Twenty-first century Edens, tropical forests are the heart of biodiversity, the lungs of the planet, and the concert halls to the planet’s greatest living symphonies. Armed with a few basic principles, your sound designs can become soul-changing experiences.
Our body’s largest organ, our skin, feels completely at home in a tropical forest. That tells us something. And how often are the words tropical and paradise heard together? No wonder tropical forests are among the world’s favorite vacation destinations.
EARTH IS A SOLAR POWERED JUKEBOX
Tropical forests lie directly below the sun at some point during the year and therefore receive more energy than other forests. If it’s healthy, a tropical forest will be loud! Healthy forests have escaped the heavy hand of mankind, and in tropical locations the diverse species have evolved in place rather than migrated from somewhere else. This means that the species have co-evolved, learning how to share resources to minimize competition to the advantage of all. The acoustic environment is a natural resource as necessary and advantageous as food and water. To survive, species need to effectively communicate with each other, and at times with other species. They do so to attract a mate, defend territories, and avoid predation. Little wonder wildlife are as busy communicating as we are.
But since the acoustic environment is a shared environment, the potential for conflicting uses among different species is high. Think of scores of radio stations wishing to broadcast simultaneously. Nature’s solution in the forest is similar to that of the Federal Communications Commission, “dividing” the frequency spectrum into bandwidths and “assigning” species a set of bandwidths and times of broadcast. This results in an extremely efficient bioacoustic communication system in tropical forests with long histories of coevolution between species and a pronounced symphonic structure. Some species, like insects, dominate the higher frequency range of human hearing. Their sound emissions are produced by a variety of means and are triggered by time of day, by the amount of sunlight and temperature, to sound-off at just the righttime to communicate with members of their same species. Bird calls are largely mid to high frequencies, not as continuous as insects, most noticeably at dawn and dusk, with less frequent communications during the day. Mammals are predominately nocturnal and occupy mid and low frequencies, communicating loud and elaborate songs and alarm calls only occasionally, when necessary, and more typically communicating via simple, short contact calls that allow members of the same social group to remain in touch despite thick, sight-blinding vegetation. In this way, healthy tropical forests produce music to our ears – distinct enough for us to hum all day.
You can read more about this process of resource sharing by different species under the term resource partitioning, a basic ecological principle that results in the eventual branching out of the evolutionary tree to produce new species.
This symphonic performance – harmonious in a healthy forest, or discordant in a disturbed forest – will communicate to your audience the spirit of place that will fundamentally drive your overall sound design.
SPIRIT OF PLACE
Deserts and canyons are examples of habitats that are dry, spacious, and often sonically sparse. Sound propagation is generally poor in arid conditions. So naturally, the scenery commands our attention first. Our ears relax, and our thoughts turn inward. Such arid places are better suited for a vision quest than an aural awakening.
Tropical forests are completely different. Warm, humid atmospheric conditions allow sounds to propagate more quickly and travel farther than in arid cold places. The diversity and density of animals produces a 24/7 rippling of information through the ecological pyramid, sometimes called the trophic pyramid. Our thoughts migrate outward to include all things existing at the same moment, eclipsing inner thoughts. Tropical forests, therefore, are ideal for powerful settings and spiritual transformations of another kind than vision quests. Tropical forests are places where life is no longer about you, separate from nature, but you as part of the much larger, complex, web of life.
ECOLOGICAL PYRAMIDS
The ecological pyramid (AKA, trophic pyramid), shows how biomass is divided into producers (plants) and animals (consumers), each level feeding on the level beneath it. Plants on the bottom and humans at the very top, or so we would like to imagine. The greater the biodiversity, the more layers an ecological pyramid will have, ultimately resulting in more complex music.
As food, energy, and nutrients are passed up the food ladder, the biomass of each trophic level decreases. Given that each broad group of animals communicates and sounds differently, there’s also, in effect, a sound pyramid, one often used in music composition and performance.
Pairing a sound pyramid with ecological information can be a valuable tool for designing tropical forest soundscapes. To do so, first draw a pyramid with a wide base for stability, many layers above for diversity, and at the top, a select few featured soloists. By replacing the musical instruments in a sound pyramid with creature classes, it’s easy to appreciate that healthy tropical forests are indeed symphonic soundscapes.
Sound designers may find soundscape pyramids useful for creating ecological balance or imbalance as the sound design may require. For instance, add more layers to the sample pyramid above for more symphonic places or reduce the number of layers to design locations that would sound more like a classical orchestra short on musicians during flu season. By adjusting the angle of the pyramid’s sides you can balance the sound to taste–but not too much as this would sound unnatural. Wide bases are more stable, abundant food supplies for each layer above to feed. Narrow bases to indicate a poorly supported ecosystem that may be on the edge of ecological doom.
The base layer of all pyramids will be Plants and these sounds will show up during windy periods. If there are no plants there’s no energy to support the layers above, so any sounds will be by transient species. The next soundscape layer above plants for tropical areas will be Insects, above that Frogs and other consumers of insects, and above that their predators, and so on. In this way you can either select or construct your soundscape to match the intention of your sound design. You may have a different soundscape pyramid for each scene depicted in your production. In the graphic above you could add sides to represent evening and dawn, transitional times that are exceptionally dramatic.
Let’s review the layers in the soundscape pyramid and how they will sound. Plants are periodic, a reflection of time of day and weather fronts. In tropical for
ests you’ll hear the clatter of leaf collisions high above, with the resulting dropping of debris. Insects most commonly dominate the tropical forest soundscape, both day and night, as they are the primary consumers of plants. Be sure to have insects dominate your tropical soundscape, except when you intentionally want to create a weird, unnatural setting. Insects are fascinating minstrels. Some even sound like birds, and they are keenly aware of daylight changes too small to be detected by the human eye. Use insects liberally.
Expanding your chorus, you might include frogs and toads – sparingly during the day with an isolated croak or trill and then more generously at night when they form choruses. Far less prevalent than insects and amphibians, birds are most active during twilight conditions when territories are established. When the heating action of the sun on the atmosphere above the forest canopy stirs and mixes the air, inhibiting sound propagation, bird vocalizations are much less frequent. Mammals, unlike birds, which are almost without exception active during the day, are active at night – occasionally making bold statements with full bravado. One aptly named rainforest star is the howler monkey, which safely perched atop a tree, roars fearlessly, claiming territory for miles in every direction.
It is interesting to note that as we go up the ecological ladder, highly evolved creatures make sounds less often. When they do, they communicate messages important enough to risk predator detection.
In sharp contrast to this rule, humans and modern soundscapes appear to have de-evolved. Humans chatter incessantly, and our thunderous machines have come to dominate the shared acoustic environment, overriding the needs of wildlife to communicate essential messages to complete their life cycle. The conclusion is inevitable: Based on their soundscape pyramids, modern humandominated soundscapes are unhealthy places.
EACH GEOGRAPHIC LOCATION PLAYS ITS OWN MUSIC
Because each location on our planetary solar jukebox has a unique set of physical and biological characteristics, largely determined by latitude and longitude, each locale plays a distinct tune. These tunes cycle through the day, days into seasons, and seasons into a gradual evolutionary change. In the beginning, there were only the sounds of the physical world, then the sounds of primal life, and today life as we know it. This evolutionary progression can be useful to sound designers wishing to introduce larger themes during a program. Meaning, start out simple and build to symphonic–that is, if there’s to be a happy ending.
The most common mistake of an inexperienced sound designer is borrowing sound files from different tropical forests, perhaps even located on different continents, and mixing them together. While the results may be good enough to fool other inexperienced listeners, the end product will most likely result in a odd sounding, discordant soundscape because the species are not members of the same bioacoustic system that evolved in place thereby minimizing competing communications. In this patchwork, different species will likely overlap – a bit like trumpets and clarinets playing different tunes at the same time. We expect this in modern disturbed ecosystems where invasive, non-native species, have been introduced (such as Hawaii). But we do not want unintended results in our sound design, unless we’re actually seeking chaotic results. Accordingly, a sound designer should generally pick just one location for the entire scene or even project.
The second common mistake is to use daytime insects and nighttime insects interchangeably, or even birds at night or a bird chorus with open air acoustics inside a forested area. Inexperienced uses of nature sounds in building authentic soundscapes is becoming more and more common as both sound designers and audience members live in cities and spend less and less of their lives in natural places.
More than half of the world’s population now lives in urban centers. Faked sound designs will only further separate humanity from reconnecting with the Earth and intelligently addressing our global ecological crises. Ultimately, we simply save what we love and the details will take care of themselves. It is the moral obligation of sound designers to present Earth’s living music authentically.
FINDING THE RIGHT SONG
There are many kinds of tropical forests: wet, dry, lowland, upland. Some forests at the equator might even receive snow if rooted at high elevations. You might be free to pick the location that best meets your need, but more commonly, the sound designer is furnished artwork, scene shots, or footage that must be supported by sound. Your job is to work magic – satisfy your boss’s preconceived, and often erroneous, idea of what the end result should sound like, and also be faithful to the location and allow your sounds to communicate messages to the audience.
If you are free to select any tropical forest for your sound design, then start by listening to a wide variety of locations. You will immediately hear the effects of elevation and rainfall on the overall sound quality. As elevations increase, the forest height declines as the result of weather stress, wind, drought exposure, and dehydration. Tropical forests at lower elevations are less exposed and more protected from weather and thus generally achieve greater heights, especially in ravines blessed with fertile soils. Forest height affects two dramatic sound qualities. The lower the forest, the shorter the decay time. The space will sound smaller, more confined, as if walking into a concert hall with five foot ceilings. Wind sounds will also be closer and more pronounced. Since higher elevation tropical forests are also cooler this means sound travels slower, and the rarified atmosphere increases attenuation – resulting in a loss of clarity when compared to low elevation forests with warmer temperatures.
Low elevation tropical forests are taller, less exposed, and warmer. So sounds travel faster, attenuate less over long distances, and more importantly, as a result of larger spaces within the forest canopy, have a longer decay time similar to concert halls. When wind is audible, we hear an indistinct roar coming from a distance. Then, as it passes high overhead, we may occasionally hear debris fall from above. (We do not hear the spatial details found at higher elevation forests.) Even as the wind increases according to its daily cycle, the floor of the forest remains calm. The protective influence of forest canopies on the forest floor produces distinct microclimates where atmospheric conditions are favorable to sound propagation. In sharp contrast, outside of this microclimate in the exposed air layer immediately above the forest, a steep daytime temperature gradient often exists, and being unfavorable to sound propagation, deflects sounds waves, preventing them from entering the forest.
There are two acoustic worlds – one within the forest and the other above – in continuous tropical forests. The astute sound designer can use these two worlds to send a message within one world and have it not detected by the other, thereby constructing a sense of parallel realities. Listen to numerous tropical forest locations and become familiar with how their acoustic qualities vary in accordance with elevation and forest height. Several ecotour services offer forest s
ky walks where you can listen to the differences between the two acoustic worlds below and above the forest canopy.
Rainfall is just as important as elevation for characterizing how a tropical forest will sound. Low annual precipitation produces wider spaced trees and often lower canopy heights. Areas with high annual precipitation will be dense jungles featuring plants called epiphytes that grow entirely without soil on tree branches. Listen carefully to samples of wet tropical forests before you begin your sound design.
Discover the right combination of elevation and precipitation and you’ve found the right song. Stick with this location for all your sound needs and the rest of your sound design will fall into place quickly.
If you do not have the freedom to select an optimal combination of elevation and precipitation, but instead, have been furnished with artwork that requires sound, then the process is a bit different. If the artwork depicts a real location then you have only one choice – find sounds from that location or one nearby that appears visually the same. If your sound search does not produce enough matches, then location recording is required (see [BEHIND THE SCENES] How to Record Tropical Forests).
If your location is not a real place but an imagined forest, typical of gaming environments, then immediately consider sunlight and vegetation. We already know that the ambient sound will be loud if the setting is a tropical forest or jungle–at least if it hasn’t been compromised. Is it mid-day, twilight, or night? You can look at the angle of light as well as the light spectrum to make your determination. As in prairies and all other habitats, plant diversity translates into wildlife diversity and becomes sonic diversity–so the more complex the vegetation appears the more complex the soundscape should be. However, tropical forest trees often look identical even though they are different species, so even seeminglyuniform forests can still sound diverse. This is not true for other habitats.
DRIPS
Wet tropical forests are drippy places for more reasons than just the ample rainfall they receive. First, let’s remember that in open areas we often hear the direct impact on rain drops on the ground – small or large, raindrops are heard hitting rocks, leaves, puddles, each making a different kind of splat, tap, or plop. Raindrops rarely hit the ground directly in tropical forests. Instead, rain strikes the leafed-over forest canopy, coalesces with other raindrops, then rolls and drips to the ground. Drips are much larger than raindrops and therefore louder when they plummet and strike thick broadleaves, branches, and puddles. Furthermore, long after a rainstorm has passed, the canopy continues to drip. And finally, even without rain, a natural process called guttation causes many tropical forests to drip heavily under even starry skies. Plants take up water through the roots and transport minerals and nutrients up to the plant leaves. This process is driven by evaporation during the day at the leaf margins. Relatively dry air passes over the leaf, evaporating water and allowing more water to pass up the water column from the roots. This is transpiration. Tropical forests growing on wetter soils have such a vigorous transpiration flow that when the sun sets, curtailing evaporation from the leaves, the momentum of the water flow up the plant continues to push water out of the leaves. The resulting sound is almost identical to rain-caused drips. Therefore, a sound designer is encouraged to use drippy ambiences even on sunny mornings. But be careful, for as the day advances, evaporation will again occur and the drips will gradually die down and then become absent.
DEBRIS
Tropical forests are highly productive and grow rapidly under full sunlight. This produces a lot of small plant parts (debris) that fall day and night. Sometimes, this will be a rain-like cascade of particles dislodged during the first breeze of morning. Other times, day or night, there’ll be a random shower of small particles. Sound designers, who might normally edit out brief clicks, ticks, and taps, because they distract the audience, are advised to use restraint if you wish to remain authentic. Debris falls all the time in tropical forests, and the loud roar of a tree falling to the forest floor, echoing far and wide, is almost a daily event.
AUDITORY HORIZON EXCEEDS VISUAL HORIZON
A basic sound design question is, Can my sound design employ sounds that are not supported visually? For example, would it be acceptable to include a loud howler monkey in the middle of the night even though the audience will not see one? Some producers want to use only those sounds that support the visuals. But especially in tropical forests we rarely see more than 100 feet; yet we hear for miles! So here, more than anyplace else on Earth, the sound designer is free to haunt the audience with unknowns. Tropical forests are lush, wild, and until recently, relatively unmapped places. It’s a jungle out there! These are suspenseful settings where deadly snakes lay camouflaged among tree roots, poisonous caterpillars hang concealed under leaves, insects swam, and maneating cats stalk their prey on padded feet. A loud unexplained sound will signal danger to your audience and trigger their survival instincts, especially their sense of hearing.
SUMMARY
Tropical Forests offer opportunities for sound designers to produce dramatic musical compositions without a single man-made musical instrument. Pick your location wisely and work from its innate sounds only. By applying a few basic ecological concepts and keeping your work organized with soundscape pyramids – one for each major setting – you will transform the way your audience listens to the world around them. Be prepared to use lots of drips (not drops), and restrain from removing clicks and taps. It’s a jungle out there so feel free to go wild!
If you haven’t done it yet, you should definitely take a look at our TROPICAL FORESTS audio preview: click here!