There’s more to life than meets the eye, and you don’t have to see it to believe it. Limited by organs of perception, human beings develop many technologies (such as telescopes and microscopes) to provide a window into worlds hidden in plain sight. These invisible worlds hold keys to emerging methods of communication and medicine, such as x-rays, infrasound used to sensitize cancer cells, telephones, and radio waves. The more we study the unseen world, the more we realize its impact on life. NASA has even suggested that 95% of the known universe consists of “dark matter” and “dark energy,” stating that: “Everything on Earth, everything ever observed with all of our instruments, all normal matter — adds up to less than 5% of the universe.” Simply put: we don’t know what we don’t know. Although we can’t hear them, infrasound and ultrasound are here, and they’re making waves in science and medicine.

Heat, gravity, light, and sound permeate our lives, yet we perceive only a narrow bandwidth of their frequencies (such as the 20-20,000hz human hearing spectrum). It is difficult to imagine how other lifeforms experience sound. For instance, bats produce frequencies 10 times higher than human hearing, and they use these sounds to “see” using echolocation. Sound waves are emitted by the bat, and the length of time it takes for them to echo back is used to calculate the distance of objects and form a mental map. Sonar and ultrasound imaging make use of the same principle. Thanks to ultrasound, we’re able to generate highly detailed images of underwater terrain.

Many blind people use echolocation to navigate on a daily basis. Daniel Kocieliński developed blindness at the age of seven. In speaking with me, he shared: “Some people are very good with echolocation, it’s a matter of training. Anyone can develop that.” His process of memorization was also affected after becoming blind. “[When I was young] somebody could tell me a long series of numbers and I could immediately remember it by visualization. Later on I developed more ‘sound memory.’ When someone tells you a number, you can remember it by sound. Other people need to write it down to remember something.” Although some of his sensory capacities deteriorated, others were enhanced. Blindness forced Kocieliński to use more sonic information to assess his surroundings and interpret people’s emotions, information most of us overlook.

In a sense, we’re all “blind” to a vast spectrum of information in the environment. Infrared and ultraviolet light are invisible to human eyes, just as infrasound and ultrasound waves are inaudible to human ears, but their effects on the body are profound. The UK government’s Health Protection Agency published a 200 page report, which concluded that: “ultrasound is capable of causing permanent damage to biological tissues.” They also stated: “At high levels of infrasound, aural pain and eardrum rupture can occur.” Using this knowledge, sonic weapons have been deployed by the military. The Wall Street Journal reported a suspected radio frequency attack on the U.S. Embassy in Havana, Cuba, causing diplomats and intelligence officers to experience, “dizziness, headache, fatigue, nausea, anxiety, cognitive difficulties and memory loss.”  Although the precise technology behind the alleged attack is uncertain, “some incidents of Havana Syndrome are most likely caused by directed energy or acoustic devices and can’t be explained by other factors.”

Like any tool, sound can be used to help or harm. Although infrasound and ultrasound can cause physiological damage, healing uses have also been explored. The Health Protection Agency reports that: “Ultrasound has been used as a technology to promote the treatment of contaminated soil wastes. The contaminated soil is mixed with water and exposed to a source of ultrasound. Complex pollutant molecules are destroyed.” Sound can even be used to stimulate plant growth. BioMed Research International published a study showing that, “sound is effective for stimulating the germination and growth of mung beans, suggesting that this technique has interesting possibilities in biophysics.” The effects of sound on the natural world have been increasingly studied in recent decades.

Bernie Krause is a soundscape ecologist (someone who studies the sonic aspects of ecosystems). When he heard of a logging project that claimed it would leave no environmental impact due to selective harvesting practices, he was skeptical. Although before and after images showed virtually no change in the outward appearance of the forest, Krause suspected there was an untold story. Using spectograms (graphic renderings of sound frequencies over time), he demonstrated that noise generated by logging equipment created sonic competition for local wildlife. In another study, he hypothesized that frogs were adversely affected by jet flight paths, which made it hard for them to synchronize their calls and easier for predators to locate them. After changing and reducing these flight paths, the frog population was able to recover. The modern world is increasingly saturated with noise-pollution emitted by human-made technologies. We must consider the effects these vibrations have on the natural world — whether we hear them or not — or risk the unintended consequences.

Jacqueline Schertz was born deaf. Through email exchange she writes, “I have been profoundly deaf since birth and do not benefit from hearing aids or cochlear implants. ASL [American Sign Language] is my visual language and so is English for reading and writing.” Nonetheless, sound waves do affect her, even though she can’t “hear” them in the traditional sense. “During a visit to Niagara Falls,” she writes, “I felt the power of the water falls when I grasped the railing at the falls overlook. People tap their feet on a wood floor to get my attention. I went to an airshow and could feel the jets when they flew near me overhead.” Shertz is in touch with sound on a visceral level. Interestingly, she observes that many hearing people have underdeveloped visual capacities. “I find that some hearing people are lacking in their peripheral vision. Since sounds do not distract me, I have total focus on things.”

Sound and light are not separate as you might think. Photons are particles of light (electromagnetic waves), whereas phonons measure the vibratory behavior (oscillation) of mechanical pressure waves, or sound. Every object, down to the atomic level, produces both light and sound. An article published by MIT explains: “In a crystal, the atoms are neatly arranged in a uniform, repeating structure; when heated, the atoms can oscillate at specific frequencies. The bonds between the individual atoms in a crystal behave essentially like springs…When one of the atoms gets pushed or pulled, it sets off a wave (or phonon) traveling through the crystal.” Even though we can’t hear these “atomic sounds,” they happen every second, everywhere, inside and around us.

The subtlest form of sound is mental. Internal monologue — far from being inconsequential to the physical world — plays a significant role in how one experiences life. Matt Canale grew up in the suburbs of Connecticut, spent 13 years in New York City, and now lives in the rural mountains of Upstate New York. I interviewed him in the plains of Colorado, overlooking the distant silhouette of Pike’s Peak. “I think there’s a lot to be said for environment, but there should be more emphasis on the inner environment of the individual, and the inner environment is created through all the stimuli that we experience in our lives, whether it be the sounds, the people, the media that we take in...When I’ve been able to be out in nature for days at a time, I feel more like myself, and I feel like nature supports that journey inwards and it also helps to clean the residue from all the different stimuli.”

Connecting with silence (both internally and externally) is an antidote to overstimulation. Inundated with music, media, environmental noise, thoughts and daily interactions, we don’t always recognize the impact of these interactions on our nervous system, energy levels and emotions. “Physically speaking,” says Canale, “it’s easy to be like, ‘this is mine and this is yours,’ when it comes to possessions, but when it gets to people's emotions — peoples thoughts, — for a lot of us, I think it's hard to distinguish what's ‘ours’ and what belongs to somebody else. And I think with nature there is no imposition, nothing that's trying to be forced upon us. We’re all trying to get back to our natural state of being.”

Although infrasound and ultrasound are natural, human beings use them in ways that are not found in nature. The prevalence of high-spectrum frequencies via radio waves and low-spectrum frequencies from industrial noise-pollution are taking a toll on human, plant and animal populations. If we continue to implement sonic technology without considering the way these frequencies interact with human physiology and the communication methods of other life-forms, we may crowd them out and cause widespread damage to our inner and outer environment. For instance, the Natural History Museum reported on the detrimental impact of noise pollution on whale populations: “Anthropogenic [human-made] noise can change a whale's behavior, such as causing the marine mammals to feed less or to produce fewer calls. Shipping noise also causes whales to become stressed, with the build-up of stress related chemicals linked to growth suppression, lower fertility and poor immune system function.” On the other hand, the more we understand the unseen world, the more we can harness infrasound and ultrasound to produce beneficial advances in technology, particularly in the fields of medicine and communication.