In biology, noise, a comprehensive term of unwanted disturbance and fluctuation, is understood as a variability in measured data when identical experiments are repeated or when bio-signals cannot be measured without distorting the desired variation. Noise is typically observed as an unwanted element or disturbance to a system, but it has an immense impact on many aspects of science and technology. However, Noise is at the core of the stochastic resonance theory, and it is an example showing the importance of fluctuation in non-linear systems. Stochastic resonance is recognized to be an important statistical phenomenon that can be beneficial to signal and information processing in non-linear systems that occurs artificially or naturally. From this perspective, noise can potentially be beneficial when properly used. In order to achieve the positive effect, a more in-depth study on noise is required. Previous studies have focused on removing static noise. This indicates that it would be meaningful to conduct studies from a new perspective; By changing harmful noise into beneficial noise based on the SR phenomenon, noise can potentially induce pleasant emotions both psychologically and physiologically.
This study compared white and pink noises among 1/f noises to identify brain activities according to stochastic resonance (SR). This study also aimed to identify changes in brain activities according to stochastic resonance through binaural beats and noise stimulation. Therefore, this study focuses on mixed noise and binaural beat pink noise based on colored noise (white and pink noise). (1) The first is to examine the white and pink noises to compare an brain activity. (2) The second objective is to examine the mixed noise according to brain activity. (3) The third objective is to examine the binaural beat pink noise to change brain activity.
Section 2 contains detailed brain activity results for the white and pink noises. Twenty undergraduate students (10 male and 10 females), ranging in age from 20 to 29 years (mean, 23.3 ± 2.14) participated in the experiment. The participants were presented with noise stimuli while comfortably seated in a chair, and electroencephalogram (EEG) was measured during the experiment. The participants were required to self-report emotion changes over the task. The subjective evaluation (seven-point scales) comprised four independent factors: positive, negative, arousal, and relaxation.
Section 3 contains detailed brain activity results for the mixed noise. Twenty undergraduate students (10 male and 10 females), ranging in age from 20 to 28 years (mean, 25.3 ± 1.38) participated in the experiment. The participants were presented with noise stimuli while comfortably seated in a chair, and electroencephalogram (EEG) was measured during the experiment. The participants were required to self-report emotion changes over the task. The subjective evaluation (seven-point scales) comprised four independent factors: positive, negative, arousal, and relaxation.
Section 4 contains detailed brain activity results for the binaural beat pink noise (40 Hz). Twenty undergraduate students (10 male and 10 females), ranging in age from 20 to 30 years (mean, 26.1 ± 2.53) participated in the experiment. The participants were presented with noise stimuli while comfortably seated in a chair, and electroencephalogram (EEG) was measured during the experiment. The participants were required to self-report emotion changes over the task. The subjective evaluation (seven-point scales) comprised four independent factors: positive, negative, arousal, and relaxation.
This study was able to examine the following brain activity according to 1/f noises.
● White and pink noise: The results of subjective score for negative factor was commonly high, which is believed to reflect the basic characteristics of noise. Despite this result, the interesting fact was that pink noise resulted in a higher mean subjective positive score than white noise. Moreover, pink noise also resulted in higher arousal and relaxation scores than white noise. When listening to pink noise, theta, alpha, low beta, mid beta and gamma bands increased more than white noise, while high beta bands decreased. In comparison to white noise, pink noise stimulation positively activated the right hemisphere of the temporal lobe and frontal lobe, which correlated with improved relaxation, concentration and reduced stress-related arousal.
● Mixed noise: When compared to mixed noise-white, listening to the mixed noise-pink [white(1) : pink(3), speaker] resulted in an increase of alpha, low beta, mid beta, and gamma bands and decrease of high beta bands, [white(3) : pink(1), speaker]. Moreover, when following a stimulation of mixed noise-pink, there were significant increases in alpha waves throughout all regions, except temporal regions (T3, T4). Specifically, slow alpha relative power showed significant increases in all regions, except temporal regions (T3, T4), whereas fast alpha relative power did not show significant differences in any electrode areas.
● Binaural beat (BB) pink noise (40 Hz): Pink noise induced psycho-physiological stability and concentration more so than white noise was confirmed. In this study, the same results were evident when 40 Hz binaural beat pink noise stimulation was presented. However, assessment of subjective positive/negative and arousal/relaxation showed that negative scores were lower, and positive, arousal, and relaxation scores were higher with binaural beat pink noise. Based on such facts, this study suggested that subjective feelings were mediated by changes in central nervous system (CNS) brain activities, induced by binaural beat pink noise.
This study suggests that the effect of potential 1/f noise by EEG regions based on stochastic resonance. Studies to date considered noise as a harmful factor and attempted to eliminate it. However, it is likely that future researches will prove it as an essential tool for exhibiting creativity. Moving forward, noise will become an important factor in inducing positive psycho-physiological states, and reducing auditory discomfort as noise from various locations are properly mixed such as an urban traffic, factories, construction, and environmental noise. This study can be used for finding positive use of noise, going beyond the concept of simply being harmful noise, and as a preliminary study in auditory neuroscience. Accordingly, this study was significance in the fact that it compared changes in EEG according to SR based on 1/f noise stimulation.

keyword: Colored noise, Stochastic resonance, Pink noise, White noise, 1/f noise, Binaural beat, Mixed noise, Noise