Essex Study Classroom Acoustics: David Canning London Borough Newham d.canning@ucl.ac.uk

Overview Purpose of the Essex study Practical aspects of the study Principal acoustic findings

The question posed by Essex CC Purpose of the Study: How should we refurbish mainstream classrooms so that they are acceptable listening environments for hearing impaired children. Supplementary questions: What is the impact of modifying the physical acoustical performance on the occupied class engaged in learning? Is there a measureable acoustic impact? Is there an impact on teaching and learning? -If there is an impact, then how does this information contribute to the specification and design of teaching spaces?

Introduction

Introduction

Three principles: Experimental Approach Generalisable Achievable We chose to design an approach that would be useful in determining causality Generalisable Change one variable only Staff and children blind to condition Analysis of acoustic data will be carried out blind to the condition Achievable Given all the constraints, time, possible disruption, cost, equipment and support from the school and LEA.s We decided to undertake an experimental approach to answering these questions:

Classroom Selected Typical cellular classrooms, typical of the majority of school buildings for children 11yrs – 16yrs in the UK:

Practical Aspects of the study Chose one curriculum area: Mathematics. 4 Identical classrooms Sound treatments that visually as similar as possible. The school kindly redecorated the rooms. Ability to change the acoustic performance of all classrooms in the study over a weekend Staff willing to tolerate and eventually ignore measurement equipment, observation and repeated questionnaires over a period of at least 6 months Mathmatics, or math, one of the most studied subject areas and most consistently taught.

Classroom Acoustic Treatment Before Hard walls and ceiling. Windows on two sides. Carpet bonded to concrete floor. Area = 50sqm After Suspended ceiling added. Acoustics Tiles and Wall Panels. New lights and a coat of paint to all rooms.

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

Schedule of Room Treatments Experimental Condition British Association of Teachers of the Deaf (batod) Rt <=0.4sec 125Hz – 4Khz BB93 classrooms designed for use with HI Mid Frequency (500Hz – 2Khz) mean = 0.4sec BB93 (500Hz – 2Khz) mean = 0.8sec Untreated (Rt > 0.9s mid frequencies) Pre test (all untreated) Classrooms A,B,C& D Phase 1 Classroom A Classroom B Classroom C Classroom D Phase 2 Phase 3

Selection of Groups 10 teachers Teacher class combinations Children 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 and class combinations were included in the study Groups included grades 7 (11yrs) to 10 (14yrs) Top, middle and bottom ability sets Children 400 children included in the study Including 17 children with hearing impairment

Outcome measures -Occupied Sound Levels, -Signal to noise levels Room Unoccupied Physical Acoustics: Rt, EDT, C50 etc Functional Acoustics Signal to Noise measurements sound levels Teacher and Child ratings LIFE UK Hearing performance: Speech discrimination Interviews and observations Expert panels

Principal acoustics findings 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’ 0.4 0.8

L90 plotted against RT (reverberation time) Each of the tree classrooms Ultra strict teacher 7 Teachers Control Classroom Ultra relaxed teacher

Predictor Importance

Predictor Importance

65dB exceedence level

The significance of acoustic absorbency (short reverberation times) On Functional Signal TO Noise Levels 0.4

Pupil views

Ideal Classroom for Group Work http://eastafrica.usaid.gov/images/Photo.300.1407.aspx