Bridget Shield

THE EFFECTS OF NOISE ON CHILDREN AT SCHOOL: A REVIEW

This paper reviews research on issues relating to the effects of noise on children at school. Areas covered include factors affecting speech intelligibility in the classroom; the effects of environmental and classroom noise on childrens academic performance; childrens annoyance due to noise; and surveys of classroom noise levels. Consistencies and discrepancies between the results of various studies are highlighted. The paper concludes by outlining some current acoustic standards for classrooms.

The effects of environmental and classroom noise on the academic attainments of primary school children.

While at school children are exposed to various types of noise including external, environmental noise and noise generated within the classroom. Previous research has shown that noise has detrimental effects upon childrens performance at school, including reduced memory, motivation, and reading ability. In England and Wales, childrens academic performance is assessed using standardized tests of literacy, mathematics, and science. A study has been conducted to examine the impact, if any, of chronic exposure to external and internal noise on the test results of children aged 7 and 11 in London (UK) primary schools. External noise was found to have a significant negative impact upon performance, the effect being greater for the older children. The analysis suggested that children are particularly affected by the noise of individual external events. Test scores were also affected by internal classroom noise, background levels being significantly related to test results. Negative relationships between performance and noise levels were maintained when the data were corrected for socio-economic factors relating to social deprivation, language, and special educational needs. Linear regression analysis has been used to estimate the maximum levels of external and internal noise which allow the schools surveyed to achieve required standards of literacy and numeracy.

Acoustical barriers in classrooms: the impact of noise on performance in the classroom

There is general concern about the levels of noise that children are exposed to in classroom situations. We report the results of a study that explores the effects of typical classroom noise on the performance of primary school children on a series of literacy and speed tasks. One hundred and fifty eight children in six Year 3 classes participated in the study. Classes were randomly assigned to one of three noise conditions. Two noise conditions were chosen to reflect levels of exposure experienced in urban classrooms (Shield & Dockrell, 2004): noise by children alone, that is classroom–babble, and babble plus environmental noise, babble and environmental. Performance in these conditions was compared with performance under typical quiet classroom conditions or base. All analyses controlled for ability. A differential negative effect of noise source on type of task was observed. Children in the babble and environmental noise performed significantly worse than those in the base and babble conditions on speed of processing tasks. In contrast, performance on the verbal tasks was significantly worse only in the babble condition. Children with special educational needs were differentially negatively affected in the babble condition. The processes underlying these effects are considered and the implications of the results for children’s attainments and classroom noise levels are explored.

Children’s perceptions of their acoustic environment at school and at home

This paper describes the results of a large-scale questionnaire survey that ascertained childrens perceptions of their noise environment and the relationships of the childrens perceptions to objective measures of noise. Precision, specificity, and consistency of responding was established through the use of convergent measures. Two thousand and thirty-six children completed a questionnaire designed to tap (a) their ability to discriminate different classroom listening conditions; (b) the noise sources heard at home and at school; and (c) their annoyance by these noise sources. Teachers completed a questionnaire about the classroom noise sources. Children were able to discriminate between situations with varying amounts and types of noise. A hierarchy of annoying sound sources for the children was established. External L(Amax) levels were a significant factor in reported annoyance, whereas external L(A90) and L(A99) levels were a significant factor in determining whether or not children hear sound sources. Objective noise measures (L(A90) and L(A99)) accounted for 45% of the variance in childrens reporting of sounds in their school environment. The current study demonstrates that children can be sensitive judges of their noise environments and that the impact of different aspects of noise needs to be considered. Future work will need to specify the factors underlying the developmental changes and the physical and location dimensions that determine the school effects.

Noise in open plan classrooms in primary schools: a review.

This paper presents a review of research carried out in the past 40 years into various aspects of noise in open plan classrooms. The emergence of open plan classroom design in response to progressive educational reforms is discussed. A limited amount of evidence of the effects of noise in open plan classrooms is presented. Surveys of both background and intrusive noise levels in open plan classrooms are summarized and compared. Differences between noise levels in open plan and enclosed classrooms are also considered. Recommended noise limits and acoustic design criteria for open plan classrooms are discussed, together with some current international standards. The paper concludes with a discussion of appropriate noise control measures to reduce noise and maximize speech intelligibility and speech privacy in open plan classrooms.

The prediction of speech intelligibility in underground stations of rectangular cross section

Long enclosures are spaces with nondiffuse sound fields, for which the classical theory of acoustics is not appropriate. Thus, the modeling of the sound field in a long enclosure is very different from the prediction of the behavior of sound in a diffuse space. Ray-tracing computer models have been developed for the prediction of the sound field in long enclosures, with particular reference to spaces such as underground stations which are generally long spaces of rectangular or curved cross section. This paper describes the development of a model for use in underground stations of rectangular cross section. The model predicts the sound-pressure level, early decay time, clarity index, and definition at receiver points along the enclosure. The model also calculates the value of the speech transmission index at individual points. Measurements of all parameters have been made in a station of rectangular cross section, and compared with the predicted values. The predictions of all parameters show good agreement with measurements at all frequencies, particularly in the far field of the sound source, and the trends in the behavior of the parameters along the enclosure have been correctly predicted.

Computer prediction of sound distribution in enclosed spaces using an interference pressure model

Abstract Current computer models for the prediction of sound distribution in enclosed spaces use intensity to represent the sound radiating from various sound sources. This approach reduces the amount of information to be calculated and makes the modelling system simple enough to be represented on a desktop computer. With the advent of new computer technology it has now become practical to model sound distribution using pressure, including phase information, in empty enclosed spaces. Measurements taken have shown that in empty enclosed spaces sound interference can be observed both close to and, to a lesser extent, far from the sound source. Independent measurements have also shown the measured sound pressure level at the same floor position to fluctuate significantly with receiver height. A comparison of predictions by both an intensity and a pressure based model showed that the general shape and accuracy of the propagation curves predicted by the pressure model were similar to those measured, whereas the intensity based model gave curves that did not predict interference effects.

Modelling of sound fields in enclosed spaces with absorbent room surfaces. Part I: performance spaces

This paper introduces a three-part report describing research into the use of Millington absorption coeAcients in the computer modelling of sound fields in enclosed spaces with absorbent room surfaces. The historical background to the prediction of reverberation time is presented together with three types of computer models used in the investigation. In part one, the computer models are described, the Millington reverberation time formula is validated, Millington absorption coeAcients are derived and the sound field in a concert hall is predicted. This enables the accuracy of the three types of computer models to be compared and the eAect of applying diAerent absorption coeAcients to be studied. Part two of the report consists of an extensive investigation into the prediction of reverberation time in multiple configurations of an experimental room with absorbent material partially covering the room surfaces. This determined the accuracy of reverberation time formulae and the computer models using both standard and Millington absorption coeAcients under controlled conditions. The final part contributes a verification of the accuracy of the predictions using Millington absorption coefficients in a factory space with a barrier installed, and a refined diAraction model based on a ray-tracing model. # 1998 Elsevier Science Ltd. All rights reserved.

A survey of acoustic conditions and noise levels in secondary school classrooms in England

An acoustic survey of secondary schools in England has been undertaken. Room acoustic parameters and background noise levels were measured in 185 unoccupied spaces in 13 schools to provide information on the typical acoustic environment of secondary schools. The unoccupied acoustic and noise data were correlated with various physical characteristics of the spaces. Room height and the amount of glazing were related to the unoccupied reverberation time and therefore need to be controlled to reduce reverberation to suitable levels for teaching and learning. Further analysis of the unoccupied data showed that the introduction of legislation relating to school acoustics in England and Wales in 2003 approximately doubled the number of school spaces complying with current standards. Noise levels were also measured during 274 lessons to examine typical levels generated during teaching activities in secondary schools and to investigate the influence of acoustic design on working noise levels in the classroom. Comparison of unoccupied and occupied data showed that unoccupied acoustic conditions affect the noise levels occurring during lessons. They were also related to the time spent in disruption to the lessons (e.g., students talking or shouting) and so may also have an impact upon student behavior in the classroom.

A survey of acoustic conditions in semi-open plan classrooms in the United Kingdom

This paper reports the results of a large scale, detailed acoustic survey of 42 open plan classrooms of varying design in the UK each of which contained between 2 and 14 teaching areas or classbases. The objective survey procedure, which was designed specifically for use in open plan classrooms, is described. The acoustic measurements relating to speech intelligibility within a classbase, including ambient noise level, intrusive noise level, speech to noise ratio, speech transmission index, and reverberation time, are presented. The effects on speech intelligibility of critical physical design variables, such as the number of classbases within an open plan unit and the selection of acoustic finishes for control of reverberation, are examined. This analysis enables limitations of open plan classrooms to be discussed and acoustic design guidelines to be developed to ensure good listening conditions. The types of teaching activity to provide adequate acoustic conditions, plus the speech intelligibility requirements of younger children, are also discussed.