Luis J. Villanueva-Rivera

Soundscape Ecology: The Science of Sound in the Landscape

This article presents a unifying theory of soundscape ecology, which brings the idea of the soundscape—the collection of sounds that emanate from landscapes—into a research and application focus. Our conceptual framework of soundscape ecology is based on the causes and consequences of biological (biophony), geophysical (geophony), and human-produced (anthrophony) sounds. We argue that soundscape ecology shares many parallels with landscape ecology, and it should therefore be considered a branch of this maturing field. We propose a research agenda for soundscape ecology that includes six areas: (1) measurement and analytical challenges, (2) spatial-temporal dynamics, (3) soundscape linkage to environmental covariates, (4) human impacts on the soundscape, (5) soundscape impacts on humans, and (6) soundscape impacts on ecosystems. We present case studies that illustrate different approaches to understanding soundscape dynamics. Because soundscapes are our auditory link to nature, we also argue for their protection, using the knowledge of how sounds are produced by the environment and humans.

Automated classification of bird and amphibian calls using machine learning: A comparison of methods

Abstract We compared the ability of three machine learning algorithms (linear discriminant analysis, decision tree, and support vector machines) to automate the classification of calls of nine frogs and three bird species. In addition, we tested two ways of characterizing each call to train/test the system. Calls were characterized with four standard call variables (minimum and maximum frequencies, call duration and maximum power) or eleven variables that included three standard call variables (minimum and maximum frequencies, call duration) and a coarse representation of call structure (frequency of maximum power in eight segments of the call). A total of 10,061 isolated calls were used to train/test the system. The average true positive rates for the three methods were: 94.95% for support vector machine (0.94% average false positive rate), 89.20% for decision tree (1.25% average false positive rate) and 71.45% for linear discriminant analysis (1.98% average false positive rate). There was no statistical difference in classification accuracy based on 4 or 11 call variables, but this efficient data reduction technique in conjunction with the high classification accuracy of the SVM is a promising combination for automated species identification by sound. By combining automated digital recording systems with our automated classification technique, we can greatly increase the temporal and spatial coverage of biodiversity data collection.

Using Automated Digital Recording Systems as Effective Tools for the Monitoring of Birds and Amphibians

Abstract There is a need to improve the quantity and quality of data in biodiversity monitoring projects. We compared an automated digital recording system (ADRS) with traditional methods (point-counts and transects) for the assessment of birds and amphibians. The ADRS proved to produce better quantity and quality of data. This new method has 3 additional advantages: permanent record of a census, 24 h/d data collection and the possibility of automated species identification.

A primer of acoustic analysis for landscape ecologists

In this paper we present an introduction to the physical characteristics of sound, basic recording principles as well as several ways to analyze digital sound files using spectrogram analysis. This paper is designed to be a “primer” which we hope will encourage landscape ecologists to study soundscapes. This primer uses data from a long-term study that are analyzed using common software tools. The paper presents these analyses as exercises. Spectrogram analyses are presented here introducing indices familiar to ecologists (e.g., Shannon’s diversity, evenness, dominance) and GIS experts (patch analysis). A supplemental online tutorial provides detailed instructions with step by step directions for these exercises. We discuss specific terms when working with digital sound analysis, comment on the state of the art in acoustic analysis and present recommendations for future research.

Variable response of anuran calling activity to daily precipitation and temperature: implications for climate change

Long-term monitoring of frog populations is needed to understand the effects of global change. To better understand the relationships between climate variation and calling activity, we monitored an anuran assemblage in a Puerto Rican wetland by sampling the acoustic environment for one minute every 10 minutes, for 41 months. By automating data collection using passive acoustic monitoring hardware, we collected more than 110,000 recordings. These recordings were analyzed using species-specific identification algorithms of four Eleutherodactylus species. The peak calling activity of E. coqui (>0.3 detection frequency) and E. cochranae (>0.2) occurred between April and September, and there was a clear decline in activity during the dry months of January–March. There was no clear annual pattern in E. brittoni or E. juanariveroi, but E. juanariveroi did show a significant decline in calling activity over the 41-month study (∼0.5 to ∼0.35). Calling activity of E. coqui and E. cochranae was positively correlated...

Pumilio: A Web‐Based Management System for Ecological Recordings

Systems that record sounds automatically, known as autonomous recording units (ARU), have allowed researchers to readily collect sound recordings at intervals of time (e.g., Acevedo and Villanueva-Rivera 2006, Hutto and Stutzman 2009, Steelman and Dorcas 2010). These recordings are now being used in a variety of ecological studies, such as to monitor breeding patterns (Laiolo 2010), assess community diversity and animal population levels (Sueur et al. 2008b, Dawson and Efford 2009), and to characterize soundscape composition of various ecosystems (Dumyahn and Pijanowski 2011a, b, Pijanowski et al. 2011a, b, Villanueva-Rivera et al. 2011,). However, ARUs can generate a massive number of files, presenting challenges to researchers in terms of archiving, querying, analyzing, and retrieving sound files. Such capabilities are beyond the scope of traditional bioacoustics software, such as Raven (Charif et al. 2006), which have been designed for processing and analyzing single acoustic files.

Eleutherodactylus frogs show frequency but no temporal partitioning: implications for the acoustic niche hypothesis

Individuals in acoustic communities compete for the use of the sound resource for communication, a problem that can be studied as niche competition. The acoustic niche hypothesis presents a way to study the partitioning of the resource, but the studies have to take into account the three dimensions of this niche: time, acoustic frequency, and space. I used an Automated Digital Recording System to determine the partitioning of time and acoustic frequency of eight frogs of the genus Eleutherodactylus from Puerto Rico. The calling activity was measured using a calling index. The community exhibited no temporal partitioning since most species called at the same time, between sunset and midnight. The species partitioned the acoustic frequency of their signals, which, in addition to the microhabitat partitioning, can provide some insight into how these species deal with the problem. This data also suggest that monitoring projects with this group should take place only before midnight to avoid false negatives.

Soundscape ecology: A review of a new synthesis area of acoustics of landscapes

Soundscape ecology is an emergent area of acoustics that attempts to synthesize the concepts of landscape ecology, bioacoustics, noise, music, ethics, and biogeography. By focusing on the interplay of three main sources of sound: biological, geophysical, and anthropogenic, we hope to understand how humans impact ecosystems at a variety of spatial and temporal scales. Another focus of our work is the identification of special ecological places that possess unique and highly valued soundscapes. I will review the current state of the science and efforts to move this field forward using the expertise across these varied disciplines along with the work that we are conducting in the temperate forest, tropical, and desert ecosystems of North America.