Manage and Improve the Sound in your Electronic Classrooms

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Manage and Improve the Soundin yourElectronic
Classrooms
SUNY Technology Conference 2004

• Bennett M. Brooks, PE
• Brooks Acoustics Corporation
• Vernon, CT
• www.brooks-acoustics.com
• 15 June 2004

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• Manage and Improve the Sound in your Electronic
  ClassroomsSUNY Technology Conference 2004
• Abstract
• Many universities and colleges are facing
  increasing student populations, in older,
  outdated buildings. In response, new or
  renovated facilities are being planned which
  integrate the best of current educational
  programs. The environmental and physical design
  of the new classroom or lecture hall should
  reflect its intended modes of instruction.
• The educational specifications may wisely
  recognize the importance of the sense of sound to
  the learning process. This can be expressed by
  the need for a high quality acoustical
  environment. Special acoustic requirements that
  should be considered include sound isolation in
  the classrooms and adjoining spaces, mechanical
  system noise control, and the instructional and
  performance functions of music/theatre program
  classrooms.
• Additional considerations may be given to the
  acoustical quality of meeting spaces, large and
  small, distributed throughout the university,
  which can be important resources for large group
  learning activities. These spaces will be forums
  for significant student, faculty and community
  events, and the importance of a good acoustical
  environment for verbal communication is a key
  issue. Effective speaking and listening in these
  spaces must be addressed for traditional
  unamplified speech, as well as for
  state-of-the-art multimedia presentations.

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Manage and Improve your Sound

• Acoustical Functional Requirements
• Classrooms
• Lecture Halls
• Tele/Video conferencing
• Distance Learning

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• Acoustical Functional Requirements----------
• Good speech communication
• Quiet background
• Low reverberation

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• Acoustical Basics
• For
• Learning Spaces
• Low mechanical system noise
• Low intrusive noise
• Low reverberation

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Manage and Improve your Sound

• WHAT IS ACOUSTICS?
• The Science of Sound --
• a branch of Physics

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Manage and Improve your Sound

• WHAT IS SOUND?
• Organized vibrations of air molecules

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Manage and Improve your Sound

• SOME ACOUSTICAL FACTS
• Sound has two important qualities
• Qualities that we can hear - and measure
• Frequency
• And
• Level

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Manage and Improve your Sound

• ACOUSTICAL FACTS
• Sound Frequency
• - Frequency -- also called "pitch"
• low pitch (hum)
• high pitch (hiss)
• - Sound frequency is described by the
• measurement unit of "hertz" (Hz)
• or "cycles per second
• - Sound frequency is related to something
  called
• "acoustic wavelength" or "wave size"

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Manage and Improve your Sound

• MORE ACOUSTICAL FACTS
• What is the size or dimension of sound?
• (spacing between wave peaks)
• Speed of Sound - 1100 feet per sec at room temp.
• Acoustic wavelength
• As frequency (pitch) goes higher, wavelength
• gets smaller.
• - At 100 hertz wavelength is 10 feet
• - At 1000 hertz wavelength is 1 foot
• - At 10,000 hertz (10 kHz) wavelength is 1
  inch

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Manage and Improve your Sound

• MORE ACOUSTICAL FACTS
• Sound frequency demo
• Listen to sine waves signals on the
• Virtual MR1 NTI Minirator signal generator.
• Free download at
• http//www.nt-instruments.com/minstruments

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• SOME ACOUSTICAL FACTS
• Sound Level
• - Sound Level -- also called "loudness"
• or "intensity"
• low intensity (whisper)
• high intensity (jet plane take-off)
• - Sound level is described by the
• measurement unit of "decibel" (dB)
• named after A.G. Bell (telephone inventor
• and advocate for the Hearing Impaired)

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• Sound Level
• Definition of Sound Pressure Level
• as given in decibels (dB)
• SPL 20 Log ( Pacoustic / P0 )
• where P0 20 micro-pascals (µPa)
• approximate threshold of hearing

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Manage and Improve your Sound

• ACOUSTICAL QUALITY OF LIFE
• What contributes to acoustical quality
• Noise
• Communication
• Aesthetics

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• WHAT IS NOISE?
• Noise is UNWANTED sound!

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• Classroom Acoustics Standard
• ANSI/ASA S12.60-2002
• Maximum A-weighted 1-hour average
• Steady background noise level
• 35 dB
• sometimes you will see notation
• 35 dBA
• This is equivalent to a quiet whisper
• ??? What is noise level in this room ???

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• Classroom Acoustics Standard
• ANSI/ASA S12.60-2002
• Maximum reverberation time (RT)
• Sound in 500, 1000, 2000 Hz octave bands
• 0.6 seconds
• (0.7 seconds for rooms gt 10000 cu ft)
• ?? What is reverberation time in this room ??

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• Classroom Acoustics Standard
• ANSI/ASA S12.60-2002
• Noise Isolation Requirements
• Wall, Floor/ceiling, Roof/ceiling
• Assemblies
• STC 50 minimum

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• Special Function Room
• Acoustics Specifications
• Telecommunications
• Distance Learning
• Max background noise level
• 30 dBA (NCB / RC 25)

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• Special Function Room
• Acoustics Specifications
• Telecommunications
• Distance Learning
• Maximum reverberation time
• 0.5 seconds

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• NOISE FROM ROOM
• VENTILATION
• (HVAC) SYSTEMS
• Major cause of classroom noise
• What type of system causes the most noise?
• What is the noise like?
• How does it affect the learning environment?

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Manage and Improve your Sound

• HVAC Noise Sources
• w Air distribution fan (rumble, whoosh)
• w Cooling unit compressor (hum, whine)
• w Heat pump (hum, whine)
• w Supply and return ducting grills/vents
  (hiss)

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• Affects of HVAC Noise on Learning
• Cause of distraction, loss of attention
• (especially during on/off cycling)
• Loss of understanding -- missed words (poor
  speech intelligibility)
• Garbling of perceived speech
• Cause of listener fatigue
• Cause of vocal strain

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Manage and Improve your Sound

• Examples
• Lecture Hall Speech vs. Noise
• Lecture Hall Speech vs. Reverb
• Lecture Hall Crosstalk
• Classroom vs. Outside noise
• Classroom vs. Interior noise

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• Examples
• Listen to demos
• Available on free cd from NASA
• http//www.grc.nasa.gov/WWW/AcousticalTest/Hearing
  Conservation/AuditoryDemonstrations2.htm

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• Examples
• Lecture Hall Speech vs. Noise
• NC 30 --- max
• NC 35
• NC 40
• NC 45
• NC 50

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• Examples
• Lecture Hall Speech vs. Reverberation Time (RT)
• 0.0 seconds
• 0.125 seconds (1/8 sec)
• 0.25 seconds (1/4 sec)
• 0.5 seconds (1/2 sec) ---- max
  telecomm
• 0.875 seconds (7/8 sec)
• 1.250 seconds
• 2.0 seconds
• 2.7 seconds
• 4.0 seconds

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Manage and Improve your Sound

• Examples
• Lecture Hall Speech vs. Crosstalk
• STC 20
• STC 25
• STC 30
• STC 35
• STC 40
• STC 45
• STC 50 ---- minimum
• STC 55
• STC 60

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• Examples
• Classroom Instruction vs. Environmental Noise
• STC 20
• STC 35
• STC 50 -- minimum (ANSI S12.60)

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• Examples
• Classroom vs. Interior Noise
• RT 1.25 seconds, HVAC noise nearby basketball
  game (STC 20)
• STC increased to 40
• HVAC reduced 3 times to 35 dBA
• RT reduced to 0.5 second

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• Solution Strategies
• Build owner designer (A/E) awareness of issues
• Address early in design
• new / renovation

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• Solution Strategies
• Reduce mechanical noise
• Reduce room reverberation
• Increase wall floor/ceiling STC

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• CONCLUSIONS
• Early awareness builds project success
• Apply good design principles first
• Continue research on architectural design and
  speech intelligibility
• Develop design guidelines

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• Classroom Acoustics -- Resources
• Listening for Learning Series
• The importance of good classroom acoustics
• Will our new classrooms meets the standard?
• Counting the costs of noisy vs. quiet
  classrooms
• A checklist for classroom acoustics
• Retrofitting a noisy classroom
• Available from U. S. Access Board
• http//www.access-board.gov/publications/acoustic-
  factsheet.htm

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• Classroom Acoustics -- Resources
• Acoustical Society of America
• American National Standards Institute (ANSI)
• American National Standard --
• Acoustical Performance Criteria, Design
• Requirements, and Guidelines for Schools
• ANSI S12.60-2002
• http//asa.aip.org
• click on Standards Store --- 35

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• Classroom Acoustics -- Resources
• Acoustical Society of America
• Publications and Text books available for
  download
• Classroom Acoustics 1 -- Creating Learning
  Environments with Desirable Listening Conditions
• Classroom Acoustics 2 -- Acoustical Barriers to
  Learning
• http//asa.aip.org click on Technical Committees
  Architectural Acoustics