Psychophysiological Experiments on Extent of Disturbance of Noises Under Conditions of Different Types of Brain Works

Abstract

For quantitative evaluation of human conditions, subjective evaluation obtained through psychological measurements is generally used for assessment of an acoustic environment. It is also important that human reactions to surrounding environments be objectively evaluated from physiological aspect. In the field of architectural environment, Authors reported that auditory information processing was affected by the priority of processing in the brain (Akita et al., 1995). From this finding, it was demonstrated that the Electroencephalogram (EEG) was effective for objective evaluation as a physiological index. In the field of psychophysiology, the distinct EEG theta rhythm from the frontal midline area observed during performance of mental tasks such as continuous addition was defined as the frontal midline theta rhythm (Fmθ) (Brazier et al., 1952; Ishihara et al., 1972). In the studies on Fmθ, it was found that Fmθ was associated with concentration on the task, with higher Fmθ values indicating higher concentration (Ishihara et al., 1975; Ishihara et al., 1976; Ishihara et al., 1991; Suetsugi et al., 2002). As the previous studies on the influence of various noises on task performance, for example, Hashimoto et al. investigated the effects of familiar noises with a moderate sound level of 60 dB LAeq on physiological responses, task performance and psychological responses (Hashimoto et al., 1999). From the results, it was shown that the effect of noise on task performance depended on the kind of noises, it strongly influences the task performance as the task became increasingly more complex. Author has studied relationships between extent of disturbance caused by sounds and EEG during simple calculation task up to now (Tsujimura et al., 2006; Tsujimura et al., 2008). As the finding in the paper, information processing mechanism of cerebral cortex relevant to disturbance was reported (Figure 1) (Tsujimura et al., 2006). Moreover, to clear an effect of meaning of noise on task performance or extent of disturbance, we have investigated the effect of meaningless and meaningful noises on extent of disturbance caused by noises and task performance of two kinds of brain works (Tsujimura et al., 2007). In this paper, in order to find influence of noise including verbal information on the extent of disturbance or EEG during different types of brain works, the psychophysiological experiment was conducted. The relationships between extent of disturbance and EEG were examined during each brain work.