  Noise has both auditory and extra-auditory effects. Some of the most
deleterious extra-auditory effects of noise are those leading to sleep
disturbances. These disturbances seem to be related to both endogenous
(physical parameters) and exogenous (sex, age) factors of noise. Despite
correlative relations between noise level and awakenings, the scientific
community has not reached consensus regarding a specific action of these
factors on the different sleep stages. In animal research, 2 complementary main
fields of research exist. One is focused on the positive modulation of sleep by
repeated tone stimulation. The other concerns noise-related sleep disturbances.
The few studies that have investigated noise-related sleep disturbances suggest
the following conclusions. First, sleep disturbances are greater upon exposure
to environmental noise, whose frequency spectrum is characterized by high and
ultrasonic sounds, than white noise. Second, unpredictability and pattern of
noise events are responsible for extractions from both SWS and PS. Third,
chronic exposure to noise permanently reduces and fragments sleep. Finally, in
chronic noise exposure, an inter-individual variability in SWS deficits is
observed and correlated to a psychobiological profile related to an
incapability to face stressful situations. Based on results from other
research, acute noise-related sleep perturbations could result from an
imbalance in the sleep-wake cycle in favor of arousing ascending systems.
Chronic noise-related sleep disturbances may arise due to imbalance of the
sleep-wake cycle and malfunctioning of the hypothalamo-pituitary-adrenal axis
which may both contribute to the development of pathology.
