Download A Brain-Based Perspective

A Brain-Based
Perspective
Photo Credit: Ablestock
Classroom Acoustic
Accessibility:
By Carol Flexer, Ph.D., LSLS Cert. AVT, and John Rollow, B.S.
T
ypical mainstream classrooms
are auditory-verbal environments where instruction is
presented through the teacher’s spoken communication. Children
in a mainstream classroom, whether or
not they have a hearing loss, must be
able to hear the teacher and each other
for learning to occur. If the brains of
children cannot consistently and clearly
receive spoken instruction, the major
premise of the educational system is
undermined and that is what “acoustic
accessibility” is about.
Children Have Organic
Listening Limitations
We “hear” with the brain; the ears are
just a way for sounds to get in. The
problem with hearing loss and with
poor auditory environments is that
intact sound is barred from reaching the brain. The purpose of having
favorable listening environments and
appropriate acoustic access technologies is to enhance acoustic saliency
by channeling complete words efficiently and effectively to the brain
(Flexer, 2004). Typical classroom
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acoustic environments can be roadblocks to the brain accessing sufficient
sounds unless active measures are
taken (Nelson, Smaldino, Erler, &
Garstecki, 2008).
It is important to recognize that
children are not able to listen like adults
listen; they have organic listening
limitations in two main ways. First,
the human auditory brain structure is
not fully mature until about 15 years
of age; thus a child does not bring a
complete neurological system to a
listening situation (Chermak & Musiek,
2007). Second, children do not have the
years of language and life experience
that enable adults to fill in the gaps of
missed or inferred information (such
filling in of gaps is called auditory/
cognitive closure). Therefore, because
children require more complete,
detailed auditory information than
adults, all children need a quieter room
and a louder signal – a better signal-tonoise ratio (SNR) (Anderson, 2004). The
goal is to develop the brains of children
– to create new brain maps – unlike
adults where sound enters an already
developed brain.
SNR and Acoustic
Accessibility
SNR is the relationship between the
desired auditory signals to all other
unwanted sounds – that is, the level
of the speaker’s voice relative to the
background noise. The more positive the
SNR, the more intelligible the spoken
message. Adults with typical hearing require a SNR of approximately +6
dB to hear a consistently intelligible
spoken message. For them, the desired
signal needs to be about twice as loud as
background sounds.
However, some populations require
a much more favorable SNR in order to
receive intelligible speech. These groups
need the SNR to be approximately +15
dB to +20 dB – that is, the desired signal
needs to be about 10 times louder than
background sounds! These populations
include all children, who generally do not
develop auditory maturity until about 15
years of age, and especially children with
any type of hearing problems, including
ear infections and unilateral hearing loss
(Crandell, Smaldino, & Flexer, 2005).
Unfortunately, most classrooms
contribute to an inconsistent and poor
VOLTA VOICES • SEPTE M BER/ OCTOBER 2009
Photo Credit: Ablestock
Proper acoustical environments provide students with optimal access to language and learning.
SNR. In a typical classroom, the SNR
can vary minute by minute from about
+5 dB to worse than -20 dB, depending
on teacher and student positions and
background noise levels. The teacher’s
voice, at a distance in the room, may be
only 40 or 50 dBA. (A-weighted decibels,
or dBA, are an expression of the relative
loudness of sounds in air as perceived
by the human ear, and is the common
measurement used for environmental
and industrial noise.)
Children Are the
Primary Source of
Noise in a Classroom
Acknowledging that the interfering sound
levels in a room originate with the occuVOLTA VOICES • SEPTEMBER/OCTOBER 2009
pants themselves is not a usual part of
architectural acoustics design (American
National Standards Institute, 2002). There
have been few measurements of sound
levels in occupied rooms, and little recognition that students and teachers are truly
the source of noise in classrooms.
In recent years, however, several studies have shown the reality of classroom
occupants as the primary source of noise.
The British acoustician Bridget Shields,
who pioneered studies published in 2002
on the effects of classroom noise on student performance, reported background
sound-pressure levels (SPL, or Basic
SPL) of 56 dBA for classrooms where all
students were engaged in the activity of
“silent reading and writing” (Dockrell
& Shield, 2006). In 2004 at the Gratts
Elementary School in Los Angeles, tests
conducted in a fourth-grade classroom
with 30 students showed that average
“working” classroom SPL was between 65
and 70 dBA, and Basic SPL was between
47 and 53 dBA (Rollow, 2004a; 2004b).
Most significantly, extensive studies in
Germany have provided solid field test
results clearly showing that the dominant noise levels in classrooms are generated by the occupants and are rarely less
than 45 dBA (Oberdorster & Tiesler,
2007; 2008).
So, as these studies show, the background sound level (the Basic SPL) in
all the working classrooms was almost
never less than 45 dBA, and is often 50
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Classroom Acoustic Accessibility:
A Brain-Based Perspective
dBA or more. With this recognition, the
question persists: How can we achieve
a SNR of +15 dB or greater in the
working classroom?
Assistive Listening
Devices
Assistive listening device (ALD) is a
term used to describe a range of products designed to solve the problems of
noise, distance from the speaker and
room reverberation or echo that cannot
be solved with a hearing aid or cochlear
implant alone (Boothroyd, 2004). ALDs
enhance the SNR to improve the intelligibility of speech, expand the child’s
distance hearing and enable incidental
learning through the use of a remote
microphone worn by the talker.
The types of ALDs most relevant
to children might be referred to as
SNR-enhancing devices, which include
personal-worn FM systems and soundfield IR and FM (classroom) amplification
systems. By enhancing the SNR, these
devices augment the audibility and intelligibility of the speaker’s voice and allow
better sound access to the brain.
So why are SNR enhancing devices
effective as a learning tool, especially for
children with hearing loss? Information
about brain neuroplasticity offers
insights about how and why acoustic
access is so important for children’s
learning (Doidge, 2007).
Learning a new task or acquiring information requires the brain to form neural
maps. In order for the brain to develop
these maps, the information first has to
reach the brain, a process that requires
sound to travel from the speaker (the
teacher in this case) to the brain of the
listener through the environment of the
classroom. In order for the information
to be useful, the child has to remember
it. “When we want to remember something we have heard, we must hear it
clearly because memory can be only as
clear as its original signal…muddy in,
muddy out” (Doidge, 2007, p. 68).
Doidge also writes that learning new
information/tasks/skills requires active
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attention. “While we can learn with
divided attention, divided attention
does not lead to abiding changes in your
brain maps” (2007, p. 68). More positive
SNR is provided by personal-worn and/
or soundfield technology, which in turn
facilitates auditory attention.
Summary
Acoustic accessibility is critical because
in environments relying on spoken
language instruction, sounds have to
reach the brain in order for learning to
occur. Therefore, we need to consider
the environment of the classroom – a
place where the interfering background
noise is generated by the students,
where that noise can be mitigated by
architectural design features, and
where the noise barrier can be overcome with soundfield technologies and
assistive listening devices – in order
to provide the brain access to spoken
instruction.
References
American National Standards Institute (ANSI). (S12.60-2002). Acoustical Performance Criteria, Design
Requirements, and Guidelines for Schools. New York: American National Standards Institute (ANSI
S12.60).
Anderson, K. (2004). The problem of classroom acoustics: The typical classroom soundscape is a
barrier to learning. Seminars in Hearing, 25(2), 117-129.
Boothroyd, A. (2004). Room acoustics and speech perception. Seminars in Hearing, 25(2), 155-166.
Chermak, G.D., & Musiek, F.E., Eds. (2007). Differential Diagnosis, Related Neuroscience, and
Multidisciplinary Perspectives on (C)entral Auditory Processing Disorder. San Diego, CA: Plural
Publishing Inc.
Crandell, C.C., Smaldino, J.J., & Flexer, C. (2005). Sound-field amplification: Applications to speech
perception and classroom acoustics, 2nd ed. New York, NY: Thomson Delmar Learning.
Dockrell, J.E., & Shield, B.M. (2006). Acoustical barriers in classrooms: The impact of noise on
performance in the classroom. British Educational Research Journal, 32(3), 509-525.
Doidge, N. (2007). The BRAIN That Changes Itself. London, England: Penguin Books Ltd.
Flexer, C. (2004). The impact of classroom acoustics: Listening, learning, and literacy. Seminars in
Hearing, 25(2), 131-140.
Nelson, E.L., Smaldino, J., Erler, S., & Garstecki, D. (2008). Background noise levels and reverberation
times in old and new elementary school classrooms. Journal of Educational Audiology, 14, 12-18.
Oberdorster, M., & Tiesler, G. (2007). “Modern Teaching” Needs Modern Conditions – Room Acoustics
as an Ergonomic Factor, Paper presented at 19th International Congress on Acoustics, Madrid, 2-7
September 2007.
Oberdorster, M., & Tiesler, G. (2008). Noise – a stressor? Acoustic ergonomics of schools. Building
Acoustics, 15(3), 249-262.
Rollow, J. (2004a). Field Report: Background Sound Levels In Classroom. Gratts Elementary School,
Los Angeles Unified School District, May 11, 2004.
Rollow, J. (2004b). Field Report: Continuous Sound-Level Recording In Classroom. Gratts Elementary
School, Los Angeles Unified School District, May 11-13, 2004.
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