What Is a Soundscape? Listening to a Place Instead of Looking at It

The framework most commonly used divides a place's sound into three sources, and the distinction is useful because each responds to different pressures. Geophony is the sound of non-biological natural processes, meaning wind, water, rain, thunder, ice and the movement of vegetation, and it sets the acoustic background a place has always had. Biophony is the sound produced by living organisms, from insects and frogs to birds and mammals, and it is the component that carries ecological information. Anthrophony is human-generated sound, divided in practice between controlled sound such as speech and music and incidental sound such as traffic, aircraft and machinery. The analytical claim that made the field productive is that these occupy different frequency bands and time slots, and that in an undisturbed habitat the biophony partitions itself, with species calling at frequencies and times that avoid overlapping with each other, an arrangement described as the acoustic niche hypothesis and supported by spectrograms showing remarkably clean separation.

Recording and analysing environmental sound has become a working method in several fields:

• •Ecoacoustic monitoring, deploying autonomous recorders that run unattended for months and produce data on species presence, activity timing and community change far more cheaply than field surveys
• •Biodiversity indices calculated directly from recordings, using measures of acoustic complexity and frequency occupancy as proxies for species richness, which is fast and imperfect
• •Detecting species that are otherwise very hard to survey, including bats, frogs, insects and nocturnal birds
• •Marine monitoring, tracking whales, fish spawning aggregations and shipping noise from moored hydrophones
• •Documenting change, since a recording made decades ago provides a baseline that no memory or written description could supply
• •Urban planning and noise mapping, where the aim is not only reducing decibels but understanding which sounds a population finds pleasant, tolerable or intolerable at the same level

The term and much of the framework come from work by the Canadian composer R. Murray Schafer and the World Soundscape Project from around 1970, which combined environmental concern, composition and a critique of industrial noise, and which argued explicitly that listening is a skill that industrial society has allowed to atrophy. That project produced field recordings, comparative studies of villages across Europe and a vocabulary that is still used, including the idea of a keynote sound that a community hears constantly without noticing and a sound mark that is distinctive to a place and worth preserving in the way a landmark is. The naturalist and recordist Bernie Krause developed the biophony framework and has argued from decades of recordings that many habitats have fallen acoustically silent even where they still look intact, which is a striking claim that supplies an argument for recording as a conservation record. The field has since split into an artistic strand and a quantitative ecological one that share methods and cite each other only occasionally.

Protecting natural quiet has become an explicit management objective in several places. National park services in the United States and elsewhere measure acoustic conditions, model the effects of aircraft overflights and roads, and set targets, on the reasoning that the sound of a place is part of what visitors come for and part of what wildlife needs. One well-publicised project identified and marked a point in a temperate rainforest intended to remain free of human noise, and reported how few such intervals remain even in protected areas. Europe requires strategic noise mapping of large urban areas and major transport routes, with action plans that include identifying and protecting quiet areas explicitly. The evidence on human benefit is reasonable, with natural sound associated with lower stress markers and better recovery in experimental settings, while noise exposure is linked to sleep disturbance, cardiovascular effects and cognitive effects in children near airports. The practical difficulty is that quiet has no owner and no market, so it is protected only where somebody chooses to.

A place's sound divides into natural physical processes, living organisms and human activity, and species in undisturbed habitats separate themselves cleanly across frequency and time. Autonomous recorders left for months now survey bats, frogs and whales far more cheaply than fieldwork. The framework came from a composer's critique of industrial noise around 1970. Protecting natural quiet is now an explicit management target in parks and in European noise law.