Classroom noise : exposure and subjective response among pupils

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 development 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 measurement of acoustic characteristics. Recommendations made and targets set by authorities are often stated in terms of equivalent Aweighted 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. 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.