Though test subjects do not need to lie down on the "proverbial couch" they seem to feel kind of uneasy when psychologist Dr. Andreas Liebl (a scientist with Fraunhofer Institute for Building Physics IBP) hands out his questionnaires for them to fill in. But don't worry - this test is not about good or bad school marks, it's all about concentration and memory, about evaluating sources of disturbance and environmental parameters like noise or silence, light or darkness, heat or cold. Indoor spaces with their thermal, acoustic, olfactory and lighting parameters are in the focus of the ergonomic issues of common interest to both disciplines, building physics and psychology, in order to explore the complex interaction between human beings and the built environment. If people are supposed to be productive and efficient while enjoying their work and staying healthy, the surrounding space – no matter if it's an office, a class room, or a compartment in a train - needs to meet some specified criteria. Which of these criteria are most important and what consequences arise from them is subject to research done by the scientists of IBP's work group on "Cognitive Ergonomics and Psychoacoustics" led by Dr. Liebl at Fraunhofer IBP. Acoustic comfort in offices shared by several employees and its impact on human cognitive performance is the subject of these empirical investigations, which - according to Dr. Liebl - put an end to the widely held misconception that »psychologists would mainly deal with behavioural disorders and mental problems«. Here, for instance, psychology is being applied to ensure performance, well-being and contentment of working people.
Yet the disturbing factor noise has more effects than just these. According to research conducted by Fraunhofer IBP scientists, noise clearly has a negative impact on the cognitive performance of individuals. "Comprehensible speech as a background noise will automatically drain a person's attention and thus consume part of his/her cognitive resources," thus Dr. Liebl's conclusion. The measured loss of efficiency in test subjects' short-term memory performance was found to range between five and thirty per cent. Moreover, this also implies a loss of acoustic privacy at the workplace, which is perceived as rather annoying by the majority of the interviewees. These findings were clearly confirmed in the scope of a large-scale employee attitude survey recently conducted by Fraunhofer IBP on behalf of a major company.
But how can researchers actually ascertain under which conditions specific environmental factors will cause stress? To find out, Fraunhofer IBP has established a special laboratory, the so-called "HiPIE-Lab" (High Performance Indoor Environment). This lab allows to selectively modify key parameters of buildings physics, including acoustics, indoor environment, and lighting to examine their interaction and related effects on individuals. For instance, a built-in sound system (which is based on the principle of wave field synthesis) is used to model real sound fields, like various office scenarios. Wave field synthesis is a technique that allows to physically reconstruct the original sound field. Hence one of the laboratory's special features is the option to distribute and move many sound sources across the space. In this way it is possible to simulate the specific acoustic properties of existing office spaces and other working environments. To perform tests on specific materials and material systems, even the space enclosing surfaces can be modified for installation.
It is a fact that the physical properties of an office space (e.g. the lighting conditions, indoor climate and acoustics) substantially affect the quality of people's work. The better physical parameters are adapted, the better are employees' contentment and well-being and, consequently, their performance. "A field study conducted by Fraunhofer IBP among clerical employees states that the improvement of the acoustic situation is given highest priority," Dr. Liebl sums up the findings. Particularly in offices shared by several workers the acoustic design is crucial, as it is here that the conflict between seemingly incompatible requirements (adequate verbal communication versus the need for undisturbed, highly concentrated work) becomes most apparent. In this analysis it was found that about 75 percent of the interviewees perceived disturbances due to background conversations of other staff members at the workplace as annoying. Compared to that statement, non-speech noise is a minor problem.
In the scope of a laboratory experiment Dr. Liebl and his staff investigated the correlation between background noise at different levels of speech intelligibility (Speech Transmission Index, STI), cognitive performance and the perceived acoustic comfort of test subjects. The Speech Transmission Index (STI), a technical parameter for assessing speech intelligibility, is based on modelling speech by using a test signal. A strong relationship between speech intelligibility and cognitive performance as well as acoustic comfort was found. The experimental investigations regarding the impact of speech intelligibility on cognitive performance and acoustic comfort comprise two parts: a room acoustics test and tests involving subjects and interviews. These tests suggested statistically significant differences between the test subjects' error rates resulting from varied conditions of background noise. The perceived annoyance increased along with the STI.
Experts are currently discussing whether the Speech Transmission Index should be used as a physical reference value for calculations to assess open-plan offices. Speech intelligibility in spaces is subjected to several influences. Reverberation, the size of a room and its construction, the arrangement of the workplaces and associated furnishings, but also disturbing noises will have an impact on the degree of speech intelligibility. So far, there are no binding proposals how to use the STI in offices for several occupants. To solve the conflict between seemingly irreconcilable requirements regarding adequate verbal communication on the one hand and undisturbed, concentrated work on the other hand, a database is needed which describes the STI characteristic inside a space as a function of the office shape, furnishing and equipment, and the workplace density. Fraunhofer IBP experts analyse problem areas and do contract research for companies interested in finding satisfactory solutions.
Today, many people are spending more than 90 percent of their time indoors, with a growing tendency to spend even more of that share in offices. Office design hence is a major factor to decide on pain or pleasure at the workplace. Dr. Liebl focuses on research to optimize the design of indoor spaces so as to ensure well-being, contentedness, and good performance of human beings in indoor environments. He describes his great objective as follows: "My ideal concerning people in indoor spaces: I wish for them to experience the feeling of being completely absorbed in their current activity«. In psychology, this state is described as 'Flow'."
Also you can participate in this research process if you join the team as a test person. If you are interested in taking part in further investigations, please e-mail your contact data (stating the reference "Pool of Test Persons") to firstname.lastname@example.org. You will then be included in the group of prospective participants, which will keep you informed on the subject, duration and reimbursement in preparation of future investigations.