Effects of Active Noise Control on Physiological Functions

Abstract

The noise inside an automobile exerts various influences on the driver. In this context, the concept of ac- tive noise control (ANC), which reduces the noise in the automobile, has been reported. Subjective evaluation has furnished empirical evidence regarding the effects of ANC. However, few studies have investigated the ef- fects of ANC using a physiological evaluation. Therefore, we studied the effects of ANC on the physiological functions using recorded driving noise with ANC ON and OFF conditions. Ten male subjects participated in this study. They completed four consecutive sessions: a 20 min quiet period as baseline, a 10min noise expo- sure with ANC ON or OFF, a 60min mental task period during noise exposure with ANC ON or OFF, and a 20 min recovery period. We measured electrocardiogram, photoplethysmogram, electroencephalogram, blood pressure (BP), baroreflex sensitivity and internal secretion indexes such as cortisol. Before and after the task, the subjects were evaluated on the Kansei-gakuin Sleepiness Scale, and after the task, they answered the NASA-TLX. Two experiments with ANC ON and OFF conditions were conducted at the same time of day on separate days. Data of the ANC ON condition and ANC OFF condition were compared by the paired t-test. We found that systolic BP, diastolic BP and sympathetic nerve activity during the ANC ON condition were sig- nificantly lower than those during the ANC OFF condition. Furthermore, parasympathetic nerve activity during the ANC ON condition was significantly higher than that during the ANC OFF condition. The results sug- gested that ANC effectively reduces the stress level in physiological functions, especially the cardiovascular system. Key