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We summarize the foundational elements of a new area of research we call soundscape ecology. The study of sound in landscapes is based on an understanding of how sound, from various sources—biological, geophysical and anthropogenic—can be used to understand coupled natural-human dynamics across different spatial and temporal scales. Useful terms, such as soundscapes, biophony, geophony and anthrophony, are introduced and defined. The intellectual foundations of soundscape ecology are described—those of spatial ecology, bioacoustics, urban environmental acoustics and acoustic ecology. We argue that soundscape ecology differs from the humanities driven focus of acoustic ecology although soundscape ecology will likely need its rich vocabulary and conservation ethic. An integrative framework is presented that describes how climate, land transformations, biodiversity patterns, timing of life history events and human activities create the dynamic soundscape. We also summarize what is currently known about factors that control temporal soundscape dynamics and variability across spatial gradients. Several different phonic interactions (e.g., how anthrophony affects biophony) are also described. Soundscape ecology tools that will be needed are also discussed along with the several ways in which soundscapes need to be managed. This summary article helps frame the other more application-oriented papers that appear in this special issue.

Many marine ecosystems, including in the Northwest Atlantic, are expected to experience a sudden and sustained increase in underwater noise due to ocean development. To investigate the response of sea turtles to impulsive sounds, specifically those generated from seismic surveys, we equipped leatherback sea turtles at a seasonal foraging ground in coastal Massachusetts with data loggers to record video footage, sound, depth, and location. We then exposed the tagged turtles to a controlled short burst (0.25 ms), broad frequency (~ 300—1200 Hz), high intensity (sound source level of 221 dB re 1μPa) impulsive sound produced by a seismic sparker towed from a vessel. We collected a mean (± SD) of 109.4 ± 35.3 min of footage from 13 leatherbacks across four days in 2023, with the sparker exposure lasting 52.2 ± 11.6 min per turtle. Underwater peak sound pressure level of frequencies within the hearing range of leatherbacks (100—1200 Hz) were between ~ 128.5—176.2 dB during the tag deployments. We assessed the effects of peak sound pressure level on turtle behavior metrics and found that there was a significant effect on tortuosity, dive duration, and probability of foraging from the sound intensity coinciding with the emitted impulsive sound, while swim speed was more correlated with proximity to the sparker vessel regardless of sound intensity level. Probability of foraging declined by ~ 64% during the exposure period. These behavioral shifts along with their potential to decrease individual fitness, should be considered when evaluating the environmental impacts of intense acoustic stimuli on sea turtles.

Anthropogenic noise from navigation is a major contributor to the disturbance of the acoustic soundscape in underwater environments containing noise-sensitive life forms. While previous studies mostly developed protocols for the empirical determination of noise source levels associated with the world’s commercial fleet, this work explores the radiated noise emitted by small recreational vessels that thrive in many coastal waters, such as in the St. Lawrence Estuary beluga population’s summer habitat. Hydrophone-based measurements in the Saguenay River (QC, Canada) were carried out during the summers of 2021 and 2022. Shore-based observations identified 45 isolated transits of small, motorized vessels and were able to track their displacement during their passage near the hydrophone. Received noise levels at the hydrophone typically fell below the hearing audiogram of the endangered St. Lawrence Estuary beluga. Monopole source levels at low frequencies (0.1–≲2 kHz) held on average twice the acoustic power compared to their mid-frequency (≳2–30 kHz) counterparts. The speed over ground of recreational vessel showed a positive correlation with the back-propagated monopole source levels. Estimations of the mid-frequency noise levels based on low-frequency measurements should be used moderately.

Context Relationship between soundscapes, habitat types, and landscape structure are insufficiently assessed in mountain landscapes. Characterizing soundscape patterns is important for understanding how human and natural processes affect mountain acoustic environments. Objectives We aim to characterize summer soundscapes across major mountain habitats by examining how acoustic characteristics and soundscape components vary spatio-temporally and relate to multiple environmental variables. Methods We deployed audio recorders across 44 sites in the Garmisch-Partenkirchen district of the Northern European Limestone Alps, Germany, covering nine habitat types during summer. We characterized their soundscapes by using eight acoustic indicators and soundscape components (anthrophony, biophony, and geophony), examining their relationships with habitat types, landscape structure, and diel periods. Results Soundscapes varied by habitat type, with alpine grasslands and rocky habitats featuring less diverse, distinct soundscapes compared to montane and valley habitats (e.g., intensively and extensive used grasslands, forests, lakes/rivers), with persistent aircraft sound in alpine sites. Differences in soundscape characteristics were related to elevation, distance to infrastructure, and landscape structure. Diel patterns revealed that biophony dominates at dawn, while anthrophony prevailed at other times, with habitat-specific variations. Conclusions In mountain landscapes, soundscapes vary according to habitat type, landscape gradients, and diel period, with anthrophony present even in high-alpine areas. Incorporating landscape characteristics into soundscape assessments offered insights into important covariates at a broader spatial scale. The results emphasize the potential of integrating soundscape considerations into mountain landscape management accounting for acoustic environments.

ContextMost data collection and analyses in soundscape ecology have focused on summer or breeding seasons in urban or protected landscapes, missing important acoustic dynamics in winter, non-breeding periods and in agricultural landscapes, a land-use that constitutes 39% of ice-free surface globally.ObjectivesTo address these gaps, we examined the variation of winter soundscapes across a rural agricultural landscape of Nebraska, USA. We compared high and low traffic sites, testing if traffic levels affected soundscape structure.MethodsWe recorded sound over two winters at 19 sites located adjacent to major and minor roadways. We calculated eight unique soundscape indexes to quantify the soundscape over time as a function of traffic and land cover. We applied filters at 80, 1000, and 2000 Hz.ResultsWe found clear statistical differences between high and low traffic sites in 7 of 8 soundscape indexes. Soundscape varied throughout the day, but not throughout the season. There was a clear negative correlation between technophony (human-derived sounds) and biophony (ecologically derived sounds) across sites. We found that not all indices may be suitable for all ecosystems.ConclusionsWe quantified the effects of noise pollution on the soundscape of understudied habitats during winter months. By using soundscape indexes as surrogates for biodiversity, acoustic sampling could be an effective method for monitoring biodiversity when traditional methods may be ineffective or too costly. However, caution needs to be taken when choosing indices.

Marine soundscape is the aggregation of sound sources known as geophony, biophony, and anthrophony. The soundscape analysis, in terms of collection and analysis of acoustic signals, has been proposed as a tool to evaluate the specific features of ecological assemblages and to estimate their acoustic variability over space and time. This study aimed to characterise the Capo Caccia-Isola Piana Marine Protected Area (Italy, Western Mediterranean Sea) soundscape over short temporal (few days) and spatial scales (few km) and to quantify the main anthropogenic and biological components, with a focus on fish biophonies. Within the MPA, three sites were chosen each in a different protection zone (A for the integral protection, B as the partial protection, and C as the general protection). In each site, two underwater autonomous acoustic recorders were deployed in July 2020 at a depth of about 10 m on rocky bottoms. To characterise the contribution of both biophonies and anthrophonies, sea ambient noise (SAN) levels were measured as sound pressure level (SPL dB re: 1 μ Pa-rms) at eight 1/3 octave bands, centred from 125 Hz to 16 kHz, and biological and anthropogenic sounds were noted. Fish sounds were classified and counted following a catalogue of known fish sounds from the Mediterranean Sea based on the acoustic characteristic of sound types. A contemporary fish visual census had been carried out at the test sites. SPL were different by site, time (day . night), and hour. SPLs bands centred at 125, 250, and 500 Hz were significantly higher in the daytime, due to the high number of boats per minute whose noise dominated the soundscapes. The loudest man-made noise was found in the A zone, followed by the B and the C zone, confirming that MPA current regulations do not provide protection from acoustic pollution. The dominant biological components of the MPA soundscape were the impulsive sounds generated by some invertebrates, snapping shrimps and fish. The vast majority of fish sounds were recorded at the MPA site characterized by the highest sound richness, abundance, and Shannon-Wiener index, coherently with the results of a fish visual census. Moreover, the acoustic monitoring detected a sound associated with a cryptic species ( spp.) never reported in the study area before, further demonstrating the usefulness of passive acoustic monitoring as a complementary technique to species census. This study provides baseline data to detect future changes of the marine soundscapes and some suggestions to reduce the impact of noise on marine biodiversity.

Biophony and anthrophony analysis as part of the urban soundscape is an efficient approach to bird biodiversity monitoring and to studying the impact of noise pollution in urban parks. Here, we analyzed the soundscape composition to monitor the diversity of birds using acoustic indices and machine learning in 21 urban parks of Isfahan, Iran, in spring 2019. To achieve this purpose four-step method was considered: (i) choosing parks and sampling of sound and bird species; (ii) calculated the six acoustic indices; (iii) calculated the six biodiversity indices; and (iv) statistical analysis for predicting biodiversity index from acoustic indices. Three regression models including support vector machine (SVM), random forest (RF), and elastic net regularization (GLMNET) applied the acoustic indices with minimum and maximum recorded thresholds to feature extraction to measure biodiversity indicators. The optimization model was applied to reduce the independent variables. Generally, more than 18,000 samples were modeled for the dependent variables in each model. The regression results demonstrated that the highest R square was related to the songbird (0.93), evenness (0.92), and richness (0.9) indecies in the SVM model and the Shannon index (0.86) in the RF model. The results of acoustics analysis demonstrated that the Acoustic Entropy Index (H), Normalized Difference Soundscape Index (NDSI), Bioacoustics Index (BI), and Acoustic Complexity Index (ACI) indices were suitable because they could serve as proxies for bird richness and activity that reflect differences in habitat quality. Our findings offer using acoustic indicators as an efficient approach for monitoring bird biodiversity in urban parks.

The soundscape is an important habitat feature for marine animals, and climate change may cause large changes to the Arctic marine soundscape through sea ice loss and increased anthropogenic activity. We examined the marine soundscape over eight months near Ulukhaktok, Northwest Territories, Canada, and assessed the relative contribution of the geophony (wind and wave sounds), biophony (marine mammal and fish sounds), and anthrophony (noise from vessel traffic). Sound pressure levels (SPL) were significantly higher during the summer than during the autumn and winter, and these differences were caused by increased wind/waves and vessel traffic in the summer. Increased wind speed drove increased SPL, while increased ice concentration resulted in decreased SPL. When vessel traffic was closer, SPL was higher. Marine mammal and fish vocalizations did not influence SPL; however, timing of vocalizations of both whales and seals matched seasonal patterns shown in other studies within the region. Overall, the marine soundscape near Ulukhaktok varied greatly through time and may be prone to large changes in the future as the ice-free season continues to lengthen and more vessels travel through the region.

Structured biogenic habitats are biodiversity hotspots that host a wide range of soniferous species. Yet in deep-water systems, their soundscapes are largely undescribed. In September of 2016 we deployed 3 underwater acoustic recorders for approximately 4 d in and around a glass sponge reef in the Outer Gulf Islands sponge reef fishing closure, British Columbia, Canada. The 2 recordings from the reef (within and at the margin of the reef footprint) were significantly louder in the mid- and high-frequency bands (100 to 1000 Hz and 1 to 10 kHz, respectively) than the recordings made in soft-bottom habitat away from the reef. These frequency bands are known to correlate with aspects of the biological community as well as benthic cover in shallow-water systems; visual surveys conducted in the area confirmed the presence of several known soniferous species. More fish sounds were recorded on the reef compared to the off-reef site. Our results suggest that this glass sponge reef has a distinct soundscape and that future work linking aspects of the soundscape to the ecology of the ecosystem are warranted.

ContextIt is widely accepted that wildlife is subjected to detrimental human noise within urban landscapes but little is known about how the intensity of land use changes soundscapes.ObjectivesThe objective of this research was to produce quantitative associations between characteristics of ambient soundscapes and land use intensity. These relations were used to examine the 2 kHz demarcation between anthrophony and biophony and compare the impact of different sized contributing areas on ambient soundscape characteristics.MethodsThis study related the surrounding land use intensity of 67 sites in north central Florida (USA) to several metrics describing their recorded soundscapes. Land use intensity was measured remotely at three scales using the landscape development intensity index (LDI).ResultsThe analysis revealed that the LDI index had a statistically significant effect on soundscape characteristics after controlling for important factors such as climate, season, and attenuation due to hard ground. The trends between LDI and soundscape confirmed that human generated sounds are loud, continuous, and occupy low frequencies. The evenness of the sound distribution decreased with landscape intensity and LDI correlated significantly with sound below 3 kHz. Land use intensity within a 100 and 500-m radius contributing area were most closely related to soundscape metrics.ConclusionsLDI is a tool with the potential to predict the extent and intensity of anthropogenic noise disturbance on wildlife from remote sensing data. The utility of this tool allows for widespread application to identify and mitigate conflicts in the acoustic realm between human noise and wildlife.