Effect of Natural Background Noise and Man-Made Noise on Automated Frog Calls Identification System

Frog identification based on their calls becomes important for biological research and environmental monitoring. However, identifying particular frog calls becomes challenging particularly when the frog calls are interrupted with noises either in natural background noise or man-made noise. Hence, an automatic identification frog call system that robust in noisy environment has been proposed in this paper. Experimental studies of 675 audio obtained from 15 species of frogs in the Malaysian forest and recorded in an outdoor environment are used in this study. These audio data are then corrupted by 10dB and 5dB noise. A syllable segmentation technique i.e. short time energy (STE) and Short Time Average Zero Crossing Rate (STAZCR) and feature extraction, Mel-Frequency Cepstrum Coefficients (MFCC) are employed to segment the desired syllables and extract the segmented signal. Subsequently, the Local Mean k-Nearest Neighbor with Fuzzy Distance Weighting (LMkNN-FDW) are employed as a classifier in order to evaluate the performance of the identification system. The experimental results show both of natural background noise and man-made noise outperform by 95.2% and 88.27% in clean SNR, respectively.

Acoustic parameters of sounds emitted by Sotalia guianensis : dialects or acoustic plasticity

Selective pressure from the environment on species may select adaptations as a whole, including the specific context of acoustics. Some authors report that the acoustic repertoire of Sotalia guianensis presents dialects as a geographical reflection. However, others propose that the environmental characteristics are the factor that imposes these variations. The present study evaluated if S. guianensis modifies its sound emissions at the Curral Cove (CC) and the Guaraíras Lagoon Complex (GLC), different habitats at similar latitudes. At the GLC, dolphins use higher whistle frequencies as well as higher number of click per second, facts that may be related to sound precision for communication between individuals and prey capture. Variations in the dolphins’ sounds may be related to differences in the environments such as natural background noise—biotic and abiotic—and characteristics such as turbidity, temperature, salinity, and modification in sound propagation due to depth and bottom properties. The pulsed calls’ sound category did not present modification between habitats probably due to context in which they are used since they occur during high physical contact. It is possible that the variation of the sound parameters between the CC and GLC environments is a reflection of the species’ adaptive potential, since a population can adjust the sounds emitted by its individuals to the environment’s features, revealing acoustic plasticity. A pressão seletiva do ambiente sobre as espécies ali viventes pode selecionar adaptações como um todo, inclusive no contexto acústico específico. Alguns autores relatam que o repertório acústico de Sotalia guianensis apresenta dialetos como reflexo geográfico; entretanto, outros autores propõem que as características do ambiente são o fator que impõem essas variações. O presente estudo avaliou se S. guianensis modifica suas emissões sonoras entre a Enseada do Curral (CC) e o Complexo Lagunar de Guaraíras (GLC), habitats diferentes localizados em latitudes semelhantes. No GLC, os golfinhos utilizam frequências mais altas de assobios assim como maior número de cliques por segundo, fatos que podem estar relacionados com a precisão dos sons para a comunicação entre indivíduos e a captura de presas. As variações nos sons dos golfinhos podem estar relacionadas às diferenças nos ambientes, como ruídos de fundo naturais—bióticos e abióticos—características como turbidez, temperatura e salinidade; e modificação da propagação do som devido profundidade e propriedades do fundo. A categoria sonora grito não apresentou modificação entre os habitas provavelmente devido ao contexto em que são usados, pois ocorrem durante alto contato físico entre os indivíduos. É possível que a variação dos parâmetros sonoros entre os ambientes de CC e GLC seja reflexo do potencial adaptativo da espécie, pois uma mesma população pode ajustar os sons emitidos pelos seus indivíduos às características do ambiente revelando uma plasticidade acústica.

As Bad as Things are for Radio Astronomy in the Protected Bands -- They are Worse for SETI!

ABSTRACTIf the funding that has been requested in NASA’s FY89 budget is forthcoming, the Search for Extraterrestrial Intelligence (SETI) will inaugurate its microwave search program on Columbus Day, 1992. This systematic search for evidence of narrowband microwave signals generated by another technology will continue at several sites around the world until at least 1998. The search will be conducted in two modes: a sensitive targeted search of selected solar type stars covering 1 to 3 GHz, and an all sky survey that covers 1 to 10 GHz. This region of the spectrum is the quietest in terms of natural background noise from astrophysical sources and/or the terrestrial atmosphere, which is why it was chosen. Unfortunately, at the same time that terrestrial technology has enabled this systematic search, it also threatens to render the search all but impossible from the surface of the Earth. Terrestrial transmissions generated for an enormous number of different purposes will be the signals most frequently detected by the SETI systems! This paper describes the design decisions and observing plans that the SETI Program is now making in order to have a chance of successfully “listening” throujgh this heavily utilized portion of the spectrum. We do not yet know precisely how heroic our efforts to discriminate against and identify RFI may have to be, but we have been accumulating observational experience and data that demonstrate convincingly that the situation is rapidly growing worse. Because of the real-time nature of the signal processing being planned, SETI systems will provide an excellent opportunity to monitor, and perhaps identify, sources of narrowband interference within the radio astronomy bands at each site where observations are being conducted.