UMEÅ UNIVERSITY MEDICAL DISSERTATIONS New Series No ISSN ISBN - PDF

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UMEÅ UNIVERSITY MEDICAL DISSERTATIONS New Series No ISSN ISBN From the Department of Public Health and Clinical Medicine, Occupational Medicine, Umeå, Sweden CLASSROOM NOISE

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UMEÅ UNIVERSITY MEDICAL DISSERTATIONS New Series No ISSN ISBN From the Department of Public Health and Clinical Medicine, Occupational Medicine, Umeå, Sweden CLASSROOM NOISE -Exposure and subjective response among pupils- Pär Lundquist CLASSROOM NOISE -Exposure and subjective response am ong pupils- Pär Lundquist, Occupational Medicine, Dept of Public H ealth and Clinical Medicine; Umeå University, SE Um eå, Sw eden. ABSTRACT In Sweden, all children must have access to education of equal value and the curriculum points out the importance of a good environment for developm ent and learning. Modern working methods differ a lot from the traditional. Teaching nowadays is focused on problem-solving. Students are more interactive, working in groups and projects. The teacher has become a supervisor, guiding not lecturing. Hearing loss, vegetative responses, biochemical effects, speech interference, behavioural effects and subjective reactions are all part of the problem of noise exposure. There is no unequivocal method of assessing noise and its effects. The most common method of noise assessment and appraisal of negative noise reactions is based on m easurem ent of acoustic characteristics. Recommendations made and targets set by authorities are often stated in terms of equivalent A- weighted sound level L (A)eq. The purposes of this thesis have been to increase knowledge of noise exposure in classrooms and the subjective response among pupils and also to identify factors of special importance when assessing negative noise effects in the classroom. The work consists of five separate articles considering different aspects of sound exposure and its adverse effects on pupils in school: three field studies, one article on development of a mood-rating instrum ent and one laboratory study. Analyses of exposure were based on equivalent sound levels and subjective responses were evaluated using ratings on a visual analogue scale and forced choice questions. The results point to speech and structure-borne sounds as the most annoying sound sources to the pupils. Annoyance will increase with variability of the exposure. This is typical of the character of structure-borne sounds such as footsteps, scraping of chairs and tables and slamming of doors, as well as of speech. The background sound level exposure levels in the classrooms ranged between 33 and 42 db(a)eq. The background sound in about 2 /3 of the classrooms investigated was considered to be LFN. Pupils exposed to high LFN levels were not more annoyed than pupils exposed to low LFN levels. The activity sound level ranged between 47 and 69 db(a)eq. These are levels that must be considered high for a work environment such as the school, which has at all times to be conducive to steady concentration, communication and learning. The risk of hearing damage during this exposure must be concidered as low. The thesis also describes the development of a mood-rating instrument to identify effects of noise and other aspects of the classroom environment. The questionnaire is easy to administer, takes little time to complete and is therefore well suited to studies in field settings. The ratings of annoyance in the classroom correspond to the verbal definition Somewhat annoying - Rather annoying . Data from the field studies does not support the idea that the negative responce will increase with higher sound levels. In the laboratory setting, a relationship between increasing sound level and increase in rated annoyance was displayed. Keywords: school, teaching, students, annoyance, children, sound, mood UMEÅ UNIVERSITY MEDICAL DISSERTATIONS New Series No ISSN ISBN From the Department of Public Health and Clinical Medicine, Occupational Medicine, Umeå, Sweden CLASSROOM NOISE -exposure and subjective response am ong pupils AKADEMISK AVHANDLING som med vederbörligt tillstånd av Rektorsämbetet vid Umeå Universitet för avläggande av medicine doktorsexamen, kommer att offentligen försvaras i Stora föreläsningssalen, ALI Norr, torsdagen den 5 juni 2003, klockan av Pär Lundquist Fakultetsopponent: Docent Rauno Pääkkönen, Tampere Regional Institute of Occupational Health, Tam pere, Finland UMEÅ UNIVERSITY MEDICAL DISSERTATIONS New Series No ISSN ISBN From the Department of Public Health and Clinical Medicine, Occupational Medicine, Umeå, Sweden CLASSROOM NOISE -Exposure and subjective response among pupils- Pär Lundquist * O V Umeå 2003 Copyright 2003 by Pär Lundquist ISBN Printed in Sweden by Solfjädern Offset AB, Umeå Till örat genom luftens vågor fortplantar sig livets stora frågor. Men livets stora svar, jag undrar vilken väg dom tar. Tage Danielsson To me INTRODUCTION 1 BACKGROUND 3 Noise 3 Appraisal of noise 3 Noise exposure in classrooms 5 Sound levels in classrooms 6 Effects of noise 7 Hearing loss 7 Vegetative responses and biochemical effects of noise 8 Speech interference 8 Behavioural effects of noise 10 Subjective reactions 12 Non-acoustical factors 13 Assessing subjective response to noise 14 AIMS 15 METHODS 16 Paperi 16 Paper II 17 Paper III 17 Paper IV 18 Paper V 18 Environments 18 Participants 19 Analysis of exposure 20 Effects 21 Statistics 23 Paper I 23 Paper II 23 Paper III 23 paper IV 24 Paper V 25 RESULTS 26 Paper I 26 Paper II 28 Paper III 30 Group 1 30 Group 2 30 Paper IV 32 Sound levels 32 Class room sound levels and background sound levels 33 Sound levels and type of subject 33 Noise levels and number of pupils 34 Sound levels and grade of education 34 A multiple comparison 35 Effect 36 Paper V 37 Annoyance 37 Effort 39 Performance 40 Task orientation 40 Inattentiveness 40 Outliers 40 DISCUSSION 42 Noise exposure in classroom 42 Self reported mood 45 Annoyance 46 Low frequency noise in the classroom 47 CONCLUSION 48 ACKNOWLEDGEMENT 50 REFERENCES 51 ABSTRACT CLASSROOM NOISE -Exposure and subjective response among pupils- Pär Lundquist Occupational Medicine, Dept of Public Health and Clinical Medicine; Umeå University, SE Umeå, Sweden. NIWL North, Box 7654, SE Umeå, Sweden. In Sweden, all children must have access to education of equal value and the curriculum points out the importance of a good environment for development and learning. In the classroom, as many as 30 pupils and a teacher are working together. Modern working methods differ a lot from the traditional. Teaching nowadays is focused on problemsolving. Students are more interactive, working in groups and projects. The teacher has become a supervisor, guiding not lecturing. Hearing loss, vegetative responses, biochemical effects, speech interference, behavioural effects and subjective reactions are all part of the problem of noise exposure. There is no unequivocal method of assessing noise and its effects. The most common method of noise assessment and appraisal of negative noise reactions is based on measurement of acoustic characteristics. Recommendations made and targets set by authorities are often stated in terms of equivalent A-weighted sound level L (A)eq. The purposes of this thesis have been to increase knowledge of noise exposure in classrooms and the subjective response among pupils and also to identify factors of special importance when assessing negative noise effects in the classroom. The work consists of five separate articles considering different aspects of sound exposure and its adverse effects on pupils in school: three field studies, one article on development of a mood-rating instrument and one laboratory study.analyses of exposure were based on equivalent sound levels and subjective responses were evaluated using ratings on a visual analogue scale and forced choice questions. The results point to speech and structure-borne sounds as the most annoying sound sources to the pupils.in the literature, speech appears to be more disturbing than other sources, and annoyance as well as negative effects on performance will increase with variability of the exposure. This is typical of the character of structure-borne sounds such as footsteps, scraping of chairs and tables and slamming of doors, as well as of speech. The sound levels in empty classrooms were mainly due to ambient noise from ventilation, other classrooms and corridors. The background sound level exposure levels in the classrooms were distributed within the interval of db(a)eq. The background sound in about 2/3 of the classrooms investigated was considered to be LFN. Pupils exposed to high LFN levels were not more annoyed than pupils exposed to low LFN levels when the l_ceq - LAeq difference was used to identify LFN. The activity sound level ranged between 47 and 69 db(a)eq. These are levels that must be considered high for a work environment such as the school, which has at all times to be conducive to steady concentration, communication and learning. The risk of hearing damage during class - music, woodwork and gymnastics excluded - is low. The thesis also describes the development of a mood-rating instrument to identify the effects of noise and other aspects of the classroom environment of importance to the children's scholastic performance. The questionnaire that is involved is quite easy to administer, takes little time to complete and is therefore well suited to studies in field settings. The ratings of annoyance in the classroom correspond to the verbal definition Somewhat annoying - Rather annoying . Data from the field studies does not support the idea that higher sound levels increase annoyance and inattentiveness, or impair task orientation. In the laboratory setting, a relationship between increasing sound level and increase in rated annoyance was displayed. ORIGINAL PAPERS This thesis is based on following papers referred to by their Roman numerals: I. Lundquist P, Holmberg K, Landström U. Annoyance and effects on work from noise at school. Noise and Health, 8, 39-46, I I. Lundquist P, Holmberg K, Burström L, Landström U. Low frequency noise and annoyance in class room. Journal of Low Frequency Noise, Vibration and Active Control, voi 19, No 4, , I I I. Lundquist P, Kjellberg A, Holmberg K. Evaluating effects of the class room environment. Development of an instrument for the measurement of self-reported mood among school children. Journal of Environmental Psychology, 22, , IV. Lundquist P, Landström U. Sound levels in classrooms and effects on self-reported mood among school children. Accepted for publication in Perceptual and Motor Skills, V. Lundquist P, Landström U, Hygge S. Subjective effects of environmental noise in children aged years. Manuscript. This Thesis was financed by grant from Swedish Council for Work Life Research. Introduction INTRODUCTION The most obvious role of the school is to educate, to foster cognitive development, to transmit information about the subjects of the curriculum, and to communicate joy and excitement about education (Rivlin and Weinstein 1984). To transmit the ideas and values of society, prepare children for their adult roles and responsibility and support each individual's psychological development is central. All children - irrespective of gender, geographical place of residence and social and economic conditions - must have access to education of equal value (Ministry of Education and Science 1997) and the curriculum points out the importance of a good environment for development and learning (Ministry of Education and Science and National Agency for Education 2001). A recent study by the Swedish National Board of Occupational Safety and Health (2003) points out that noise and acoustic problems are among the most common environmental problems in schools in Sweden. Pupils spend about 45% of the school day engaged in listening activities (Berg 1987) and the daily activities in the classroom are based on communication and concentration. In Sweden, school is the largest place of work, with approximately 1.5 million people active there (Statistics Sweden 2003), and since 1990 the Swedish Occupational Safety and Health Act has covered all pupils at school from the first grade. The purpose of the Act is to prevent ill-health and accidents at work and generally to ensure a good working environment. The foundation of the Act is that the working environment should be satisfactory with regard to the nature of the work and to the social evolution and technological development of society. Working conditions should be adapted to people's differing physical and mental aptitudes. Work should be planned and arranged in such a way that it can be carried out in healthy and safe surroundings, equipped to provide a suitable 1 Introduction working environment in which atmospheric, acoustic and lighting conditions are satisfactory. The Swedish National Board of Occupational Safety and Health has also issued special regulations on noise (Swedish National Board of Occupational Safety and Health 1992). The statute book points out that it is impossible to indicate a general connection between exposure and subjective annoyance. However, for teaching and other activities demanding steady concentration and/or undisturbed communication a maximum equivalent sound level exposure during normal working day of 40 db(a) is recommended to avoid annoyance. Sound contributed by the individual's own activity is not to be included. Further, the statute book emphasizes that conditions often require a careful review of the working premises and sources of the noise problem and that it may be appropriate to try to rank the sources in terms of disturbance, number of people affected, type of action which can be taken, and the cost and benefits of measures against the noise problem (Swedish National Board of Occupational Safety and Health 1992). The National Board of Health and Welfare in Sweden points out that school is a critical environment since noise affects speech communication and concentration and that classrooms may require background sound levels as low as 25 db in order to reach an acceptable speech intelligibility for certain sensitive groups (National Board of Health and Welfare 1996). The following chapters present a brief overview of noise, noise exposure and its effects as a basis for the presentation and discussion of objectives and results from five studies on noise exposure and subjective responses among pupils in classroomenvironments. 2 Background BACKGROUND Noise Depending on the context there are many ways to describe a sound. In a physical sense sound is mechanical oscillations propagated as a wave motion in an elastic medium. The concept of sound may also be defined psycho-physically, as an auditory perception. Noise is generally defined as unwanted sound (World Health Organisation 1980). Unwanted because it can be perceived as unpleasant or bothersome, it interferes with activities or it is believed to be physiologically harmful in some way (Kryter 1970). It is therefore impossible to define noise exclusively on the basis of physical parameters (Berglund and Lindvall 1995). Appraisal of noise Despite the extensive concern over too much noise, there is no unequivocal method of assessing noise and its effects. The most common method of noise assessment and appraisal of negative noise reactions is based on measurements of the acoustical characteristics. The equivalent A-weighted sound pressure level, L (A)eq, is commonly used to quantify noise exposure (Sailer and Hassenzahl 2000). Recommendations and objectives from authorities are often stated in terms of equivalent A-weighted sound level (e.g. Swedish National Board of Occupational Safety and Health 1992). The A-weighting of a sound is intended to indicate a level with a closer relation to loudness (the perceived sound level) than the unweighted sound pressure level, adapted for risk assessment of hearing damage as well as annoyance. A young person, with no hearing impairment, perceives sounds within the frequencies Hz. The same sound level at different frequencies is not perceived in the same way. Extensive research, initiated by 3 Background Fletcher and Munson (1933), has led to the ISO standardised equal loudness curves (International Standardization Organization, 1985). The A-weighting resembles the inverted equal loudness curve for 40 phone. Phone is the unit for loudness level. Equivalent A-weighted sound pressure level is the mean root mean squarevalue of a sound pressure variation over a specific time period. It is the level of a steady sound that, over a stated time period and at a stated location, has the same A-weighted sound energy as the time varying sound (Harris 1979). One question that has been raised is whether frequency weighting with an A- filter gives a correct result when assessing annoyance and other subjective responses to noise, especially noise containing strong low-frequency noise (LFN) components (Persson Waye 1995; Holmberg 1997). The interval between the hearing threshold and an unacceptable level is much smaller for LFN than for noise at higher frequencies (International Standardization Organization 1985). At LFN exposure, annoyance thus may appear close to the hearing threshold level. Persson Waye (1995) presents results indicating that annoyance experienced from LFN is greater than annoyance from noise without dominant LFN components at the same A-weighted sound pressure level. The definition of LFN varies and there is no internationally agreed definition. Berglund et al. (1996) suggest that frequencies up to 250 Hz should be regarded as LFN. Dealing with annoyance, an appropriate definition of LFN could be noise with a dominant frequency content of 20 to 200 Hz (Persson Waye 1995). One method that has been used in some Swedish recommendations on identification of LFN is the db(c) - db(a) difference (Swedish National Board of Health and Welfare 1996). This will constitute an estimate of how much energy is to be found in the low frequency part. A limit of db is also given, above which the noise is to be considered to be LFN (Swedish National Board of Health and Welfare 1996). Persson Waye (1999) suggests that this method should only be used when the level is above 30 db(a). 4 Background Noise exposure in classrooms In the classroom, as many as 30 pupils and a teacher are working together. The working methods differ a lot from the traditional lecturing methods. Teaching nowadays is focused on problem-solving. Students are more interactive, working in groups and projects. The teacher has become a supervisor, guiding not lecturing. Due to these changes most of the noise is likely to originate from human activities. A Danish survey (Bredo 2000) identifies chatter and laughter, noise from chairs and tables, and noise from other classrooms as the forms of noise most annoying to the pupils. Schools, business premises, service institutions and offices are examples of environments where speech is often regarded as a serious problem (Kjellberg and Landström 1994; Landström et al. 2002). A study by Kjellberg and Sköldström (1991) indicates speech to be more disturbing than meaningless random noise and in a recent study speech was found to be more disturbing than meaningless noise when difficult verbal tasks were being performed (Landström et al. 2002). Annoyance and effort ratings were higher and performance ratings lower in speech than in broadband noise conditions. The effects were more pronounced during verbal tasks than during work without verbal information. Irrelevant speech may also cause annoyance and interfere with the performance of several tasks requiring retention of verbal material (Jones and Morris 1992, Tremblay et al. 2000). A specific type of noise exposure in the classroom is that caused by footsteps, chairs, tables and doors. The hazard of this type of activity is complicated by the prominent risk of transmission through the building structure, i.e. the propagation of structure-borne noise. Due to its temporal character, sounds from footsteps, doors, etc may be
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