Sasquatch Chronicles Blog

Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz or cycles per second, the “normal” limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high.

The ear is the primary organ for sensing infrasound, but at higher intensities it is possible to feel infrasound vibrations in various parts of the body.

Infrasound and Ghosts
If infrasound hits at just the right strength and frequency, it can resonate with human eyes, causing them to vibrate. This can lead to distorted vision and the possibility of “ghost” sightings. Or, at least, what some would call ghost sightings. Infrasound may also cause a person to “feel” that there’s an entity in the room with him or her, accompanied by that aforementioned sense of dread.

This bizarre phenomenon has been documented on multiple occasions. For example, one night while working at a “haunted” laboratory, Vic Tandy of Coventry University experienced feelings of anxiety, and even witnessed a dark “blob” out of the corner of his eye. The hairs on the back of his neck stood up. But when he turned to face the strange figure, he found nothing there.

The next day, Tandy saw the dark figure again, and he also noticed that the fencing foil he was working with — clamped to a vice — was inexplicably vibrating. So he decided to investigate.

As it turned out, there was a silent fan in the laboratory. The fan was giving off low-frequency sound waves at 18.98 Hz, right around the resonant frequency of the human eye. It had also created a standing wave in one area of the room, which is what caused the foil to vibrate.

According to Tandy, “When we finally switched it off, it was as if a huge weight was lifted.”

The strange vibrations, optical illusions, and depressed feelings were due to infrasound, and had given the laboratory the reputation of being haunted. But it was all because of a vibrating fan.

Mystery of elephant infrasounds revealed
In the current edition of Science, an international team of voice researchers and cognitive biologists led by Christian Herbst, Angela Stoeger and Tecumseh Fitch, provides new insights into the production of Elephant communication. The so-called “infrasounds,” i.e. sounds with pitches below the range of human hearing, are found to be produced with the same physical mechanism as human speech or singing.

Elephants can communicate using very low frequency sounds, with pitches below the range of human hearing. These low-frequency sounds, termed “infrasounds,” can travel several kilometers, and provide elephants with a “private” communication channel that plays an important role in elephants’ complex social life. Their frequencies are as low as the lowest notes of a pipe organ.

Although the sounds themselves have been studied for many years, it has remained unclear exactly how elephant infrasounds are made. One possibility, favored by some scientists, is that the elephants tense and relax the muscles in their larynx (or “voice box”) for each pulse of sound. This mechanism, similar to cats purring, can produce sounds as low in pitch as desired, but the sounds produced are generally not very powerful.

The other possibility is that elephant infrasounds are produced like human speech or singing, but because the elephant larynx is so large, they are extremely low in frequency. Human humming is produced by vibrations of the vocal folds (also called “vocal cords”), which are set into vibration by a stream of air from the lungs, and don’t require periodic muscle activity. By this hypothesis, elephant infrasounds result simply from very long vocal folds slapping together at a low rate, and don’t require any periodic tensing of the laryngeal muscles.

To find out, researchers at the University of Vienna, led by voice scientist Christian Herbst and elephant communication expert Angela Stoeger, removed the larynx from an elephant (which died of natural causes), and brought it into the larynx laboratory of the Department of Cognitive Biology (headed by Tecumseh Fitch). By blowing a controlled stream of warm, humid air through the larynx (substituting for the elephants lungs), and manually placing the vocal folds into the “vocal” position, the scientists coaxed the vocal folds into periodic, low-frequency vibrations that match infrasounds in all details.

Since there can be no periodic tensing and relaxing of vocal fold muscles without a connection to the elephant’s brain, low-frequency vibrations in the excised larynx clearly demonstrate that the “purring” mechanism is unnecessary to explain infrasounds. Thus, elephants “sing” using the same physical principles as we do, but their immense larynx produces very low notes.

As an additional insight, the scientists were able to get a very clear look at some fascinating types of vibration called “nonlinear phenomena.” When a baby cries, or a heavy metal singer screams, the vocal folds vibrate in an irregular manner, which is very grating to our ears. Young elephants also scream and roar, and the mechanism they use is again identical to that seen in humans.

This research shows that the physical principles underlying the human voice extend over a remarkable range, from bat’s incredibly high vocalizations (too high for us to hear), all the way down to elephants’ subaudible infrasounds. How whales, the largest animals, make their even lower frequency sounds remains to be determined.

The Secret Of A Tiger’s Roar
A tiger’s intimidating roar has the power to paralyze the animal that hears it and that even includes experienced human trainers. Elizabeth von Muggenthaler, a bioacoustician from the Fauna Communications Research Institute in North Carolina, presented her research at the Acoustical Society of America meeting in Newport Beach, California on December 7. Bioacoustics is the study of the frequency or pitch, loudness, and duration of animal sounds to learn about an animal’s behavior. At the meeting, von Muggenthaler discussed her work analyzing the frequency of tiger sounds to better understand the part of a tiger’s roar that we can feel, but can’t hear.

Does Bigfoot Use Infrasound?
There’s a lot of debate & contraversy in the bigfoot community about whether bigfoot’s can produce infrasound, and if that’s what is responsible for some of the bizarre effects people experience during and after their encounters.