A descriptive cross-sectional study of annoyance from low frequency noise installations in an urban environment.

In order to improve the living conditions for respondents highly exposed to traffic noise, it has been recommended that one side of the building should face a "quiet side". Quiet may, however, be spoilt by noise from installations such as ventilation and air-conditioning systems. The noises generated by installations of this kind often have a dominant portion of low frequencies (20-200 Hz) and may be a source of great annoyance and sleep disturbance. This paper describes the cross-sectional part of an intended intervention study among residents exposed to traffic noise on one side of the building and to low frequency noise from installations on the other side of the building. A questionnaire masked as a general living environment study was delivered to a randomly selected person in each household. In total 41 respondents answered the questionnaire (71% response rate). Noise from installations was measured indoors in a bedroom facing the courtyard in a selection of apartments and outdoors in the yard. 24h traffic noise outdoor and indoor levels were calculated. The noise levels from installations were slightly above or at the Swedish recommendations for low frequency noise indoors with the window closed and exceeded the recommendations by about 10 dB SPL when the window was slightly opened. The proportion of persons who reported that they were very or extremely annoyed indoors from noise from installations was more than twice as high as for traffic noise. Installation noise also affected respondents' willingness to have their windows open and to sleep with an open window. The high disturbance of installation noises found in this study indicates the importance of also regulating the noise exposure on the "quiet side" of buildings. Further studies will give a better base for the extent of annoyance and acceptable levels of installation noises.