This study was commissioned by the Department of Transport from the Department of Safety, Environment and Engineering at the Civil Aviation Authority (CAA). The study has been conducted by the CAA in conjunction with research teams from the Universities of Loughborough, Manchester, and Southampton. The objectives of the study were to determine: (a) the relationships between outdoor aircraft noise levels and the probability of sleep disturbance; and (b) the variation of these relationships with time of night. To meet these objectives it was also necessary to investigate the influence of non-acoustical factors upon disturbance of people's sleep including their age, sex and personal characteristics, their general views about the neighbourhood, their perceptions about sleep quality. A major aim of this study was to observe the sleeping patterns of people in homes which are affected by aircraft noise.