Management of APD
CLASSROOM ACOUSTICS AND
(SIGNAL) ENHANCEMENT
STRATEGIES
DAVID CANNING
HEAR2LEARN
HTTP://TINYURL.COM/UCLAPDCA
Educational Video 1953
Learning points:
 Noise in classrooms is usually generated within the
classroom by the children and adults present.
 Without clear strategies for managing ‘noise’ (including
work noise), sound levels can become high.
 Careful management can control noise even the most
unpromising room – the ‘Miss Bradley’ effect.
 Broader questions to do with learning within the
classroom
 And was the expression of terror on the boys face real
after he broke his pencil
Overview
 Reasons for considering classroom/educational
acoustics:
Educational Law and Building Requirements
 School related studies and hearing performance

 Acoustic parameters relevant to education: Control of
noise

Traditional classrooms:


Essex study
Open Plan Classrooms:
 Signal enhancement strategies


Linking goals to educational needs
Options
 Concluding remarks
Education of Children with Special Educational
Needs (SEN)
 The Education Act 1996 says that 'a child has special
educational needs if he or she has a learning difficulty
which calls for special educational provision to be made
for him or her.
 ‘Where a child has a special educational need then LEAs
must make decisions about which actions and provision
are appropriate for which pupils on an individual basis.
This can only be done by a careful assessment of the
pupils’ difficulties and consideration of the educational
setting in which they will be educated’. DCSF formerly the DfES
SEN continued
 “The real question ... is whether [the statement] is so
specific and clear as to leave no room for doubt as to
what has been decided and what is needed in the
individual case.“
L v Clarke & Somerset County Council
It would be helpful for the professional specifying
classroom acoustics for a particular child to have
available measures of the aided hearing, including
acceptable levels of noise, desirable
reverberation times and required signal to
noise levels. (BB93 p77)
Reverberation time
 Binaural Headphone test, 217 children 17 adults,
constant Signal to Noise levels
Yang and
Bradley 2009
Room modes (standing waves)
Noise Levels in Classrooms
Greenland (2009)
Signal to Noise
Sato and Bradley 2006
Signal to Noise
Signal to noise
distributions
in 28
classrooms
Sato and Bradley 2006
Age and Signal to Noise Level
Bradley and Sato (2008)
41 classrooms and 2285 individual speech recognition tests
PAVT (Paediatric Audiovisual Test)
S represents a child
whose performance is
adversely affected by
noise
Work in progress: 48 children in 4
classrooms
England and Wales Building Regulations
 “Each room or other space in a school building shall
be designed and constructed in such a way that it has
the acoustic conditions and the insulation against
disturbance by noise appropriate to its intended use.”
Requirement E4 from Part E of Schedule 1 to The Building
Regulations 2000 (as amended). (Building Bulletin 93 p3)
UK Acoustic Standards
USA
UK
USA
Standards
(Reverberation time
and Background
Noise Levels)
Government
Approved building
Document E and
BB93 specifically
(many stakeholders
and extensive public
consultation)
ANSI/ASA
Enforced by
Local Building
Control Officers
Local Building
Inspectors
Web address
teachernet.gov.uk/ac
oustics
Google ANSI
(many stakeholders
and public
consultation?)
Noise
Teaching spaces used by children with
hearing impairment or are deaf or
have special hearing requirements
BB93 section 1
Anticipated
Revisions
Reverberation Time
Anticipated
Revisions
Teaching spaces used by children with
hearing impairment or are deaf or have
special hearing requirements
0.4s
125Hz – 4kHz
Alternative acoustic standards in the absence of
child specific information
BB93 Section 6
Classroom acoustics and the Enhancement
of the Speech Signal
 Traditional classrooms
Essex Study:


Provide guidance for the acoustic design and
specifications of classrooms in schools identified
as resource schools.
Systematically explore the impact of the
classroom acoustics on the classroom ecology:
Auditory environment
 Teaching and learning environment


4 identical classrooms within the same teaching
faculty and money to modify the rooms
repeatedly
Selection of Groups
 10 teachers


8 Classes taught exclusively in one of the rooms
3 of the 4 classrooms were predominantly used by the same
teacher
 Teacher class combinations



10 teacher class combinations were included in the study
Groups included grades 7 (11yrs) to 10 (14yrs)
Top and bottom ability sets
 Children


400 children included in the study
Including 17 children with hearing impairment/special hearing
requirements
Schedule of Room Treatments
Experiment
al Condition
British
Association of
Teachers of the
Deaf (batod)
Rt <=0.4sec
125Hz – 4Khz
BB93
classrooms
designed for
use with HI or
special
listening
requirements
Mid
Frequency
(500Hz –
2Khz) mean
= 0.4sec
BB93
Untreated
Mid
Frequency
(500Hz –
2Khz) mean
= 0.8sec
(Rt > 0.9s
mid
frequencies)
Pre test (all
untreated)
Classroom A
Classroom B
Classroom C
Classroom D
Phase 1
Classroom A
Classroom B
Classroom C
Classroom D
Phase 2
Classroom C
Classroom A
Classroom B
Classroom D
Phase 3
Classroom B
Classroom C
Classroom A
Classroom D
Topic of this
talk
Outcome measures
Unoccupied
Physical
Acoustics:
Rt, EDT, C50 etc
Expert panels
Functional
Acoustics
• Signal to Noise
measurements
• sound levels
Interviews and
observations
Room
Teacher and
Child ratings
• LIFE UK
Hearing
performance:
Speech
discrimination
Reverberation
Time &
Occupied
Sound Levels
Classroom noise and Sound Treatment
Original
Treated
Selection of Acoustic Materials
Acoustic panels absorb
sound energy.
The nature of the material
used, and the manner in
which is used all have an
impact on the absorption
characteristics
Acoustic treatment and classroom noise
Very significant changes in
occupied sound levels:
17dB from untreated to
highest level of treatment
(1.2 s to 0.4s)
9dB Reduction in
Background Noise
from current
standard to
proposed standard
for children with
‘special hearing
requirements’
c
Acoustic treatment and classroom noise
Herriot Watt Study 1996-1999 (70 Primary Schools) David McKenzie
Considerable reductions in occupied noise levels reported following acoustic
treatment to reduce reverberation times.
Average Background Noise Levels
Untreated
Treated
Room
Unoccupied
44.77
40.1
Pupils Silent
55.5
46.5
Pupils Working
77.3
70.1
The auditory significance of reducing occupied
sound levels
 The lower the sound level the greater the likelihood
of achieving adequate signal to noise levels




Teacher talking to the whole class
Children talking to the whole class
Children talking to each other during group work
Whole host of non auditory benefits explored in the literature
but not the topic of this talk.
Sample Important Communication Events:
Signal to noise in a good primary classroom:
Teacher talk
School 1: Strong control of class
Comparison of findings Teacher talk:
 School 2: Sound field system
Group work
Signal to noise in a good primary classroom
 School 1
Group Work: Comparison
 School 2
Recap
c
9dB Reduction in
Background Noise
from current
standard to
proposed standard
for children with
‘special hearing
requirements’
Miss Bradley Approach?
 Not all classes changed:
 Note the low noise levels in all
conditions
 Another teacher using this room
said

‘Before – it was all about isolating and
controlling the class, now I can teach’.
Changes in Education
Exemplar Rural Secondary School
Exemplar Schools
Flagship Buildings
Bexhill Academy
Noise Levels in Open Plan Classrooms
Greenland (2009)
Interim Summary
 Physical Acoustics have a significant impact on the
behavioural acoustics of the classroom.
 It is relatively easy to alter the physical acoustics
of a classroom



Best done at the planning stage whether new build or
refurbishment
Cost estimated to add 1% - 5% additional cost of a typical
school
Added an extra £1000 to the £20 000 cost of a typical
classroom refurbishment.
Signal Enhancement
 2 Approaches
 Control of the environment


Attention to the physical acoustics of the teaching space – ‘Low
tech, can be very cheap and permanent’
 Work organisation and use of teaching spaces
 Behaviour management
Enhancement of the signal directly
Whole classes
 Individual Approaches

Enhancement of the signal:
Whole class approaches
Sound Field Systems
(Classroom PA
systems)
Considerable history
of successful use in
schools in the USA 30
years and in the UK
for the last 10 years.
A selection of current classroom products
Flat Panel Infra Red systems
Traditional
Loudspeaker Infra
Red systems
Modelling Classroom Acoustics
 Available from http://www.arthurboothroyd.com/
Enhancement of the signal:
Individual Approaches
 Personal FM systems:
 Phonak Edulink and iSense
Individual Receivers either ear worn or ‘ipod’ style
Fm
transmitter
Phonak iSense
Provide 15dB advantage in a range of listening
conditions
-Good for 1:1 communication
e.g. Teacher to child
A multitransmitter (multitalker network)
can allow upto 10 talkers
-Good for group work
e.g. Several children using the
transmitters and one or more children
listening
Summary
 Signal to Noise Enhancement can be achieved
through:

Control of the noise
Physical acoustics
 Management of the class


Enhancement of the signal
Whole class approaches
 Individual approaches
 Management (proximity)



Solution is will need to be related to the local environment and
the specific needs of the child with special hearing
requirements
Most likely to involve of all of the above
Conclusion
 Concluding Advice
 Be very specific about functional auditory needs
Signal to noise levels
 Impact of noise on listening
 Classroom observation
 Child and teacher opinion


Translate that into very specific recommendations that can be
measured or put in place and evaluated.

E.g. Needs signal to noise levels of +20dB and working noise levels
of less than 40dB. Identify classroom strategies required to be put
in place by the teacher.
Miss Bradley and Professor McDaniel
Selected References
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Bradley, J. S. and H. Sato (2008). "The intelligibility of speech in elementary school classrooms." J Acoust Soc Am 123(4): 207886.
Dockrell, J. E. and B. Shield (2004). "Children's perceptions of their acoustic environment at school and at home." J Acoust Soc
Am 115(6): 2964-73.
Dockrell, J. E. and B. M. Shield (2006). "Acoustical Barriers in Classrooms: The Impact of Noise on Performance in the
Classroom." British Educational Research Journal 32(3): 509-525.
Greenland, E. E. (2009). Acoustics of open plan classrooms in primary schools. London, London South Bank University. PhD.
Larsen, J. B., A. Vega, et al. (2008). "The effect of room acoustics and sound-field amplification on word recognition performance
in young adult listeners in suboptimal listening conditions." Am J Audiol 17(1): 50-9.
McKenzie, D. J. (2000). Noise Levels and Sources in UK Schools. International sysposium on noise control and acoustics for
educational buildings, Yildiz Technical University, Turkish Acoustical Society.
Picard, M. and J. S. Bradley (2001). "Revisiting speech interference in classrooms." Audiology 40(5): 221-44.
Sato, H. and J. S. Bradley (2008). "Evaluation of acoustical conditions for speech communication in working elementary school
classrooms." J Acoust Soc Am 123(4): 2064-77.
Shield, B. and J. E. Dockrell (2004). "External and internal noise surveys of London primary schools." J Acoust Soc Am 115(2):
730-8.
Shield, B. M. and J. E. Dockrell (2003). "The Effects of Noise on Children at School: A review." Building Acoustics 10(2): 97-116.
Shield, B. M. and J. E. Dockrell (2008). "The effect of amplification on children's performance in the classroom." J Acoust Soc Am
123(5): 3918.
Shield, B. M. and J. E. Dockrell (2008). "The effects of environmental and classroom noise on the academic attainments of primary
school children." J Acoust Soc Am 123(1): 133-44.
Tiesler, G. and M. Oberdoerster (2008). "Noise - A stress factor? Acoustic ergonomics at schools." J Acoust Soc Am 123(5): 3918.
Yang, W. and J. S. Bradley (2009). "Effects of room acoustics on the intelligibility of speech in classrooms for young children." J
Acoust Soc Am 125(2): 922-33.
Computer modelling
www.arthurboothroyd.com then navigate to downloads/classroom_simulations
( or type in http://chhs.sdsu.edu/slhs/aboothro/Classroom_simulation/