Random noise in which all frequencies possess the same energy density is white noise. Specifically, white noise is a monotonous, continuous, full-spectrum humming sound. Due to its uniform frequency distribution characteristics, white noise can mask abrupt noise disturbances in the environment, creating a quieter environment conducive to relaxation. Photo taken in Huangshan, China Natural sounds such as rain, flowing water, and birdsong are the closest real-world approximati

When we remain for extended periods in crowded meeting rooms, enclosed classrooms, or poorly ventilated buildings, we often experience dizziness, difficulty concentrating, and even chest tightness and shortness of breath. Most people attribute these symptoms to "hypoxia" (oxygen deficiency). However, modern medicine indicates that the true culprit is often the quietly rising concentration of carbon dioxide CO₂ in the indoor air. Photo credit: unsplash An issue that cannot be

In winter, outdoor temperatures are low, and people tend to keep doors and windows tightly closed to maintain indoor warmth, resulting in poor air circulation between indoors and outdoors. Occupants continuously exhale CO₂ without corresponding ventilation measures, causing indoor CO₂ concentrations to accumulate continuously and greatly exceed standard levels. Photo credit: unsplash Research indicates that in ordinary living rooms with doors and windows closed, the activity