Improving
Classroom
Acoustics: Low
to High Tech
Strategies
October 25, 2013
Diane L. Meyer and Mike Brummer
Did you know?

That normal hearing children can miss as much as 1/3 of what
their teacher says due to poor classroom acoustics. Even in an
acoustically ‘good’ classroom, children ‘receive’ 83% of a
teacher’s voice ‘signal’ when they are seated in the front row;
66% in the middle rows and only 55% in the back row.
(Crandell & Smaldino, 1994)

A child's hearing abilities are not fully developed until age 15.
Children cannot hear and neurologically process what they
hear the same as an adult. (Crandell1995; Flexer 2002)

Up to 43% of primary level students fail a minimal 15 dB
hearing screening on any given day, in part due to the 14.9%
(or approximately 8 million) school-aged children that have a
permanent hearing loss and the 10-15% of children that have
a temporary hearing loss from middle ear infections. (MARRSU.S. Dept. of Education Study; American Medical Association )

The teacher’s voice drops 6 decibels for every doubling of
distance meaning that children seated in the middle to
back rows have significantly greater difficulty attending to
the teacher’s verbal instruction.

In 1996, the United Nations issued a report over the
concern that 10-12% of school-aged boys in the United
States were being prescribed the drug Ritalin. During the
1990’s there was a 700% increase in the use of
psychostimulants in the United States. Effectively, the
U.S. was consuming over 90% of 8.5 tons of Ritalin
produced world-wide each year.
Factors Affecting Acoustic Access

The teacher’s voice decreases 6 decibels as the
distance from him/her doubles.
 Ambient classroom noise may mask the teacher’s
Instructional
voice for students sitting in the middle and back of
Message:
the classroom.
Inverse Square
Law
 http://www.classroomhearing.org/Videos/Inverse_
Square_Law.html
Inverse Square Law
Children’s Listening Abilities
Children’s cognitive auditory capabilities are not fully
developed until age fifteen. This means that children do
not hear and process what they hear, the same as an
adult. Therefore they cannot understand the difference
between sounds comprehend what they are hearing the
same as an adult. They must exert more energy than an
adult to concentrate on and process the sounds they are
hearing. Because of these immature auditory abilities,
children require a better acoustical environment than does
an adult in order to understand what they are hearing.1
2Acoustical
Surfaces Inc.
Background Noise Sources

Through walls from adjacent classrooms

Over the ceiling from adjacent classrooms

Through doors, around the frame and under the door

Through ventilators or louvers above door units

Through HVAC ductwork from adjacent rooms

HVAC noise from ceiling diffusers

Through the light fixtures

From outside, through exterior walls and windows

From floor above
Strategies to
Improve Acoustic
Access
Environmental Strategies
Areas to Consider
Ceiling
Floors
Windows
Walls and
Doors
Seating and
Furniture
Ventilation
Lighting
Special Purpose
Areas
Ceiling
•
Installing acoustical ceiling tile is the most effective way of
absorbing distorted middle and high frequency noise and
improving speech perception ability.
•
A ceiling height less than 12 feet is optimal for the listening
environment.
•
Suspend banners, student work, and hanging plants from
the ceiling
Floors
•
Carpeting
•
absorbs excessive reverberation of high frequency
consonant sounds
•
dampens noise from students and movement of
classroom furniture
•
Use rubberized or resilient tile versus flat, reflective tile
•
Use area rugs or carpeting for uncarpeted areas
Windows
•
Drapes on the sides of windows absorb sound
•
Keep windows closed to prevent outside sounds from
entering the classroom
•
Walls
and
Doors
•
Place rectangular extension
rods in opposite corners of
the room and hang a curtain
• Creates round corners
to reduce reverberation
• Provides small storage
area
• Place cabinets at angles in the corners –soften the fronts with fabric
curtains on magnetic rods or cover with cork boards
Seating
and
Furniture
•
Place a drape or cork on the front of solid areas
teacher’s desk
•
Use curtains to cover/conceal open shelving
units
•
Use tennis balls or rubber chair leg caps on
tables and chairs
•
Think about traffic flow in the room: where is supplies kept in
relation to your teaching zones
•
Place noisy items (pencil sharpener) away from teaching areas
•
Create assigned zones during small group work so that groups
are spread out
Ventilation
•
Replace noisy blowers
•
Cover ventilation openings with strips of material
•
Do not use desk or floor fans
Lighting
•
Make sure florescent lights are functioning correctly
• Ballast will make high frequency sounds when they begin to
burn out
•
If your room is equipped with a motion sensor, position students
with hearing aids out of the directional path of the doorway
Special
Purpose
Areas
•
Carpeting
•
Use rubberized or resilient tile versus flat, reflective
tile
•
Hang banners or flags from the ceiling
•
Place material or cloth banners on the walls
Instructional Strategies
Rate of Speech
 Immature central nervous system needs a slower
rate of speech in order to process the acoustic
linguistic code
 PK to 3rd grade need 120 words/minute
 4th grade can process 124 to 128 words /minute
 Middle school can process 135 words per minute
 High school can process 145 words per minute
 Model a Preschool or Kindergarten teacher rate
Repeating of peers’ questions,
comments, answers
 Inverse Square Law – signal decreases 6 dB every time
distance doubles
 Students 20 feet from speaker will function like a person with
a mild hearing loss
 Repeat/Rephrase/Summarize all verbal communications
Control competing background
noise
 Close doors
 Turn off radios
 Use headphones for computer centers
Face students when
speaking
 Address the students when instructing
 Speech signal travels through the air to the

students’ ears versus traveling to the board
reflecting off the board
Allows students to access the speaker’s face for
any visual support
Talk at a normal volume level
 Increasing the volume increases the distortion of

the auditory signal
Increasing the volume alters how you produce
speech sounds making it difficult to speechread
Technological Solutions
Classroom
instruction without
assistance
Classroom instruction with
assistance
Soundfield Systems
•
Surround sound systems
for teachers and students
•
Group or classroom
systems for instruction of
large audiences
•
Personal systems for
individuals with hearing
loss
•
Can be wired or portable
References
2Acoustical
Surfaces Inc.
http://www.acousticalsurfaces.com/soundproofing_tips/html/crashcourse.ht
m
Banotal, Alyssa (2008). “How to Talk to Children” – Linguistic ability and the CNS.
Advance Magazine, Vol. 18, Issue 3, p. 6.
Crandell, Carl, and Smaldino, Joseph (1994). “The importance of room
acoustics”. In R. Tyler & D. Schum (Eds.), Assistive listening devices for
the hearing impaired (pp. 142-164). Baltimore,MD: Williams & Wilkins.
TED: “Why Architects Need to Use their Ears” - Classroom Acoustics by Julian
Treasure
http://www.ted.com/talks/julian_treasure_why_architects_need_to_use_thei
r_ears.html
1The
Institute for Enhanced Classroom Hearing
www.classroomhearing.org