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"Indirect wind is more comfortable" The effect of cooling environment demonstrated using brain waves. New Research may provide benefit to schools and offices.

A comparison with direct wind at "small amplitudes": Associate Professor Okamoto’s group at the Kyushu University, performed an experiment with students

2021.07.13

The differences between "Wind from an air conditioner hitting directly" and "Cooling indirectly." determine whether one can concentrate on work or study. Associate Professor Tsuyoshi Okamoto’s research group at the Kyushu University Faculty of Arts and Science demonstrated that the wind direction setting of an air conditioner affects not only the thermal environment around the person in the room, but it also simultaneously affects the subjective evaluation, psychological response, and physiological response. This outcome was published in PLOS ONE.

A total of 19 healthy students (8 women, 11 men) who did not know the study goal participated in this experiment. They were asked to wait for 20 minutes in an environment of 32 °C, enter the room set at 20°C, and wear electroencephalography equipment for 20 minutes. Thereafter, each individual performed four tasks three times each in a direct or indirect wind environment (20 minutes) and then repeated them in the opposite environment. The results were then compared. First, in terms of the thermal environment, the room temperature was 1°C warmer in the indirect wind, while the wind speed right next to the individuals was much lower in the indirect wind. The surface temperature of each student’s face was almost the same in the indirect wind, but it decreased by about 1.5°C in direct wind. Despite this, the students claimed that the temperature was "just right" with the indirect wind and that comfort was also higher. Furthermore, when the difference between the internal time of the students and real time when counting 10 seconds was measured, the internal time was longer in indirect wind conditions, and negative emotions such as boredom were suppressed.

In the electroencephalography measurement, the amplitude of the gamma and beta waves in the F7 region, which is related to thermal discomfort, was larger in the direct wind than in the indirect wind conditions. Looking at the correlation between comfort and gamma and beta waves, the smaller amplitude correlated with comfort. In other words, the smaller the amplitude, the greater the comfort. Furthermore, parasympathetic nerve activity decreased, and sympathetic nerve activity increased in indirect wind environments compared to direct wind environments.

Associate Professor Okamoto said, "Direct wind activates parasympathetic nerve activity and internal organ movement, while indirect wind activates physical and brain activities. In other words, in offices and schools, indirect winds that activate mental and physical activities are advantageous. " Associate Professor Okamoto continued, "It took more than two years to achieve this result. It was empirically known that comfort levels were higher in the absence of wind, but it was difficult to summarize the statistically significant differences in brain waves, electrocardiography, and subjectivity as evidence."

This article has been translated by JST with permission from The Science News Ltd.(https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.

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