Unwanted sound (noise) has been documented to be a serious problem for hospitalized patients. In some cases, different forms of intensive care noise levels can reach levels that are above what is advisable from a health and safety perspective (work environment perspective). In many hospitals, noise levels are not a threat to healthy people and are in the vicinity of what we would find acceptable for an office (for ex 50 dB (A)). Room acoustics influence sleep in a negative way.
Is noise considered a problem in today’s hospitals? The answer probably lies in the fact that being ill and having to be hospitalized means that the patient has lost the sense of control over the surrounding environment. Any type of stressor can have a negative impact. Losing out on sleep has shown to be one such stressor for patients.
The sleep study by Dr. Sören Berg, University Hospital of Lund investigated what effects 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. They slept three nights in an unused department in a small hospital in the south of Sweden. During the night they 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 standard Ecophon ceilings. The subjects were unaware of the modifications to the environment.
On 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 fewer EEG-defined awakenings.
The findings suggest that a room with a short reverberation makes it possible to ‘shield off’ sound during sleep. When sound appears in a room like this it might be perceived as less threatening and our brain sees no point in waking the person up or increasing the level of activation for the individual.
a room with a short reverberation makes it possible to ‘shield off’ sound during sleep
Impact of reduced reverberation time on sound-induced arousals during sleep, Sleep, 2001 May 1, 24(3):289-92.