Abiotic Sounds Research Articles

Soundscapes in Urban Green Spaces of a Megacity Across an Urban–Rural Gradient: A Case Study of Shanghai

Urban soundscapes are valuable indicators of urban biodiversity and ecosystem health. This study investigated the spatial and temporal characteristics of soundscapes in megacity green spaces and their relationship with the urban environment. An acoustic index was formulated and calculated using long-term data from Shanghai’s urban green spaces. The results show a significant increase in the acoustic index during spring and summer, peaking during these periods, while a decrease was observed from December to February, dominated by abiotic sounds. Diurnal variations indicate a rapid increase in the acoustic index at sunrise, reflecting heightened avian activity during the dawn chorus. Human interference in the urban center limited acoustic activity, whereas the outer suburbs, with their more natural environments, supported greater acoustic richness.

A mixture of artificial and biological sounds improves the effective range of an acoustic repellent for an invasive lizard species

AbstractFurther range expansion of invasive animal species can be prevented by controlling their behavior. Acoustic repellent is a promising approach to deter problematic animals from ecologically sensitive areas. To develop an acoustic repellent system for a green anole that was introduced to the Ogasawara islands in Japan, this study evaluated the deterrent effect of (1) a pattern sound of machine noise and (2) a mixture of artificial and biologically relevant sounds. We created a sound level gradient inside a small experimental cage in a laboratory setting and measured whether green anoles avoided the vicinity of a speaker. In approximately 80% of cases, both the pattern machine sound and the mixture sounds prevented green anoles from stepping into the vicinity of a speaker (<24 cm). The mixture sounds maintained the deterrent effect at a middle distance from a speaker (<72 cm), whereas the pattern machine sound did not work as a strong acoustic repellent at this distance. These results imply that the mixing of biotic and abiotic sounds can improve the effective range of acoustic repellent for green anoles. However, several shortcomings of the acoustic repellent system were also highlighted. Since a green anole is an insectivore predator, our findings will contribute to protecting endangered native insect fauna from the predation of non‐native lizard species.

Biotic sound SNR influence analysis on acoustic indices

In recent years, passive acoustic monitoring (PAM) has become increasingly popular. Many acoustic indices (AIs) have been proposed for rapid biodiversity assessment (RBA), however, most acoustic indices have been reported to be susceptible to abiotic sounds such as wind or rain noise when biotic sound is masked, which greatly limits the application of these acoustic indices. In this work, in order to take an insight into the influence mechanism of signal-to-noise ratio (SNR) on acoustic indices, four most commonly used acoustic indices, i.e., the bioacoustic index (BIO), the acoustic diversity index (ADI), the acoustic evenness index (AEI), and the acoustic complexity index (ACI), were investigated using controlled computational experiments with field recordings collected in a suburban park in Xuzhou, China, in which bird vocalizations were employed as typical biotic sounds. In the experiments, different signal-to-noise ratio conditions were obtained by varying biotic sound intensities while keeping the background noise fixed. Experimental results showed that three indices (acoustic diversity index, acoustic complexity index, and bioacoustic index) decreased while the trend of acoustic evenness index was in the opposite direction as signal-to-noise ratio declined, which was owing to several factors summarized as follows. Firstly, as for acoustic diversity index and acoustic evenness index, the peak value in the spectrogram will no longer correspond to the biotic sounds of interest when signal-to-noise ratio decreases to a certain extent, leading to erroneous results of the proportion of sound occurring in each frequency band. Secondly, in bioacoustic index calculation, the accumulation of the difference between the sound level within each frequency band and the minimum sound level will drop dramatically with reduced biotic sound intensities. Finally, the acoustic complexity index calculation result relies on the ratio between total differences among all adjacent frames and the total sum of all frames within each temporal step and frequency bin in the spectrogram. With signal-to-noise ratio decreasing, the biotic components contribution in both the total differences and the total sum presents a complex impact on the final acoustic complexity index value. This work is helpful to more comprehensively interpret the values of the above acoustic indices in a real-world environment and promote the applications of passive acoustic monitoring in rapid biodiversity assessment.

Soundscape_IR: A source separation toolbox for exploring acoustic diversity in soundscapes

Abstract Soundscapes contain rich acoustic information associated with animal behaviours, environmental characteristics and human activities, providing opportunities for predicting biodiversity changes and associated drivers. However, assessing the diversity of animal vocalizations remains challenging due to the interference of environmental and anthropogenic noise. A tool for separating sound sources and delineating changes in acoustic signals is crucial for an effective assessment of acoustic diversity. We present soundscape_IR, an open‐source Python toolbox dedicated to soundscape information retrieval in which nonnegative matrix factorization is applied. This toolbox provides algorithms for supervised and unsupervised source separation (SS). It also enables the use of a snapshot recording for model training and subsequently applying adaptive and semi‐supervised SS when target species produce sounds with varying features and when unseen sound sources are encountered. Our results demonstrated that SS could enhance the vocalizations of target species, characterize the complexity of vocal repertoires and investigate the spatio‐temporal divergence of soundscapes. In tropical forest soundscapes, the application of SS effectively detected the rutting vocalizations of sika deer and revealed a graded structure in their acoustic characteristics. In subtropical estuarine soundscapes, SS automated the process of identifying distinct biotic and abiotic sounds, and the result uncovered divergent sound compositions between inshore and offshore waters. Implementation of SS in soundscape analysis offers a promising method for streamlining the assessment of acoustic diversity in diverse environments. Future application of SS will open new directions to acoustically quantify ecological interactions across individual, species and ecosystem levels.

Soundscape dynamics of a cold protected forest: dominance of aircraft noise.

ContextOne mainstay of soundscape ecology is to understand acoustic pattern changes, in particular the relative balance between biophony (biotic sounds), geophony (abiotic sounds), and anthropophony (human-related sounds). However, little research has been pursued to automatically track these three components.ObjectivesHere, we introduce a 15-year program that aims at estimating soundscape dynamics in relation to possible land use and climate change. We address the relative prevalence patterns of these components during the first year of recording.MethodsUsing four recorders, we monitored the soundscape of a large coniferous Alpine forest at the France-Switzerland border. We trained an artificial neural network (ANN) with mel frequency cepstral coefficients to systematically detect the occurrence of silence and sounds coming from birds, mammals, insects (biophony), rain (geophony), wind (geophony), and aircraft (anthropophony).ResultsThe ANN satisfyingly classified each sound type. The soundscape was dominated by anthropophony (75% of all files), followed by geophony (57%), biophony (43%), and silence (14%). The classification revealed expected phenologies for biophony and geophony and a co-occurrence of biophony and anthropophony. Silence was rare and mostly limited to night time.ConclusionsIt was possible to track the main soundscape components in order to empirically estimate their relative prevalence across seasons. This analysis reveals that anthropogenic noise is a major component of the soundscape of protected habitats, which can dramatically impact local animal behavior and ecology.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10980-021-01360-1.

Earth-Bound Sound: Oscillations of Hearing, Ocean, and Air

Earth-Bound Sound:Oscillations of Hearing, Ocean, and Air Raviv Ganchrow (bio) I Global Sounds This text1 follows oscillations of hearing, water and air in conjunction with notions of sound that are terrestrially situated, geologically invested, contextually distributed and predominantly earth-bound.2 Why sound and why now? In other words, why should we recalibrate sound and hearing at this particular moment? One answer could gesture towards the pervasiveness of sonorities in times of political and ecological crisis and address the urge to attend to those sounds' inherent plurality as a means of negotiating the current complexities: the sounds of calving glaciers and noises of social unrest interspersed with uncanny silences of pandemic lockdowns.3 Acoustic attentions are at least timely if not altogether symptomatic of this juncture. Interests in sound's malleable qualities come not only from attentions to a densely sonorous milieu, but also from the manner sound's behaviors are analogous to experiences of interlinked environs cluttered with migrations, shifting identities, precarious existences and alarming environmental change. Today, awareness of evanescence seems to be more of a common trait than a quality reserved for sounds. On the other hand, there is much to be learned from the making and unmaking of sonic entities. After all sound is a quintessential shape-shifting materiality. Sounds are distinctively situated but also importantly transitional. The spaces and identities heard in sound accurately reflect the extents of hearing and dynamics of context. Different kinds of listening reflect the diversity and scope of sounds that can be heard. It's in that sense that closer attention to sound's manners of manifestation and modes of operation could become paramount for rethinking other context-bound materializations and spatiotemporal entities in our midst. Sounds partake in physical processes that cannot be divorced from qualities, and their spatial operations are entwined with the contexts through which those qualities manifest. [End Page 67] Earth-bound Sound Sounds are native to their circuits of propagation, inhabiting locales and distributing over non-localized contexts. Vibrations traveling through air, water and ground have their historicity not only in the 200-year career of acoustics in science, culture, technology and warfare, but also in the natural history of terrestrial movements. Everything sounding in surrounds relies on a meshwork of earth-bound interconnections sustaining their operations. The audible characteristics of fluctuations in air rely on structural aspects of the gasses in which they propel that are themselves outcomes of billions of years of energetic modulations in biota and geology. The sounds we hear would not be the same sounds when heard through alternate gasses. Neither would the shapes and mechanisms of listening likely be the same. Biological organs, their environments of hearing, and techniques of sounding and listening are all tightly knotted and continually shifting in complex terrestrial circuits. Technologies of hearing and listening, along with impressions of sound and sonic experience, are part of those earth-bound circuits and partially contribute to the dynamics. The coevolution of earth's crust, organisms, oceans and air is a physical fact latent to anything that sounds. Sound radiates environments, coevolving with organisms, coevolving with flora, coevolving with minerals, coevolving with topography, coevolving with oceans and atmosphere. Admittedly, this cascade is not plainly audible as the features holding vibrations in auditory attention are the same ones masking the continuities. Vibrations take on structure as they coevolve. Vibrational appearances are as distinctive as leaf shapes or animal hide patterns. Sonic structures are not merely the result of processes but in fact are processes sounding their contexts of operation. Sounds that squawk, rattle, chirp, squeak, squeal, grunt, hiss, roar, bark, howl, warble, purr, yelp, tweet, hoot, screech and speak, join in to accompany other, abiotic sounds such as babbling brooks, rumbling thunder, murmuring wind, pattering rain, white noise waterfalls, pink noised earth warble (and heartbeats), and brown noised meandering dust. These and other behavioral energetics travelling through ground and waters constitute the substance-borne multitude of earth-bound effervescence. Air that conducts human hearing is not merely a medium for signals in transit but are, in fact, aspects in the structuring of the earth's atmosphere. Ears, the vibrations to which they attend, and the gasses...

Exploring coral reef biodiversity via underwater soundscapes

Information on biodiversity is essential to evaluate the ecological status of coral reefs. Sounds produced by reef-associated organisms have been used as a biodiversity indicator. However, the interference from abiotic sounds and the lack of a comprehensive audio library have impeded effective evaluation. This study investigated the application of underwater soundscapes as a remote-sensing method to detect biological and anthropogenic activities. Using techniques including the visualization of long-duration recordings, source separation, and clustering, soundscapes were separated into sounds of anthropogenic and biological sources. Our results revealed the dynamics of biological sounds among coral reefs off Sesoko Island, Okinawa, Japan. Biological sounds were much more prominent in shallow-water reefs than in upper-mesophotic reefs, but their spectral features and compositions differed. The shallow-water reefs were dominated by broadband sounds of crustaceans and low-frequency transient fish calls, whereas the upper-mesophotic reefs were characterized by a diverse array of fish choruses and transient sounds. We also discovered that shipping noise heavily interfered with the soundscapes from the upper-mesophotic reefs and represented an invisible threat to life in the low-light habitat. The applied techniques of soundscape information retrieval revealed the distinct ecological status of coral reefs and the behavior change of sound-producing organisms in high temporal resolution. Implementation of soundscape monitoring can generate ecological information on habitat quality, reef biodiversity, human activities, and their interactions. Global collaboration on underwater soundscapes will establish a data-informed platform and help stakeholders assess the resilience of coral reefs to environmental and anthropogenic stressors.

Soundscape Viewer: An integrated toolbox of audio source separation for soundscape-based ecosystem assessment

Soundscapes contain collective information on habitat quality and ecosystem dynamics. Current soundscape assessment methods, including clustering and ecoacoustic indices, may deliver unsatisfied performance when multiple sound sources are recorded simultaneously. We introduce an open-source Soundscape Viewer toolbox for separating soundscapes into sounds of biological, environmental, and anthropogenic sources. Based on non-negative matrix factorization (NMF), Soundscape Viewer enables audio source separation in both supervised and unsupervised manners. Conventional supervised NMF learns spectral features from labeled animal vocalizations, yet the performance is sensitive to noise levels. By assuming source-specific periodicity in unsupervised NMF, Soundscape Viewer can learn discriminative features between animal vocalizations and background noise. To cope with dynamic acoustic environments, Soundscape Viewer also integrates adaptive and semi-supervised learning approaches. Adaptive learning improves model generalization when sound characteristics differ from the training data, and semi-supervised learning allows the model to recognize new sound sources. We applied Soundscape Viewer in the evaluation of soundscape dynamics and the automatic detection of animal vocalizations. Our results reveal that the mutual interference between sound sources can be effectively reduced in various ecosystems. Source separation will facilitate biodiversity assessment and increase our understanding of biotic and abiotic sounds' interactions.

Biotic and abiotic sounds affect calling activity but not plasma testosterone levels in male frogs (Batrachyla taeniata) in the field and in captivity

In animals, the expression of diverse reproductive behaviors is hormonally regulated. In particular, vocalizing during courtship has been related to circulating androgen levels, and reciprocally, conspecific vocalizations are known to modulate androgen secretion in vertebrates. The effect of natural sounds of abiotic origin on hormonal status has virtually not received attention. Therefore, we evaluated the vocal responses of male Batrachyla taeniata frogs to conspecific chorus and rainfall sounds in natural and controlled laboratory settings, measuring the testosterone levels of exposed individuals. In field and laboratory conditions, testosterone levels of frogs exposed to 31.5 min of chorus and rain sounds and non-exposed individuals were similar. In the field, frogs increased their call rate in response to playbacks of chorus and rain sound, but the evoked calling activity was unrelated to plasma testosterone. In contrast to the field, frogs showed limited responsiveness to 31.5-min acoustic exposures in the laboratory. Similarly to the field, for vocally active males tested in the laboratory there was no association between call rate and testosterone levels. Additionally, in this group, testosterone levels were higher in vocally active males relative to non-calling individuals. Overall, these results indicate that in B. taeniata testosterone levels are not altered following a short-term exposure to conspecific biotic and to abiotic sounds. Our results are suggestive of a threshold influence of testosterone on the vocal activity of the species studied. Further explorations of the influence of abiotic sounds on endocrine activation are required to understand how animals respond to variable acoustic environmental conditions.

Do singing humpback whales (Megaptera novaengliae) favor specific frequency bands?

Many species alter their acoustic signals in response to environmental or anthropogenic factors. Differential use of frequency bands may occur as a result of overlapping biotic and abiotic sounds that interfere with communication signals between conspecifics. Singing humpback whales produce units with frequencies ranging from 30 Hz to over 10,000 Hz, but may favor specific frequency bands during song production. We tested the prediction that singing humpback whales consistently produce units with energy focused in specific spectral bands by measuring the consistency of peak frequency bands in the southeastern Pacific stock G population of humpback whales in the Gulf of Tribugá, Colombian Pacific. Preliminary results document extensive use of units with peak frequencies clustered in two different bands between 300 Hz and 1000 Hz for the dominant theme, and additional peak frequency bands between 300 Hz and 3000 Hz for other song themes. These analyses will allow for further spatial and temporal comparisons across distinct population segments, and can be used in future studies to assess whether singers change their use of frequency bands in response to increased anthropogenic noise or as themes evolve over time.

Food approach conditioning and discrimination learning using sound cues in benthic sharks.

The marine environment is filled with biotic and abiotic sounds. Some of these sounds predict important events that influence fitness while others are unimportant. Individuals can learn specific sound cues and 'soundscapes' and use them for vital activities such as foraging, predator avoidance, communication and orientation. Most research with sounds in elasmobranchs has focused on hearing thresholds and attractiveness to sound sources, but very little is known about their abilities to learn about sounds, especially in benthic species. Here we investigated if juvenile Port Jackson sharks could learn to associate a musical stimulus with a food reward, discriminate between two distinct musical stimuli, and whether individual personality traits were linked to cognitive performance. Five out of eight sharks were successfully conditioned to associate a jazz song with a food reward delivered in a specific corner of the tank. We observed repeatable individual differences in activity and boldness in all eight sharks, but these personality traits were not linked to the learning performance assays we examined. These sharks were later trained in a discrimination task, where they had to distinguish between the same jazz and a novel classical music song, and swim to opposite corners of the tank according to the stimulus played. The sharks' performance to the jazz stimulus declined to chance levels in the discrimination task. Interestingly, some sharks developed a strong side bias to the right, which in some cases was not the correct side for the jazz stimulus.

Developing an Underwater Sound Recorder: The Long and Short (Time) of It...

Passive acoustic recording of marine noise has advanced considerably over recent years. For a long time, a lack of widely available technology limited the acquisition of long-term acoustic data sets to a small number of large, cabled installations mostly restricted to military use. For other users, recordings were limited by the available technology to short snapshots of minutes to possibly days of data at a time. As technology has improved, passive acoustic monitoring has shown marine soundscapes are filled with biotic and abiotic sounds that occur on a range of often unpredictable timescales. Thus, snapshot recordings can lead to biased data. In 1999, the Centre for Marine Science and Technology, together with Australia’s Defence Science and Technology Organisation, began developing remote underwater sound recorders to increase the duration and quality of recordings. As time passed, the sound recorders were developed significantly, have been deployed over 600 times at a variety of Australian and international locations and have identified a plethora of biological, geophysical and anthropogenic sound sources. This paper presents a brief history of the recorders’ development and characteristics, some examples of the information they have provided and future direction for their next generation.

Black-capped chickadees, Poecile atricapillus, avoid song overlapping: evidence for the acoustic interference hypothesis

Many animals produce sounds that overlap the sounds of others. In some animals, overlapping is thought to be an aggressive signal important in resource defence. Yet, overlapping can also occur by chance, and therefore its function is controversial. In this study, we conducted two experiments to test the function of overlapping in black-capped chickadees, Poecile atricapillus. In experiment 1, we simulated territorial intrusions by broadcasting songs inside established chickadee territories. Resident males overlapped the playback-simulated intruders significantly less than expected by chance, as in most species in which overlapping has been described. Chickadees also overlapped more when they were farther from the intruder. This pattern suggests that chickadees avoid overlapping as a mechanism for reducing acoustic interference (‘interference avoidance hypothesis’). However, the pattern could also constitute submissive signalling if chickadees signal de-escalation (associated with greater distance between opponents) through increasing rates of overlapping (‘submissive signalling hypothesis’). Therefore, in experiment 2, we contrasted these two hypotheses by comparing responses to playback stimuli with low or high interference potential and low or high signal value. We manipulated interference potential by broadcasting stimuli at different amplitudes. We manipulated signal value by broadcasting either song stimuli, which elicit aggression, or white noise stimuli with matching time-amplitude characteristics. If overlapping is a submissive signal, then we predicted that chickadees would avoid overlapping song stimuli, but not white noise stimuli, which lack signal value. Contrary to this prediction, chickadees overlapped song and white noise stimuli equally often, but significantly less often than expected by chance. Furthermore, chickadees overlapped both types of stimuli more often when they were broadcast at lower amplitudes (i.e. lower interference potential). Together, these findings provide compelling evidence that overlapping is not a signal in this species, and that chickadees avoid overlapping both biotic and abiotic sounds as a mechanism for reducing interference.

On the Possible Detection of Lightning Storms by Elephants.

Simple SummaryWe use data similar to that taken by the International Monitoring System for the detection of nuclear explosions, to determine whether elephants might be capable of detecting and locating the source of sounds generated by thunderstorms. Knowledge that elephants might be capable of responding to such storms, particularly at the end of the dry season when migrations are initiated, is of considerable interest to management and conservation.Theoretical calculations suggest that sounds produced by thunderstorms and detected by a system similar to the International Monitoring System (IMS) for the detection of nuclear explosions at distances ≥100 km, are at sound pressure levels equal to or greater than 6 × 10−3 Pa. Such sound pressure levels are well within the range of elephant hearing. Frequencies carrying these sounds might allow for interaural time delays such that adult elephants could not only hear but could also locate the source of these sounds. Determining whether it is possible for elephants to hear and locate thunderstorms contributes to the question of whether elephant movements are triggered or influenced by these abiotic sounds.