©Arlene R. Taylor PhD
“How do dog whistles work?” asked the young man.
“They work,” replied the vet, “by emitting sounds above 20,000 Hz. Dogs can hear those sounds while people cannot.”
The vet went on to explain that the normal higher limit of adult human hearing is about 20,000 Hz (Hertz) or cycles per seconds while the lower limit is about 20 Hz.
“And a cat’s purr?” asked the young man. The vet laughed.
“Cat purrs generally fall within the range of from 20 to 50 Hz so most are within the capability of the human ear. Your dog must know the word ‘cat’ because his heart rate just increased.” The young man nodded, laughing.
“I suppose you’ve heard of infrasounds?” asked the vet. This time the young man shook his head.
Infrasounds are low-frequency sounds, lower than the normal limit of human hearing. They consist of a very long wave that goes between particles and molecules rather than bouncing off them. High-intensity infrasoundsextend in the megahertz range and well beyond but their frequency level is below 20 Hz. Sometimes you can hear part of the sound and just sense the infrasound. Sometimes you can only feel the infrasound.
“I know about them,” continued the veterinarian, “because infrasounds are prevalent among creatures in nature. Hippopotamuses, alligators, and giraffes reportedly use infrasounds to communicate over considerable distances. Sumatran Rhinoceros produce infrasounds as low as 3 Hz with similarities to the song of the humpback whale. Elephants trumpet at 15-35 Hz and as loud as 117 decibels, the sound traveling distances up to six miles. The infrasounds are used to coordinate the movement of herds and allow mating elephants to find each other. Elephants also produce infrasounds that travel through solid ground and are sensed by other herds using their feet, although the herds are separated by hundreds of miles. Elephants have bet low-frequency (infrasound) hearing than any other mammal tested so far.
“I had no idea!” exclaimed the young man. ‘”That’s absolutely fascinating. Actually, I heard a comment recently that I didn’t understand until now. Recent research by Jon Hagstrum of the US Geological Survey suggests that homing pigeons use low frequency infrasounds to navigate.”
“And then there is the roar of the tiger,” said the vet. “Tiger roars can be both heard and felt.”
The roar of a tiger contains audible sounds and infrasounds of 18 Hz and lower—which can penetrate solid objects like walls, permeate buildings, pass through mountains, and travel for miles. Its prey feels the infrasounds in addition to hearing the threatening roar—usually the last thing the victim hears—which can reach 114 decibels a few feet away (25 times as loud as a gas lawn mower). The infrasounds can paralyze its prey, which helps the tiger catch it. Sometimes the creature dies of fright before the tiger can kill it. Humans can feel the tiger’s roar, too, a sensation that can cause momentary paralysis, even in trainers who have worked with tigers for years.
Human beings react to both loud sounds and infrasounds, pouring out stress hormones that impact both brain and body in a myriad of differing ways. Physiologically, stress hormones are about survival, which always comes first. Always. Other functions take second or third place. When stress hormones are released, they shut down any function or process that is not immediately required: digestion stops, immune system function slows, libido decreases, and so on. Extreme levels of stress hormones can increase one’s risk of stroke and, in rare cases, even cause death.
Hormones are secreted all the time, dribbling out bit by bit. The body also attempts to rebalance itself all the time. Therefore it seems logical that (unless the damage is so severe it cannot be reversed) learning how to manage stressors effectively may help (at least going forward) to help the body be healthier. So will any strategy that can help the body rebalance itself easily, effectively, and accurately.
Some evidence exists that actions you take and behaviors you exhibit today can impact the immune system four to twenty-four months later. Learning to manage stressors now can positively impact your brain and body down the line. If you plan to be alive in the future, do something now that will impact your life positively up two years from now.
And remember the roar of a tiger....