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When comparing our hearing acuity to other animals, we can’t come close when it comes to detecting certain high and low sounds. Bats and some toothed whale species echolocate using high frequencies we can’t even begin to hear. They do this by sending out loud, short bursts of precisely targeted sound in ranges where the return echoes provide an acoustic snapshot of the target prey. The return signal instantly reveals all the information bats need in order to decide whether the targets are worth expending the energy to pursue. Then there’s the greater wax moth, which can hear frequencies as high as 300kHz.
For you musicians reading this, that’s about six and a half octaves higher than the highest note on a piano and about four times higher than a young child with the full human range of hearing can detect. The ability of these animals to accurately target and process the information they receive gives new meaning to the term awesome.
In one lab test done in the late 1960s, while I was interning with the late marine scientist Dr. Thomas Poulter, a harbor seal in an indoor lab pool was able to perceive the difference between two coins the size of a quarter—one made of aluminum, the other of steel—using echolocation from 25 yards away! Underwater!
Elephants and some large whales (again) send out very low-frequency vocalizations to communicate over long distances. When conditions are right, an elephant’s low-frequency signals can travel through the air a couple of miles in a forest if unimpeded by human industrial sound like chainsaws, generators, drilling and mining equipment, and large logging trucks. With the elephants’ ground signals, the surface layer across the terrain vibrates as the signals are transmitted and received through the large pads of their feet. Moreover, under optimum conditions, low-frequency elephant vocalizations could be detected up to 20 miles away (the distance across the widest part of Long Island)! Meanwhile, some whales’ low-frequency voices are powerful enough to circle the globe if not blocked by landmass or human noise pollution in their marine biomes. Those particular whale voices are so low that we can’t actually hear them. But we can feel the sounds viscerally if we’re within range and in the water at the same time those signals are being transmitted.
Still, we humans retain the same hearing equipment that all other mammals have—the eardrum, the tiny middle ear bones we call the hammer, anvil, and stirrup, and the net- work of sensitive hair cells and nerves in the inner ear that sends those signals to the brain where they are sorted and given meaning or filtered out as being of little or no value.
With the presence of noise, our brains expend a lot of energy evaluating many useless signals that, nonetheless, have an effect on us, whether we want them to or not. Even equipped with the same general listening tools as other mammals, our devolution to substandard hearing may be primarily due to our lopsided reliance on vision to engage with our surroundings.
Or maybe it’s just disuse. In the wild, acute hearing is crucial for detecting potential prey and the approach of predators and other dangers. Not only did we use our hearing when we hunted, but—here’s the kicker—it served as an aural GPS to guide us through unfamiliar terrain at night without the aid of artificial light and where there was no way to navigate by starlight because of the dense forest canopy overhead.
Natural environments aren’t necessarily less complex than noisy urban habitats, although, if a wild biome is healthy, it’s likely to be way more acoustically organized into neat sonic niches, with each critter or species’ voice establishing its own special bandwidth or acoustic turf just like instrumental voices are organized in a musical composition.
Think of the soundscapes of a particular place as a 24/7 environmental news report. It’s where each habitat produces its own cohesive biophonic expression, an understandable narrative portrayed in an ancient protolanguage. Urban soundscapes, on the other hand, tend to be far more disorganized and incoherent.
Complexity is a key feature of urban anthropophonies. Walk through any construction zone in New York City, where wrecking balls are taking down a building, water hoses are wetting down the dust clouds created by the collapsing walls, and compressors can be found running off roaring generators. Trucks, meanwhile, jockey in and out of the area removing debris. All this stuff is hopelessly loud, with lots of competing and irritating sound sources. But there is no clear message to be heard within all that racket.
Even if we try, our brains become overwhelmed when attempting to make sense of the chaos. Natural environments tend to be more organically (naturally) structured—an expressive refrain containing lots of detailed information, voices that have evolved to stay out of one another’s acoustic turf. The other is human-generated, utterly random, and assertively driven. One is healthful for you. The other, no matter how resilient you think you are, can literally make you ill.
When we hear these unstructured urban soundscapes, our mind reacts because the signals clash with our brain’s need for order. Those that we receive contain combinations that we don’t necessarily comprehend. We may generally recognize the source, but since the sounds themselves are not structured for focused messaging, our brains expend energy trying to filter and make sense of the signal. Incoherent electromechanical signals are not part of the natural environments from which we’ve evolved, so we fail. Consequently, when in the presence of acoustic incoherence we’re often left feeling tired or stressed in response, with no clear means to alter the effect. No matter how hard your brain tries to sort out the signals, a steady diet of urban noise is not easy to manage.
You may not be entirely conscious of the physiological impact on your system during these eruptions of noise. But it’s likely that your blood pressure and glucocorticoid enzyme (stress indicator) levels will become measurably elevated. In this case, it happens when we find ourselves afflicted by disruptive types of soundscapes. We hear the noise, but the signals, other than affecting our physical wellbeing and coming across as annoying, produce no other obvious outcomes—in the beginning, at least. Other than affecting our sleep cycles, a garbage truck picking up trash at 4:30 in the morning means little or nothing to our mammalian brains.
Noise takes up space in the parietal and temporal lobes of our brain’s processing centers. If its presence is too overwhelming and prolonged, you may well feel the anxiety that that noise induces and discover too late that it can weaken your immune system. These types of sound are not therapeutic.
Just for the fun of it ...
1. Pay careful attention to the ways you communicate within a field of noise.
2. How much energy do you expend ...
Excerpted from The Power of Tranquility in a Very
Noisy World by Bernie Krause. Copyright © 2020
by Bernie Krause. Reprinted with permission of
Little, Brown and Company. All rights reserved
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