There is not much research done on how traffic noise on schoolyards affect children and teachers although noise pollution from traffic often are high and affect both groups in several ways. It is a well-established fact that a positive sound environment affects health and learning as well as the working capacity by reducing stress levels. The purpose of this study is to examine whether sound pollution is prevalent in elementary schools in Umeå, if the personnel have knowledge pertaining to the effects of sound pollution, and whether the examined schools have specific routines and self-monitoring mechanism for dealing with sound pollution. The study also aims to inquire whether the schools take any preventive measures with regards to minimizing sound pollution and if they have assigned responsibility for these matters to anyone in the organization. Two methods were used in the study, a questionnaire for teachers and interviews with the principals. The questions were formed in such a way so as to shed light on the above mentioned purposes of this study. The answers to the questionnaire illustrate if and how the teachers perceive and deal with sound pollution on the schoolyard. The interview questions aimed to assess the perception of the principals regarding the sound pollution in their respective schools, the level of knowledge the school management had with regards to sound pollution as well as the routines used for ameliorating and preventing sound pollution on the school yard. The study was performed in four elementary schools in the municipality of Umeå and the questionnaire had 32 respondents. One major reason for using a questionnaire was to maximize the amount of respondents in a time efficient manner. The study intends to shed light on a problem (i.e. sound pollution) that schools usually tend to disregard but nevertheless a problem that, possibly, could lead to dire consequences if not taken into account. The results of the study show that 10 of the 32 teachers perceive traffic noise as a problem that affects both children and educational activities negatively on their schoolyard. The results of the study indicate that teachers perceive sound pollution to be a problem on their schoolyard. However, they seem to lack adequate knowledge regarding the health outcome of such noise pollutants. In conclusion, it is evident that teachers need more support information, resources and education in order to enable them to achieve a positive sound environment on their workplace - both for themselves and the children. The results show that there still remains a lot to improve in schools with regards to noise pollution. In many cases, even those responsible at the schools lacked the knowledge necessary to understand the health problems with noise pollution.

This study presents comprehensive active cancellation of booming noise caused by the engine and the driveline inside a passenger car. In modern noise control systems for vehicles, booming noise caused by engine harmonics could be effectively suppressed by employing active noise control. However, practical attempts or studies for the active suppression of driveline booming noise are scarce. One of the reasons may be that since the booming noise caused by the driveline is not harmonic with the engine speed, reference signals cannot be generated conventionally. Thus, passive approaches are generally employed to improve the driveline noise. To address this limitation, we propose a method for generating reference signals from engine revolution speed to suppress the driveline noise, such as propeller shaft and tire noise. Reference signals for driveline noise suppression were generated using the information from the torque converter, gear ratio, and final drive ratio. A practical active noise control system was implemented in a six-cylindered large sedan to validate the proposed method. The experimental results showed that the engine firing order was suppressed by 8.0 dB. Moreover, the first order of the propeller shaft and the second and third orders of the tires were suppressed by 5.5 dB, 3.9 dB, and 2.3 dB for entire seat positions. Furthermore, the results presented in this study were considered effective for improving annoyance perception through subjective evaluation.