Hearing Many Stories At Once

Elephants call to one another across great distances by making rumbles that then flow through the ground. They hear these sounds using dense patches of sensory cells in their feet, supplemented with transmission of the sound through their leg bones to the neck and then the inner ear. These rumbles are very low, too deep to be heard by humans, a frequency that transmits especially well over long distances in the soil. The great diversity of sonic expression across the animal kingdom has its origin, in part, in the varied physical properties of Earth. When we hear a song or cry, we hear the material context in which it evolved. We are also surrounded by sounds inaccessible to our unaided ears, each one tuned to its environment. Our senses live confined in a small part of the whole. Yet we can imagine that under the river’s surface are fish drumming to one another. Off the seacoast, whales sing into the deep sound channel and listen to answers from half a world away. In the trees and on the stems of grasses and flowers, insects duet. It is two in the morning and I lie awake, listening to the rain forest. The cabin is in a small clearing, the top half of its walls open to the forest save for a shield of mosquito netting.

Goodbye To Innocence

My companions, scientists working at the Tiputini Biodiversity Station in the Ecuadorian Amazon, are asleep, worn out by treks on muddy trails. I woke from deep sleep into a glory of sound, an exultation born in the voices of hundreds of species. A crested owl growls a sonorous oor, repeating every five seconds. This is the deepest sound in the forest tonight, delivered with the slowest tempo, a languorous bass. Twin white plumes crown the head of each adult, contrasting with their chocolate plumage. The youngster is all white. In the rain forest, we rarely see the animals whose sounds surround us, and so this family group is much photographed by visitors. It rained earlier in the night, and drips from the soaked vegetation that overarches the cabin enliven our tin roof with snaps and spatters. In the forest, tree frogs yelp from low vegetation. Their call is tight and nasal, yup! I hear them all around the cabin, answering one another. I feel caught in the middle of a ball game among half a dozen frogs. On my left, a call smacks the rubbery projectile into the forest, then another frog on my right whacks it in a different direction, to a singer near my head, back and forth, the sound vaulting over me.

Best Of Both Worlds

The songs of insects are not as easily localized by my ears as owl and frog sounds. I can pinpoint the direction of only a few crickets and katydids, but mostly I’m wrapped in their sonic mists. The clouds of sound are not homogenous, though. Dozens, perhaps more, of pitches, timbres, and rhythms coexist. Here in the Amazon, species diversity is ten or more times higher, a magnificent convergence of sounds. In the lower registers, a katydid gives short fibrillating bursts. This is overlain with higher, shimmering songs, like dry rice cascading into a steel bowl. Alongside, a hacksaw delivers regular strokes, the harsh bite of teeth on metal. A sweet trill floats over, pulsing once every second. Alongside, three species give continual buzzes, quite close in pitch, one ringing clear and bright, another slightly fuzzy, and the third very arid, like a stick dragging through sand. An irregular sound like the tinkle of metal shavings skips over the buzzes and whirs, so clear and bright that I see silver flashing. Pitched even higher are more pulses, some pumping every second or so, others coming in streams.

Where Is the Love?

There is yet more sound here at higher frequencies, but the human ear cuts it out, a space we call ultrasonic but is, in fact, not beyond sound but merely beyond our perceptual abilities. At least thirty genera of treehoppers live here, comprising an unknown number of species, as do more than four hundred species of planthoppers. In the audible range, the insect sounds seem to occupy two bands. One is about the frequency of high birdsong. This is where most of the insects sing, a range familiar to anyone who has heard chirping crickets and katydids in parks or forests outside of the tropics. The other is much higher, a fine, crystalline gleam of sound. The lowest frequencies and the midrange seem sparser, save for the lowest insect trills, the owl, and tree frogs. As I lie in the humid cabin air, sweat easing down my face and neck, pooling in my clavicles, I am befuddled by the experience of listening. I can attend to the insects in one of only two ways. Either let the sound wash over me as a whole or pick out one single species and focus on its shape and qualities. There is too much richness here to hold multiple species in close attention, as I do in temperate forests. In forests in northern Europe or the North American mountains, I can revel in the combination of several singing species, like enjoying the convergence of several spices in a meal. In the tropical forest, hundreds of flavors and aromas coexist at once, an extreme blast of sensory diversity that stuns my auditory palate. This wonderful but unsettling experience is also radically unlike listening to human music. Whether in a folk song, a jazz improvisation, or a symphony, the human mind crafts sonic layers, each in close relation to the others, all emerging from instruments designed to complement one another. One or, sometimes, a small number of people compose the music. Human music contains complex, divergent, and sometimes discordant narratives but emerges from a narrow generative source, the minds of its composers and the proclivities of the human ear. Many aesthetics and narratives coexist here. Listening in the rain forest is challenging and delightful because we hear many stories at once, each expressed with a voice suited to the aesthetic of its own species.