No place on Earth offers a more rewarding wild sound recording experience than a tropical forest. Because sunlight powers bioacoustic systems such forests are more alive and louder than any others.
Blessed with the world’s highest species diversity, these thunderous soundscapes are also symphonic. And, warm temperatures and humidity, coupled with a calm atmosphere within the forest canopy, means sound waves travel faster and clearer than in colder, drier, and windier habitats. Tropical forests have a characteristic echo we often associate with concert halls. A well-recorded tropical forest will quickly become one of your most treasured recordings.
TROPICAL FORESTS
If you haven’t experienced the soul swelling, awe inspiring symphony of a truly wild tropical forest, then place it at the top of your Bucket List. You will not be disappointed. If you’ve already heard and felt the wonder of tropical forests then read on. This guide should answer a few nagging questions about how to make your equipment run longer, help you stay safer, and make your recordings more compelling. Tropical forests vary around the world. Some are dry, and some are wet; some are low along river basins, and some are high on mountainsides. However, several characteristics are shared. All tropical forests lay directly below the sun at some time of the year, falling between the Tropic of Cancer to the North and Tropic of Capricorn to the South.
The species of both plants and animals are highly evolved since no glacial sheets scraped this habitat clean and these areas were the recipients of additional species pushed towards the equator from more temperate latitudes. Periods of species expansion (ice sheet retreats) allowed adaptive radiation, a genetic process relatively free of competition that allowed many genetic traits to coexist. A subsequent period of compression (ice sheet expansion) and natural selection then eliminated some genetic characteristics or in some cases, caused species extinction. Think of Evolution as having a life of its own, and the periods of expansion (adaptive radiation) and compression (intensified natural selection) as deep breaths that enabled evolution to run a faster race.
The outcome of this evolutionary race, accelerated today under global climate change, is that the tropical forests have the greatest number of species of any place on Earth. Species diversity always means sonic diversity, as wildlife communicate just as urgently as humans do.
Paradoxically, tropical forests do not always look diverse. In fact, they typically look relatively simple. Nearly all the trees appear almost exactly alike, same color and bark texture, trunk diameter, same leaf shape tree to tree. And yet tropical forests sound incredibly symphonic. How could that be?
On more careful and patient inspection, you discover the trees aren’t so alike after all. When they flower, they reveal themselves as scores of unique species – each tree’s flower a different color and shape, in some cases even mimicking insect genitalia in order to entice a specific pollinator. Such high plant diversity in dense forests requires efficient pollination systems. This is where insects (more than wind, birds and bats), reign supreme and multiply quickly. Highly genetically adaptable, the insects of tropical forests fit the plants’ needs like hand in glove.
Hearing provides more information about a tropical rainforest than sight ever will. The visual horizon inside the enclosed forest canopy is seldom more than 50 feet – and since many of the trees appear the same, it is extraordinarily easy to get lost. One tree trunk blocks the view of what’s behind it. The GREEN curtain, as some photographers refer to it, does not invite landscape photography. In sharp contrast, our ears lap up the aural bounty, pulling in sound from miles away in every direction under ideal conditions. A tree will not block a sound, but rather echo it.
I was once deep inside the Ecuadorian Amazon rain forest with my guide, Phil, a native Cofan.
He stopped me. Do you hear that?
I listened carefully… I heard so much – the insects, birds, water drips onto thin layers of decomposing broadleaves. Surely he was talking about something different. No.
Monkeys, he announced.
How far? I asked.
Quarter-mile. Phil looked surprised that I could not hear them. He added, They are coming this way.
Patiently we waited. About 10 minutes later, a troop of Wooly monkeys arrived, drawn towards us over that comparatively great distance by the Ching of Phil’s machete cutting us a path through thick underbrush. The largest males tossed branches down towards us to encourage us to leave their territory. Phil and I laughed, but obeyed.
TROPIC-CENTRICITY
Forty per cent of the world’s population lives in the tropics, and by 2050 that percentage is predicted to climb to 55, even with global warming. The world is becoming tropic-centric. So, you must do your homework, if you expect to find a tropical forest with relatively little noise pollution. Below we see the distribution of tropical forests around the world. South America is a standout.
But how compromised by man-made noise is a location likely to be? Let’s check out South America’s population density compared to the rest of the world.
South America’s vast Amazon Basin is looking good. Now let’s consider biodiversity. In the illustration below we see the most diverse places on the planet in red and then trailing off into a light blue for the least diverse.
The Amazon Basin is the heart of world biodiversity.
But in our modern world, where even the North Pole receives noise pollution from continent-hoping jets, we must now take into account all transportation corridors: air, water, land. The computer generated image of transportation over and on the surface of the globe confirms our final wish. The Amazon Basin is a theoretical dream come true.
The Amazon Basin is 2.76 million square miles – that’s still a lot of ground to cover. To narrow our search further let’s consider the effects of deforestation.
Twenty percent of Earth’s land surface area was originally tropical forests. Today, that’s down to only seven percent. Among the many reasons for this disappearance is the unique soil, which sets the stage for irreversible damage. Aged during millions of years through a process known as soil genesis, heavy rainfall has le
ached the minerals needed by rainforest plants. Everything that plants need from the soil to grow was already taken up during the course of evolution, and retained in the biomass, passed on from one plant to the next. This natural recycling center is made up of a relatively thin layer of severed branches, leaves and a few logs on top of the soil with a tight snarl of living roots ready to catch easily accessible assets – the minerals and nutrients released during decay. A fallen leaf decomposes within days, its abandoned resources quickly taken up by mycorrhiza fungi that assist the plant root hairs in retrieving precious minerals and nutrients. If logging occurs, the biomass is removed and this essential cycle stops dead in its tracks. Worse, the barren soil, now lacking roots, compresses, and turns into a concrete-like impenetrable substrate resistant to plant colonization. In short, only virgin tropical forests will produce truly symphonic recordings.
The logging of tropical forests has resulted in what could become the greatest single ecological disaster the Earth will ever experience. Aided by the invention of the motorized chainsaw in the 1920’s, the past 40 years has seen 20 percent of the Amazon forests harvested, more than in the previous 450 years since European colonization. The consequences aren’t just local or regional, they’re global. Plants use carbon dioxide during photosynthesis and produce the oxygen we need to breathe. The Amazon Basin is more than the heart of biodiversity, it is also the lungs of the planet. If we continue logging at the present rate we threaten planetary cardio-pulmonary failure.
YOUR DESTINATION
The Cofan people of Ecuador are an ancient society anthropologists once thought extinct. They surfaced in the mid-twentieth century, registered with the Ecuadorian government, and began the bureaucratic process of birth certificates and marriage certificates. Ultimately, the Cofan received some of their original territory as protected reserves for their continued survival. They are still in transition, carefully dancing along that fine line of traditional subsistence living while also integrating modern technologies. Their land is rich with oil and gold, attracting multinational corporations and poachers. The Cofan now need money for legal defense and to finance patrols to deter poaching. Without your help they will not survive. The Cofan Survival Fund offers ecotours that will accommodate your recording needs. I visited the Cofan in 2012 and hope to return there again soon.
RIVER TRAVEL
Rivers and tributaries provide the major transportation corridors. Your travel will be by boat, so you’ll need to find a place with navigable tributaries that are long enough to escape the loud Thud-thud-thud of the largest river boats that regularly transport goods and passengers on the major rivers. Follow the expert advice of your guide.
WHAT TO BRING
Gear that I consider essential:
- Enough insect repellent to last a lifetime
- Insect netting to cover your head
- A hat for shade in open areas and to support head-netting
- Hand sanitizer wipes to remove insect repellent from your hands before touching your equipment
- A handheld GPS that you know how to use in the dark
- A headlamp (and backup headlamp)
- A roll of white survey flagging, not colored, because flashlights and headlamps do not provide illuminate colors, only contrast. Dark red flagging will appear dark grey – same as leaves
- Nutrition bars to squelch a hungry, grumbling stomach and thereby not ruin a recording
- Umbrella large enough (golf size) to protect you and two shoulder bags from rain, plus serve as blind and provide shade
- A sound pressure level meter to record decibel level immediately after ending a recording session (described in more detail below)
Add to this list as you see fit, and remember this, too: almost as important as insect repellent, you need to bring microphones that perform well under saturated humidity. Your choice of microphones should have a level frequency response and low inherent self-noise, among other specifications. The Sennheiser MKH series of microphones is an excellent choice.
House all your gear in drying bags (not just dry bags, details can be found in „How to Record Thunder and Rain“). Your microphone shoulder bag and your recorder field bag (two separate bags) will be your carry-on bags to minimize loss or delays during travel. Everything else will go in checked luggage at the airport, in cases ready to endure torrential downpours in an open boat. I recommend two Pelican type hard cases with O-ring seals. One case will have a backup set of recording gear, and the other case will have everything else (cloths, meal bars, etc.). Two cases are easier to carry than one big case on slippery surfaces, and remember to distribute the weight evenly. International travel usually has strict weight restrictions on luggage; a few pounds extra could tip the scales and cost hundreds of dollars more. When in doubt – go without.
SIMPLE BUT ESSENTIAL ADVICE
Mark your location into your GPS device as soon as you arrive. A GPS without a reference marker for base camp is worse than useless–without a marker to locate your way back you will only know where you are lost.
While walking through the forest your upright stance appears large to a predator and you will likely not be challenged. But that of course changes as soon as you get low to the ground. You will necessarily want to kneel, crouch, and sit to remain comfortable during long recording sessions. When you do, make a habit of assuming this otherwise vulnerable position with your shoulder blades against a tree. This way, a tree will have your back, protecting you from an unexpected lunge by a jaguar.
Know that other dangers await. Walk slowly, observe carefully. You’ll see, a tangle of roots on top of the forest floor thinly covered by leaves. Poisonous snakes look nearly the same. By walking slowly, you’ll allow snakes to detect your footfall vibrations and slither out of the way.
Do not push aside vegetation with your hands and arms. Use a stick or machete, as there are many kinds of poisonous insects on the undersides of leaves. Watch your guide, notice how he moves, how little he speaks, and do exactly what he does. His habits limn carefully honed rules of etiquette for living safely in the tropics.
QUIET ENJOYMENT
It is a good idea to keep your guide with you or nearby during your recording sessions. He will likely be curious about your equipment. Use his curiosity to your benefit. As soon as you setup to record, hold out your headphones for your guide to listen – he will quickly recognize that your gear is as perceptive as many of the creatures he hunts. Let him listen for several minutes or longer – the longer the better. Now, gently rub your fingers together a few feet from the microphone. You might even have him speak about what he hears. Not only may this be the first time that this locati
on has been recorded, but many of the sounds and their interpretation may never have been heard by Western ears. Your guided recording will likely be an important historical document worth retaining and also valuable should you decide to include species identification in your catalog notes.
The first time I handed my headphones over to my guides, I was with two: Phil and Alfonso, both Cofans, seated next to me in a four-person canoe. My microphone sat on the unoccupied seat. Still, the likelihood of one of us audibly moving during the next hour and spoiling my recording was high. But after my quick demonstration of the sensitivity of the microphones, I went on to record sunrise on the Zabalo River — unmarred by human noise. Although I saw the guides occasionally adjust their positions, they dutifully did so silently.
RECORDING ON THE EDGE
I find, and I’m sure you will too, that the edge of the river, the edge of the forest, the edge of any discernible difference between one place and the next produces a more interesting recording. Species usually associated with one kind of habitat overlap in these transitional areas that the science of plant ecology refers to as ecotones.
This edge-seeking strategy to increase content in a recording can be extended to include the edge of day and night, the edge of wet season and dry season, and other transitional opportunities.
One of my favorite exercises in the field is to record literally at the edge of a large object, such as a rock wall or a massive tree trunk. While you listen over headphones move your microphone towards edges and notice the shift in the background tone. Now reverse position, so the microphone faces outward into the forest and slowly move the microphone away from the object – you will notice the difference in sound quality and learn how to tune your sound portrait to the local conditions, because at a large scale, everything is on the edge of something else.
NIGHT RECORDING
Tropical forests are louder and more active places at night than temperate forests, either coniferous or deciduous. You will be fascinated by the rapid sequence of sound changes at nightfall, a time when the birds become inactive (almost all bird species are diurnal), and the insects begin to dominate the darkness. After this rapid transition it might seem, upon casual listening, that the many layers of insect rhythms have stabilized. You may assume that the night sounds will also remain the same. Nothing could be further from the truth.
To record at night and still get a good sleep, I recommend that you do this: set up deep in the forest during plenty of daylight, at least far enough from your intended place of repose to avoid recording yourself snoring. You will want to position your equipment so that it will stay dry if it rains. I always look for shelter beneath a large leaning tree. Stake down the microphone stand (tripod) just in case a curious jaguar nudges it with an inquisitive sniff. Then set the recorder controls to enable plenty of “headroom” so that close events producing loud sounds won’t distort and your recording will won’t require needed edits. I generally set the ambience at -20 dB below peak level before distortion. After you engage RECORD and begin your recording during weakening daylight, you will now retreat back to camp, stopping every 10 feet or so to tie a short piece of white survey flagging onto a twig. These white flags will be clearly visible day or night, as colors do not show well by headlamp. Most, if not all digital recorders will write a continuous series of files until you stop the recorder the next day, or you run out of batteries. So be sure to start with fresh batteries!
NOTE TAKING
You’ll want a notepad handy to jot down day-to-day information, but you will not want to use this method for permanent record keeping – scraps of paper invariably get lost. The only method I trust is to speak clearly into the microphone – where you are, time of day, what has attracted you to set up in this location, and measured dBA. By using a sound level meter and measuring decibels A-weighted I can reliably reproduce the original sound.
If we look at the curves on the left we see the full range of human hearing, the lowest frequency to the left (20 vibrations per second) and the highest frequency to the right (20,000 vibrations per second). The curves illustrate how our perceived loudness of a frequency depends on its strength. The lowest curve is at the threshold of human hearing (0dB at 1 kHz), typical of a volcanic crater, while the highest curve is as loud as a rock concert. Notice how the curves, one on top of the other, change shape as we listen to louder and louder recordings. If your recordings are played back at volumes higher than original conditions the entire frequency spectrum will shift. Accordingly, you will often hear rumble – and other frequency boosts because a different curve now applies. This is neither good nor bad, unless you want your audience to listen to your carefully recorded natural concert accurately – as in a museum exhibit.
SUMMARY
Tropical forests are the most highly evolved and most symphonic of Earth’s habitats. These lush concerts are rapidly vanishing. Every serious nature sound recordist will want to experience the sine qua non tropical forest, the Amazon basin while good listening opportunities still exist. But bring the right equipment and heed a few key safety tips, if you expect to bring back any heirlooms. I personally recommend the Cofan Survival Fund as an expert guide service for your specific requirements. Patronage of the Cofan will not only help assure your success and safety, but will help these indigenous people defend their lands from profit-seeking multinational corporations that threaten their ancient ways of life.
Stay tuned for more Behind The Scenes material
We want to say THANK YOU for putting your trust in our SFX. Stay tuned for more “Behind The Scenes” specials of our new TROPICAL FORESTS library.
If you haven’t been there yet, take a look at our TROPICAL FORESTSaudio preview: click here!