There are many animals and natural phenomena that communicate using sound waves at frequencies below the range of human hearing. This lower frequency range is often referred to as infrasound.
Elephants: Elephants produce infrasound vocalizations that can travel over long distances. These low-frequency sounds, below the range of human hearing, are used for long-distance communication between individuals and potentially for detecting distant threats or locating other elephants.
Whales: Whales, such as blue whales and humpback whales, are known to produce infrasound calls that can travel for hundreds of kilometers underwater. These low-frequency vocalizations are used for communication, mating calls, and possibly navigation.
Earthquakes and Volcanoes: Seismic activity, including earthquakes and volcanic eruptions, can generate low-frequency sound waves that are often below the range of human hearing. These infrasonic waves can be detected and measured using specialized instruments and seismographs.
Wind and Weather Phenomena: Strong winds, tornadoes, and hurricanes can generate infrasound waves as they interact with the environment. These infrasonic waves can sometimes be detected and studied to understand the behavior and characteristics of these weather phenomena.
Some Musical Instruments and Industrial Machinery: Certain musical instruments and industrial machinery can produce infrasound as a byproduct of their operation. For example, large pipe organs or some types of industrial equipment can generate low-frequency vibrations that may be below the threshold of human hearing but can still be detected and measured using specialized equipment.
These are just a few examples of organisms and phenomena that utilize sound waves at frequencies below the range of human hearing for communication or other purposes.