sound & acoustics in technology classrooms · sound & acoustics in technology classrooms...

David P. Stadler CTS, DMC-E, MS

Senior Manager

Media Technology Services

Carnegie Mellon University

Sound & Acoustics In Technology Classrooms

• Established 1900

• Private research university

• 1,368 Faculty

• 6,000 Undergraduates & 5,420 Graduate & Doctoral students

• Main campus: Pittsburgh, Pennsylvania

• Undergraduate branch campus: Doha, Qatar

• 13 graduate branch campuses in 11 countries

• Athletics: 17 Division III athletic teams - Tartans

Carnegie Mellon University Fast Facts

• Classroom Technologies

• Media Production

• Videoconferencing

• AV & Media Consultation

• Facility Design

Media Technology Services

David P. Stadler CTS,MS

Senior Manager

Media Technology Services

Carnegie Mellon University

Qualifications and Biases

A: 10

C: 100

B: 64

D: 18

50:50

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$1 Million

$500,000

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$1,000

$500

$300

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How many total

campuses are in the

SUNY system??

Has your college or university ever conducted an acoustical evaluation of your learning spaces?

A. Yes

B. No

What priority do you give sound in designing an integrated media learning space?

A. Sound then display

B. Display and sound equal

C. Display then sound

What was the percentage of acoustical exhibitors who were on the Infocomm 2010 show floor?

A. 2%

B. 5%

C. 20%

D. 30%

InfoComm 2010

• 925 exhibitors

• 21 acoustical exhibitors

representing 2% of exhibitors

a/V Manufacturers • Historically focused on maximizing visual

displays

Digital revolution

•Auditory content- second string

How do we see classroom sound?

How do we see classroom sound?

Learning Space Acoustical Standards

Acoustic Basics

• Sound Isolation

Sound Ratings

Signal to Noise ratio (S/N)

• Reverberation

• Reflected Sound

• Room Modes

Sound Isolation

• Keep out exterior room sound

• Preserve generated sound inside a room

• Reduce unwanted interior room sound

• Implement during construction

Architectural components – Walls, Doors Floors, Ceilings, HVAC

Sound Isolation – Rating Systems

• STC- Sound Transmission Class

Based on ASTM E413-87 (1994)

125-4000 Hz

Typically used for speech and media

• OITC-Outdoor Indoor Trans. Class

Based on ASTM E1332 (1990)

80-4000 Hz

Typically used for exterior sound

Sound Isolation

• STC for walls - higher STC values more efficient in reducing sound transmission

STCratings.com

Sound Isolation

Changes in STC rating Changes in apparent loudness

+/- 1 Almost imperceptible

+/- 3 Just perceptible

+/- 5 Clearly noticeable

+/- 10 Twice as loud

+/- 20 Four times as loud

STCratings.com

Demonstration

Learning Space Sound Isolation Recommendations

• Wall ceiling and floor if adjacent to:

STC-45: corridor, staircase, office or conference room

STC-50: core learning space, speech clinic, health care room or outdoors

STC-53: restroom

STC-60: music room, mechanical equipment room, cafeteria, gymnasium or indoor swimming pool

• Door ratings:

STC -30: classroom doors

STC-40: music room doors

STC-45-60: ancillary space separation

Acoustics.com

STC • Use as a reference for targeting new

construction and architecture

• Calculation

Best left to the professionals

• Do it yourself

Small room acoustic forum http://forum.studiotips.com/viewtopic.php?t=140

Sound Isolation

Isolation will be improved by extending walls to structural deck, not just the ceiling.

A. True

B. False

STCratings.com

Sound Isolation

Sound will travel through speaker and electrical outlet penetrations.

A. True

B. False

STCratings.com

Demonstration

Sound Isolation

Installing insulation within a wall or floor/ceiling cavity will improve the STC by 4-6 points.

A. True

B. False

STCratings.com

Sound Isolation

Changes in STC rating Changes in apparent loudness

+/- 1 Almost imperceptible

+/- 3 Just perceptible

+/- 5 Clearly noticeable

+/- 10 Twice as loud

+/- 20 Four times as loud

STCratings.com

Sound Isolation

Metal studs perform better than wood studs.

A. True

B. False

STCratings.com

Learning Space Background Noise Level

< 20,000 cubic feet < 35 dBA for spaces

> 20,000 cubic feet < 40 dBA for spaces

Need a sound-to-noise level of 15 dB.

Nelson,Soli & Seltz (2002) Acoustical Barriers to Learning- Acoustical Society of America

Reverberation

Definition:

Prolongation of the sound in a space caused by continued multiple reflections.

Acoustics.com

Reverberation

Acoustics.com

Learning Space – Reverberation Standards

Space volumes. . .

• < 10,000 cu. ft. are not relevant

• > 10,000 cu. ft. should be < 0.6 seconds

• between 10,000 and 20,000 cu. ft. should be < 0.7 seconds

• > 20,000 cu. ft. (see ANSI.ASA S12.60 guidelines )

Acoustics.com

Learning Space - Speech Intelligibility

Combination of reverberation time (RT) and signal-to-noise ratio (S/N)

• 0.5 second RT and +10 dB S/N - 90 % speech intelligibility

• 0.5 second RT and 0 S/N - 55 % speech intelligibility

• 1.5 second RT and +10 S/N – 75 % speech intelligibility

• 1.5 second RT and 0 S/N – 30 % speech intelligibility

Seep,Glosemeyer, Hulce, Linn& Aytar (2000) Classroom Acoustics- Acoustical Society of America

Reflected Sound

• Sound strikes a surface or several surfaces before reaching the receiver

• Reverberation is continuous multiple reflections

• Controlling the reverberation time in a space does not alleviate reflection problems

Acoustics.com

Reverberation & Reflected Sound Remediation

• Fiberglass/Foam non-parallel walls

• Bass Traps

• DIY

Owens Corning 703 & 705 panels 48"x 24"x__

Fabric covered

Flexible mounting

Reverberation & Reflected Sound Remediation

• Mid and high frequency traps

Reverberation & Reflected Sound Remediation

• Bass traps

4” thick 705-FRK and spaced 16 inches away from the wall can be quite effective for frequencies below 125 Hz

Room Mode

Definition

• Sound having the same pitch as a natural resonance of the room will sound louder and have a longer decay time than other notes.

Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991

Optimize Room Modes

• Use standard modal approach

Create as many different resonances as possible spread evenly across the frequency spectrum

• Proper space design

Create space with length, width, and height ratios that are as unrelated as possible

Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991

Room Mode

Optimum room dimensions

According to the modal design theory, the worst possible room shape is a cube.

Ballou, Glen, Ed., Handbook for Sound Engineers, 2nd ed, Howard Sams, Carmel, Indiana, 1991

Dimension Design #1 Design #2 Design #3

Width 1.14 x Height

1.28 x Height

1.60 x Height

Length 1.39 x Height

1.54 x Height

2.33 x Height

Realtraps.com

Realtraps.com

Room Modes - Remediation

• Bass traps can improve room modes

• Moving walls and ceilings are the only true solution

Acoustic Focus for Learning Spaces

• Background noise

All learning spaces

• Reverberation

Large learning spaces

• Reflection

All learning spaces

− Dead spots

• Room Modes

Specialized or media integrated learning spaces

How do we see classroom sound?

CMU Learning Space - Acoustic Evaluation

• Existing classrooms

Background sound level

Isolation

Reverberation

Reflection

− Dead spots

CMU Equipment Operating Noise Evaluation

• Equipment selection

• Integrated room design

High volume, low velocity

Integrated room design – component selection

2 dBA increase in baseline room noise

0 dBA

Cost Savings

Integrated room design – component selection

2 dBA increase in baseline room noise

0 dBA

Cost Premium

Crossing the Chasm Marketing and selling high-tech products to the mainstream customers

Geoffrey A. Moore

David P. Stadler CTS, DMC-E, MS

Senior Manager

Media Technology Services

Carnegie Mellon University

Sound & Acoustics In Technology Classrooms