[2] However, urban habitats are relatively recent in humankind history and evolution, and natural soundscapes have preceded the apparition of Homo sapiens, some 300,000 years ago.
More broadly, HAE aims to encourage hearing scientists who traditionally work on speech and music perception in urban settings to collaborate with soundscape ecologists, ecoacousticians and neuro-ethologists, and share expertise with environmental and architectural acousticians, anthropologists, philosophers and geographers.
[7][8][1] From such a perspective, HAE is based on (i) concepts derived from soundscape ecology such as the acoutic adaptation and acoustic niche hypothesis,[10][11][5][4] and (ii) psychophysical and neuroscientific models and methods.
Moreover, HAE investigates the extent to which these monitoring functions are adapted to specific information conveyed by natural soundscapes, whether they operate throughout the life span or whether they emerge through individual learning or cultural transmission.
[29] The statistics of these sounds and scenes could be characterized further using the large, ecologically valid databases collected by soundscape ecologists and ecoacousticians, allowing to test further efficient-coding principles positing that perceptual systems (e.g., the auditory system) have evolved to encode environmental stimuli in the most efficient way, and that the properties of auditory mechanisms closely match the statistical properties of natural sounds and scenes.
In contrast, the majority of experimental studies of human auditory perception have utilized parametrically generated stimuli which lack acoustic complexity of natural environmental sounds.
Furthermore, traditional psychoacoustic methods have relied primarily on detection and discrimination tasks in which a specific acoustic parameter is manipulated (e.g. frequency or intensity) under conditions of low stimulus uncertainty and performed by trained listeners.
Overall, traditional psychoacoustics has been highly successful in describing human auditory abilities in relationship to underlying anatomy and physiology, leading to tremendous breakthroughs and achievements in communication and audio technology.
[36][37] A growing awareness of these limitations to ecological validity in traditional psychoacoustics has led to the broadening of theoretical approaches and modifications of experimental procedures used in the studies of auditory perception to include tasks involving sound identification, categorization and comprehension.
For instance, listeners can accurately judge the size and behavior of objects, such as predicting the timing of successive bounces of different types of balls, dropped from different heights, based on preceding sounds.
[40] Efforts have been also made to develop comprehensive ecologically based taxonomies that would apply to sounds of everyday listening environments[41][36] and integrate them into broader acoustic communication frameworks.
[42] Furthermore, unlike HAE, previous approaches to the study of auditory perception have made no systematic distinction between natural (biophonic or geophonic) versus mechanically or electronically generated and technophonic sounds.
More precisely, these studies showed that naive (untrained) listeners hear changes in habitat (forest, meadow, grassland, chaparral), moment of the day (dawn, dusk, etc.)
Many natural environments, such as a flock of birds singing in the trees or a swarm of insects chirping in the grass are composed of large numbers of similar sound events.
Indeed, adults rated a wide range of scale-invariant, but not variable-scale, sounds as natural recordings of brooks and streams, and qualitatively described them as various forms of water.
[75] Examples of beneficial outcomes of listening to natural sounds included decreased pain, lower stress, improved mood, and enhanced cognitive performance[75] Soundscape studies play an important role within the framework of HAE, focusing on human sensory and emotional auditory processing.
[76][77] Defined by ISO 12913 as the acoustic environment perceived by humans within a contextual framework,[78] soundscape studies diverge from traditional environmental noise research by emphasizing positive health and perceptual outcomes,[79] particularly regarding the (measurable) restorative properties of natural sounds.
Advancements in the field include innovative methods for visualizing and analyzing quantitative soundscape data,[84] alongside prediction models that simulate human perceptions of present and future/hypothetical acoustic environments.
[87][88][89] However, when tested under more challenging conditions which closer approximate everyday listening environments, older adults with and without hearing loss require greater signal-to-noise ratio (SNR) to identify sounds in scenes.
[8] The ability to experience sounds of nature can lead to feeling less pain, lower stress, enhanced mood and improved cognitive performance.
[104][105][106][107][108] Nevertheless, when explicitly tested, the ability of cochlear implant users to identify common environmental sounds shows considerable decrement compared to normal hearing peers.
[36][112][113] environmental sound perception appears to be a fertile area for theoretical and applied auditory perception research[38] Adults with permanent, sensorineural hearing loss do not experience a full range of emotional responses to non-speech sounds; they report emotional responses that are extreme (less pleasant and less unpleasant) than do their similarly aged peers with normal hearing.
[115] Therefore, improving audibility of high frequency cues, such as with a hearing aid or cochlear implant, would be expected to expand the range of emotional responses to sound.
This is exemplified by the invasive ant Wasmannia auropunctata affecting the local fauna and therefore silencing the forest of New Caledonia,[120] the soundscape's diversity showing a flat response in burned area in comparison to unburned area, 3 years after a massive wildfire in the Chiricahua national monument in Arizona[121] or the increase in biological sounds in cities during the COVID-19 pandemic.
[122] Altogether, these findings warrant detailed psychoacoustical investigations aiming to assess the ability of human listeners to hear changes reflecting local disturbances within ecosystems.