In offices, noise control should be a priority as unwanted sound causes stress. Continuously elevated stress levels are a health risk.
Turku University of Applied Sciences and University of Turku have conducted the first Finnish medical study on the physiological, psychological, and performance effects of irrelevant speech. Office noise consists primarily of this kind of sound. The unique study shows that exposure to even moderate sound level of irrelevant speech increases stress hormone levels in less than an hour.
The study compared stress reactions under three sound conditions: irrelevant speech (sound level 65 dB), steady-state noise (65 dB), and silence (35 dB), all having similar relative frequency contents. The steady-state noise sounded like ventilation noise. Irrelevant speech consisted of a radio talk show.
The participants were exposed to one out of three sound conditions on average for 45 minutes while performing tasks requiring concentration. Participants’ performance, psychological experience, and various physiological stress reactions (e.g. stress hormone levels, heart rate variability) were measured. Between tasks, participants answered questions concerning their experiences of the sound environment and its workload.
Speech causes more stress than steady-state noise
During steady-state noise and irrelevant speech, the level of the stress hormone in plasma was elevated compared to silence. However, irrelevant speech disturbed concentration and reduced work efficiency the most. It was also perceived as the most disturbing and workload-increasing.
– Surprisingly, although irrelevant speech was by far the most disturbing sound, steady-state noise and irrelevant speech in short term increased physiological stress and reduced work efficiency in equal measure compared to silence.
In long term, however, irrelevant speech caused more stress than steady-state noise, says Valtteri Hongisto, head of the research group at Turku University of Applied Sciences.
Irrelevant speech disturbs concentration
In office work, the factors causing high environmental dissatisfaction are irrelevant speech of colleagues and lack of privacy. Among the different types of noise, concentration is most affected by irrelevant speech, i.e., speech that people do not want to hear.
– When we hear any speech at all, our brains automatically try to interpret the content of the words. If our job involves numbers, words or text, a conflicting situation arises in our brains. This has a significant impact on work efficiency in tasks that require working memory, Hongisto says.
Research results help design work environments
The study by Turku University of Applied Sciences and the University of Turku shows that exposure to moderate sound level of irrelevant speech increases stress hormone levels in less than an hour.
– This suggests that the effects of prolonged exposure would likely be even greater. Every effort should be made to reduce noise, as long-term stress is known to be harmful. From the point of view of occupational health, it would be beneficial if working environments and their use were designed in a way that minimizes noise exposure. This is especially important in schools, kindergartens, hospitals, and offices, says Hongisto.
The study was part of the Anojanssi project, which was funded by Business Finland, the Finnish Ministry of Social Affairs and Health, the Finnish Ministry of the Environment and partnering companies.
Author: Arto Rauta, Concept Developer for Office Environments at Ecophon