to surface) I sol a t or : Resilient coupler to reduce transmission of sound or vibration by materials

• Resilient Wall Mountings, springs, elastomers-in-shear, flex pipe/conduit SOUND TRANSMISSION PATHS A i r b or n e S o u n d: sound propagation through air or other gas Li qu i d b or n e sou n d/vi b r a t i o n : sound or vibration propagation through liquid S t r u c t u r e b or n e S ou n d: “casual” term for airborne sound radiated from solid surface due to structure borne vibration propagation from another location S t r u c t u r e b or n e V i b r a t i o n : vibration propagation or transmission through solid Gr ou n d b o r n e vi b r a t i o n : vibration propagation through soil (seismic)

Room Acoustics 9/16/09 1:13 PM

RE V E RB E RA TI ON: Optimum reverberation varies with room function, room volume, and surface finishes

• Music is dominant program > 1.5 sec • Music w/ No speech/ singing > 1.75 sec • Speech intelligibility is needed < 1.5 sec • Classroom (re: ANSI S12-60) < 0.6 sec • Recorded Speech/Audio, cinema < 1.0 sec

T=0.05 x (V/A) English, T=0.16 x (V/A) Metric T=seconds, V= volume, ft3 , m3, A=absorption, ft2 , m2 (A=sum of surface areas times absorption coefficients)

Also note occupants (people) and furnishings add absorption

Noi se B u i l d-u p i n Re ve r b e r a n t S pa c e : Change in reverberant noise reduction with change in absorption: NR = 10 log x (A1/A2), NR = noise reduction (dB), A1=initial absorption, A2=new absorption Note: reverberant noise build-up is normally 1dB – 10 dB in small to medium size room, therefore 0% absorption(hard) has about 10 dB and 100% absorption (soft ) has about 1 dB RE FLE C TI ONS : Angle of Reflection = Angle of Incidence (use to direct sound) Flutter Echo: Between Parallel Surfaces (avoid) Reflection to Origin: 90° Corner (avoid) Diffusion: reflection spreads out from articulated surface. Focus: reflection(s) concentrate Notes:

• Slope ceiling clouds to “aim” sound toward seats for “reinforcement”

• Use wall reflections to fill in dead spots in seating

• Do not permit rear wall “back-slap” to stage – use absorption or diffusion

• Avoid flutter echo, focus and reflection to origin

• Avoid parallel ceiling and floor or walls, doors

Privacy / Sound Insulation 9/16/09 1:13 PM

Partition Performance Estimator*: Note: Excluding Door or Window insertion S TC -3 9 : 3-5/8” Stud @ 24”o.c., 1 Layer ½” GWB each side S TC C h a n g e A dd or Modi fy -1 t o -9 Delete Acoustical Sealant at edges & penetrations -3 t o -5 Change m e t a l studs to w ood studs -1 Change stud spacing from 24” to 16” o.c. 0 C h a n g e ½” GW B t o 5 /8 ” GW B + 1 Wood studs / Add resilient GWB mounting channels + 1 t o + 2 Add Resilient Channels to metal studs + 3 t o + 5 Add Sound Attenuation Blanket (SAB or batt) + 2 Add 1 layer of GWB (to basic partition) + 4 Add 2 layers of GWB (to basic partition) + 3 Change 3-5/8” studs to 6” studs + 5 Stagger studs or Double (unattached) studs * Based on Architectural Acoustics, 1999, Cavanaugh & Wilkes, John Wiley, Fig 3.13, pg 123

Generic Partition Performance Table by JEAcoustics:

D oors:

STC 17-20: No Acoustical seals

STC 29-22: Hollow Wood with seals

STC 24-27: Hollow Metal with seals

STC 26-29: Solid or Filled with seals

STC 32-52: Sound Rated Assembly

W ind ow s:

STC 31, OITC 29: 1/4” Plate Glass

STC 36, OITC 33: 1/2” Plate Glass

STC 35, OITC 35: 1/4” Laminated Glass

STC 35, OITC 28: 1” Insulated Glass

• ¼” Gl, ½” Air, ¼” Gl

STC 39, OITC 31: 1” Insulated Laminated

• ¼” Lam, ½” Air, ¼” Gl

STC 42, OITC 33: 1” Insulated 2X Lam

• ¼” Lam, ½” Air, ¼” Lam

See Ceiling Manufacturers’ Ceiling Attenuation Class (CAC) rating

Background Noise Control 9/16/09 1:13 PM

ALLOWABLE CONTINUOUS BACKGROND NOISE: building systems, excluding occupant generated noise

R oom Criteria (RC) is preferred by ASHRAE.

Others: N oise Criteria (NC), B alanc ed N oise

Criteria (NCB) or N oise R ating (NR) in Europe

Establish at beginning of project for MEP engr.

SPECTRAL CONTRIBUTIONS:

16-63 Hz octaves: fan instability, air turbulence

63-500 Hz octaves: fans, pumps , compressors

125-2000 Hz: ducts, air terminals, VAV units

250-1000 Hz: chillers, recip., centrifugal, screw

1000-4000 Hz, duct, diffuser & register noise

R ec om m end ed D esign Goals: Various Spaces

R esid ential Living Spaces RC 30-40, Sleeping RC 25-30 Note that Room and Noise Criteria are

H otel Guest Rooms RC 25-30, Corridors RC 35-40 for unoccupied space background noise.

Hotel Meeting, Banquet Room RC 25-30, Exhibition RC 30-35 Occupant noise addition is anticipated

H ospital, Clinic Patient Room RC 25-35, Corridors RC 35-40 Transient intrusive noise is anticipated

Physician Office, Exam Rooms, Conference/Consult RC 30-35

O f f ic e Conference, Board Room, A/V Conf & Training RC 25-30 RC “A” and “B” regions denote low

Executive and Private Office RC 25-35, Open Office RC 35-40 frequency noise that acoustically

E d uc ational Facility: Classroom RC 25-30, Library RC 35-40 induces vibration in light-weight

Perf orm ing Arts/Assembly: Drama, Music RC-20-25 structures, such as partitions, ceilings,

L ec ture Hall, A/V Presentation, Cinema RC 25-30 windows and vibration-sensitive lab

L aboratory; Teaching RC 30-40, Research RC 35-45 equipment and medical imaging

A rc hitec tural S pac e Planning: Avoid locating spaces labeled less than RC-35 immediately adjacent

to Central Plant, Mechanical, Electrical & Elevator Equipment Rooms or Primary duct and pipe riser shafts.

Also avoid quiet room locations immediately above or below building systems spaces. Do not permit MER or

EER doors to open into occupied spaces. Do not rigidly attach partition framing to MER, EER or Shaft walls.

Do not permit ceiling, light or other hangers to touch or connect with HVAC or other building services.

H V A C E quipm ent & S ystem L ayout: Do not permit large ducts to be routed above or through rooms

labeled RC-35 or lower – locate over corridors and utility spaces. Do not locate air terminals above ceilings

of rooms labeled less than RC-35. Do not penetrate demising partitions of RC 30 or lower rooms with

supply or return branch ducts, except through corridor demising partitions, i.e. do not penetrate partitions

between quiet or sensitive spaces, but place penetrations between quiet room and corridor.

Require acoustically lined transfer boots at sensitive room demising partition penetrations.

Environmental Noise in Architectural Design 9/16/09 1:13 PM

ENVIRONMENTAL NOISE CRITERIA

• External noise entering property / intruding into building, such as aircraft, trucks, trains

• Noise sources on property crossing property boundaries or intruding into building, such as

outdoor equipment like cooling towers, air-cooled chillers, roof-mounted AHUs, exhausts

• Municipal Building Codes and Noise Ordinances

• HUD criteria for residential, church, hospital, or sensitive receivers

• Environmental noise intrusion criteria for LEED, ANSI S12-60 classrooom acoustical std.

o Free National Classroom Acoustics Standard download: http://asastore.aip.org/

• Medical/Healthcare: Facilities Guidelines Institute( FGI), Green Guide for Healthcare (GGHC)

Building Site Selection, Facility Orientation, Siting, Outdoor Equipment Location on Site

• Determine allowable noise level at property boundary, based on ordinance, code or occupancy

o Select equipment or design noise mitigation to meet allowable at property boundary

• Determine existing or allowable noise level at building envelope

o Select Window glazing, wall, roof, penetration materials to attenuate noise intrusion

o Consider composite transmission loss for walls with multiple materials,

o Glass is often weakest element of building envelope – select for best attenuation in

frequencies of greatest noise.

For example, roadway noise is louder at +/- 250 Hz (exhausts) and +/- 2000

Hz (tire noise on pavement). Normal plate glass (single pane or insulating has

acoustical weaknesses near those frequencies. Laminated glass has better

noise reduction at engine exhaust and tire noise frequencies.

Architectural Acoustics and the ARE 9/25/09 5:23 PM

ADDITIONAL RESOURCES

www.JEAcoustics.com - “Publications” link: case study papers previously presented at technical mtgs.

“Architectural Acoustics – Principals and Practice,” W.J. Cavanaugh & J.A. Wilkes, Eds, John Wiley & Sons,

New York, 1999 (ARE bases many questions on this well-known text)

“ARE Building Systems – ARE Sample Problems and Practice Exam,” 3rd Ed., H.W. Leppo & D.K. Ballast,

Professional Publications, Inc., Belmont, CA, 2008

Kinsler, L., Frey, A., Coppens, A., & Sanders, J., Fundamentals of Acoustics, Wiley, New York, 1999.

Probably the most widely used book to introduce engineering graduate students or advanced

undergraduates to acoustics.

Irvine, L., & Richards, R., Acoustics and Noise Control Handbook for Architects and Builders, Krieger

Publishing Co., Malabar, FL, 1998. About $45. By two acoustical consultants, concisely presents much

useful information, including some discussion of community noise and industrial noise control.

Harris, C., Noise Control In Buildings - A Guide for Architects and Engineers, McGraw- Hill, Inc. 1994,

republished by Institute of Noise Control Engineering, Poughkeepsie, NY, 199X. Edited by a pioneer in

architectural acoustics, includes discussions of building materials, structures, and mechanical systems

noise control.

Selection of an Acoustical Consultant National Council of Acoustical Consultants, -www.NCAC.com

“A Practical Guide to Noise and Vibration Control for HVAC Systems”, M.E. Schafer, American Society of

Heating, refrigerating and Air-Conditioning Engineers Inc, Atlanta, GA, 1991

“Green Guide for Healthcare” (PDF) www.GGHC.org

ANSI/ASA S12.60-2002 (R2009) American National Standard Acoustical Performance Criteria, Design

Requirements, and Guidelines for Schools, sponsored (no-cost) download: http://asastore.aip.org/

LEED for Schools and LEED for Healthcare

“Guidelines for Design and Construction of Health Care Facilities” The Facility Guidelines Institute (FGI),

The American Institute of Architects Academy of Architecture for Health (AIA) and US Dept HHS, AIA,

Washington, DC, 2006 (new edition in due Jan 2010)

Warnock, A.C.C. 2007. “Sound Insulation – Airborne and Impact,” Chap. 105 in Handbook of Noise and

Vibration Control, edited by Malcom J. Crocker (Wiley, Hoboken, NJ).

ASHRAE. 2007. “Sound and Vibration Control,” ASHRAE Handbook of HVAC Applications. Atlanta, GA:

American Society of Heating Refrigerating and Air-Conditioning Engineers, Inc., Chap. 47, pp. 47.31-47.34.

“Acoustic Problems and Solutions for Rehearsal and Practice Spaces” www.wengercorp.com/.../Solving%20A c o u s t ic %20P r o b le m s %20SBO%204- 02.pdf

E n v ir o n m e n t a l N o is e T o p ic s -Handbook of Acoustical Measurements and Noise Control, 3rd. ed., C.M.

Harris (ed.), McGraw-Hill, Inc., New York, NY, 1991.