Most people who live in cities or suburbs have never experienced true acoustic silence—the absence of traffic, machinery, air conditioning, and human voices. The soundscape that fills our normal environments is so constant that we process it automatically, without conscious awareness of its presence. A gorilla trek in Bwindi Impenetrable National Park strips this ambient human noise away over the course of several hours, and what replaces it is not silence but a different kind of richness—a forest soundscape of extraordinary complexity and beauty that most modern humans have never consciously heard.
Acoustic ecology: the science of natural soundscapes
The field of acoustic ecology—pioneered by Canadian composer R. Murray Schafer in the 1970s—studies soundscapes as ecological and cultural phenomena. Schafer distinguished between “hi-fi” soundscapes (low ambient noise, high signal clarity, characteristic of natural environments) and “lo-fi” soundscapes (high ambient noise, low signal clarity, characteristic of urban environments). Bwindi is one of the world’s most extreme hi-fi soundscapes: the dominant sounds are biological—bird calls, insect stridulation, water, wind through canopy, animal movement—with zero anthropogenic noise contribution from vehicles, generators, or machinery once the trekking group enters the forest interior.
Research in acoustic ecology has demonstrated measurable physiological effects of hi-fi natural soundscapes on human listeners: reduced cortisol, lower heart rate, improved mood, and enhanced cognitive restoration compared to lo-fi urban soundscapes. The “attention restoration theory” of environmental psychology proposes that natural environments engage a form of “soft fascination”—effortless, low-demand attention—that allows the directed attention system (which manages work, traffic, conversation, and screens) to recover from the fatigue of sustained use. Birdsong, running water, and wind in trees are the archetypal soft fascination stimuli.
What you hear when you stop talking
The sonic layers of Bwindi’s forest emerge in awareness as the trekking group quietens. The lowest layer is the ambient white noise of water: Bwindi’s streams, groundwater seeps, and rainfall drip from the saturated moss create a continuous low-frequency hiss that pervades the forest floor. Above this, insects provide a complex mid-frequency layer of scraping, clicking, and buzzing that varies with temperature—cooling as the group ascends to higher altitude, intensifying in sunny clearings. The highest layer is the bird community: 350 species recorded in Bwindi produce a canopy soundscape of remarkable variety, from the deep resonant honking of hornbills to the thin, liquid notes of sunbirds in the understorey.
The gorilla group itself adds to this soundscape in ways that most trekkers do not immediately identify: the deep belch vocalisations that express contentment, the quiet tearing sound of vegetation being stripped for eating, the soft footfalls of knuckle-walking, and occasionally the chest-beat display of the silverback—a series of rapid pops that travel remarkably far through the dense forest. Learning to hear these gorilla sounds as foreground against the forest’s background turns the trekking experience from a visual event into a fully multisensory one.
Practising acoustic attention
Before the gorilla family is reached, try a brief acoustic attention exercise: stop walking, close your eyes for 30 seconds, and count how many distinct sound sources you can identify. Most people, on their first attempt in a natural forest, identify 3 to 5 sources. With 10 to 15 minutes of practice, the same person can typically identify 15 to 20 distinct sources in the same soundscape—not because the sounds changed, but because their capacity to separate figure from ground within the acoustic field has increased. This exercise, practised during rest stops on the trail, prepares the ear for the gorilla encounter in the same way that vocabulary preparation prepares the mind for a conversation in a foreign language.
