One natural phenomenon that makes sounds but is undetectable by human ears is infrasound. Infrasound refers to sound waves that have a frequency below the lower limit of human hearing, which is typically considered to be around 20 hertz (Hz). Infrasound can be generated by various sources, including earthquakes, volcanic eruptions, wind, ocean waves, and certain animal activities.
While humans cannot perceive infrasound audibly, it can still have an impact on our bodies. In some cases, people may experience physical sensations or discomfort when exposed to intense infrasound, such as feelings of unease, dizziness, or vibrations. Despite being undetectable to our ears, sensitive instruments and equipment can measure and record infrasound for scientific purposes.