Prior to the Industrial Revolution and the introduction of artificial light, people were bi-phasic, sleeping in two four-hour intervals, with a waking time in between that they used for prayer, meditation or really great sex! Our current mono-phasic form of attempting to sleep eight hours straight is a modern social convention and has been called the “golden age of rest”.
The sound of running water is helpful for meditation and also helpful for those who are having trouble sleeping. The slow whooshing noises are the sounds of non-threats, which is why they work to calm people. They are soothing to our brains.
In a study last year, people who took eight weeks of mindfulness meditation training had far fewer cases of colds and flu and less severe infections compared to a group of non-meditators.