Deciduous Forests (aka, Hardwood Forests) are among the most important natural environments for sound designers to master, owing to the fact that most of our audience, i.e., the world’s economically developed population, resides at temperate latitudes, home to the sounds of deciduous forests.
In the previous chapter, Sound Designing with Tropical Forests, we learned that our model (Earth as a solar powered jukebox) predicts deciduous forests, receiving less average daily sunlight than tropical forests, will not be as loud. True indeed.
But louder is not necessarily better, as we quickly discover, because here, for the first time, we can reliably experience the poetics of space – the afterlife of each sound as expressed by its echo. Not only can we hear animal solos, but we can now also clearly hear the acoustics of Earth’s greatest natural cathedrals.
Deciduous Forests are surely our original places of worship–the models for the world’s earliest cathedrals, such as Old St. Paul’s Cathedral in 11th Century London. If in doubt, just look up in St. Paul’, or any cathedral’s ceiling for that matter, and witness how the large columns produce spreading branches. Are not songbirds nature’s angels?
In Sound Designing with Tropical Forests we learned how ecological pyramids (AKA trophic pyramids) can be combined with sound pyramids to marry ecological information with musical compositional technique to produce more authentic natural soundscapes. We will now explore soundscape pyramids more thoroughly to master our design process.
SOUNDSCAPE PYRAMIDS
This is a standard template that I rely on to determine which soundscapes will work in my design. Let’s study it in general terms and then apply it to seasonal scenarios.
We see plants (solar panels) support the entire bioacoustic system above it. We have insects, amphibians, birds, and mammals as the key performers.
To the right is the Master Volume Level. Like a mixing board we want to set our output level to match the energy available to our bioacoustic system. The graph below shows the amount of solar energy reaching the Earth’s surface (insolation) at any given latitude throughout the year. This information can be used to approximate the loudness of different habitats at different latitudes and times of the year. But a word of caution is needed before we interpret this information, because the data does not take into account the absence or presence of plant leaves needed to harvest the energy, nor does it consider cloud cover that intercepts solar energy, reflecting it back up into the atmosphere.
The dotted colored lines trace the changing levels of insolation depending on how close our location is to the equator. Each color is a different month. To the left is the South Pole and to the right is the North Pole. In the center is the Equator. We can also see in the temperate latitudes of deciduous forests, between 25° and 50°, that there is a difference in monthly sunlight during different months; the range is defined by the red line for December (winter solstice) and the blue line for June (summer solstice). This graph is most useful for determining which are the louder months of the year and which are the quieter. One surprising fact revealed by this graph is that temperate and polar latitudes receive far more sunlight on certain days of the year than the equator ever does! So why aren’t these latitudes louder than the equator? Well, sometimes they are—such as the noisy rookeries of arctic shorebirds in June. But overall, tropical forests remain the loudest because the harsh conditions of winter in temperate and polar latitudes reduce species diversity and limit the total expanse of living solar panels.
Returning to our template, there are Mute buttons that we can use to notate whether or not a given sound class will be present. Each layer in our template has a separate mute button, and of course there’s also a Master Volume Level button. By using these Mute buttons knowledgeably we can omit certain classes of sounds that we know are not active during certain times of day and in different seasons. For example, if conditions are cold, then all cold blooded animals (insects, frogs and toads) would be muted. So let’s get to work and create a series of soundscape pyramids, at least one for each season, and get some practice using soundscape pyramids.
SPRING
The official first day of spring is the precise point when the Earth reaches the Vernal Equinox position on its orbit. For the first time in six months, day and night are equally balanced at 12 hours each. This astronomical definition, however, is not very useful to sound designers. Consider that this year I mowed my lawn outside Seattle on March 20th while folks in Boston, at about the same latitude and maritime climate, were yet again shoveling snow.
A much more practical ID for season is leaf maturity, because again, plants are the solar panels that drive jukebox Earth. Early spring is when miniature leaves are still enclosed in scaled leaf buds in the trees. But plants on the ground, thanks to warmer conditions on the forest floor, will have already begun to produce leaves and sometimes even flowers.
Let’s start our series of seasonal soundscape pyramids with one of many possible fill-in-the-blank outcomes.
The Master volume indicator shows a 35 dBA average–which is quiet overall, but peak volume is 70 dBA, almost as loud as a person shouting at a moderate distance.
The temperature of 38°F is too cold for toads or insects, although some might become active if the temperature climbs higher. I also elected to omit of the Forces of Nature (wind, thunder and rain, flowing water, waves), because I want to start out simple. Mammals are not heard (most are nocturnal) although I could have chosen a nice coyote solo, but I will hold this and other aces for later in the production. This entire natural soundscape, I think, will be composed of scattered songbirds, awakening, moving into position, and then feature one soloist who flutters close-by to belt out a jubilant tune. No one could doubt that a new day has begun.
Now that I have something to stare at and listen to with my imagination, my ideas develop further. I’ll begin with the hoot of an owl…let the echo decay to silence…then hear the first few notes of a distant bird… then another bird chimes in. More follow as the first line of daylight moves this way. I’ll stick with our featured performer, have him flutter slightly right-center stage and belt out his tune. This is will be a st
rong, dramatic opening to a production, so transitioning to another setting could be difficult unless I employ a spring shower. (Read more about transitions in How to Sound Design with Thunder and Rain.)
Spring introduces all the major players in our natural soundscape, plus, as the leaves fill out completely, the creation of cathedral-like acoustics.
Let’s envision another soundscape pyramid later in spring; this time during the evening for comparison between these two important twilight periods for wildlife.
We note that the Master Volume Level is a quiet 34 dBA (typical of a deserted office space after hours with nobody talking and computers off). The overall feeling I want to create is restful, arriving calm after a busy day. In this soundscape pyramid I have described a sonically diverse environment. It is warm enough that toads will be trilling off in the distance from an ephemeral wet area, possibly from an earlier rain. Winged insects are in flight, getting the last nectar of the day and adding a tranquil hum. Since the sun has set, the wind has almost vanished, except for a wisp that passes overhead to communicate to the audience the dimensions of our concert hall. Birds give their last songs of the day, sounding a bit spent. One in particular provides that peak 45 dBA, very likely an American Robin with a distinct song and then a chortle at day’send.
Toads continue to trill as temperatures drop and the night becomes even quieter. Perhaps an owl hoots way down the valley. As the air settles completely and with the forest canopy overhead to allow microclimates to fully develop, sound not only travels much farther than during daytime, but some sounds are reflected from the forest canopy back down to our ears. These could be secretive sounds of a hidden reality—like rainwater percolating through the forest soil and into a reverberant root cavity.
SUMMER
Summer is distinguished by mature leaves reinforced by structural sclerenchyma cells that support these living solar receptors. Warmer temperatures and ample sunlight result in accelerated plant growth, which in turn, feeds exponential growth in insect populations and then on up the food chain. Many birds are now off the nest. The young have fledged, and we hear a pronounced shift in bird vocalization from characteristic territorial songs to short social contact calls and a weakening of the dawn chorus that will not resurge until the autumn, and even then, only briefly. Wet forest floor depressions used earlier by toads have now dried up. Young toads have thus dispersed, eating some of the abundant insects on their way to a new habitat.
In the above pyramid of a summer night in a deciduous forest we see that the Master Volume Level is set fairly high, temperatures are warm and birds (which are diurnal) and toads (which have finished mating) are muted. The dominant players are plants, insects, mammals, plus thunder and rain. Note the absence of wind.
A glance at this pyramid tells me right away that insects will dominate. The warm temperatures and ample food have allowed their numbers to swell. Deciduous forests support a variety of crickets and katydids, which weave intricate choruses. Rain is possible but not likely, as summer thunderstorms typically occur in the afternoon, so just a few rolls of distant thunder will contrast nicely with the multi-layered insect choruses. Mosquitoes would be likely, but unless artfully used, will annoy audiences rather than draw them into the experience. Any plant sounds will be caused by mammals (which are dominantly nocturnal), like raccoons or an opossum, curiously exploring the night for something to eat.
ATUMN
Autumn is defined by the transition of the forest to a leafless stage. The parent tree begins to extract resources from its aging and now brightly colored leaves in preparation for abscission, the dropping of leaves. Food resources are shrinking as the harvest season shouts last call. Meanwhile, insect populations have grown to all time highs, just before dropping seasonal temperatures bid them farewell.
Nighttime autumn insect choruses are as spectacular as the spring choruses of songbirds. Strangely, songbirds begin to sing again because day lengths now match those of spring, although nesting will not take place until the dark winter months have long since passed. Their songs, while not as bold as earlier in the year, sound better rehearsed, at least to my ears. There is something very romantic about the autumn days just before the first leaf drops. At any moment a transformative gust may free leaves by the scores, triggering a final applause of colliding leaves. When the tree limbs are bare, at last, the forest’s cathedral-like acoustics are gone–its ceiling is now open to the heavens.
Let’s look at this soundscape pyramid of a late night in autumn. We see that this is surprisingly loud at 60dBA peak level–as loud as typical human speech, and the average is 48 dBA, comparable to a private conversation. Birds and toads are set to mute. There’s no noticeable presence of wind, thunder or rain, flowing water or waves. This is the last hurrah for the legions of insects that rule the night, and complex rhythmic textures interweave, holding the audience’s attention, if necessary, for sustained periods to let your story completely unfold. Occasionally we hear a leaf or two drop from the forest canopy, like sonic confetti, celebrating all that we have heard. And now, coyotes that may have made a cameo appearance in early spring howl out a tribute to the year.
WINTER
Winter is the season of silence. This is a dormant time when tree branches are bare, insects are hibernating, frogs and toads lie buried away, birds have either departed or have flocked together to pool warmth. Mammals, which have adapted in various ways to the scarcity of food, are rarely vocal, except in my experience, for very long distance communication between wolf packs (under ideal conditions their sounds may travel more than ten miles to human ears). But cold dry air does not propagate sound as well as the warm humid air of summertime. Winter acoustics can become desert-like. But there is a sound to this silence: the hush of falling snow.
This is a soundscape pyramid of a winter day. I could go either way with this depending on the needs of my design. The wind could roar ferociously, as if the bitter cold will eat the audience alive. In that case, there will be strong branch rattles too, and the high pitched sounds of creaking trees that will also inform our audience of the biting cold. But this would almost never do at the end of the story. Most stories end in silence – one way or another – so why not bring silence intentionally into the production rather than by default? I would use the softest roar of wind through bare branches, one that builds and then passes on to the vanishing point of the listener’s horizon.
SUMMARY
We can hear in this series of soundscape pyramids not only the passage of the seasons in a deciduous forest, but birth and maturation and death in both flora and fauna—stages of life that offer metaphoric support to the protagonist on the screen. So during your sound design process it is sometimes helpful, while you stare at a blank template of a soundscape pyramid, to ask yourself: “What stage of life is my character?” And place him in the most appropriate season. Or consider his actions. Even a single cinematic day can hypothetically hold all four seasons: spring (dawn), summer (day), autumn (evening), winter (night).
We know that deciduous forests are important natural environments for a sound designer to master, because more than any other environment, audiences are generally familiar with its sounds. While not as loud or as diverse as tropical forests, deciduous forests can be more alluring and even provocative, for by using the changing sounds of the seasons intelligently, plus with the increased opportunity for quieter times in nature’s cathedral, we can be moved by the poetics of space. Using multiple soundscape pyramids, at least one for every season, will keep your work organized and intelligently impactful.
If you haven’t done it yet, you should definitely listen to our DECIDUOUS FORESTS audio preview: click here!