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Room acoustics’ influence on sleep

Unwanted sound (noise) has been documented to be a serious problem for hospitalised patients. In some cases, most often different forms of intensive care noise levels can reach levels that are above what is advisable from an health and safety perspective (work environment perspective). In many hospitals noise levels are not a threat to healthy people and is the vicinity of what we would find acceptable for an office (for ex 50 dB (A)).

Is noise considered a problem in today’s hospitals? The answer probably lays in the fact that being ill and having to be hospitalised means that the patient has lost the sense of control in relation to the surrounding environment. Any type of stressor can have a negative impact. Loosing out on sleep has shown to be one such stressor to patients.
The sleep study by Dr Sören Berg, University Hospital of Lund investigated what effects an improved room acoustics had on objective sleep quality. Even though no such research has been performed before, the hypothesis was that improved room acoustics would lead to lesser fragmentation of sleep when subjects were sleeping under noisy conditions. Objective sleep quality was assessed by EEG. Through this information it is possible to derive the quality of sleep as well as the distribution of the sleep stages (1-4 and REM).
12 young students (20-25 years) acted as subjects in the study. The slept three nights in an unused department in an small hospital in the south of Sweden. During all the night the were subjected to 12 environmental sounds in the range of 27-58 dB (A). The first night was used to get the subjects used to the electrodes, the bed etc, and no EEG data was recorded.
The second night the room was equipped with a sound reflective ceiling (gypsum board with Akutex T paint) that was impossible to distinguish from standards Ecophon ceilings. The subjects were unaware about the modifications to the environment.
The third night the room was equipped with a sound absorbing ceiling and all the other procedures were repeated. In the room used for the study the use of a sound absorbing ceiling did not affect the noise level in the room. The average improvement in the reverberation time was 0,12 seconds giving the room a reverberation time of approximately 0,4 seconds.
What did the study show?
In the situation with short reverberation time (sound absorbing ceiling) sleep was less disturbed by the 12 environmental sounds. This means that sleep was less fragmented, i.e. caused less EEG defined awakenings.
The findings suggests that a room with a short reverberation makes it possible to ”shield of” sound during sleep. When sound appears in a room like this it might be perceived ass less threatening and our brain sees no point in waking the person up or increasing the level of activation for the individual.
Impact of reduced reverberation time on sound-induced arousals during sleep, Sleep, 2001 May 1, 24(3):289-92.
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