Acoustic Behavior Research Articles

Caller identification and characterization of individual humpback whale acoustic behaviour.

Acoustic recording tags provide fine-scale data linking acoustic signalling with individual behaviour; however, when an animal is in a group, it is challenging to tease apart calls of conspecifics and identify which individuals produce each call. This, in turn, prohibits a robust assessment of individual acoustic behaviour including call rates and silent periods, call bout production within and between individuals, and caller location. To overcome this challenge, we simultaneously instrumented small groups of humpback whales on a western North Atlantic feeding ground with sound and movement recording tags. This approach enabled a comparison of the relative amplitude of each call across individuals to infer caller identity for 97% of calls. We recorded variable call rates across individuals (mean = 23 calls/h) and groups (mean = 55 calls/h). Calls were produced throughout dives, and most calls were produced in bouts with short inter-call intervals of 2.2 s. Most calls received a likely response from a conspecific within 100 s. This caller identification (ID) method facilitates studying both individual- and group-level acoustic behaviour, yielding novel results about the nature of sequence production and vocal exchanges in humpback whale social calls. Future studies can expand on these caller ID methods for understanding intra-group communication across taxa.

Using before-after control-impact methodology to quantify effects of full ship shock trial explosions on marine fauna

In the summer of 2021, the US Navy conducted a Full Ship Shock Trial (FSST) for the USS Gerald R. Ford. This involved three large underwater explosions off the coast of Florida, USA. We collected underwater acoustic recordings, using low-sensitivity recorders, for the Naval Undersea Warfare Center to validate their underwater acoustic propagation models. We also deployed SoundTraps on the shallow moorings to collect additional acoustical biologics data in hopes of measuring any acoustic responses of marine fauna to the explosions. The acoustic energy of the explosions did not propagate up the continental slope and were hence not captured by the SoundTraps on the shallow moorings. However, our analyses did yield some notable changes in acoustic behavior after as compared to before the explosions. Here, we describe how our field plan was designed for before-after control-impact (BACI) hypothesis testing and discuss our analyses and findings of the few significant cases. These results lend insight for improving the impact assessments and conducting behavioral response studies during a future FSST or other large underwater explosions.

Quantifying northern bottlenose and sperm whale acoustic behavioural responses to anthropogenic noise in Baffin Bay, Canada

Marine mammals rely on their auditory system for a myriad of life functions (e.g., navigating, foraging, socializing) and consequently, are vulnerable to loud human activities (e.g., vessel traffic, fishing, military activities). These activities can impede communication, cause behavioural disturbances, and can even cause injuries. As the Arctic warms and sea ice coverage decreases, more opportunities for human activities are arising. How noise impacts the acoustic behaviour of Arctic marine mammals is unclear. In October 2022 and 2023 controlled noise exposure experiments were conducted using military sonar (source level of 176.4 dB re 1 μPa) on northern bottlenose and sperm whales in Baffin Bay while they were foraging around vessels actively fishing. Hydrophone suction-cup biologgers (DTAGs; n = 5, ∼72 cumulative hours) were used to capture vessel and sonar noises, and whale vocalizations before, during, and after the noise exposure periods. Using a click detector, focal whale clicks were identified and quantitatively compared to received noise levels. This information will then be used to determine noise thresholds for acoustical behavioural responses. These results will support risk-mitigation strategies for the Department of National Defence Canada and Fisheries and Oceans Canada, as well as address Inuit concerns about the effects of military sonar on marine mammals.

Exploiting passive acoustic recordings of seismic survey datasets

Marine seismic reflection surveys provide a dense and abundant dataset covering a large region of geological interest in the ocean. These data provide an opportunity for acoustic analysis with varying environmental characteristics, both in the water column and the seabed. In a typical survey, an airgun array is fired tens to hundreds of thousands of times, and hundreds of receiver channels record the acoustic signal reflected from the seabed after each shot. Additionally, the high amplitude signal broadcast from airgun arrays used in these surveys may be measured passively by hydrophones located close to the survey. In this work, we consider the data measured by Ocean Observatories Initiative (OOI) hydrophones adjacent to two seismic surveys, MGL1905, and MGL2104. In each case, a 6600 in3 airgun array is fired ∼every 37.5 m along multiple survey lines extending 10s to 100s of kilometers. Each survey generates multiple terabytes of acoustic data, and many of the shots are also captured by OOI hydrophones. This work aims to combine these two datasets to evaluate the acoustic behavior of airgun shots over a variety of conditions and examine the relationship between various environmental factors and acoustic propagation behavior. [Work supported by ONR.]

Droplets for acoustic vaporization: Formulations, properties and applications

The Acoustic Droplet Vaporization (ADV) (1), a phase-change of the droplets core from liquid to vapor phase upon ultrasound irradiation, burst renewed interest in droplet emulsions, a traditional topic of colloidal science, opening up innovative applications in biomedicine. Droplets undergoing ADV share similar liquid cores, typically perfluorocarbons (PFCs), however, the nature of the shells can be polymeric (2) or lipidic (3, 4). Such difference imparts to phase-change droplets diverse acoustic and mechanical behaviors (5). In this contribution we present some results concerning a general strategy for the formulation of polymer or lipid shelled submicron droplets. Other key points for the use of ADV-responsive in biomedical applications will be addressed. Recently we have extended the concepts of ADV to radiation responsive droplets for dosimetry in cancer treatment with hadronic radiation. Results on this activity will be also reported (6).

Acoustical behaviour of “baroque” trumpets with vent holes

The trumpets for which baroque composers including Bach and Handel wrote viruoso solo parts were natural (valveless) instruments approximately twice the length of a modern C trumpet. Playing chromatically in the high register of a natural trumpet requires great skill, since only the approximately harmonic resonances of the fixed-length air column are available. In the second half of the twentieth century several makers collaborated with performers to develop variants of the natural trumpet incorporating three or four finger-holes. Such instruments, widely used in modern ensembles playing baroque music, are best described as ‘vented trumpets’. The way in which the finger-holes are used differs from the use of tone-holes on the cornett, the keyed trumpet and the keyed bugle. In general, vented trumpets are designed to approach the timbre of natural trumpets while facilitating control of intonation and accuracy in playing. In the present paper, the acoustical foundations for the function of the three- and four hole systems are explored. The study draws on input impedance measurements, computational modelling, and playing tests of typical vented and natural trumpets. Parameters quantifying the timbre of vented trumpets are compared with corresponding values for natural trumpets.

Some considerations on the simulation of meta-materials acoustic behavior

One of the major advantages behind the success of metamaterials is related to the possibility to design them based on theoretical assumptions or when theory gets complicated, thanks to numerical methods. Many efforts have been made in the last years to better support researchers with benchmark tools that allow us to make their calculations more reliable, offering the opportunity to directly model the sound propagating inside the material or allow the determination of the parameters that can be used to feed phenomenological models. However, like any other simulation tool, a proper knowledge of the physics and the ways it is approximated are required to get the best results. The paper presents a selection of issues that may play a relevant role to improve the final results, including geometrical discretization, modelling of boundary conditions, and use of periodical structures. A discussion follows also pointing out the differences pertaining to transmission and absorption problems.

One-dimensional acoustic modeling of the şimşal considering the external Interaction of the open finger holes

A one-dimensional model in Python was developed to analyze the acoustic behavior of the Kurdish wind instrument, the şimşal. This model was developed using the Transmission Matrix Method (TMM), which was refined by taking into account the external interactions between the open tone holes. This research focuses on the acoustic resonator part of the şimşal with the lattice of finger holes in different cross-fingering patterns. The results were validated by measurements using an impedance probe, CapteurZ, which was developed by LAUM[1] and CTTM[2] The results are in good agreement with the measurement and despite the possible sources of error, which are discussed, the deviations are within an acceptable range. [1] The Acoustics Laboratory of the University of Le Mans [2] Le Mans Technology Transfer Center.

Vocal and genetic variation between a land-bridge island and mainland populations of the Black-crowned Antshrike (Thamnophilus atrinucha)

Island-mainland systems serve as natural laboratories for studying communication signals. We explored potential divergence in the song of the black-crowned antshrike between Gorgona Island, a land-bridge island off the Pacific coast of Colombia, and several mainland populations. We found that the perching song of this species, the so called loudsong, was distinctly different on Gorgona Island. This differentiation encompassed an increase in frequency bandwidth, a decrease in vocal performance, and a reduction in song duration. All are consistent with documented patterns of divergence observed in avian acoustic signals on oceanic islands. The observed distinctions in loudsong acoustics, including variations in frequency and temporal features, led to the inference that the population on Gorgona Island produces the least complex loudsong dialect across the entire species range. This pattern of how an innate vocalization manifests within a land-bridge island, which was connected to the mainland not long ago, lends support to the Character Release Hypothesis. To ensure an unbiased comparison, we considered genetic clusters and analyzed them by comparing ten acoustic signals between the land-bridge island and several mainland populations. Combined with the gene genealogy, this finding supports the validity of two geographic forms: Thamnophilus atrinucha atrinucha and Thamnophilus atrinucha gorgonae (island). However, they also reveal the existence of additional unrecognized dialects of loudsong that transcend current taxonomic classifications. We provide evidence that challenges the long-standing presumption suggesting minimal intraspecific geographic variation in the vocalization among non-vocal learning species.Significance statementSignificant evolutionary implications exist for an intriguing pattern of variation of the loudsong behavior in the Black-crowned Antshrike over a land-bridge island. Our gene tree does provide evidence of the enormous haplotypic diversity accumulated in the trans-Andean region long after the final uplift of the northern Andes. The acoustic divergence of the loudsong suggests substantial geographic variation within a non-vocal learning suboscine. Genetic and loudsong divergence on a land-bridge island add to document that evolution of acoustic traits may be relaxed in islands as compared to those observed on the species-rich mainland. The island-mainland system is one of the few definitive biogeographic contexts for understanding evolution of acoustic behavior.

Acoustic source characterization of shock-associated noise in an installed, full-scale F404 engine

Shock-associated noise in supersonic jets is an important factor in acoustic radiation, particularly in the upstream direction. A previous paper [L. T. Mathews et al., J. Acoust. Soc. Am. 154, A325 (2023)] discussed a preliminary source characterization of shock-associated noise in a full-scale, installed tactical jet engine. Acoustical holography was used to reconstruct the acoustic behavior near the jet and high-amplitude features were produced that were consistent with shock-associated noise sources. This paper presents a more detailed characterization of shock-related noise in the jet using higher-fidelity methods, such as subarray processing and bandwidth extension. The spatial and spectral characteristics of the shock cell noise sources are discussed. A virtual reference decomposition method is used to examine the source and radiative characteristics of each detected shock noise source. The results are compared with shock noise characteristics in the literature. [Work supported by ONR Grant No. N00014-21-1-2069.]

Moderate Anthropogenic Noise Exposure Does Not Affect Navy Bottlenose Dolphin (Tursiops truncatus) Whistle Rates

Bottlenose dolphins (Tursiops truncatus) rely on frequency- and amplitude-modulated whistles to communicate, and noise exposure can inhibit the success of acoustic communication through masking or causing behavioral changes in the animal. At the US Navy Marine Mammal Program (MMP) in San Diego, CA, dolphins are housed in netted enclosures in the San Diego Bay and exposed to noise from vessels, unmanned underwater vehicles, and other remote sensing devices. The acoustic behavior of 20 dolphins was monitored and whistle rates during noise events were quantified. Whistle rates during the onset of the event (i.e., the first 5 min) did not significantly differ from the pre-onset (5 min immediately preceding). Whistle rates were also not significantly different for the entire duration of the event compared to a matched control period. The noise’s frequency range (i.e., control, mid-frequency (0–20 kHz) or high-frequency (21–80 kHz)), signal-to-noise ratio, and sound pressure level were not significantly related to the dolphins’ whistle rate. Considering this is a location of frequent and moderate noise output, these results lend support to established guidelines on anthropogenic noise exposure for cetaceans, suggesting that moderate noise exposure levels may not impact communication efforts in bottlenose dolphins.

A comparative study of modeled and measured room responses

At the heart of Brown University’s Lindemann Performing Arts Center is a shape-shifting hall capable of supporting a wide range of performance types. Acoustic simulation played a crucial role in optimizing each of the hall’s five primary configurations during design. Leading up to the opening events 2023 and 2024, the lengthy commissioning and tuning process provided an invaluable opportunity to measure subtle and drastic changes in the hall’s form and materiality for comparison to the predictive simulation. Drawing from the Lindemann set, the paper compares modeled and measured data from the PAC to that from other projects designed using similar tools. The paper identifies points of uncertainty during design and delves into commonalities and differences between ray-based simulation and measurement in performance spaces of varying form. This paper will address the inherent complexities of approximating acoustic behavior with side by side comparison of measurement and simulated data, we will share insights that inform our future modeling process.

Five years of data collection, student theses, and disseminating information soundscape studies in the Gulf of Tribugá, Colombia

In 2018, the Ports, Humpbacks, y Sound In Colombia (PHySIC) Project began to record soundscapes in the Gulf of Tribugá, Northern Colombian Pacific, for the first time. This was of interest to local conservation groups who were against building a megaport in the native mangrove habitat that provides livelihoods for the people of Chocó. Five years later, no port has been built, documentaries about the ecosystem have won awards, before-after/control-impact studies have been done on fish and humpback whale acoustic behavior, delphinid call catalogs have been assembled, propagation modeling has mapped acoustic connectivity, and a new vocalization category for humpback whales has been discovered. The work has been executed through internships, and undergraduate and masters theses at various universities. This project has a variety of data-to-information challenges: storing data for access across various countries, navigating data analysis and dissemination in two languages, transferring knowledge as students graduate, and tailoring results for general conservation groups and policymaking audiences. To celebrate the colleagueship and academic successes of the first five years of PHySIC, this talk will describe the list of discoveries and studies done in the Gulf of Tribugá, which was named a UNESCO World Heritage site in the summer of 2023.

Numerical modeling of a saxophone and comparison with experimental measurements

Saxophones making has long relied on craftsmanship, associated with an empirical knowledge of their acoustic functioning. The design process is now mainly based on the study of the input impedance, accessible experimentally or computationally. The numerical approaches are currently limited either by the accuracy (analytical models) or by the computation time (numerical resolution of PDEs). The challenge is to propose a numerical method combining both, to access the acoustic pressure and velocity fields in the instrument. Our objective was to develop a high-performance parallel numerical tool based on FEM to model accurately (a few cents on the resonances) the acoustic behavior of the resonator under playing conditions. The computation time was reduced by an order of magnitude compared to the brute force approach, using different modeling strategies specific to wind instruments: First, the modeling of the visco-thermal losses at the walls; then, the reduction of the size of the linear systems and finally, the reuse and model reduction to limit the effect of the multiple resolutions imposed by the wide frequency range of interest. The model is validated by comparison with experimental measurements. An impedance measurement system allowing acquisitions under controlled flow has been developed to reproduce realistic playing conditions.

Digital Fracture Surface Morphology and Statistical Characteristics of Granite Brazilian Tests after Non-Steady-State Thermal Disturbance

With the widespread advent of digital technologies, traditional perspectives in rock mechanics research are poised for further expansion. This paper presents a Brazilian test conducted on granite after non-steady-state thermal disturbance at 25 °C, 200 °C, 400 °C, and 600 °C, with detailed documentation of the damage process and failure response using an acoustic emission (AE) apparatus and a digital image correlation (DIC) system. Subsequently, utilizing point cloud data captured by a three-dimensional (3D) laser scanning system, a digital reconstruction of the failed specimen’s fracture surface was accomplished. The 3D fractal characteristics and roughness response of the digitized fracture surface were studied using the box-counting method and least squares approach. Furthermore, texture information of the digitized fracture surface was calculated using the Gray Level Co-occurrence Matrix (GLCM), and statistical characteristics describing the elevation distribution were analyzed. The results elucidate the influence of thermal disturbance temperature on the mechanical parameters of the specimen, acoustic emission behavior, surface strain field evolution, and digital fracture morphology characteristics. The findings indicate a non-linear degradation effect of temperature on the specimen’s tensile strength, with a reduction reaching 80.95% at 600 °C, where acoustic emission activity also peaked. The rising thermal disturbance temperature inhibited the crack initiation load at the specimen’s center but expanded the high-strain concentration areas and the growth rate of horizontal displacement. Additionally, varying degrees of linear or non-linear relationships were discovered between thermal disturbance temperature and the 3D fractal dimension of the fracture surface, average roughness (Ra), peak roughness (Rz), and root mean square roughness (Rq), confirming the potential of Rsm in predicting the 3D fractal dimension of Brazilian test fracture surfaces. The study of the GLCM of the digitized 3D fracture surface demonstrated a high dependency of its four second-order statistical measures on thermal disturbance temperature. Finally, the statistical parameters of the fracture surface’s elevation values showed a significant non-linear relationship with thermal disturbance temperature, with a critical temperature point likely existing between 400 and 600 °C that could precipitate a sudden change in the fracture surface’s elevation characteristics.

Linear enhancement of mechanical compliance by zeolite filling in a compact loudspeaker

A zeolite filling in the rear cavity of a compact loudspeaker enhances the sound pressure amplitude of the loudspeaker system with a frequency range up to ∼500 Hz, but its intrinsic mechanisms remain elusive. We theoretically consider the gas adsorption–desorption behavior on zeolite that can be dynamically perturbed by sound pressure from the diaphragm of the loudspeaker. By merging equivalent circuit theory with gas thermodynamic theory, a linear relationship between mechanical compliance and zeolite volume in the rear cavity is quantitatively modeled. Confirmed by electroacoustic impedance experiments, the linear relationship with a slope of 1.92 mF cm−3 reveals the intrinsic ability of porous material to enhance mechanical compliance by adsorption of gas onto the zeolite in the rear cavity. This study correlates the kinetic behavior of air molecules on zeolite and acoustic behavior; it offers a novel insight to improve the performance of a compact loudspeaker by simple filling with porous material and introduces a comprehensive method for evaluating gas adsorption–desorption dynamics in porous media.

Graded alarm call behavior in wild fox squirrels (Sciurus niger).

Distress or alarm calls are vocalizations made when animals are in stressful situations or faced with a predator. Squirrels (Sciuridae) are known for being very vocal; however, most studies on alarm vocalizations are limited to ground squirrels. We investigated the acoustic behavior of the arboreal fox squirrel (Sciurus niger) under different conditions. Specifically, we tested the hypothesis that fox squirrels modify acoustic alarm behavior in response to different perceived threat levels and that this response is affected by sex and individual experience. Squirrels were trapped, and acoustic data were collected during periods in which the squirrels were alone, approached by humans, manipulated in traps, and handled by humans. Calls were categorized based on acoustic features, and we quantified the call rate (calls/s) across conditions. Threat level significantly affected vocal rate, with squirrels producing more calls overall when alone but shifting the proportion of emitted call types as threat level increased. Sex, capture history, and individual had no effect on call rate. These results suggest that fox squirrels use a graded alarm call response system to respond to threatening situations.

Effect of Insert Porosity on Combustion Instability in a Lean Premixed Combustor Analyzed by a Proper Orthogonal Decomposition-Based Phase Reconstruction Technique

Abstract Lean premixed (LPM) combustion is very effective at mitigating emissions but is vulnerable to strong thermoacoustic instabilities. A porous insert in the shape of an annular ring placed at the dump plane of the combustor has been proven to be an effective passive technique for mitigating these instabilities across a wide range of operating conditions. However, it is unclear if the change results from the insert geometry or porosity of the insert. In this study, swirl-stabilized LPM combustion is investigated for three configurations—without any insert, with a porous insert, and with a geometrically similar solid insert. Acoustics, flow, and heat release rate behavior of the three test geometries are investigated using diagnostics including dynamic pressure and acoustic probes, particle image velocimetry (PIV), and OH* chemiluminescence (OH*CL) imaging. Synchronized measurements at a fixed equivalence ratio were acquired at 40 kHz using sound probes and at 3.5 kHz using PIV and OH*CL. Results include time-series and spectral measurements of pressure, velocity, and OH*CL, and mode analysis by proper orthogonal decomposition (POD). In addition, the dynamics of the instability are investigated by high-resolution phase reconstructions of velocity and OH*CL data using a novel implementation of POD introduced in this work. Results show two different instability modes: a longitudinal instability for the solid insert case and a helical, precessing vortex driven instability for the no insert case. In both cases, the flow field and heat release rate oscillations are coupled to produce the instability. No such coupling or oscillations is observed for the porous insert case. These results ascertain the unique capabilities of the porous insert in protecting against instability from different, simultaneous driving mechanisms and demonstrate that the insert porosity and flow dynamics associated with it are the primary mitigating factors.

Numerical Equivalent Acoustic Material for Air-Filled Porous Absorption Simulations in Finite Different Time Domain Methods: Design and Comparison

Extracting the microscopic parameters of a porous material is a complex task, and attempts have been made to develop models that can simulate their characteristics, gathering the least amount of information possible. As a case in point, tests to evaluate macroscopic behaviors such as tortuosity, which depends directly on the microscopic fluid velocities, are highly susceptible to generate errors if the precision of the measurement devices is not correct, and the same goes for the other parameters. For this reason, in this paper, a sound propagation model in porous materials with a rigid frame is presented based on a local theory, which tries to simplify, even more, the way to obtain the basic characteristics of porous materials, such as their absorption coefficient at normal and random incidence, and their normal surface impedance. The proposed linearized equivalent fluid model presents four phenomenological coefficients, which characterize acoustic propagation trough the material. Their values are obtained from the material thickness and a measurement in an impedance tube following the ISO 10534 standard. Thus, what is only required is the measured absorption coefficient, either on one third or one octave bands, to fully represent the acoustic behavior in the finite different in time domain (FDTD) method. The model has been simulated with FDTD in porous and fibrous kernels, and the results show a strong agreement with the laboratory measurements and with the analytical results calculated with well-established semi-phenomenological models.

Studies of the acoustic activity of white whales (in captive conditions and the possibility of their signals using to control behavior of fish in fishing process

The purpose of the work: identification of acoustic activity of belugas in conditions of aviary keeping and justification of the possibility of using their signals in fishing.The material of research was digital audio recordings of hydroacoustic signals of belugas collected from 2016 to 2018.Methods used: analysis of hydroacoustic data, visualization of the daily acoustic activity of belugas in different seasons, identification of stereotypes of acoustic behavior and characteristic signals in captive conditions and during fish hunting. Novelty: for the first time a substantiation for the possibility of using signals of one of the species of toothed whales — belugas registered in the captive conditions, to influence on the behavior of hydrobionts and solve practical problems of fishing and fish protection is given.Results: the highest acoustic activity of white whales is observed during the day and noticeably decreases at night with increase and decrease in the morning and evening hours. Maximum acoustic activity precedes the feeding of dolphins.The most common tones are those containing the fundamental frequency and harmonics. Characteristic features of the sounds are high variability of duration from 0.25 to 2.5 s, pronounced frequency components in the 500–2500 Hz spectrum zones, amplitude and frequency modulation, sound pressure levels of the signal up to 500 Pa /1 m.Acoustic activity of belugas during fish hunting and in the period preceding feeding in captive conditions, stereotypical. Typical are low-frequency frequency-modulated calls and whistles in the hearing range of fish, as well as a curtain of air bubbles and body and tail slaps. Possible ways of using beluga whale signals to increase the efficiency of fishing are proposed.Practical significance: the results of the study open up the possibility of using the signals of belugas to remotely control the movement of fish, create artificial concentrations and deterrent of hydrobionts in the intended areas.