acoustics: sounds sustainable design · pdf filelearning objectives •discuss how...

Acoustics: The Sounds of Sustainable Design

JUNE 9, 2014

LEARNING OBJECTIVES

• Discuss how acoustics impact productivity, learning and occupant comfort

• Examine the differences between STC, NRC, RT, and IIC.

• Illustrate best practices for managing acoustic concerns

• Analyze how acoustics contribute to sustainable design certifications like LEED

COURSE OUTLINE

Acoustic Impacts

The Acoustical ABCs

Design Best Practices

Sustainable Certifications

ACOUSTIC IMPACTS

OFFICE ENVIRONMENTS

CLASSROOM ENVIRONMENTS

RESIDENTIAL ENVIRONMENTS

OFFICE ENVIRONMENTS

“Acoustical conditions profoundly impact human performance in office settings…”

‐ David M. Sykes, PhD“Productivity: How Acoustics Affect Worker’s Performance In Offices and Open Areas”

OFFICE ENVIRONMENTS

Improving acoustical conditions to improve speech privacy resulted in the following gains:

Source: David M. Sykes, PhD: “Productivity: How Acoustics Affect Worker’s Performance In Offices and Open Areas”

• Focus improved by 48%

• Error‐rates decreased by 10%

• Physical symptoms of stress were decreased by 27%

“With a classroom having good acoustical characteristics, learning is easier, deeper, more sustained, and less fatiguing.”

‐ ANSI/ASA S12.60‐2010

Classroom acoustics are especially important because:

• Young children do not effectively listen and understand speech in reverberant conditions

• Many children have trouble focusing their attention in noisy environments

• Many students have low proficiency in English or are non‐native language speakers

Source: Acoustical Society of America: “Acoustical Barriers to Learning”

The Acoustical Society of America and the American National Standards Institute, Inc. have developed acoustical performance criteria, design requirements and guidelines for schools.

Noise is the No. 2 litigation issue brought before the courts by owners and residents of condominiums, apartments and co‐ops.

‐ McGraw Hill Construction MagazineDecember 2005

• Many building codes contain acoustical requirements for separating dwelling units

• Special attention to acoustics can be an important marketing feature for multifamily residences

• Exterior noises such as traffic and airport noise can decrease property values.

PRIMARY ACOUSTICAL CONCERNS

Interior Noise

Transmission

Exterior Noise

Transmission

Background Noise

Reverberationor Echo Impact Noise

K‐12 Schools ● ● ● ●Higher Ed ● ● ●Open Offices ● ●Private Offices ● ●Multifamily ● ● ●Single Family ● ●

THE ACOUSTICAL ABCs

ABSORPTION

BLOCKING

COVERING

ABSORPTION• Used to control reverberation and echo• Measured through a material’s Noise Reduction

Coefficient (NRC) or Sound Absorption Average (SAA) and the resulting Reverberation Time (RT)

ABSORPTION

REVERBERATION TIME (RT): the period of time it takes for a sound to decay by 60 dB after it has stopped.

Reverberation time is directly related to the amount of absorptive material in a space and the spatial volume of the space.

ABSORPTION

Designing for appropriate reverberation times is a primary means of enhancing speech intelligibility.

ABSORPTION

Reverberation Time

.8 – 1.3 1.4 – 2.0 2.1 – 3.0 OptimumSpeech Good Fair – Poor Unacceptable 0.8 – 1.1

Contemporary Music Fair – Good Fair Poor 1.2 – 1.4

Choral Music Poor‐ Fair Fair – Good Good – Fair 1.8 – 2.0+

ABSORPTION

No Reverberation 0.6 sec RT 0.8 sec RT

1.3 sec RT 2.0 sec RT 5.0 sec RT

Audio File Source: www.mcsquared.com

NOISE REDUCTION COEFFICIENT (NRC): a representation of the amount of sound energy that is absorbed upon striking a specific surface. An NRC of 0 indicates perfect reflection and an NRC of 1 indicates perfect absorption.

NRC is a single number value that averages absorption at four 1/3 octave frequencies: 250, 500, 1000 and 2000 Hz.

ABSORPTION

Image Source: www.egger.com

SOUND ABSORPTION AVERAGE (SAA): a representation of the amount of sound energy that is absorbed upon striking a specific surface. An SAA of 0 indicates perfect reflection and an SAA of 1 indicates perfect absorption.

SAA is a single number value that averages absorption at twelve one‐third octave bands from 200 to 2500 Hz

ABSORPTION

Perfect Reflection‐ NRC or SAA = 0

ABSORPTION

Perfect Absorption‐ NRC or SAA = 1

ABSORPTION

Partial Absorption‐ NRC or SAA around .8

ABSORPTION

Source: Architectural Acoustics, M. David Egan

Material NRC

Brick .00 ‐ .05

Carpet .15 ‐ .55

Concrete .00 ‐ .20

Cork (floor – ¾”) .10 ‐ .15

Cork (wall – 1”) .30 ‐ .70

Drapery .05 ‐ .60

Gypsum Board /Plaster .05

Glass .05 ‐ .10

Linoleum .05

Marble/Terrazzo .00

Wood .05 ‐ .15

Material NRC

Seating (occupied) .80 ‐ .85

Seating (unoccupied), metal .30

Seating (unoccupied), wood .30

Seating (unoccupied), fabric .60

Seating (unoccupied), leather .50

Acoustical Ceiling Tile .40 ‐ .80

BLOCKING

BLOCKING• Used to combat noise transfer between spaces• Measured through Sound Transmission Class

(STC) and Impact Insulation Class (IIC)

BLOCKING

Sound Transmission Class (STC):a rating of how well a building assembly attenuates (blocks) the transfer of airborne sound. A larger number means greater attenuation.

Like NRC, STC also assesses multiple frequencies of sound (125 – 4000 Hz).

Calculated as an assembly.

BLOCKING

STC can be increased by:

• Adding mass

• Adding air space

• Adding absorptive material inside an assembly

BLOCKING

STC 38 ‐ 40

STC 43 ‐ 44

STC 32 ‐ 35

STC 34 ‐ 39

BLOCKING

STC 43 ‐ 45

STC 45 ‐ 52

STC 34 ‐ 39

STC 39 ‐ 40

BLOCKING

STC 45 ‐ 59STC 46 ‐ 47

Wall Thickness Hollow Units Sand Filled Grout Filled

4” STC 44 STC 46 STC 47

6” STC 46 STC 49 STC 51

8” STC 48 STC 52 STC 55

10” STC 53 STC 55 STC 60

BLOCKING

Masonry Wall STC Values

BLOCKING

Flanking Paths: a path for sound to travel over, under, around or through an assembly.

Noise Leaks: areas of poor sealing that can allow sound to pass through an assembly.

Image Source: www.STCratings.com

F1‐ Open plenums aboveF2‐ Common ductworkF3‐ Adjacent exterior windowsF4‐ Common floor heatersF5‐ Open ventsF6‐ Louvered doorsF7‐ Under doors

L1‐ Poor seal at wall/ceiling connectionL2‐ Poor seal at wall/wall connectionL3‐ Poor seal at wall/mullion connectionL4‐ Poor seal around outlet penetrationL5‐ Poor seal at wall penetrationL6‐ Poor seal at floor penetrationL7‐ Poor seal at wall/floor connectionL8‐ Poor seal around door

Noise Leaks Flanking Paths

BLOCKING

Impact Insulation Class (IIC): a rating of how well a building assembly attenuates impact sounds. A larger number means greater attenuation.

Like NRC, IIC also assesses multiple frequencies of sound (100 – 3150 Hz).

Calculated as an assembly.

BLOCKING

IIC can be increased by:

• Adding layers of resilient materials

• Adding layers of fibrous materials

BLOCKING

Topping (on concrete slab) IIC

None, Ceramic Tile or Marble Tile 28

Vinyl Flooring 35 ‐ 40

Hardwood Flooring 30 ‐ 35

Hardwood flooring on 6mm resilient underlayment 45 ‐ 50

Concrete topping over 25mm mineral fiber board 60 ‐ 65

Carpet and Underlay (pad) 75 ‐ 85

BLOCKING

Topping (on wood floor joists) IIC

Ceramic Tile or Marble Tile 40

No Topping 45

Vinyl Flooring 47

Hardwood Flooring 47

Hardwood flooring on 6mm resilient underlayment 47

Resilient Flooring on 35 mm concrete topping 52

Carpet and Underlay (pad) 75 ‐ 85

COVERING

COVERING• Use of sound masking to “cover” other noises• Measured through the decibel level of masking

COVERING

White Noise: a random signal with constant power spectral density that contains sounds across the frequency range. White noise is often used to block sound distractions and increase focus.

COVERING

HVAC Background Noise: the sound an HVAC system uses can be used as a covering mechanism, but at higher or inconsistent levels, it can also be a distraction.

COVERING

Space Type Decibel LevelApartment 35 ‐ 45Private Home 30 ‐ 38Private Office 40 ‐ 45Open‐plan Office 45 ‐ 50Conference Room 35 ‐ 40Classrooms 35 ‐ 40

Recommended Background Noise Levels

DESIGN BEST PRACTICES

WALL COVERINGS

SOUND INSULATION/ SEALING

WHITE NOISE

CEILING MATERIALS

FLOORING

HVAC NOISE

FURNITURE

AIR SPACE

WHICH STRATEGIES CAN DECREASE

REVERBERATION TIME?

WALL COVERINGS

WHITE NOISE

CEILING MATERIALS

FLOORING

HVAC NOISE

FURNITURE

AIR SPACE

WALL COVERINGS

CEILING MATERIALS

FLOORING

FURNITURE

WHICH STRATEGIES CAN INCREASE WALL STC?

WALL COVERINGS

WHITE NOISE

CEILING MATERIALS

FLOORING

HVAC NOISE

FURNITURE

AIR SPACE

WALL COVERINGS

AIR SPACE

WHICH STRATEGIES WILL INCREASE FLOOR IIC?

WALL COVERINGS

WHITE NOISE

CEILING MATERIALS

FLOORING

HVAC NOISE

FURNITURE

AIR SPACE

CEILING MATERIALS

FLOORING

WHICH ARE COVERING STRATEGIES?

WALL COVERINGS

WHITE NOISE

CEILING MATERIALS

FLOORING

HVAC NOISE

FURNITURE

AIR SPACE

WHITE NOISE

HVAC NOISE

FURNITURE

OFFICE ENVIRONMENTS

DESIGN STRATEGIES

PRIMARY ACOUSTICAL CONCERNS

Interior Noise

Transmission

Exterior Noise

Transmission

Background Noise

Reverberationor Echo Impact Noise

K‐12 Schools ● ● ● ●Higher Ed ● ● ●Open Offices ● ●Private Offices ● ●Multifamily ● ● ●Single Family ● ●

PRIVATE OFFICE

Primary Concerns:• Interior Noise Transmission (STC)• Background Noise• Reverberation Time

PRIVATE OFFICE

Full height STC 50 Wall‐metal stud with resilient

channels

Acoustical Sealant

PRIVATE OFFICE

Low Velocity HVAC System

PRIVATE OFFICE

Absorptive Carpet

Cork Board

OPEN OFFICES

Primary Concerns:• Background Noise• Reverberation Time

OPEN OFFICES

High velocity HVAC system used as sound masking

OPEN OFFICES

Absorptive Carpet

High NRC Ceiling Tile

ELEMENTARY SCHOOL CLASSROOM

Primary Concerns:• Interior Noise Transmission (STC)• Exterior Noise Transmission (STC)• Background Noise• Reverberation Time

Full height STC 50 masonry wall between classrooms

High STC Window Assembly

STC 65 Masonry Cavity Wall

Constant volume, low velocity HVAC

system

Absorptive Carpet

MIDDLE/HIGH SCHOOL SCHOOL CLASSROOM

Full height STC 45 metal stud wall with 4 layers of gypsum board between classrooms

High STC Window Assembly

STC 65 Masonry Cavity Wall

Sound Reinforcement System

Low Velocity HVAC System

Fabric Baffles

Gypsum Board Walls

UNIVERSITY CLASSROOM

Full height STC 50 Wall‐metal stud with resilient

channels between classrooms

Medium velocity, constant volume HVAC system

Absorptive Wall Pads

High NRC Ceiling Tiles

MULTIFAMILY HOUSING

Primary Concerns:• Interior Noise Transmission (STC) • Background Noise• Impact Noise (IIC)

MULTIFAMILY HOUSING

Full height STC 50 Wall‐metal stud with resilient channels between rooms

Use of storage between rooms (increases mass and

air space)

Single room HVAC system to limit flanking paths

MULTIFAMILY HOUSING

Medium velocity, constant volume HVAC system

MULTIFAMILY HOUSING

Primary Concerns:• Interior Noise Transmission (STC) • Background Noise• Impact Noise (IIC)High IIC ceiling/floor

assembly of carpet on wood joists.

Image Source: www.blenture.com

SINGLE FAMILY HOUSING

Primary Concerns:• Exterior Noise Transmission (STC) • Background Noise

Exterior wall and vegetation to block environmental noise

Well sealed, high STC windows

Radiant Floor Heating

SUSTAINABLE CERTIFICATIONS

Many sustainable certification programs have requirements or points that relate

to acoustics.

LEED 2009

LEED for New Construction and Commercial Interiors

The base rating system does not have any acoustics related prerequisites or credits. However, there is a “pilot credit” that has background noise requirements, reverberation time requirements, STC requirements, and requirements for sound reinforcement and sound masking in certain situations.

LEED 2009

The base rating system does not have any acoustics related prerequisites or credits. However, there is a “pilot credit” that has background noise requirements, reverberation time requirements, STC requirements, and requirements for sound reinforcement and sound masking in certain situations.

Background Noise Requirements: As prescribed by ASHRAE

RT Requirements: As prescribed for each space type

STC Requirements: 45 – 60 depending on adjacent space types

Sound Reinforcement: Required in spaces for 50 or more people

Sound Masking: Must not exceed 48 dB

There is a new credit for acoustic performance that limits HVAC background noise, sets STC requirements and reverberation time requirements and requires sound reinforcement and sound masking systems in certain situations.

Background Noise Requirements: As prescribed by ASHRAE

RT Requirements: As prescribed for each space type

STC Requirements: 45 – 60 depending on adjacent space types

Sound Reinforcement: Required in spaces for 50 or more people

Sound Masking: Must not exceed 48 dB

LEED 2009

LEED for Schools

This version of the LEED Rating System has an acoustics prerequisite that has limits for HVAC background noise and reverberation time. There is also a credit that lowers the acceptable HVAC background noise levels and adds STC requirements for interior and exterior walls.

Background Noise Requirements: 45 dB max for HVAC

RT Requirements: High NRC (0.70) ceilings in small spacesReverberation time of 1.5 seconds or less

PREREQUISITE REQUIREMENTS:

LEED 2009

LEED for Schools

This version of the LEED Rating System has an acoustics prerequisite that has limits for HVAC background noise and reverberation time. There is also a credit that lowers the acceptable HVAC background noise levels and adds STC requirements for interior and exterior walls.

STC Requirements: Meet ASHRAE requirements in core learning spaces

CREDIT REQUIREMENTS:

LEED for Schools

The acoustics prerequisite in this version of the rating system is very similar to that contained in LEED 2009 for Schools, but it adds an exterior noise control requirement and lowers the allowable HVAC background noise decibel level. Similarly, the related credit also lowers the allowable HVAC background noise level.

RT Requirements: High NRC (0.70) ceilings in small spacesReverberation times meet Design Guideline

Exterior Noise Control: High noise sites must control exterior noise

PREREQUISITE REQUIREMENTS:

LEED for Schools

The acoustics prerequisite in this version of the rating system is very similar to that contained in LEED 2009 for Schools, but it adds an exterior noise control requirement and lowers the allowable HVAC background noise decibel level. Similarly, the related credit also lowers the allowable HVAC background noise level.

STC Requirements: Meet ASHRAE requirements in core learning spaces

CREDIT REQUIREMENTS:

LEED 2009 and

LEED for Homes

The base rating system does not have any acoustics related prerequisites or credits. However, there is a “pilot credit” for acoustics.

Background Noise Requirements: HVAC guidelines or 40 dB

Exterior Noise Control Requirements: Sealing and STC

STC Requirements: 55 between dwelling units

IIC Requirement: 55 for floors between dwelling units

• Requires separation of noisy occupancies and other common sense strategies

• Open offices have sound masking

• STC requirements for wall, doors and windows

• IIC of 50 for all floor/ceiling assemblies

• Reverberation time maximums by space volume

• Requires separation of noisy occupancies and other common sense strategies

• Open offices have sound masking

• STC requirements for wall, doors and windows

• IIC of 50 for all floor/ceiling assemblies

• Reverberation time maximums by space volume

• May vary by state

• Prerequisite has background noise and RT requirements

• Credit has lower background noise requirements

CONCLUSIONSUnderstand each space’s acoustic design priorities

Keep the alphabet soup straight

Identify strategies that can multi‐task

Collect some credits!

SHP LEADING DESIGN4805 Montgomery Road, Suite 400Cincinnati, OH 45212www.shp.com

QUESTIONS?

Allison McKenzieamckenzie@shp.comwww.buildingmygreenlife.com

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