The effects of excessive classroom noise

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• The effects of excessive classroom noise
• Major sources of classroom noise
• Noise reduction strategies

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Interference with speech communication by noise
is among the most adverse effects of noise on
people, and
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Some Useful Terms

• Background noise Sound level present in an
  empty room.
• Decibels (dB) Sound pressure or loudness of
  sound.
• Decibels A (dBA) Sound loudness as perceived
  by human hearing (500-2000 Hz range.
• Otitis Media with Effusion (OME) Inner ear
  infection.
• Reverberation/Reverberance Reflected sound, or
  echo.
• Signal to Noise Ratio (SNR) Loudness
• of speech compared to background noise.

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Noise is a Hazard for

• Fetus
• Newborns

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Free and easy speech communication is probably
essential for full development of individuals and
social relations, and freedom of speech is but an
empty phrase if one cannot be heard or understood
because of noise.
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Excessive classroom noise impedes the acquisition
of language

• The acquisition of language is essential to brain
  and intellectual development.

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Noisy Toys
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Excessive classroom noise interferes with
childrens learning of language by

• Decreasing motivation
• Reducing speech intelligibility
• Increasing behavioral problems

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In excessively noisy environments, children may

• Function below normal in energy levels, social
  support, and self-esteem
• Become vulnerable to learned helplessness
• Exhibit signs of higher levels of stress.

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Another Useful Term Speech Intelligibility

• This is how much of the spoken message is
  received (and understood) by the listener.

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Factors that influence speech intelligibility

• Signal to noise ratio (SNR)
• Background noise
• Reverberance

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Signal to noise ratio (SNR)

• Is the volume comparison between a sound source
  and the competing background noise

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Adults can usually understand speech with a SNR
of 0 - 10 dBA.Children require a SNR of at
least 20 dBA
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Speech Volume Levels

• The average teachers voice (at normal level, not
  screaming) is about 65 to 70 dBA.
• Some classrooms have background noise levels of
  55 to 75 dBA.
• Acoustical Society of America (ASA) recommends
  background noise levels of less than 35 dBA.

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Because of Sound Energy Loss

• Front of classroom 95 volume level
• Middle of class (3 seats back) 70 volume
  level and
• Rear of class 55 of original volume level.

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To improve the Signal to Noise ratio

• Reduce background noises especially those with
  similar frequency as speaker
• Seat high-risk children nearer to the speaker
• Reduce room Reverberance.

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Reverberation is the reflected sound (echo)
that persists in a room after a sound is generated

• It can mask the spoken message and contribute to
  background noise
• It can greatly decrease speech intelligibility

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Speech in a room with a 5 second reverberation
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Heres an example of 2.5 second reverberation
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Heres what .8 second reverberation (still twice
the maximum recommended by the ASA).
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Finally, the announcement with no reverberation.
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Background noise

• Is the noise present in an unoccupied space
• Can be from indoor or outdoor sources
• May not be equal throughout a room
• It is most damaging when at the same frequency as
  the spoken message
• May be present in the form
• of background music.

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Classroom Communications
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A noisy classroom poses the greatest risk to
children who

• Are just acquiring language
• Have English as a second language
• Have a hearing loss
• Have a learning disability
• Have behavioral problems.

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Otitis Media (OM or OME)(Inner ear infection)

• The most common medical diagnosis for young
  children
• More prevalent in younger children
• Often not diagnosed

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Otitis Media (continued)

• Symptoms last about 1 month
• Hearing loss can be as much as 40dB
• 25 or more of a class of young children may have
  some hearing loss due to OM.

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Best conditions for classroom hearing

• Background noise level below 35 dBA
• Reverberation of .4 second or less
• SNR above 20 dBA

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Ways to reduce background noise

• Remove or isolate local sources (a.c. units,
  fans, etc.)
• Install double-pane windows
• Put up drapery
• Provide rugs soft furniture
• Muffle chair legs (on wood floors).

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Reducing Reverberation

• Add sound-absorbing materials to walls, ceiling,
  floors
• Reduce ceiling height
• Add soft room furnishings.