Acoustic Variables Research Articles

DYNAMIC ACOUSTIC PROPERTIES OF PAKISTANI ENGLISH: A DESCRIPTION OF FORMANT VARIATIONS OF F1 & F2 PRODUCED BY PAKISTANI SPEAKERS

The current study explores the variations of formant frequency of English vowels produced by eighty students of BS English and English language at NUML and International Islamic University Islamabad. The research defines the acoustic monophthongal variations under the influence of gender and four standard regional varieties of Pakistan and presents a macro-level description of Monophthongs of Pakistani English. The respondents belong to Balochi, Pushto, Punjabi, and Sindhi languages. This study explores monophthongal formant variations among these speakers through the lenses of the ‘Formant Frequency Model’ (Lindblom, 1979). For this purpose, the poem entitled, “The North Wind and the Sun” has been used to collect the required data. The formant values have been extracted from PRAAT, a software presented by (Boersma & Weenink, 2019). The manually extracted data from PRAAT were analyzed via statistical tools of SPSS and ANOVA. The findings of this research disclose that monophthongal formant variations are related to the unclear realization of sounds like /ə / and /ʌ/, paucity in realizing the vowel pairs of English, identical articulation of /ɒ/ and /ͻ:/ among the groups. The findings of the research would contribute to the phonological system of Pakistani English, which is an Asian- variety of the Outer-Circle. The findings would assist English language teachers to teach pronunciation of English with an acoustic-phonetic perspective. Keywords: PakE, Acoustic & Statistical Analysis, Formant Frequencies, Monophthongs

Identifying a Sound-Producing Object’s Direction of Motion and Change in Speed

ABSTRACT In natural settings, a wide variety of events frequently occur in our vicinity. Previous research has revealed individuals can accurately identify events when relying solely on what is heard. Although previous research suggests sound intensity is a dominant factor affecting event perception, event identification is likely dependent on additional acoustic variables. The present study examined the ability of individuals to identify and discriminate between events that had intersecting and variable temporal and acoustic properties. Participants were exposed to 60 audio recordings of an object that either moved in a particular direction (approached or withdrew) or changed in speed (accelerated or decelerated). The task of the participant was to identify which of four actions occurred on a particular trial. The findings revealed that, with the exception of events involving acceleration, participants were quite poor at event identification. The results further revealed object speed and event duration were the dominant factors affecting perceptual accuracy. It is argued that the observed perceptual error and perceptual ambiguity resulted from the variability and similarity in temporal and acoustic properties of the events used in the present study. The findings of the present study are believed to provide valuable insight into the information supporting auditory event perception and the ability of individuals to identify events in real-world settings.

Newly Designed 3D-Printed Sonication Test Cell Optimized for In Vitro Sonication Experiments

Precise control over the ultrasound field parameters experienced by biological samples during sonication experiments in vitro may be quite challenging. The main goal of this work was to outline an approach to construction of sonication test cells that would minimize the interaction between the test cells and ultrasound. Optimal dimensions of the test cell were determined through measurements conducted in a water sonication tank using 3D-printed test objects. The offset of local acoustic intensity variability inside the sonication test cell was set to value of ±50% of the reference value (i.e., local acoustic intensity measured at last axial maximum in the free-field condition). The cytotoxicity of several materials used for 3D printing was determined using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. The sonication test cells were 3D printed from polylactic acid material, which was not toxic to the cells. Silicone membrane HT-6240, which was used to construct the bottom of the test cell, was found to reduce ultrasound energy minimally. Final ultrasound profiles inside the sonication test cells indicated the desired variability of local acoustic intensity. The cell viability in our sonication test cell was comparable to that of commercial culture plates with bottoms constructed with silicone membrane. An approach to construction of sonication test cells minimizing the interaction of the test cell and ultrasound has been outlined.

Ecological factors drive the divergence of morphological, colour and behavioural traits in cactus wrens (Aves, Troglodytidae).

The study of ecological mechanisms influencing organisms' phenotypic variation is a central subject of evolutionary biology. In this study, we characterized morphological, plumage colour and acoustic variation in cactus wrens Campylorhynchus brunneicapillus throughout its distribution. We assessed whether Gloger's, Allen's and Bergmann's ecogeographical rules, and the acoustic adaptation hypothesis relate to geographical trait variation. We analysed specimen coloration in belly and crown plumage, beak shape and structural song characteristics. We tested whether the subspecific classification or the peninsular/mainland groups mirrored the geographical variation in phenotypes and whether ecological factors were associated with patterns of trait variation. Our results suggest that colour, beak shape and acoustic traits varied across the range, in agreement with two lineages described by genetics. The simple versions of Gloger's and Allen's rules are related to variations in colour traits and morphology. Conversely, patterns of phenotypic variation did not support Bergmann's rule. The acoustic adaptation hypothesis supported song divergence for frequency-related traits. Phenotypic variation supports the hypothesis of two taxa: C. affinis in the Baja California peninsula and C. brunneicapillus in the mainland. The ecological factors are associated with phenotypic trait adaptations, suggesting that divergence between lineages could result from ecological divergence.

Phenotypic differentiation in populations of a gladiator tree frog: environment, genetic drift and sexual selection

Abstract Phenotypic differentiation among animal populations is common, yet few studies have simultaneously examined the adaptive and neutral mechanisms behind it. Such evolutionary processes become more relevant in species with complex behaviours that undergo global and local selective pressures throughout their geographical range. Here we measured and compared morphological and acoustic variation across the distribution range of a Neotropical gladiator tree frog that shows elaborate reproduction (territoriality, complex courtship and female choice). We then incorporated molecular and landscape data to examine the roles of sexual selection, genetic drift and acoustic adaptation to the environment in call differentiation, i.e. the acoustic adaptation hypothesis (AAH). We found that calls varied more than morphology among populations, but differences in calls or morphological traits were not explained by genetic differentiation. We found no evidence for the AAH, but a significant relationship in the opposite direction regarding call frequencies suggests an indirect role of sexual selection. Differentiation on call traits that are associated with individual discrimination and/or female attraction also corroborated an important role of sexual selection. We show that multitrait and multimechanism approaches can elucidate intricate processes leading to phenotypic variation among individuals and populations. We emphasize that studies of species with complex reproductive behaviours across their range may provide insights into different selective pressures leading to phenotypic differentiation.

Integrated multipole acoustic modeling and processing in general stressed formations, Part 1: An effective approach study

Velocity variation around the borehole due to stress is widely important for borehole stability, hydraulic fracturing and sanding prevention during hydrocarbon production. Theoretical formulation of the acoustic velocity variation around the borehole under stress condition is derived. The formation around the borehole is considered as an rock with two orthogonal crack sets caused by the drilling operation. The relationship between fracture shape and near-borehole stress is established. The effective modulus of elasticity of the above media is derived. The finite difference method is then used to model the acoustic properties. The modeling results show that in a stressed formation, shear wave splitting and dispersion crossover would occur for a monopole and dipole source, respectively. It also explains that the dipole wave-dispersion crossover may not be clear which is more suitable for the field data observation. The modeling results can be used as a guide to understand and interpret the acoustic measurements in stressed formations.

Experienced Listeners’ Perception of Timbre Dissimilarity Within and Between Voice Categories

The terms "soprano" and "mezzo-soprano" are frequently used by vocal pedagogues to describe a main category of singing timbre categorization, while the terms "lyric" and "dramatic" are often used to describe sub-categories of "soprano" and "mezzo-soprano". A handful of studies have reported on the perceptual dissimilarity of main voice categories, but few, if any, have focused on within voice category perceptual distinctions such as dramatic and lyric vocal timbre. Using stimuli collected from cisgender female singers of varying voice categories and voice weights across the pitches C4, G4, and F5, this study sought (1) to visualize an experienced listener's perception of vocal timbre dissimilarity within and between voice categories using the statistical technique of multidimensional scaling (MDS), (2) to identify salient acoustic predictors of voice category and voice weight, and (3) to determine any dependencies on pitch for the perception of vocal timbre. For the pitches C4, G4, and F5, experienced listeners (N=18) rated the dissimilarity of pairs of sung vowels produced by classically trained singers classified as follows: six mezzo-sopranos (three lighter and three heavier) and six sopranos (three lighter and three heavier). The resulting dissimilarity data were analyzed using MDS. Backward linear regression was used to see if one or more of the following variables predicted MDS dimensions: spectral centroid from 0 to 5 kHz, spectral centroid from 0 to 2 kHz, spectral centroid from 2 to 5 kHz, frequency vibrato rate, and frequency vibrato extent. Listeners also completed a categorization task where they rated each individual stimulus on two dimensions: voice category and voice weight. Visual analysis of the MDS solutions appears to show that both voice category and voice weight emerged as dimensions at pitches C4 and G4. Discriminant analysis, on the other hand, statistically confirmed both these dimensions at G4, but only voice weight at C4. At pitch F5, only voice weight emerged as a dimension, both visually and statistically. Acoustic predictors of MDS dimensions were highly variable across pitches. At the pitch C4, no MDS dimension was predicted by the acoustic variables. At pitch G4, the dimension associated with voice weight was predicted by spectral centroid from 0 to 2 kHz. At pitch F5, the dimension associated with voice weight was predicted by spectral centroid from 2 to 5 kHz and frequency vibrato rate. In the categorization task, voice category and voice weight were highly correlated at the pitches C4, G4, and when all pitches were presented together, but weakly correlated at the pitch F5. While voice category and sub-category distinctions are commonly used by singing voice professionals to describe the overall timbre of voices, these distinctions may not be able to consistently predict the perceptual difference between any given pair of vocal stimuli, particularly across pitch. Nonetheless, these dimensions do emerge in some fashion when listeners are presented with paired vocal stimuli. On the other hand, when asked to rate stimuli according to the specific labels of mezzo-soprano/soprano and dramatic/lyric, experienced listeners have a very difficult time disentangling voice category from voice weight when presented with a single-note stimulus or even a 3-note stimulus consisting of the pitches C3, G4, and F5.

The structure of acoustic voice variation in bilingual speech.

When a bilingual switches languages, do they switch their voice? Using a conversational corpus of speech from early Cantonese-English bilinguals (n = 34), this paper examines the talker-specific acoustic signatures of bilingual voices. Following the psychoacoustic model of voice, 24 filter and source-based acoustic measurements are estimated. The analysis summarizes mean differences for these dimensions and identifies the underlying structure of each talker's voice across languages with principal component analyses. Canonical redundancy analyses demonstrate that while talkers vary in the degree to which they have the same voice across languages, all talkers show strong similarity with themselves, suggesting an individual's voice remains relatively constant across languages. Voice variability is sensitive to sample size, and we establish the required sample to settle on a consistent impression of one's voice. These results have implications for human and machine voice recognition for bilinguals and monolinguals and speak to the substance of voice prototypes.

Talker adaptation or "talker" adaptation? Musical instrument variability impedes pitch perception.

Listeners show perceptual benefits (faster and/or more accurate responses) when perceiving speech spoken by a single talker versus multiple talkers, known as talker adaptation.While near-exclusively studied in speech and with talkers, some aspects of talker adaptation might reflect domain-general processes. Music, like speech, is a sound class replete with acoustic variation, such as a multitude of pitch and instrument possibilities. Thus, it was hypothesized that perceptual benefits from structure in the acoustic signal (i.e., hearing the same sound source on every trial) are not specific to speech but rather a general auditory response. Forty nonmusician participants completed a simple musical task that mirrored talker adaptation paradigms. Low- or high-pitched notes were presented in single- and mixed-instrument blocks. Reflecting both music research on pitch and timbre interdependence and mirroring traditional "talker" adaptation paradigms, listeners were faster to make their pitch judgments when presented with a single instrument timbre relative to when the timbre was selected from one of four instruments from trial to trial. A second experiment ruled out the possibility that participants were responding faster to the specific instrument chosen as the single-instrument timbre. Consistent with general theoretical approaches to perception, perceptual benefits from signal structure are not limited to speech.

The acoustic structure of spider monkey (Ateles geoffroyi) calls is related both to caller goal and arousal.

Analyzing the factors related to the acoustic structure of primate calls is fundamental to identifying the potential information these signals convey, and therefore, their potential function. It is well-accepted that caller arousal is an important driver of acoustic variation in call structure. However, evidence suggests that arousal alone cannot explain the production of calls with different acoustic structures. The "caller goal" framework posits that a call type (e.g., bark and chitter) is a signal which evolved to elicit specific changes on receiver behavior, and a caller's goal, not its arousal state, determines the basic acoustic structure of animal calls. To get a better insight into the effects of caller goal and arousal on the acoustic structure of primate calls, we analyzed the acoustic variation of 382 calls produced by 27 free-ranging spider monkeys (Ateles geoffroyi) in six call contexts representing three caller goals (establishing contact, engage in aggression, and predator presence) across two arousal states (high and low). Discriminant function analyses and linear mixed models showed a strong effect of caller goal on calls' acoustic structure and supported the effect of arousal state on acoustic variation; misclassified calls mainly occurred between the same caller goal categories (e.g., alarm low arousal and alarm high arousal), and acoustic differences between arousal contexts showed the same pattern across the three caller goals (e.g., low center frequency [kHz] values in high arousal contexts). Our results supported the view that caller goal is the primary driver of acoustic difference and showed the effects of caller arousal on other structural differences.

Acoustic Variation in Ictalurid Catfishes

More than 35,000 ray-finned fish (Actinopterygii) species are potentially using acoustic communication. However, of the approximately 1200 known soniferous fish species, few include North American freshwater fish. To help fill this knowledge gap in fish acoustic communication, which holds great promise for conservation monitoring, I document acoustic measurements (duration 90%, bandwidth 90%, number of pulses, center frequency, and peak time) across 4 species (Ameiurus nebulosus, Ameiurus natalis, Noturus flavus, Ictalurus punctatus) from 3 genera of the North American catfish family, Ictaluridae. This was done by recording 10 trials of disturbance calls from 28 individuals and analyzing 1294 sounds using Raven Pro 1.6 software. I hypothesized that: 1) more phylogenetically/morphologically related species would have more similar acoustic features, 2) acoustic features would correlate with one another, and 3) acoustic features would correlate with standard length (cm). For hypothesis 1, I instead found that Ameriurus nebulosus was the most acoustically dissimilar, despite having the highest level of phylogenetic/morphological similarity with Ameirus natalis. However, only Ameriurus nebulosus' number of pulses were significantly different from other species. For hypothesis 2, it was found that many acoustic measurements were correlated with one another as predicted. For hypothesis 3, only the number of pulses was found to be significantly correlated with standard length, but minimally so. These findings further support that pulsation measurements may contain a high level of phylogenetic signal, given that it is the most crucial characteristic to differentiate species.

Observations of the space/time scales of Beaufort sea acoustic duct variability and their impact on transmission loss via the mode interaction parameter.

The Beaufort duct (BD) is a subsurface sound channel in the western Arctic Ocean formed by cold Pacific Winter Water (PWW) sandwiched between warmer Pacific Summer Water (PSW) and Atlantic Water (AW). Sound waves can be trapped in this duct and travel long distances without experiencing lossy surface/ice interactions. This study analyzes BD vertical and temporal variability using moored oceanographic measurements from two yearlong acoustic transmission experiments (2016-2017 and 2019-2020). The focus is on BD normal mode propagation through observed ocean features, such as eddies and spicy intrusions, where direct numerical simulations and the mode interaction parameter (MIP) are used to quantify ducted mode coupling strength. The observations show strong PSW sound speed variability, weak variability in the PWW, and moderate variability in the AW, with typical time scales from days to weeks. For several hundreds Hertz propagation, the BD modes are relatively stable, except for rare episodes of strong sound speed perturbations. The MIP identifies a resonance condition such that the likelihood of coupling is greatest when there is significant sound speed variability in the horizontal wave number band 1/11<kh<1/5 km-1. MITgcm ocean model results are used to estimate sound speed fluctuations in this resonance regime.

Acoustic travel-time variability observed on a 150-km radius tomographic array in the Canada Basin during 2016-2017.

The Arctic Ocean is undergoing dramatic changes in response to increasing atmospheric concentrations of greenhouse gases. The 2016-2017 Canada Basin Acoustic Propagation Experiment was conducted to assess the effects of the changes in the sea ice and ocean structure in the Beaufort Gyre on low-frequency underwater acoustic propagation and ambient sound. An ocean acoustic tomography array with a radius of 150 km that consisted of six acoustic transceivers and a long vertical receiving array measured the impulse responses of the ocean at a variety of ranges every four hours using broadband signals centered at about 250 Hz. The peak-to-peak low-frequency travel-time variability of the early, resolved ray arrivals that turn deep in the ocean was only a few tens of milliseconds, roughly an order of magnitude smaller than observed in previous tomographic experiments at similar ranges, reflecting the small spatial scale and relative sparseness of mesoscale eddies in the Canada Basin. The high-frequency travel-time fluctuations were approximately 2 ms root-mean-square, roughly comparable to the expected measurement uncertainty, reflecting the low internal-wave energy level. The travel-time spectra show increasing energy at lower frequencies and enhanced semidiurnal variability, presumably due to some combination of the semidiurnal tides and inertial variability.

Source localization based on steered frequency-wavenumber analysis for sparse array.

When using a sparse array, locating the target signal of a high-frequency component is difficult. Although forecasting the direction in a sparse situation is challenging, the frequency-wavenumber (f-k) spectrum can simultaneously determine the direction and frequency of the analyzed signal. The striation of the f-k spectrum shifts along the wavenumber axis in a sparse situation, which reduces the spatial resolution required to determine the target's direction using the f-k spectrum. In this study, f-k spectra of a high-frequency signal were used for near-field source localization. Snapping shrimp sounds (5-24 kHz) from SAVEX15 (a shallow-water acoustic variability experiment conducted in May 2015) were used as the data source, and a simulation was used to evaluate the proposed method. Beam steering was performed before creating the f-k spectrum to improve spatial resolution. We found that the spatial resolution was improved, and the location of the sound source could be determined when a signal with beam steering was utilized. The shrimp sound from SAVEX15, a near-field broadband signal, was used to determine the shrimp's location (range, 38 m; depth, 100 m) and the tilt of the vertical line array. These results suggest that the proposed analysis helps to accurately estimate the location of sound source.

How heat waves, ozone and sunlight hours affect endocrine and metabolic diseases emergency admissions? A case study in the region of Madrid (Spain)

BackgroundStudies which analyse the joint effect of acoustic or chemical air pollution variables and different meteorological variables on neuroendocrine disease are practically nonexistent. This study therefore sought to analyse the impact of air pollutants and environmental meteorological variables on daily unscheduled admissions due to endocrine and metabolic diseases in the Madrid Region from January 01, 2013 to December 31, 2018. Material and methodsWe conducted a longitudinal, retrospective, ecological study of daily time series analysed by Poisson regression, with emergency neuroendocrine-disease admissions in the Madrid Region as the dependent variable. The independent variables were: mean daily concentrations of PM10, PM2.5, NO2 and O3; acoustic pollution; maximum and minimum daily temperatures; hours of sunlight; relative humidity; wind speed; and air pressure above sea level. Estimators of the statistically significant variables were used to calculate the relative risks (RRs). ResultsA statistically significant association was found between the increase in temperatures in heat waves, RR: 1.123 95% CI (1.001–1.018), and the number of emergency admissions, making it the main risk factor. An association between a decrease in sunlight and an increase in hospital admissions, RR: 1.005 95% CI (1.002 1.008), was likewise observed. Similarly, ozone, in the form of mean daily concentrations in excess of 44 μg/m3, had an impact on admissions due to neuroendocrine disease, RR: 1.010 95% CI (1.007–1.035). The breakdown by sex showed that in the case of women, NO2 was also a risk factor, RR: 1.021 95% CI (1.007–1.035). ConclusionThe results obtained in this study serve to identify risk factors for this disease, such as extreme temperatures in heat waves, O3 or NO2. The robust association found between the decrease in sunlight and increase in hospital admissions due to neuroendocrine disease serves to spotlight an environmental factor which has received scant attention in public health until now.

Diel variation in insect‐dominated temperate pond soundscapes and guidelines for survey design

Abstract Passive acoustic monitoring has been used for decades as a non‐invasive tool for quantifying biodiversity in terrestrial and marine ecosystems. Recently, there has been increased interest in the potential for the method to survey freshwater biodiversity. Fundamental aspects of freshwater soundscape phenology, however, often remain poorly understood, despite their importance for suitable survey design. To gain a greater understanding of daily acoustic variation in aquatic insect‐dominated temperate pond soundscapes, 840 hr of underwater sound recordings were collected from five ponds in the southwest of the U.K. We calculated six commonly used acoustic indices to investigate diel trends and evaluated the suitability of each acoustic index to identify biologically complex pond soundscapes. In addition, macroinvertebrates were collected from each pond to investigate potential drivers of diel soundscape variation. The ponds studied possessed clear patterns of daily acoustic variation, with acoustic activity typically peaking between 02:00 and 04:00 and around the solar noon. Acoustic Entropy showed the greatest variation between day and night soundscapes and was best suited for detecting overall daily acoustic variation in the study ponds. However, the Normalised Difference Soundscape Index and the Bioacoustic Index captured strong diel variation in aquatic insect‐dominated soundscapes. Furthermore, we calculated that a minimum hydrophone deployment time of 24 hr is required to ensure that soundscape variation is adequately captured. This study provides an increased understanding of daily acoustic variation in insect‐dominated temperate pond soundscapes, enabling us to provide guidelines for the design and implementation of future passive acoustic monitoring surveys. We suggest that a minimum of 24 hr is required to adequately capture pond soundscape variation. This will increase the chance of detecting key soniferous species in the soundscape and enable more accurate assessments of temperate pond soundscapes.

A time series comprehensive evaluation method of acoustic emission signal based on information entropy weighting and its application of red bed soft rock compression failure critical characteristics study

To deeply understand the self-organization critical phenomenon of red bed soft rock in the process of compression failure, a uniaxial compression test was carried out on silt mudstone. The acoustic emission signal was collected simultaneously during the whole test process. The information entropy theory was applied to weigh the acoustic emission signal. The translation time domain was introduced to analyze the acoustic emission signal time series variation law. Finally, the time series comprehensive evaluation index value variation law of acoustic emission signal based on information entropy weighting was obtained. (1) During the compression loading process, with the increase of time, all the time series comprehensive evaluation index values showed an increasing trend with the saturated cycle increasing. When the time series comprehensive evaluation index value remains stable, it could be considered that the red bed soft rock enters a critical state. (2) The acoustic emission three-dimensional positioning results showed that when the compression failure reaches the critical point, the time series comprehensive evaluation index value would be the largest, and the coalescence crack also begins to form. When entering the critical state, the time series comprehensive evaluation index value would be in a stable state. (3) When the compression failure reached the critical point, the positioning signal would accumulate towards the rupture area until the sample was destroyed. The acoustic emission three-dimensional positioning results revealed the silt mudstone internal defects evolution law. These internal defects evolve from the slow and random development-disordered state to the instantaneous development-ordered state. These evolution laws corresponded well with the time series comprehensive evaluation index value variation trend. (4) During the compressive loading process, the energy probability density function satisfied the power-function distribution under different saturated periods. The research results are expected to provide a theoretical reference for the study of red bed soft rock compression failure critical damage characteristics.

Dynamic Speed of Sound Adaptive Transmission-Reflection Ultrasound Computed Tomography.

Ultrasound computed tomography (USCT) can visualize a target with multiple imaging contrasts, which were demonstrated individually previously. Here, to improve the imaging quality, the dynamic speed of sound (SoS) map derived from the transmission USCT will be adapted for the correction of the acoustic speed variation in the reflection USCT. The variable SoS map was firstly restored via the optimized simultaneous algebraic reconstruction technique with the time of flights selected from the transmitted ultrasonic signals. Then, the multi-stencils fast marching method was used to calculate the delay time from each element to the grids in the imaging field of view. Finally, the delay time in conventional constant-speed-assumed delay and sum (DAS) beamforming would be replaced by the practical computed delay time to achieve higher delay accuracy in the reflection USCT. The results from the numerical, phantom, and in vivo experiments show that our approach enables multi-modality imaging, accurate target localization, and precise boundary detection with the full-view fast imaging performance. The proposed method and its implementation are of great value for accurate, fast, and multi-modality USCT imaging, particularly suitable for highly acoustic heterogeneous medium.

Intra- and inter-speaker variation in eight Russian fricativesa).

Acoustic variation is central to the study of speaker characterization. In this respect, specific phonemic classes such as vowels have been particularly studied, compared to fricatives. Fricatives exhibit important aperiodic energy, which can extend over a high-frequency range beyond that conventionally considered in phonetic analyses, often limited up to 12 kHz. We adopt here an extended frequency range up to 20.05 kHz to study a corpus of 15 812 fricatives produced by 59 speakers in Russian, a language offering a rich inventory of fricatives. We extracted two sets of parameters: the first is composed of 11 parameters derived from the frequency spectrum and duration (acoustic set) while the second is composed of 13 mel frequency cepstral coefficients (MFCCs). As a first step, we implemented machine learning methods to evaluate the potential of each set to predict gender and speaker identity. We show that gender can be predicted with a good performance by the acoustic set and even more so by MFCCs (accuracy of 0.72 and 0.88, respectively). MFCCs also predict individuals to some extent (accuracy = 0.64) unlike the acoustic set. In a second step, we provide a detailed analysis of the observed intra- and inter-speaker acoustic variation.

Time domain response of a piezoelectric layer

A number of one-dimensional models have been developed to inform the design of piezoelectric transducers. The majority of these models are in the frequency domain. In this paper, we develop a one-dimensional time-domain model for the mechanical response of a piezoelectric layer. Secondary effects, resulting from feedback between the acoustic and electric variables, are included in the model. Our approach utilizes Green's function for the Helmholtz equation with radiation boundary conditions and the methods of complex analysis. The model predictions are validated by comparison with a finite-difference time-domain numerical simulation of the governing acoustic equations in and outside the layer. This time-domain model enables efficient calculation of the secondary piezoelectric action effects and provides the mechanical response to an arbitrary electrical source.