Effects of active noise control on subjective annoyance and cortical neural activities for car engine noise

摘要

It is thought that active noise control (ANC) is able to control not only loudness but also auditory impression; however, few studies have focused on changes in the auditory impressions of noises through ANC. Some previous studies have reported significant correlations between subjective preference/annoyance of sounds and synchrony of the alpha activity, τe. In this study, auditory impressions of car engine noises varied by ANC were investigated using psychoacoustic and neurophysiological measurements. Car engine noises were modeled as harmonic complex tones. 20 stimuli were obtained by applying ANCs with several reduction-levels. First, Scheffe's paired comparison tests were performed to evaluate subjective annoyance for each stimulus. Next, magnetoencephalographic responses for the reference noise, the intermediate-, and the least-annoyed stimuli for each participant were recorded, and then τe was estimated accordingly. Annoyance decreased as the cut-off frequency and the reduction-level increased. The results indicated that decrease of loudness is important for improvements in auditory impressions. However, no significant effects of ANC were observed in τe. It is difficult to identify the cause, the annoyance levels for each stimulus were not markedly different.