Visual Inspection Of Spectrograms Research Articles

Sperm whales forage year-round in the ross sea region

We investigated the seasonal and spatial occurrence of sperm whale (Physeter macrocephalus) in the Ross Sea region of the Southern Ocean derived from passive acoustic data. Two Autonomous Multichannel Acoustic Recorders (AMARs) moored about 10 m above the seabed were deployed in the austral summer of 2018 and recovered 1 year later. The northern AMAR (A3) was located on the Pacific-Antarctic Ridge at 63.7°S and the southern AMAR (A1) at 73.1°S on the Iselin Bank, part of the continental slope of the Ross Sea. Sperm whale echolocation signals were detected using signal processing scripts and validated by visual inspection of spectrograms. Our results demonstrate that sperm whales are present in the Ross Sea region year-round. At A1, sperm whale vocalisations were detected in every month between February and November, but absent in December and January. Whales were detected most often in February with an average of 0.310 detections per hour. Sperm whale vocalisations were detected at station A3 in every month except February when we had no observations. Our results contrast to a paucity of reported sightings of sperm whales from fishing and research vessels in the Ross Sea region between December and February. Probabilities of detecting sperm whales at A3 were on average 14.2 times higher than at A1 for the same month and monthly mean detections per hour were an average of 74.4 times higher at A3 than A1. At A1, we found a significant preference for day-time foraging rather than during the night or nautical twilight. In contrast, at A3, no clear day/dusk/night/dawn differences in sperm whale occurrence were found. Low sea-ice concentration (< 80%) and open water within ∼50 km were necessary but not sufficient conditions for higher detection rates of sperm whales (>0.1 detections per hour). Overall, our research provides baseline information on sperm whale occurrence and establishes a method to track long-term change to help evaluate the conservation value of the Ross Sea region Marine Protected Area.

Phonetic variation of Irish English /t/ in the syllabic coda

The consonant /t/ is acknowledged as being an immensely variable sound in the accents of English. This study aims to contribute to accounting for this variability by analyzing the phonetic realizations of /t/ in 21 speakers (15 female, six male) of Southern Irish English. The speakers were asked to read a short text (Deterding 2006) and to speak spontaneously with the experimenter. In total, 1,519 items of /t/ in coda positions were examined by careful auditory analysis combined with visual inspection of spectrograms. The analysis shows, among others, a strong dependence on the neighbouring segmental context and semantic status of the word. Word-final /t/ is realized mostly as a flap in grammatical words linked to the following word-initial vowel, and as the traditional Irish English weakened fricative realization (slit-T) in lexical words. The second part of the analysis focuses on minor realizations of /t/ documented in the dataset which are noteworthy in their phonetic detail. We show that the slit-T – typically a voiceless apico-alveolar fricative – may exhibit sporadic voicing and, more rarely, be pronounced as a laminal [s]-like sound and as a fricative flap, in which a ballistic movement is combined with a fricative realization. An enhanced typology of /t/ lenition in Irish English is proposed based on these findings.

Speech errors and articulatory gestures: an electropalatographic investigation

One of the major findings of traditional investigations of speech errors is that a single segment is the smallest unit affected by speech errors, although the possibility that units smaller than the segment could play a role in explaining speech errors was not entirely rejected. A number of relatively recent studies using instrumental kinematic techniques for speech analysis bring evidence that errors often occur at subsegmental units of speech production, i.e. at the level of articulatory gestures. Such errors occur due to the coproduction of articulatory gestures, whereby the gestures from both the target consonant and the competing speech sound overlap. As they represent the gradient shift from one segment to another, they are often called gradient errors. Such processes are almost impossible to capture without the use of instrumental kinematic techniques, such as electropalatography (EPG). Th ere are no instrumental kinematic studies of speech errors in Croatian speech. Th us, the aim of this paper is to use EPG to investigate speech errors produced in one Croatian tongue twister. The analysis was focused on /r/ and /l/ targets produced by 10 native female speakers of Croatian, while producing the tongue twister which facilitated speech errors in these two sounds. Each token of the target consonant was classifi ed in one of the four categories: (1) perceptually and articulatorily correct production (P1A1); (2) articulatorily correct but perceptually incorrect production (P0A1); (3) perceptually correct but articulatorily incorrect production (P1A0) and (4) perceptually and articulatorily incorrect production (P0A0). Th e classifi cation was made by the authors via auditory analysis and visual inspection of spectrograms and electropalatograms prior to the quantitative kinematic analysis. Subsequent analyses showed evidence of gradient errors, which would not be detected without the use of instrumental kinematic techniques. Th is investigation supports the claim that traditional method of collecting speech errors by perceptual analysis only is not sensitive enough to detect the subtleties of erroneous productions and speech motor control.

Classification of Florida manatee (Trichechus manatus latirostris) vocalizations.

The vocal repertoire for the Florida manatee is quantitatively categorized from a sample of 1114 calls recorded from 3 different manatee habitats in Florida. First, manatee vocalizations were categorized into five call categories based on visual inspection of spectrograms and following descriptions provided in previous studies. Second, based on measurements of 17 acoustic parameters, the subjective classification scheme was validated using classification and regression trees (CARTs) and model-based cluster analysis paired with silhouette coefficients. CART analysis revealed that these five broad call categories can be successfully distinguished based on correct classification scores of 41.6%-62.5%. Silhouette coefficients determined that the manatee vocal repertoire is highly intergraded. This study supports and expands upon existing subjective categorization schemes by providing a quantifiable methodology for describing the Florida manatees' vocal repertoire. These findings contribute to the increasing number of studies suggesting many animal species vocal repertoires contain graded call types.

Acoustic recordings provide detailed information regarding the behavior of cryptic wildlife to support conservation translocations

For translocated animals, behavioral competence may be key to post-release survival. However, monitoring behavior is typically limited to tracking movements or inferring behavior at a gross scale via collar-mounted sensors. Animal-bourne acoustic monitoring may provide a unique opportunity to monitor behavior at a finer scale. The giant panda is an elusive species of Ursid that is vulnerable to extinction. Translocation is an important aspect of the species’ recovery, and survival and recruitment for pandas likely hinge on behavioral competence. Here we tested the efficacy of a collar-mounted acoustic recording unit (ARU) to remotely monitor the behavior of panda mothers and their dependent young. We found that trained human listeners could reliably identify 10 behaviors from acoustic recordings. Through visual inspection of spectrograms we further identified 5 behavioral categories that may be detectable by automated pattern recognition, an approach that is essential for the practical application of ARU. These results suggest that ARU are a viable method for remotely observing behaviors, including feeding. With targeted effort directed towards instrumentation and computing advances, ARU could be used to document how behavioral competence supports or challenges post-release survival and recruitment, and allow for research findings to be adaptively integrated into future translocation efforts.

Vocal repertoire of free-ranging adult golden snub-nosed monkeys (Rhinopithecus roxellana).

Vocal signaling represents a primary mode of communication for most nonhuman primates. A quantitative description of the vocal repertoire is a critical step in in‐depth studies of the vocal communication of particular species, and provides the foundation for comparative studies to investigate the selective pressures in the evolution of vocal communication systems. The present study was the first attempt to establish the vocal repertoire of free‐ranging adult golden snub‐nosed monkeys (Rhinopithecus roxellana) based on quantitative methods. During 8 months in Shennongjia National Park, China, we digitally recorded the vocalizations of adult individuals from a provisioned, free‐ranging group of R. roxellana across a variety of social‐ecological contexts. We identified 18 call types, which were easily distinguishable by ear, visual inspection of spectrograms, and quantitative analysis of acoustic parameters measured from recording samples. We found a great sexual asymmetry in the vocal repertoire size (females produced many more call types than males), likely due to the sex differences in body size and social role. We found a variety of call types that occurred during various forms of agonistic and affiliative interactions at close range. We made inference about the functions of particular call types based on the contexts in which they were produced. Studies on the vocal communication in R. roxellana are particularly valuable since they provide a case about how nonhuman primates, inhabiting forest habitats and forming complex social systems, use their vocalizations to interact with their social and ecological environments.

High frequency/ultrasonic communication in a critically endangered nocturnal primate, Claire's mouse lemur (Microcebus mamiratra).

The critically endangered Claire's mouse lemur, only found in the evergreen rain forest of the National Park Lokobe (LNP) and a few lowland evergreen rain forest fragments of northern Madagascar, was described recently. The present study provides the first quantified information on vocal acoustics of calls, sound associated behavioral context, acoustic niche, and vocal activity of this species. We recorded vocal and social behavior of six male-female and six male-male dyads in a standardized social-encounter paradigm in June and July 2016 at the LNP, Nosy Bé island. Over six successive nights per dyad, we audio recorded and observed behaviors for 3 hr at the beginning of the activity period. Based on the visual inspection of spectrograms and standardized multiparametric sound analysis, we identified seven different call types. Call types can be discriminated based on a combination of harmonicity, fundamental frequency variation, call duration, and degree of tonality. Acoustic features of tonal call types showed that for communication, mouse lemurs use the cryptic, high frequency/ultrasonic frequency niche. Two call types, the Tsak and the Grunt call, were emitted most frequently. Significant differences in vocal activity of the Tsak call were found between male-female and male-male dyads, linked primarily to agonistic conflicts. Dominant mouse lemurs vocalized more than subdominant ones, suggesting that signaling may present an honest indicator of fitness. A comparison of our findings of the Claire's mouse lemur with published findings of five bioacoustically studied mouse lemur species points to the notion that a complex interplay between ecology, predation pressure, and phylogenetic relatedness may shape the evolution of acoustic divergence between species in this smallest-bodied primate radiation. Thus, comparative bioacoustic studies, using standardized procedures, are promising to unravel the role of vocalization for primate species diversity and evolution and for identifying candidates for vocalization-based non-invasive monitoring for conservation purposes.

Do birds vocalize at higher pitch in noise, or is it a matter of measurement?

Studies have found that some birds use vocalizations with higher minimum frequency in noisy areas. Minimum frequency is often measured by visual inspection of spectrograms (“by-eye practice” (BEP)), which is prone to bias, e.g., if low-frequency components are masked by noise. We tested for this bias by comparing measurements of minimum frequency obtained with the BEP for the same set of red-winged blackbird vocalizations (songs and two call types “checks” and “cheers”) played back under ambient, medium, and high noise conditions using a dual playback experiment where both vocalizations and noise were introduced. We compared BEP measurements to those obtained from power spectrum analyses using a preset amplitude threshold (“threshold method” (TM)). The BEP was biased when measuring the minimum frequencies of songs and checks, which are masked by noise, but not when measuring cheers, which are higher pitched and thus not masked. Measures using the TM were not affected by noise, but this method may fail to identify the vocalizations’ lowest frequency if noise necessitates a low (i.e., conservative) threshold. Using the BEP, we also found a bias toward shorter-duration measurements for songs in increasing noise, and for checks, a bias toward increased measures of an energy distribution parameter (Freq5%), likely in correlation with increased measured minimum frequency. Measures taken from the unmasked cheers were similar regardless of the technique used. We discuss limitations of each approach and encourage the use of the TM, as studies using the BEP may lead to spurious results. Noise from human activities is ubiquitous. Researchers have found that some birds vocalize at higher frequency (pitch) in noise, hypothesizing that this may improve signal detection in low-frequency noise. Noise may also hinder detection of signal components by researchers using the most common measurement technique (the BEP), which may be mistaken for increasing frequency. To examine this bias, we conducted a dual playback experiment, in which we broadcast the same vocalizations at three background noise levels. We found that BEP measures of minimum frequency increased with increasing noise even though the vocalizations did not change. We recommend the TM which yielded similar measures across noise levels, although it excluded some lower-frequency elements included by the BEP. We encourage researchers to use the TM over the BEP and to validate their methods across noise levels of interest.

Song plasticity over time and vocal learning in clay-colored thrushes.

Songbirds have been traditionally classified into close-ended or open-ended learning species according to the length of the sensitive period during which birds are able to memorize new vocalizations. Closed-ended learners are generally not capable of changing their song after the first year of life, while open-ended learners show song plasticity as adults. A few Turdus species have been suggested to be open-ended learners, but no long-term study has been conducted to investigate their song plasticity over time. We analyzed the songs of clay-colored thrushes, T. grayi, over four successive breeding seasons to assess song plasticity in their syllable repertoires within and between breeding seasons. A total of 16,262 syllables were classified through visual inspection of spectrograms and multidimensional scaling analysis based on spectrogram correlations. On average, 563±153 (SD) syllables per male per breeding season were analyzed. Male repertoire size was 9-20 syllable types. Males were capable of modifying their syllable repertoire between the initial and final periods of the breeding season. Song plasticity within breeding seasons may be associated with imitation between neighboring males, suggesting song learning in males that were ≥2years old. This short-term plasticity is not enough, however, to explain the high proportion of change (mean=65% syllable types) in repertoire composition between breeding seasons in adult males. Song plasticity resulting from annual changes in repertoire composition could be explained by open-ended learning, but another mechanism, extended memory and re-expression, could also explain long-term plasticity. Experimental studies controlling the acoustic environment are needed to determine which mechanism is responsible for such a high level of song plasticity.

Unsupervised dictionary extraction of bird vocalisations and new tools on assessing and visualising bird activity

A broad range of organisations and individuals are collecting wildlife audio recordings. Huge amounts of audio data have been gathered in the past and since the popularisation of automatic recording units the data are piling up exponentially. The point in gathering them is to analyse them, evaluate insights and hypotheses, identify patterns of activity that are otherwise not apparent and finally design policies on biodiversity issues. For massive volumes of data even visual inspection of spectrograms is unfeasible and interesting cases that could provide valuable insight for concrete hypotheses on the biodiversity status can slip into bliss. In this paper we research a range of techniques that work with minor human supervision. These techniques will construct a dictionary of templates extracted in an unsupervised way from reference recordings and then crawl over a large number of recordings to examine the underlying bioacoustic activity. This work is general and we have applied it to many datasets of animal's vocalisations (e.g. cetaceans, mice, birds). To test our tools objectively and for the sake of reproducibility in this work we report on the MLSP 2013 bird dataset that recently has been publicly released along with all its annotations. We are not interested as to which is the best scoring approach for this dataset. Our aim is to describe novel machine learning tools that try to refine our understanding of biodiversity by answering questions such as: Is the recording under examination void of bird vocalisations or not? If there is bird activity, how many different species are in the recording? What are the most important characteristic spectral segments for recognizing a specific species? The database however is valuable to us to quantify our findings.

Repertoire Size and Syllable Sharing in the Song of the Clay-Colored Thrush (Turdus grayi)

Song repertoire size and extent of song sharing provide information about social interactions that occur in songbird species. We recorded the songs of eight male Clay-colored Thrushes (Turdus grayi) in San José, Costa Rica during the 2008 breeding season. We classified 695 songs and 5,032 syllables using visual inspection of spectrograms and spectrogram correlation analysis to measure repertoire size and syllable sharing among a local group of males. Male repertoire size was 10–17 syllable types. Males shared on average 28 ± 15% (SD) syllable types from their repertoires with other males, but a larger proportion of syllable types remained unique to particular males. Extent of repertoire sharing and distance between singing males were not related. Presence of shared and individually unique syllables in the repertoires indicate that imitation, and perhaps improvisation, contribute to development of the song of Clay-colored Thrushes.

Automatic infant cry analysis for the identification of qualitative features to help opportune diagnosis

In the infant cry analysis, the identification of qualitative features is of great importance, because this provides relevant information to differentiate between normal and pathological cries, which makes important their identification. Qualitative infant cry analysis has been done until now by medical personal through visual inspection of spectrograms and by the auditory study of the cry recordings. In this way, the success of the process depends on the subjective perception of the inspector besides being a very slow task. The information extracted from the perceptive observation of the crying waves recordings is then used as a help to emit diagnosis. With the idea of helping to make the whole process easier and faster we are developing a method to automatically identify, measure and highlight selected qualitative features in infant cry recordings. The processing of this identifier starts with the automatic discovery of infant cry units, which is performed by the use of a threshold applied to the energy of the signal along with another threshold applied to eliminate inspiratory cry segments, when not needed. From all the detected cry units, the process automatically identifies melodic shape, shifts, glides and noise concentration. In this work, we present, besides a quick review of related works, and a description of the perceptive analysis to help diagnosis, the process implementation, some experiments as well as the experimental results obtained.

Automatic detection of African elephant (Loxodonta africana) infrasonic vocalisations from recordings

Recordings of elephant vocalisations can be used to determine the size and composition of the herd, the sexual state, as well as the emotional condition of an elephant. Manual analysis of recordings (by listening to these and by visual inspection of spectrograms) to locate vocalisations is tedious. The automatic detection of vocalisations in recordings is explored. Important signal characteristics of elephant vocalisations were identified from spectrograms and a technique, based on the principles of existing voice activity detection algorithms, was developed to exploit these. Results obtained suggest that the algorithm can reliably detect elephant vocalisations from noisy recordings as long as the harmonic structure of vocalisations is not buried in background noise.

Categorization of budgerigar (Melopsittacus undulatus) warble elements.

The warble song of budgerigars is composed of a variety of elements without any obvious sequential order. Some of the elements also occur as single utterances. A previous study classified warble elements into 42 groups by visual inspection of spectrograms. However, the density of warble (about 140 elements/min, up to 30 min in duration) makes this method both laborious and time‐consuming for analyzing a large amount of warble. Here three human raters took 860 elements from 3 birds and sorted the sonograms into 9 general groups with an inter‐rater reliability of 89%. Next, these elements were used to train a neural network. This network learned to categorize a large number of warble elements efficiently with 84% reliability (compared to human raters). Further examination of other warble streams revealed that warble elements are not evenly distributed across these nine groups for the same bird, but the relative proportion of different elements in warble categories is similar across three budgerigars. Ongoin...

Applications of ENF criterion in forensic audio, video, computer and telecommunication analysis

This article reports on the electric network frequency criterion as a means of assessing the integrity of digital audio/video evidence and forensic IT and telecommunication analysis. A brief description is given to different ENF types and phenomena that determine ENF variations. In most situations, to reach a non-authenticity opinion, the visual inspection of spectrograms and comparison with an ENF database are enough. A more detailed investigation, in the time domain, requires short time windows measurements and analyses. The stability of the ENF over geographical distances has been established by comparison of synchronized recordings made at different locations on the same network. Real cases are presented, in which the ENF criterion was used to investigate audio and video files created with secret surveillance systems, a digitized audio/video recording and a TV broadcasted reportage. By applying the ENF Criterion in forensic audio/video analysis, one can determine whether and where a digital recording has been edited, establish whether it was made at the time claimed, and identify the time and date of the registering operation.

Wavelet speech enhancement based on time–scale adaptation

We propose a new speech enhancement method based on time and scale adaptation of wavelet thresholds. The time dependency is introduced by approximating the Teager energy of the wavelet coefficients, while the scale dependency is introduced by extending the principle of level dependent threshold to wavelet packet thresholding. This technique does not require an explicit estimation of the noise level or of the a priori knowledge of the SNR, as is usually needed in most of the popular enhancement methods. Performance of the proposed method is evaluated on speech recorded in real conditions (plane, sawmill, tank, subway, babble, car, exhibition hall, restaurant, street, airport, and train station) and artificially added noise. MEL-scale decomposition based on wavelet packets is also compared to the common wavelet packet scale. Comparison in terms of signal-to-noise ratio (SNR) is reported for time adaptation and time–scale adaptation of the wavelet coefficients thresholds. Visual inspection of spectrograms and listening experiments are also used to support the results. Hidden Markov Models speech recognition experiments are conducted on the AURORA-2 database and show that the proposed method improves the speech recognition rates for low SNRs.

Digital audio recording analysis: the Electric Network Frequency (ENF) Criterion

This article reports on the Electronic Network Frequency Criterion as a means of assessing the integrity of digital audio evidence. A brief description is given of phenomena that determine ENF varaiations. In most situations,to reach a non-authenticity option, the visual inspection of spectrograms and comparison with an ENF database are enough. A more detailed investigation, in the time domaine, requires short time windows measurements and analyses. The stability of the ENF over geographical distances has been established by comparison of synchronized recordings made at different locations on the same network. A real case is presented, in which the ENF Criterios was used to investigate an audio file created with a secret surveillance system. By applying the ENF Criterion in forensic audio analysis, one can determine whether and where a digital recording has been edited, establish whether it was made at the time claimed, and identify the time and date of the registering operation.

Quantitative analysis of dolphin sounds

Most analyses of acoustic communication in animals lump sounds into qualitative categories. These are usually based upon aural impressions for human listeners or visual inspection of spectrograms. Quantitative analysis of acoustic features from beluga whale sounds raise serious questions about how discrete and robust the traditional categories of beluga calls are. Other categories, such as the contour of a dolphin whistle, use features that need not relate directly to absolute measure of time and frequency. Studies of vocal development and vocal imitation often benefit from a quantitative measure of similarity between sounds and putative models. Several different methods are compared to analyze whistle contours, including multivariate analysis of time‐frequency features, dynamic time warping, and a signal compression approach. Ultimately, all such techniques need to be validated by studies of how each species perceives its own signals.

4977812 Accompaniment line principal tone determination system

In the infant cry analysis, the identification of qualitative features is of great importance, because this provides relevant information to differentiate between normal and pathological cries, which makes important their identification. Qualitative infant cry analysis has been done until now by medical personal through visual inspection of spectrograms and by the auditory study of the cry recordings. In this way, the success of the process depends on the subjective perception of the inspector besides being a very slow task. The information extracted from the perceptive observation of the crying waves recordings is then used as a help to emit diagnosis. With the idea of helping to make the whole process easier and faster we are developing a method to automatically identify, measure and highlight selected qualitative features in infant cry recordings. The processing of this identifier starts with the automatic discovery of infant cry units, which is performed by the use of a threshold applied to the energy of the signal along with another threshold applied to eliminate inspiratory cry segments, when not needed. From all the detected cry units, the process automatically identifies melodic shape, shifts, glides and noise concentration. In this work, we present, besides a quick review of related works, and a description of the perceptive analysis to help diagnosis, the process implementation, some experiments as well as the experimental results obtained.

A system of standard stars for rotational velocity determinations

view Abstract Citations (360) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A system of standard stars for rotational velocity determinations. Slettebak, A. ; Collins, G. W., II ; Boyce, P. B. ; White, N. M. ; Parkinson, T. D. Abstract Profiles for the He I lambda 4471, Mg II lambda 4481, and Fe I lambda 4476 lines were measured in the spectra of 217 bright northern and southern stars of types O9-F9, using photoelectric scans and photographic coude spectrograms obtained at the Cerro Tololo Inter-American Observatory, Kitt Peak National Observatory, and Lowell Observatory. Half-intensity widths of the observed line profiles were compared with the corresponding quantities in a set of theoretical rotationally-broadened line profiles computed using the model-atmosphere approach. The resulting v sin i's are used to establish a system of standard rotational velocity stars, for use in estimating v sin i directly from visual inspection of spectrograms. An atlas of rotationally broadened spectra is presented, showing the effects of rotation on spectra of representative B-, A-, and F-type stars. Publication: The Astrophysical Journal Supplement Series Pub Date: May 1975 DOI: 10.1086/190338 Bibcode: 1975ApJS...29..137S Keywords: Angular Velocity; Line Spectra; Reference Stars; Stellar Rotation; Stellar Spectra; Astronomical Models; Atmospheric Models; F Stars; Radiant Flux Density; Rotational Spectra; Spectral Line Width; Standards; Astronomy full text sources ADS | data products SIMBAD (219)