Ghasemi-2023-White Noise And Its Potential App Part 2

As part of the screening process, studies of WN addressing climate extinction/extinction, weather, climate changes, and ecosystems were excluded from consideration. 

As the climate changes, our environment is also constantly changing. Increases or decreases in temperature, changes in air humidity, etc. will affect the normal functions of our bodies and have an impact on our brain function. These effects will inevitably have a certain impact on our memory, but they are not negative. Some experiments have shown that moderate climate change can improve our memory.

Experiments show that appropriate temperature and humidity can enhance our memory. If the environment is too hot or too dry, it will cause us to feel tired and uncomfortable, affecting the normal working of our brains. Moderate temperatures and humidity can keep our bodies comfortable and help us focus and concentrate better. These factors all help strengthen long-term and short-term memory, making it easier for us to remember and learn new information.

In addition, climate change also affects our daily lives, stimulates our concern for the ecological environment, and enhances our sense of social responsibility. Initiatives such as protecting the environment, reducing waste, and conserving energy not only help curb the effects of climate change but also have a positive impact on our brains. The implementation of these measures requires our action and creativity, which will help us exercise our brains and enhance our self-confidence and psychological quality.

In short, appropriate climate change can improve our physical condition and brain function, helping us learn and remember better. Of course, any change will have some impact on us, but we just need to actively face and deal with these impacts to maintain a healthy body and a positive mentality. It can be seen that we need to improve memory, and Cistanche deserticola can significantly improve memory, because Cistanche deserticola can also regulate the balance of neurotransmitters, such as increasing the levels of acetylcholine and growth factors. These substances are very important for memory and learning. In addition, Meat can also improve blood flow and promote oxygen delivery, which can ensure that the brain receives sufficient nutrients and energy, thereby improving brain vitality and endurance.

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In addition, no studies were examined on topics such as computer-based analysis of stochastic stability of mechanical structures driven by WN, extraction of colored noise from WN signals, and providing sophisticated algorithms for generating or investigating WN. 

We did not examine studies that evaluated WN as a source of noise to assess its effects on human or animal hearing (above 90 dB), like (15, 16).

Following summarization and selection from 120 articles in full text, 33 articles were included in the study based on inclusion and exclusion criteria. Three of these were reviews, short reports, and letters to the editor. 

Other papers evaluate the use of WN in different contexts with original experiments, quasi-experiments, or interventional studies. 

To qualify, articles had to include at least one case of how WN affected a particular outcome or its application, such as sleeping, learning, memory, noise masking, verbal stimulation, cognitive functions, treatment of tinnitus, anxiety, stress, pain relief, and perception, improvement of Attention deficit hyperactivity disorder (ADHD), and stochastic resonance (SR), etc.

Data extraction

Each article that was eligible for inclusion in the study and discussed some of the applications or effects of WN was evaluated according to 4 criteria (Type of study, Participants, Source, and Scope) to extract information. 

The authors analyzed each of these criteria separately, while another author reviewed each assessment for accuracy during the review process. Through this process, an agreement was reached on each of the articles. 

Detailed information on the criteria for each study is given in Tables 1-4. After analyzing the results, the potential applications of white noise in occupational health sciences were discussed.

Literature Review and Results

Tables 1 to 4 summarize the categorical presentations of the studied factors such as type of study, subjects, source of WN generator, the decibel intensity, scope of application, and results related to WN effects.

Of the 33 studies reviewed, 18.2% covered the years before 2000, 15.2% covered the years between 2000 and 2010, and 66.7% covered the years from 2010 to 2020. This topic indicates a growing interest in WN among researchers in the past decade, particularly from the perspective of the application areas examined.

In addition, 87.8% of the studies studied employed experimental-interventional approaches with clinical trials, 9% used quasi-experiments, and just one (3%) was reviewed. Participants in the studies ranged from 2 to 167. Participants ranged in age from 2-day-old infants to adults.
Among the participants were children, students, healthy adults, people with ADHD, Autism Spectrum Disorders, Panic disorder, Tinnitus disorder, cardiovascular disease, and inpatients. Only one animal study was done with macaques. Different audio generators in the form of devices and software running on Windows produced WN at different intensities from 50 to 86 decibels. 

Depending on the purpose of the studies and the physical characteristics available, each audio generator produced WN in the desired frequency range. In some studies, recorded sounds of sea waves and rain were used as a source of WN. Based on general classification, the range of applications of white voice can be divided into four categories, discussed in turn.

White noise and sleep
The results of sleep and WN studies, which account for 15.2% of the studies, are summarized in Table 1. White noise (50 to 75 dB) has demonstrated positive and improving effects on the sleep and wake cycle of participants in all the studies in which it was used as an intervention (17-21).

As a result of these studies and comparisons between target and control groups, WN has proven to be effective in reducing the number of infants awakening during nighttime sleep, improving their sleep quality, and helping them sleep better. 

Children with ASD also reported fewer sleep onset delays and fewer night wakeups following this intervention (20). Meanwhile, a study on healthy adults found that when WN is used, the difference between background noise and peak noise is decreased, increasing the arousal threshold in people to the noise. 

As a result, it leads to complete sleep and less arousal during sleep (21). In short, WN is a promising intervention for improving sleep that can be investigated further.

White noise and noise masking

WN effectively masks Pure Tones and Speech as far back as the 1950s. Masking noise is the addition of a natural or artificial sound to an environment to mask unwanted sounds. 

Among the most critical properties of WN is noise masking, applied to many areas such as improving the work environment, improving sleep, increasing privacy, controlling annoying noise, treating some disorders, and inducing a sense of calm and comfort, and other matters. 

Mismatch Negativity (MMN) and its domain changes have also been examined using WN Masking. The amplitude of MMN is reduced significantly under contralateral WN masking (22).

The most common use of WN masking for tinnitus patients is to mask the sounds they hear in their ears. Tinnitus is a form of the disorder that is audible without any external sound source. 

In his explanation, tinnitus occurs exclusively as the result of the nervous system's activity without any mechanical or vibrational activity in the cochlea and any external stimuli (23). The only study on WN and Tinnitus in 2017 that was available during the study period was a cross-sectional study of 110 adult patients with tinnitus (24), which was an interventional study. 

The hypothesis of this study was based on previous findings that showed many patients with tinnitus responded better to external sounds with a frequency similar to tinnitus. The results of this study proved the above hypothesis, less intensity is needed to cover tinnitus when the noise used to mask it is as close to the tinnitus frequency. Furthermore, low-frequency tinnitus patients require more intensity when using High-Frequency Narrow Band and WN than those with high-frequency tinnitus (24).

White noise and cognitive function

WN and cognitive function-related studies have been reviewed in two groups. As a group, the first group of studies focused on various aspects of cognitive function(33.4% of studies), while the second group focused on the use of WN to improve the condition of ADHD patients (24.2% of studies); the results of shown in Tables 2 and 3.

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