Unlike other physical ambient factors (i.e. electromagnetic fields or air pollutants), noise is perceived by a specific system (auditory system) in humans. It is therefore a phenomenon that is sensed and evaluated by everybody, and this is why exposure to noise is one of the most, if not the most, frequent complaints of populations living in large cities. In these areas and their surroundings, the sources of noise most frequently cited are traffic, followed by neighbourhood noises and aircraft noises. Sleep is a physiological state that needs its integrity to allow the living organism to recuperate normally. It seems to be sensitive to environmental factors that can interrupt it or reduce its amount. Ambient noise, for example, is external stimuli that are still processed by the sleeper sensory functions, despite a non-conscious perception of their presence. Over the past 30 years, research into environmental noise and sleep has focused on different situations and environments, and therefore the findings are variable. However, it still seems necessary for some fundamental questions to be answered on whether environmental noise has long-term detrimental effects on health and quality of life and, if so, what these effects are for night-time, noise-exposed populations.