classroom acoustics slides - 2005 - fefpa · classroom acoustics slides – 2005 [g – abp –...

Classroom Acoustics Slides – 2005[G – ABP – Sales – Training – CES Presentations – Classroom Acoustics – 2005]

Classroom Acoustics

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that might be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

– 2 –

Review how acoustical design and sound quality impact the learning environment.

Explain ANSI Standard S12.60-2002 for classroom acoustics.

Identify sound reverberation and background noise reduction techniques for classrooms.

Discuss how to create a better learning environment through improved classroom design.

Classroom Acoustics Seminar

– 3 –

28% of our nation’s schools list noise as the #1 problem.

Noise causes students to miss one-third of spoken communication in class.

Noise interferes with speech intelligibility.

The effort to counter noise creates vocal fatigue in teachers.

Is Noise A Problem?

Source: Coalition For Classroom Acoustics

– 4 –

Noise affects children:

Visual or hearing impairments.Attention Deficit Disorder [ADD].English as a Second Language [ESL].Learning disorders. Middle-ear infections.Younger children learning the language.

Is Noise A Problem?

– 5 –

Due to middle-ear infections, school-aged children commonly experience a 25 decibel loss. Place your hand over your ear to experience this level of hearing loss.

The Effect Of A Hearing Loss

– 6 –

Benefit: Reduced Teacher Absenteeism

There were 2.9 million public school teachers in the U.S. in 2000.

Teachers lose an average of two days per year for vocal fatigue.

Cost for substitute teachers was about $220 per day.

The national cost for teacher vocal fatigue is estimated at $638 million. A large fraction of that cost could be saved each year if schools were quieter.

Vocal Strain A Costly Concern

Source: Acoustical Society of America

– 7 –

Standards can make possible:

An improved learning environment for all students.

Improved speech intelligibility for all students and teachers.

A better teaching environment for teachers.

Uniformity in classroom design for architects and designers.

How Will Acoustical Standards Help?

– 8 –

[Americans with Disabilities Act, Public Law 101-336,Title III, Section 36.303. Auxiliary Aids and Services]

The ADA, along with the Access Board, is making efforts to apply specific requirements on classroom acoustics.

ADA requires that “… communications with persons with disabilities be as effective as communications with others.”

The ADA’s Involvement In Speech Intelligibility

– 9 –

1997 Parents petitioned Access Board to have classroom standard developed.

1998 Draft of standard submitted to Access Board for review.

1998 Access Board issued Request For Information [RFI] on the subject.

2000 Various groups developed standard [March-June].

2001 Board received proposed standard [January].

2002 Standard completed and approved as ANSI/ASA S12.60-2002, Acoustical Performance Criteria, Design Requirements and Guidelines for Schools.

2003 ANSI Standard for Classroom Acoustics adopted in various districts throughout the United States.

Standard Development Process Timeline

– 10 –

Currently adopted:New York City Department of School Construction.New Jersey School Construction Authority.Minneapolis Public Schools.New Hampshire Department of Education.Ohio’s School Facility Commission.

States with pre-existing comparable requirements:Washington State Education Department.NY State Department of Education.

Other states:Minnesota Department of Education – proposing own.Connecticut considering adoption.Minnesota considering adoption.California – high-performing school recommendation [CHPS].

ANSI Standard Adoption – An Update

– 11 –

Acousticians

Advocates for People with Disabilities

Architects

ASTM Standards Group

Audiologists

Contractors

Government Agencies

Manufacturers

Noise Engineers

Speech Language Pathologists

Specification Writers

Teachers

Who Helped Develop The Standards?

– 12 –

AAA

AFT

AG BELL

AIA

ANSI

ASA

ASHA

ASHRAE

ASTM

ATBCB

CEFPI

CISCA

CRI

CSI

Department of Education

EAA

GA

INCE

Manufacturers of Construction Materials

NAIMA

SHHH

Organizations That Helped Develop The Standards

– 13 –

What’s the ANSI Standard S12.60-2002 all about?

Featuring:Dr. Kenneth Roy, PhD.Donna Ellis, architect, formerly with the Washington DC Public School District

ANSI Standard Video

– 14 –

1. For reverberation time:Rooms less than 10,000 cubic feet: 0.6 seconds

Rooms 10,000- 20,000 cubic feet: 0.7 seconds

New Standard Requirements

Studies show:Some classrooms today have reverberation times as high as 2.8 seconds.

– 15 –

Black arrows are direct sound. [Direct sound is good for intelligibility.]

Red arrows are reflected sound.[Reflected sound might compromise intelligibility.]

Sound In Rooms

– 16 –

When you reduce reflected sound, you lower the reverberation time. Treat the room with high NRC acoustical walls and high NRC ceilings.

Reducing Reflected Sound

– 17 –

Cost Benefit Ratio: Upgraded Ceiling Costs

Installed Cost Guide: 1000 SF Classroom [20' x 50']

$50$500$1750 – $2000NRC 0.70

24" x 48" x ¾"sag resistancesuperior acoustics

$30$300$1600 – $1800NRC 0.55

24" x 48" x ⅝"sag resistancehigher durability

$5$50$1300 – $1550NRC 0.55

24" x 48" x ⅝"cleaner visualsag resistance

$1250 – $1500NRC 0.55

24" x 48" x ⅝"no sag resistance

Annual Cost*

Difference/Classroom

Installed Cost

Ceiling Description

*Products have a 10-year life/panel warranty.

– 18 –

2. For background noise level:Core learning spaces equal to or less than 20,000 cubic feet, reduce the background noise level to amaximum 35 dBA.

Studies show:Some classrooms today have background noise levels as high as 66 dBA.

New Standard Requirements

– 19 –

Background noise is the effect of all sound sources, from both outside and inside the classroom, but excluding students and teacher.

High levels of background noise can mask speech sounds, thus reducing speech intelligibility.

Background noise is measured in dBA.

Background Noise

– 20 –

Sources Of Background Noise

– 21 –

Reduce Noise Traveling Through The Plenum

– 22 –

Reduce Noise Traveling Through The Walls

– 23 –

Minimize HVAC Noise Through DesignPlace no mechanical equipment in the classroom.Variable air volume boxes must be located away from the classroom.HVAC units should be completely isolated from the classroom.Duct attenuators should be placed upstream in the duct work.

– 24 –

Second Grade Classroom

All hard surfaces.High plaster ceiling [14'6"].Located outside the cafeteria.Large windows facing the playground.

Children had difficulty understanding the teacher and each other.

Real-World Case Study #1

– 25 –

Measure the loudness of classroom while occupied [reading class].

Measure reverberation time in empty classroom after school.

Install 0.65 NRC glue-up ceiling board during holiday break.

Repeat above measurements after installation.

Method Of Evaluation


– 26 –

Classroom Layout

27'

23'

Speaker

TeacherDesk

ComputerStation

Student Desks

Microphone

ClosetCeiling Height 14'6"

Room Volume ~ 9000 cubic feet

Door

Closets

and

Sink

windows adjacent to playground along this wall


– 27 –

Maximum Sound Levels Results

Before

After

Classroom SPL Before and After TreatmentLevels Exceeded Only 5% of Time During Reading Class

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

Frequency, Hz

Sound P

ress

ure

Lev

el,

dB

Before TreatmentAfter Treatment


– 28 –

Background Noise Levels ResultsClassroom SPL After Treatment

Minimum Levels and Levels Exceeded 95% of Time During Reading Class

0

10

20

30

40

50

60

100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

Frequency, Hz

Sound P

ress

ure

Lev

el,

dB

Exceeded 95% of TimeMinimum

35 dB 35

Before

After


– 29 –

Reverberation TimesReverberation Times Before and After Treatment

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000

Frequency, Hz

Rev

erber

atio

n T

ime,

sec

/60 d

B

Before TreatmentAfter Treatment

Open markers indicate data points which don't meet ASTM C423-99a

0.6 sec

Before

After


– 30 –

Classroom Acoustics DemonstrationLamberton School, Philadelphia PA

Acoustic evaluations and ceiling installation performed January 15-24, 2004.

Built in 1949.K-12 grades.Quiet residential area.Masonry construction.Ceilings are spray-applied fiberglass insulation on plaster.Floors are vinyl tile.

The Architecture:


– 31 –

Architecture: before change

Ceiling: Spray-up fiberglass insulationapproximately ½" thick on plaster.

Walls: CMU [concrete block] and DS[double strength] glass.

Floor: Solid vinyl tile.

Room Dimensions: 24' x 44' x 11‘.

Acoustical Design Criteria For Classrooms

ANSI S12.60 reverberation time,maximum acceptable

0.6 seconds [at 500, 1000, 2000 Hz]

Lamberton Classroom Reverberation Time

Measured performance before change

1.1 seconds [average 500 to 2000 Hz]

Classroom Before Change

– 32 –

Architecture: before change

Ceiling: Spray-up fiberglass insulationapproximately ½" thick on plaster.

Walls: CMU and DS glass.Floor: Solid vinyl tile.

Max. 0.6 seconds

Reverberation Before Change

The classroom fails to meet reverberation time per the ANSI standard at all three frequencies [highlighted]. Reverberation isn’t uniform, and speech sounds “boomy.”

The classroom fails to meet reverberation time per the ANSI standard at all three frequencies [highlighted]. Reverberation isn’t uniform, and speech sounds “boomy.”

The highlighted frequencies represent ANSI S12.60 [at 500, 1000, 2000 Hz].

Lamberton School Classroom 101, before Ceiling change

0

0.5

1

1.5

2

2.5

Frequency, 1/3 OB

Rev

erbe

ratio

n Ti

me,

sec

onds

Rev Time, sec 2.4 1.9 1.9 1.7 1.68 1.47 1.42 1.3 1.25 1.17 1.09 0.98 0.93 0.85 0.77 0.68 0.62 0.56 0.51 0.45 0.39

100 125 160 200 250 315 400 500 630 800 1k 1.25k

1.6k 2k 2.5k 3.15k

4k 5k 6.3k 8k 10k

– 33 –

Architecture: after change

Ceiling: Suspended ceiling, high NRC/highCAC, ¾" mineral fiber panels

Walls: CMU and DS glass.


Room Dimensions: 24' x 44' x 10‘.

Acoustical Design Criteria For Classrooms

ANSI S12.60 reverberation time,maximum acceptable

0.6 seconds [at 500, 1000, 2000 Hz]

Lamberton Classroom Reverberation Time

Measured performance after change

0.56 seconds [average 500-2000Hz]

Classroom With New Ceiling

– 34 –

Architecture: after change

Ceiling: Suspended ceiling, high NRC/highCAC ¾" mineral fiber panels.

Walls: CMU and DS glass.


The classroom now meets reverberation time per the ANSI standard at all threefrequencies [highlighted]. Reverberation is uniform, and speech sounds “natural.”

The classroom now meets reverberation time per the ANSI standard at all threefrequencies [highlighted]. Reverberation is uniform, and speech sounds “natural.”

The highlighted frequencies represent ANSI S12.60 [at 500, 1000, 2000 Hz].

Lamberton School Classroom 101, after Ceiling change

0

0.5

1

1.5

2

2.5

Frequency, 1/3 OB

Rev

erbe

ratio

n Ti

me,

sec

onds

Rev Time, sec 0.925 1.02 0.76 0.86 0.78 0.65 0.62 0.6 0.62 0.62 0.56 0.54 0.55 0.52 0.53 0.46 0.47 0.43 0.39 0.36 0.33

100 125 160 200 250 315 400 500 630 800 1k 1.25k 1.6k 2k 2.5k 3.15k 4k 5k 6.3k 8k 10k

Reverberation After New Ceiling

Max. 0.6 seconds

– 35 –

CeilingSuspended ceiling. High NRC 0.70/high CAC 40.¾" mineral fiber panels.

Ref. ANSI S12.60, 0.6 seconds max.500 Hz, 0.60 seconds1000 Hz, 0.56 seconds2000 Hz, 0.52 seconds

Before After

CeilingSpray-up fiberglass insulation.Approximately ½" thick.Approximate NRC 0.25.

Ref. ANSI S12.60, 0.6 seconds max.500 Hz, 1.3 seconds1000 Hz, 1.09 seconds2000 Hz, 0.85 seconds

The “before” classroom did not meet the ANSI standard for reverberation time at all three frequencies. The new “after” ceiling meets the standard at all three frequencies.

The “before” classroom did not meet the ANSI standard for reverberation time at all three frequencies. The new “after” ceiling meets the standard at all three frequencies.

Comparison Of Reverberation Time

– 36 –

Classroom Acoustics Brochure from the Acoustical Society of America – can be downloaded from: http://asa.aip.org/classroom/booklet.html

ANSI S12.60-2002 can be ordered from:http://asa.aip.org/http://www.ansi.org/

Go to the “Standards Store” at either site.

Quiet in the Classroom – can be downloaded from:http://www.armstrong.com/schools

Where Can I Find Out More?

– 37 –

Summary

We’ve reviewed:

How sound impacts the learning environment.

How choosing the appropriate acoustical ceiling can reduce sound reverberation and background noise in the classroom.

How ANSI Standard S12.60 affects classroom design.

How to create a better learning environment through improved classroom design.

classroom acoustics slides - 2005 - fefpa · classroom acoustics slides – 2005 [g – abp –...

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