Sound is not only what we hear. It extends beyond our human capacity to perceive it. There is a lot of sound in the world happening that is not audible for us. Animal species employ ultra and infrasounds, which surpass the range of human hearing, for communication, navigation, hunting and social interactions. Bats use echolocation to navigate and locate prey, emitting high-frequency sounds and interpreting the echoes that bounce back. In the world of insect communication different species like crickets and grasshoppers use sound to attract mates and establish dominance. Remarkably, many animals possess the extraordinary ability to communicate across vast distances. Elephants, for example, utilize infrasound, emitting deep, low-frequency sounds. This form of communication enables elephants to convey messages across distances exceeding 10 kilometers.
Considering that our planet is predominantly covered by vast oceans, it is unsurprising that the finest long-distance communicators inhabit these waters. Whales excel in long-distance communication, with nearly all whale species capable of conveying messages over immense distances. Their vocalizations, often referred to as „songs” are the most intricate and longest among all creatures in the animal kingdom.

As a physical wave sound it possesses the ability to influence the environment in non-auditory ways. Sound is truly multisensory, capable of serving senses other than hearing alone. Ultrasound imaging, for instance, exemplifies this concept using ultrasound to image the inside of the human body. Ultra and infrasounds have widespread applications in technology and science. Our daily lives are accompanied by ultrasound in various forms, including sonic toothbrushes, aroma diffusers or parking sensors. Infrasound, on the other hand, finds applications in geology and seismology, aiding in studying Earth structure and monitoring seismic activity. Underwater, infrasounds play a role in sonar operations. Furthermore, this kind of sound has other unconventional uses, such as sonic weapons and fire extinguishing systems employing sound waves. Extra-audible forms of sound are used in such a wide variety of fields that it is safe to say that their use enables us to explore the world on a level that is not accessible to the unarmed human sensorium.

It’s not really a non sonic sound, but a way of visualisation shaped directly by sound waves. In 1787, Ernst Chladni, a German physicist and musician, introduced a groundbreaking method for visualizing the vibration modes of a rigid surface. Chladni’s technique involved drawing a bow across a metal plate covered lightly with sand. As the plate reached resonance and vibrated, the sand moved and accumulated along the nodal lines where the surface remained still, revealing distinct patterns known as Chladni figures. His inspiration stemmed from earlier experiments conducted by Robert Hooke in 1680, who had observed a similar phenomenon using flour instead of sand. Today, this technique is still employed in the design of acoustic instruments, although with modifications such as the use of a loudspeaker instead of a bow.

Beyond the ear and the brain, we can also physically feel sound vibrations in our body. Low-frequency sounds can be sensed as vibrations in different parts of the body, such as the chest or abdomen. This is why we may feel the bass of music or deep rumbling sounds. Moreover, sound can evoke emotional and physiological responses. Certain sounds may trigger relaxation, excitement, or fear, leading to changes in heart rate, breathing patterns, and even muscle tension. This is why music, for example, has the power to elicit strong emotional and physical reactions. The processing and perception of sound involve not only the ears and the brain but also our body as a whole, encompassing both sensory and emotional experiences.

Traditional loudspeakers emit sound in all directions, filling the entire space with audible sound. In contrast, directional speakers project a focused beam of sound, restricting its audibility to specific locations. When a listener moves even a step to the side, the sound becomes inaudible. This technology presents both revolutionary and unsettling possibilities. On one hand, it offers potential solutions for sound pollution and noise reduction in public spaces. However, it also raises concerns about the potential misuse of this technology for manipulation, discrimination, and even sound violence. The advent of new sound technologies undoubtedly has a profound impact on our sound environment and the way we engage with it, but it’s hard to predict how will this kind of technology influence our sonic future.