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Presentation on theme: "CLASSROOM ACOUSTICS AND (SIGNAL) ENHANCEMENT STRATEGIES DAVID CANNING HEAR2LEARN Management of APD."— Presentation transcript:


2 Educational Video 1953

3 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

4 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

5 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

6 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)

7 Reverberation time Binaural Headphone test, 217 children 17 adults, constant Signal to Noise levels Yang and Bradley 2009



10 Room modes (standing waves)


12 Noise Levels in Classrooms Greenland (2009)

13 Signal to Noise Sato and Bradley 2006

14 Signal to Noise Sato and Bradley 2006 Signal to noise distributions in 28 classrooms

15 Age and Signal to Noise Level Bradley and Sato (2008) 41 classrooms and 2285 individual speech recognition tests

16 PAVT (Paediatric Audiovisual Test) Work in progress: 48 children in 4 classrooms S represents a child whose performance is adversely affected by noise

17 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)

18 UK Acoustic Standards

19 USA UKUSA Standards (Reverberation time and Background Noise Levels) Government Approved building Document E and BB93 specifically (many stakeholders and extensive public consultation) ANSI/ASA (many stakeholders and public consultation?) Enforced byLocal Building Control Officers Local Building Inspectors Web oustics Google ANSI

20 Noise Teaching spaces used by children with hearing impairment or are deaf or have special hearing requirements BB93 section 1 Anticipated Revisions

21 Reverberation Time Teaching spaces used by children with hearing impairment or are deaf or have special hearing requirements 0.4s 125Hz – 4kHz 0.4s 125Hz – 4kHz Anticipated Revisions

22 Alternative acoustic standards in the absence of child specific information BB93 Section 6

23 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

24 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 Selection of Groups

25 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 Mid Frequency (500Hz – 2Khz) mean = 0.8sec Untreated (Rt > 0.9s mid frequencies) Pre test (all untreated) Classroom AClassroom BClassroom CClassroom D Phase 1Classroom AClassroom BClassroom CClassroom D Phase 2Classroom CClassroom AClassroom BClassroom D Phase 3Classroom BClassroom CClassroom AClassroom D Schedule of Room Treatments

26 Room Unoccupied Physical Acoustics: Rt, EDT, C 50 etc Functional Acoustics Signal to Noise measurements sound levels Teacher and Child ratings LIFE UK Hearing performance: Speech discrimination Interviews and observations Expert panels Outcome measures Reverberation Time & Occupied Sound Levels Topic of this talk

27 Classroom noise and Sound Treatment Original Treated

28 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

29 Acoustic treatment and classroom noise c 9dB Reduction in Background Noise from current standard to proposed standard for children with ‘special hearing requirements’ Very significant changes in occupied sound levels: 17dB from untreated to highest level of treatment (1.2 s to 0.4s)

30 Acoustic treatment and classroom noise Herriot Watt Study (70 Primary Schools) David McKenzie Considerable reductions in occupied noise levels reported following acoustic treatment to reduce reverberation times. Average Background Noise Levels UntreatedTreated Room Unoccupied Pupils Silent Pupils Working

31 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.

32 Sample Important Communication Events:

33 Signal to noise in a good primary classroom: Teacher talk School 1: Strong control of class

34 Comparison of findings Teacher talk: School 2: Sound field system

35 Group work School 1 Signal to noise in a good primary classroom

36 Group Work: Comparison School 2

37 Recap c 9dB Reduction in Background Noise from current standard to proposed standard for children with ‘special hearing requirements’

38 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’.

39 Changes in Education

40 Exemplar Rural Secondary School

41 Exemplar Schools

42 Flagship Buildings Bexhill Academy

43 Noise Levels in Open Plan Classrooms Greenland (2009)

44 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 £ cost of a typical classroom refurbishment.

45 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

46 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.

47 A selection of current classroom products Flat Panel Infra Red systems Traditional Loudspeaker Infra Red systems

48 Modelling Classroom Acoustics Available from





53 Enhancement of the signal: Individual Approaches Personal FM systems:  Phonak Edulink and iSense Individual Receivers either ear worn or ‘ipod’ style Fm transmitter

54 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

55 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

56 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.

57 Miss Bradley and Professor McDaniel

58 Selected References Bradley, J. S. and H. Sato (2008). "The intelligibility of speech in elementary school classrooms." J Acoust Soc Am 123(4): 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): 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): 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): 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): 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): Shield, B. and J. E. Dockrell (2004). "External and internal noise surveys of London primary schools." J Acoust Soc Am 115(2): Shield, B. M. and J. E. Dockrell (2003). "The Effects of Noise on Children at School: A review." Building Acoustics 10(2): 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): 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): Tiesler, G. and M. Oberdoerster (2008). "Noise - A stress factor? Acoustic ergonomics at schools." J Acoust Soc Am 123(5): 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): Computer modelling then navigate to downloads/classroom_simulations ( or type in


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