PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Towards accessible acoustic criteria for inclusion
in mainstream classrooms
Emma GREENLAND1; Bridget SHIELD2
1
2

Anderson Acoustics, UK

London South Bank University, UK

ABSTRACT
New and refurbished school buildings in England and Wales need to comply with criteria for acoustics set
out in Building Bulletin 93 (BB93). However, the acoustic design strategy to comply with Equality law andto ensure that ‘people with disabilities, including those with hearing impairment, must not be placed at a
disadvantage’, is unclear and is complicated by other design factors and current funding constraints. This
paper sets out to establish acoustic criteria for inclusion of children with special, hearing and communicationneeds (SHCN) in mainstream classrooms, using a ‘reasonable adjustments’ approach (which underpins
Equality law). Listening disadvantage is quantified by each type of need according to a review of the speech
perception studies evidence base. Holistic design and management of the classroom is considered, by
quantifying the prevalence of children with SHCN; examining classroom management strategies andprovision of assistive listening systems; accounting for teacher’s voice protection; and considering otherdesign aspirations (such as sustainability) alongside acoustic design objectives.
Keywords: Classrooms, Inclusion, Special Educational Needs, Access, Speech Perception

1. INTRODUCTION
New and refurbished school buildings in England and Wales should comply with criteria for
acoustics set out in Building Bulletin 93 (BB93) (1). In accordance with UK law (2), schools are
required to make ‘reasonable adjustments’ to put children with disabilities on a more level footing.
The Government’s specification for new and refurbished school buildings (3), requires that ‘People
with disabilities, including those with a hearing impairment, must not be placed at a disadvantage by
the design of the Building’.
School Premises Regulations (SPR) guidance (4) states that ‘pupils with special needs may need
to be taught in spaces with lower noise levels and shorter reverberation times than in mainstream
classrooms’, and ‘where pupils with special needs are taught in mainstream schools, the acoustics ofthe spaces where they are taught may need to be enhanced to the same standards as those special
units’, and ‘provision will usually be required to teach these pupils in smaller groups so that noisefrom other pupils is lower and the distance between teacher and pupil is minimised ’. Acoustics ofSchools: A Design Guide (5) also acknowledges that pupils with SHCN should be taught in rooms
which meet enhanced acoustic criteria and that ‘occasionally specialised provision may be directly
attached to a mainstream class in the form of a ‘quiet room’ leading from the classroom’. The
Government specification (3) requires the school design to ‘ensure and demonstrate that all layouts
allow for disabled pupils to be able to access all activities on offer in at least one space of each typeor within each suite’. This suggests that it would be acceptable to provide a quiet room or SEN roomachieving the enhanced acoustic criteria within each teaching suite, and to send children with SHCN
to these rooms to access the majority of their teaching and learning. However, whether this practice
is inclusive is questionable (6). The acoustic strategy for inclusion in mainstream classrooms is
1
2

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emma@andersonacoustics.co.uk
shieldbm@lsbu.ac.uk

complicated by the following:a) The current funding crisis in UK schools (7) has diminished resources to teach in small groups.
b) It is difficult to achieve the enhanced reverberation time criteria in mainstream classrooms,
particularly low frequency reverberation time, given competition for wall space, and trends for
exposed soffits for sustainability reasons.
c) The UK Government’s budget does not currently allow for the enhanced BB93 acoustic criteria
for pupils with SHCN to be provided in mainstream classrooms.
b) Natural ventilation remains a priority, with indoor ambient noise levels up to 40-45 dBA.
d) Assistive listening systems are not provided per se in general mainstream classrooms (8).
e) Given the current prevalence, all mainstream classrooms should anticipate the presence ofchildren with SHCN.

2. Criteria
2.1
Acoustic Criteria
In order to comply with the Building Regulations (9) and the Government Specification (3), newschool buildings in the UK must achieve the standards in BB93 (1) as summarised in Table 1 (fornaturally ventilated classrooms). The criteria for refurbished school buildings must be achieved tocomply with the Government Specification (3). ‘Rooms intended specifically for children with SHCN’in mainstream schools include Special Education Needs (SEN) rooms and Designated Units orSpecialist Resource Provision. The enhanced acoustic criteria for these rooms are practicable forsmaller SEN rooms with low occupancy and high staff-to-student ratios, and a short communication
distance. Ambient noise level criteria are based on an assumed teacher voice level and communication
distance to obtain sufficient signal-to-noise ratio (SNR). SNR is also stipulated in the BATOD (10)and 2005 ASHA (11) guidelines.
Table 1 – BB93 acoustic criteria for naturally ventilated classrooms

Notes: a) APS = Alternative Performance Standard. b) BATOD (10) compliant. BATOD also recommends 20 dB SNR at 125-750 Hz,
and 15 dB SNR at 750-4000 Hz; c) ASHA (11) compliant. ASHA also recommends 15 dB SNR.

3. Prevalence of children with SHCN in mainstream schools
SHCN covers several different types of special need as outlined in Figure 1. BB93 (1) states “Inorder to fulfil their duties under the Equality Act 2010, school client bodies should anticipate theneeds of deaf and other disabled children as current and potential future users of the school ”. The
Equality Act also covers age discrimination (for example young children) and children with English
as an additional language (EAL) (2). Both of these groups may be disadvantaged by poor acoustic
conditions in the classroom and may also be considered as having SHCN. In order to address the5967

knowledge gap in this area, an assessment of the prevalence of children with SHCN in mainstream
classrooms was undertaken following detailed analysis of Government statistics (12, 13), see Figure1.
Overall prevalence of children with SHCN in mainstream schools (all needs combined) is 6% (seeFigure 2). The breakdown is 6.8 for primary schools and 5.6% for secondary schools. That is anaverage of just over 1 child per average sized secondary school classroom, and up to 2 per average
sized primary school classroom. The most common forms of SHCN in mainstream schools are Speech
Language and Communication Needs (3% of entire mainstream population), Specific Learning Need,which includes AD/HD and Dyslexia (2%) and Autistic Spectrum Disorder (1%). Hearing impairment
specifically has a very low level of prevalence of 0.3%, or 0.1 children per classroom, which is lessthan 1 child per average sized primary school and less than 3 per average sized secondary school.
There is a higher prevalence of children with EAL as shown in Figure 1. Children with temporary
hearing loss account for up to 4 per average sized classroom (14). Clearly primary schools will alsoneed to consider enhanced acoustic criteria which may apply to younger c hildren who are more
impacted by poor acoustics.

Figure 1 – Prevalence of SHCN in average size mainstream classrooms (primary and secondary)

Figure 2 – Prevalence of SHCN in mainstream schools (by specific need)

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Whilst the attainment gap for hearing impaired students achieving expected grades is significant(15), it is smaller than for other forms of SHCN. National progress scores for English and Maths (16)reveal a gap of up to 10% for hearing impaired children, compared to 25% for ASD and 30% forSpeech Language and Communication Needs. Whilst the use of averages should be treated withcaution and prevalence will vary with individual school location and circumstances, the analysis
reveals that the need to provide appropriate acoustic conditions for children with SHCN should be
anticipated in every classroom. It also shows that, given the low prevalence of SHCN and the very
low prevalence of children with hearing impairment, preferential seating and use of personal listening
aids may be feasible classroom management strategies to help improve acoustic conditions and hence
access to learning. Where there is a significantly larger proportion of children with SHCN in a school
cohort, this may suggest the need for a Specialist Resource Provision or Designated Unit.

4. CLASSROOM MANAGEMENT & RESPONSIBILITY
The major effect of poor acoustics in classrooms is the reduction of speech intelligibility. Acoustics
of Schools: A Design Guide (5) recognises that ‘effective classroom management by the teacher iscritical in ensuring that the pupils can have access to all that is spoken ’, but ‘classroom management
alone cannot ensure adequate speech communication’. It identifies types of personal listening aids
which may be used to ensure pupils with SHCN are able to hear the teacher and their peers. BATOD(10) also recognises the importance of classroom management and personal listening aids:“personal listening aids enhance SNR, reduce impact of unhelpful reverberation,
particularly when a headset is used by the speaker” IoA/ANC Design Guide (5)“if ambient noise level [SNR] is controlled then high RT has a minimal effect whena personal listening aid is in skilled use and set up properly ” BATOD (10)It can be concluded that provision of good listening conditions for children with SHCN inmainstream classrooms is the combined result of the acoustic design, provision of personal listening
aids and classroom management. In an attempt to identify acoustic de sign responsibility, theresponsibilities for each listening mode (17) have been assigned in Table 2, together with common
classroom management strategies. This exercise reveals that the primary responsibility of the acoustic
design is to ensure teacher-to-student speech communication in quiet. Good control of noise andreverberation time (as required to support this listening mode for SHCN) will also help to control
buildup of classroom activity noise to support other listening scenarios, and other non -spoken learningmodes.
Table 2 – Proposed classroom design and management responsibility

Notes: a) Teacher to gather younger children on carpet/mat for critical listening scenarios; b) Teacher to use visual cues to quieten
an active class before speaking; c) Address small groups/individuals and use roaming tactics around classroom. d) Teacher to repeat
child’s answer to secure speech intelligibility5969

5. REVIEW OF THE EVIDENCE
In order to help establish appropriate acoustic criteria for children with SHCN to ensure that the
acoustic design of mainstream classrooms does not place people with disabilities at a disadvantage,a detailed review of the seminal research studies on speech perception has been undertaken. In a novel
approach which seeks to quantify the disadvantage, it is proposed to examine the listening gap, ie thedifference in average % speech perception scores between the impaired group and non-impaired groupfor each type of SHCN. This reveals the ‘inherent gap’ of the impaired groups (under ideal acoustic
conditions), and the additional ‘acoustic gap’ caused by non-ideal acoustic conditions. It also helps toreveal consistencies between studies, as systematic errors/variations between studies are reduced.
Significance tests between different groups and conditions are also examined, to help establish
reasonably adjusted acoustic criteria for critical listening conditions in quiet which are robust,practicable and improve access to the mainstream classroom by disabled children.
The review was screened to include those studies which quantified speech perception by subjective
testing in realisable acoustic conditions, to reflect speech perception for teacher-to-student speechcommunication in critical listening scenarios, when classroom management is well considere d.
Unfortunately, none of the screened studies examined listening performance via a personal listening
aid, which is now commonplace.
The detrimental impact of noise on aspects of children’s learning performance other than speechcommunication (for example reading ability, attention and memory tasks) in noisy conditions(typically 65 dBA babble) are well studied, and it is generally agreed that children with SEN are
significantly more affected than their typically developing peers (18). Furthermore, occupied
classroom noise levels of 50-70 dBA have been shown to be associated with higher averageoccurrences of repetitive behaviours by children with ASD, compared to quieter classrooms (19).
Results of these studies are beyond the scope of this paper, which focuses on the impact of acoustics
on children’s speech perception in critical listening scenarios (quiet). However, they highlight theneed to consider classroom management carefully when children with SHCN are working on tasks inmainstream classrooms.
5.1 Factors to consider
It is well known that the most important parameter affecting speech intelligibility is the signal -tonoise ratio (SNR), and that this parameter is more important than reverberation time, although bothfactors affect speech intelligibility (20,21).
Ambient noise level criteria are commonly derived based on the required SNR, and assumptions
about the teacher’s voice level and communication distance to the listener (21,22). However it isimportant to ensure these assumptions account for classroom management strategies and provision of
personal listening aids. Recent analysis (14) has shown that the occupied critical listening activity
noise levels (students quiet, attentive and listening to the teacher), in average sized classrooms
achieving 40 dB indoor ambient noise level, are expected to be up to 44 dBA. All studies in thefollowing review used multitalker babble (meaningful speech) as the noise source, which may
represent worst-case noise masking, compared to stationary or environmental ambient noise sources.
The avoidance of very short reverberation times is necessary in real settings, where there is abalance to be achieved between control of reverberation time (to control activity noise levels as well
as for good speech perception), and providing the early reflections necessary to support the teacher’svoice level and hence reduce vocal effort. Near ideal conditions for speech perception can be achieved
over the range 0.2-0.5 s (20) given sufficient SNR, with acceptable conditions for normal hearing
children achieved in reverberation times up to 0.9 s. This must be balanced with minimum
recommended reverberation times of around 0.5 seconds for unoccupied classrooms to support
teachers’ voice (14,21) . Recent analysis (14) reveals ‘Raised’ vocal efforts equivalent to 65 to 67 dBA
at 1 m are typical for teachers addressing a quiet and attentive class in classroom reverberation timesof around 0.5 seconds (22, 33, 34), which equates to at least 59 dBA at a typical worst-case listening
distance of 6 m in secondary schools, indicating that +15 dB SNR is achievable throughout a typicalclassroom with a 40 dB ambient noise level, and +20 dB SNR is achievable at preferential seating5970

locations of up to 1.5 m.
Control of reverberation time at low frequency is also cited as being important for hearing impaired
listeners (5, 10) who may be reliant on their residual hearing at low frequency and more affected by
upward spread of masking. However even after consulting educational audiologists and BATOD who
informed the BB93 criteria, it has proved difficult to find experimental speech perception evidence
which examines the variation of low frequency reverberation time in isolation to support this, orquantifies the importance of low frequency room reverberation when a personal listening aid is inskilled use.
5.2 Quality of Evidence
The majority of speech perception studies which met the screening criteria (22-28) examined thelistening disadvantage of children with hearing loss (minimal-to-moderate n = 4, severe to profoundn = 2), and only two of these 6 studies looked at variation of reverberation time in addition to SNR.
However children with hearing loss represents just 0.3% of the mainstream school population. One
study looked at EAL children (19% of mainstream population) but only examined SNR under anechoic
conditions (however inferences have been made from the hearing impaired studies which examinedboth SNR and RT, to obtain a recommended signal-to-noise ratio for ideal reverberation times). One
study looked at effects of both reverberation time and SNR on age of pupils (for realistic acoustic
conditions typical of a modern compliant acoustic design), which is applicable to primary school
populations.
Many studies tested at low signal-to-noise ratios, not representative of teacher-to-student
communication in well managed critical listening scenarios, and focused on longer, non-compliant
reverberation times. Not surprisingly, test conditions of 0.9-1.2 seconds RT revealed average wordrecognition deficits (compared to listening under 0.3-0.4 s RT) of 15-20% for hearing impaired
children. Normal hearing children were similarly affected when listening to individual word tests, butthere was no significant disadvantage to listening at 0.9 s RT when they listened binaurally to test
sentences at good SNRs. This suggest that reverberation times of around 1.0 s and above are unsuitable
not only for hearing impaired children, but also for normal hearing children w ith lower language
acquisition skills who may not be familiar with the speech material and are unable to make use of theredundancy in sentential speech (for example young children or children with EAL or APD).
There is a distinct lack of speech perception evidence for children with other needs (SLCN, AD/HD,
ASD, APD, visual impairment) (14) and therefore detailed results for these needs cannot be reported
as part of this review. Studies for these groups (19, 29-32) tend to focus on benefits from using
personal listening aids, and the few studies which do address acoustic conditions have carried out
experiments in low SNR conditions (-5 to + 5 dB) and have not considered variation of reverberation
time. There is some evidence (30) that high functioning students with ASD or Asperger ’s syndrome
require up to 3.5 dB higher SNR to achieve equal speech perception and therefore the inference is totarget a classroom SNR of at least +15 dB for this group. The general lack of evidence for these needs
is a concern, considering that they form the vast majority of the SHCN population in mainstream
schools.
5.3 Results
Detailed results of the review are discussed in a previous paper (14). The summary in Figure 3
presents the total listening disadvantage as the inherent % gap (ideal near anechoic, quiet acoustic
conditions), and additional acoustic % gap (for the recommended acoustic condition). As expected,
groups with minimal hearing loss, EAL, and younger learners exhibit the smallest inherent listening
gap of less than 5%, which is not considered significant, since this gap was comparable to the standard
deviation reported within the group. However children with a significant hearing impairment weremore severely disadvantaged. Children with severe-to-profound hearing loss (listening without apersonal aid) experienced the greatest disadvantage compared to their typical hearing peers, with an
inherent listening gap of up to 12% and a total listening disadvantage of 30% or more whenreverberation times were 0.6 seconds or greater (14, 24).

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Despite variations in the experimental studies and presentation of the speech testing material,
results are remarkably consistent between the studies which examined the same need. An inherent gapof 6-7% was obtained for children with mild-to-moderate hearing loss. An inherent gap of 9-12 % was
obtained for children with severe-to-profound hearing loss.
Whilst the ideal acoustic conditions associated with the inherent listening gap may not be
reproducible naturally throughout a room, use of personal listening aids with close microphone
technique may help to approach these conditions by capturing direct sound in the near field (excluding
reverberation) and amplifying to achieve +20 dB SNR. According to Finitzo-Hieber & Tillman’s 1978
study (23) the ‘acoustic gap’ under 0.3-0.4 s RT and +20 dB SNR is an additional 7%, however it ispossible that this gap would reduce with the benefit of modern digital hearing aids, binaural listening,
and using sentential speech (rather than individual words) as test material. For the more recent studies
of children with severe-to-profound loss who benefitted from these advantages, no acoustic gap wasapparent, provided that +20 dB SNR and 0.3 s RT was maintained.

Figure 3 – Summary results of speech perception evidence review (14)

6. CONCLUSIONSThis review was undertaken to explore how classroom acoustics criteria might be reasonably
adjusted to ensure children with SHCN are not placed at a disadvantage in mainstream classrooms.
On average, all mainstream primary and secondary classrooms, need to anticipate the presence ofchildren with SHCN, who require improved acoustic conditions to avoid being placed at a
disadvantage.
On balance, a reasonably adjusted criterion for reverberation time (to protect teachers’ voice level
whilst achieving good speech intelligibility for SHCN) is considered to be 0.5 seconds unoccupied,corresponding to around 0.45 seconds occupied, in combination with +15 dB SNR. This criterion ispracticably achievable in BB93 compliant naturally ventilated typical mainstream classrooms with anambient noise level of up to 40 dBA. Pupils with hearing impairment will benefit from even shorter
effective reverberation times and boosted +20 dB SNR via skilled use of a personal listening aid.
The reasonably adjusted acoustic criteria for mainstream classrooms proposed in this paper should
be further developed by carrying out further research into the impact (or otherwise) of low frequency
reverberation time in rooms when a personal listening aid is being used, and addressing the lack ofspeech perception evidence for under-studied SHCN needs beyond hearing impairment.

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