To see past seminars, please visit the Acoustics Seminars Archive Page.

Musical Acoustics Education

Friday, November 12, 2021, 4:00 p.m. Central Time

Dr. James M. Gelb
Applied Research Laboratories
The University of Texas at Austin
https://wwwext.arlut.utexas.edu/

In Spring 2015 I introduced an undergraduate course in musical acoustics in the Mechanical Engineering Department designed for non-technical students. This course, generally offered every other year, has now been taught five times, each time with increasing enrollment. It is cross-listed in the Butler School of Music, and also in the relatively new Arts and Entertainment Technologies (AET) program created to meet the demands of electronic arts. In the present seminar I will begin by covering general concepts in musical acoustics and then provide insights into teaching technical material to students with a wide range of backgrounds. The course focuses on traditional acoustics with the theme of teaching the science of sound, treating instruments as filters, and providing an intuition for the physical and mathematical aspects of harmonics. The talk explains the physical generation of approximate pure and complex tones produced by actual instruments. In the process, you will also learn musical concepts of consonance and dissonance and the structure and perception of musical scales.

Ultrasound through the Skull: Seeing and Treating Noninvasively

Friday, November 5, 2021, 4:00 p.m. Central Time

Dr. Scott J. Schoen, Jr.
Center for Ultrasound Research & Translation
Harvard Medical School and Massachusetts General Hospital
https://curt.mgh.harvard.edu/

Ultrasound has, in recent decades, become a valuable tool for the therapy and imaging of brain diseases. Because it is non-invasive, uses no ionizing radiation, and is less expensive compared to other modalities, it is of particular interest for applications in the brain. Together with circulating microbubble agents, whose acoustic scattering and locally imparted mechanical forces may be exploited, ultrasound has made possible a wide range of new therapeutic interventions and diagnostic capabilities. However, despite rapid progress, the acoustically opaque skull remains a major challenge both for therapy and imaging. Here I will discuss methods for fast, frequency-selective, passive mapping of the acoustic field through the human skull, including applications toward improved focal targeting, controlling the microbubble dynamics, and super-resolution imaging.

Sight, Sound, and Space: Audio-Visual Learning in 3D Environments

Friday, October 29, 2021, 4:00 p.m. Central Time

Professor Kristen Grauman
Department of Computer Science
The University of Texas at Austin
https://www.cs.utexas.edu/people/faculty-researchers/kristen-grauman

Moving around in the world is naturally a multisensory experience, but today’s embodied agents are deaf-restricted to solely their visual perception of the environment. We explore audio-visual learning in complex, acoustically and visually realistic 3D environments. By both seeing and hearing, the agent must learn to navigate to a sounding object, use echolocation to anticipate its 3D surroundings, and discover the link between its visual inputs and spatial sound. To support this goal, we introduce SoundSpaces: a platform for audio rendering based on geometrical acoustic simulations for two sets of publicly available 3D environments (Matterport3D and Replica). SoundSpaces makes it possible to insert arbitrary sound sources in an array of real-world scanned environments. Building on this platform, we pursue a series of audio-visual spatial learning tasks. Specifically, in audio-visual navigation, the agent is tasked with traveling to a sounding target in an unfamiliar environment (e.g., go to the ringing phone). In audio-visual floorplan reconstruction, a short video with audio is converted into a house-wide map, where audio allows the system to “see” behind the camera and behind walls. For self-supervised feature learning, we explore how echoes observed in training can enrich an RGB encoder for downstream spatial tasks including monocular depth estimation. Our results suggest how audio can benefit visual understanding of 3D spaces, and our work lays groundwork for new research in embodied AI with audio-visual perception.

The Windsor Hum: A Prototype Environmental Noise Complaint

Friday, October 22, 2021, 4:00 p.m. Central Time

David A. Nelson
Nelson Acoustics
Bella Vista, Arkansas
https://nelsonacoustical.com/

Residents on the Windsor, Canada side of the Detroit River have been plagued for years by a “hum” of unknown origin. In 2020, however, the COVID-19 pandemic accomplished what legions of motivated neighbors and the Canadian federal government could not: the source of the “hum” was identified and the “hum” itself abruptly ceased—an industrial plant had shut down on the US side. This unique case provides an opportunity to discuss a wide range of physical, psychological, and social aspects that can make environmental noise problems difficult to understand and solve. In particular we’ll discuss the origin and characteristics of this particular noise, how weather and time of day cause intermittent complaints, the special role of low-frequency sound and infrasound, drawbacks of amateur sound recordings, and potential ambiguity caused by naive misuse of acoustical terminology.

Submarines, Sonar, and the Strategic Triad

Friday, October 15, 2021, 4:00 p.m. Central Time

Dr. F. Michael Pestorius
Former Executive Director
Applied Research Laboratories
The University of Texas at Austin
https://wwwext.arlut.utexas.edu/

This talk will initially focus on the role of the University of Texas Applied Research Laboratories in submarine sonar development, including unmanned underwater vehicles. We will then consider the three legs of the US strategic nuclear triad with a brief overview of these three legs and nuclear release procedures. Next, we will consider the development of nuclear submarine technology and the US ballistic missile submarine force. The talk will conclude with a discussion of the development of the US submarine force, and to a lesser extent the development of the UK, France, Russia, China and India submarine forces. I will also briefly discuss the Australian decision to team with the US and the UK on their submarine development.

Design and Experimental Demonstration of Reflective Coiled-Space Acoustic Metasurfaces

Friday, October 8, 2021, 4:00 p.m. Central Time

Janghoon Kang and Samuel D. Parker
Walker Department of Mechanical Engineering
The University of Texas at Austin
https://www.me.utexas.edu/

Acoustic metamaterials (AMM) can be used to provide extreme control of propagating acoustic waves in three dimensions. However, their volumetric nature is not appropriate for all applications, specifically when one wishes to control sound fields at the interfaces of three-dimensional spaces. Acoustic metasurfaces (AMS) are two-dimensional versions of AMM whose purpose is to control or manipulate the interaction of sound with interfaces and surfaces. The form factor of an AMS can be thought of as an acoustically thin coating, which allows it to be used in a wide variety of applications ranging from medical ultrasound to architectural acoustics. This seminar will present research on two types of reflective AMS: (i) an ultrathin sound diffuser and (ii) an acoustic hologram to control reflected acoustic fields. Despite the difference in use, the AMS for the sound diffuser and the acoustic hologram can be created using a similar suite of coiled-space unit cells. We will present the theory, analytical and computational modeling, and AMS design, together with techniques to fabricate unit cells and assemble a two-dimensional AMS sound diffuser and an acoustic hologram. We will also present experimental methods to characterize the broadband scattering response of these surfaces in an anechoic environment which was used to validate our AMS designs.

A Review of the Supersonic Jet Noise Problem and Its Traditional Sources

Friday, October 1, 2021, 4:00 p.m. Central Time

Dr. Charles E. Tinney
Applied Research Laboratories
The University of Texas at Austin
https://wwwext.arlut.utexas.edu/

The jet noise problem has been a topic of scientific importance for over 70 years, beginning with the seminal theoretical model developed by Sir James Lighthill that came about with the advent of the turbojet engine and the abundance of noise that it produced. Since that time, study of this problem has gone through the typical cycles of scientific effort as new propulsion platforms are introduced, new pathways for solutions emerge, and laboratory and computing tools mature. Like most areas of research, the jet noise problem relies on balanced contributions from theoretical, experimental and computational branches, and as their respective capabilities develop, the means by which they become entwined evolves. The purpose of this lecture is to provide an outline for the practicing engineer or scientist who is about to embark on an adventurous journey to understand and even participate in the development of the desired tools necessary to design high-power supersonic propulsion systems with aeroacoustics in mind.

Three-dimensional Acoustic Modeling Techniques for Underwater Object Identification

Friday, September 24, 2021, 4:00 p.m. Central Time

Dr. Aaron M. Gunderson
Applied Research Laboratories
The University of Texas at Austin
https://wwwext.arlut.utexas.edu/

Acoustic underwater object identification efforts can be supported by thorough modeling capabilities, capable of capturing complex environmental effects within acoustic scattering predictions. Scattering measurements can be strongly affected by unknown target position and orientation within cluttered or rough seafloor environments, and therefore model capability to consider such effects is highly beneficial. In this work, three-dimensional finite element model templates have been developed, which have configurability in terms of acoustic source/receiver placement, as well as target shape, properties, and placement within arbitrary seafloor environments. The templates are designed to be simple for configuring to any target/environment scenario. Certain features of the templates will be discussed, including automatic domain scaling with frequency for improved model runtime, alternative scattering formulations for improved accuracy, and far-field scattering prediction capability through numerically determined Green’s functions. The three-dimensional nature of the templates also bypasses certain symmetry constraints imposed by two-dimensional models. Template validation and verification will be presented in certain test cases through comparison to analytic scattering models and experiments, and future application of these templates will be discussed.

Experiential Design, Evolutionary Influence, and Spaces for Human Connection: Learning to Leverage Our Access to Great Design to Make Change

Friday, September 17, 2021, 3:30 p.m. Central Time

Scott D. Pfeiffer, Partner
Threshold Acoustics
Chicago, Illinois
https://www.thresholdacoustics.com/scott-pfeiffer

For three decades, Scott Pfeiffer has participated in virtually every aspect of the acoustical consulting profession, from modeling and measurements to leading the design of complex rooms, Audio and Video (AV) installations, and electronic enhancement systems. Most recently, Scott led teams as Partner-in-Charge for the acoustical and AV design of renovations to Canada’s National Arts Centre in Ottawa and the design of the Lucian and Nancy Morrison Theater and the Brockman Hall for Opera at the Shepherd School of Music on the campus of Rice University in Houston. During this talk, Scott will discuss 1) the importance of making our work understood and accessible to those outside of our professional community; 2) the importance of acoustics to human connection and spaces in which to gather; and 3) a lot of what Threshold Acoustics has done on his way to talking about how we can use what we have learned to help us do what we have yet to do. The above will be supported by an understanding of our evolutionary influences in hearing, projects where these tools have been leveraged, and finally address the small way that our profession can make strides in solving the problems we all face.

Fly-Inpired Microphones

Friday, September 10, 2021, 4:00 p.m. Central Time

Professor Neal A. Hall
Department of Electrical and Computer Engineering
The University of Texas at Austin
https://sites.google.com/site/utacousticmems/people

The parasitoid fly Ormia ochracea has the remarkable ability to locate crickets using audible sound. This ability is, in fact, remarkable as the fly’s hearing mechanism spans only 1.5 mm, which is 50 times smaller than the wavelength of sound emitted by the cricket. The hearing mechanism is, for all practical purposes, a point in space with no significant interaural time or level differences to draw from. Evolution has empowered the fly with a hearing mechanism that utilizes multiple vibration modes to amplify interaural time and level differences. Here, we present an update on our efforts to realize microphones inspired by the Ormia’s hearing mechanism. Prototypes fabricated using silicon microfabrication prove capable of replicating the remarkable sound localization ability of the special fly. The prototypes use multiple piezoelectric sensing ports to simultaneously transduce two orthogonal vibration modes of the sensing structure, thereby enabling simultaneous measurement of sound pressure and pressure gradient. We will also briefly highlight a few other team’s recent work in this arena.

Images of Energy Loss in Complex Dynamic Systems

 Friday, April 23, 2021, 4:00 p.m. Central Time

Professor J. Gregory McDaniel
Department of Mechanical Engineering
Boston University
https://www.bu.edu/eng/profile/j-gregory-mcdaniel-ph-d/

The loss factor proposed by Ungar and Kerwin in 1962 left some space for creativity in the definitions of “energy dissipated per cycle” and “total energy of vibration.” However, their loss factor is extremely powerful in its generality and independence from a specific damping model. Today, we return to that 1962 paper to understand energy loss in complex dynamic systems. Motivated by the high cost of eigenvalue analysis for these systems, the creative space left by Ungar and Kerwin is explored. We propose specific definitions for “energy dissipated per cycle” and “total energy of vibration.” These definitions only require system matrices and forced response vectors that are typically calculated at significantly lower costs than eigenvectors. We demonstrate that, under certain limits, the proposed definitions have the benefit of reducing the loss factor to the classical modal damping ratio. The notion of a loss factor image is introduced to spatially map contributions to the loss factor, such that the spatial sum of the loss factor image is equal to the loss factor. Applications of the loss factor image to design problems will be discussed and illustrated by examples. Finally, we comment on the role of loss factor images in helping us learn from model libraries

Non-Foster and Compressibility-Near-Zero
Acoustic Radiation

 Friday, April 16, 2021, 4:00 p.m. Central Time

Curtis P. Rasmussen
Applied Research Laboratories
The University of Texas at Austin
https://www.arlut.utexas.edu/

Techniques to widen the bandwidth over which a system resonates are technologically important, given the ubiquity of resonances in wave-based systems. Radiation sources, such as electromagnetic antennas and acoustic loudspeakers, typically operate near a resonance to ensure efficient radiation towards a distant receiver from a compact element. Resonances are also fundamentally important in the broad field of metamaterials, structures with exotic bulk responses arising from subwavelength elements whose resonance ensures strong wave-matter interactions in small volumes. In this seminar I will show that the quality factor of a small acoustic radiator is fundamentally limited by its volume normalized to the emitted wavelength. I will demonstrate how this bound can be overcome by realizing a piezoelectric transducer loaded with a non-Foster active circuit, showing that its radiation bandwidth can be largely extended and how it is fundamentally limited only by stability considerations. I will also discuss the promise of near-zero metamaterials for acoustic radiation and demonstrate a zero-compressibility structure that offers a promising alternative to traditional acoustic directive sources due to its design simplicity, inherent robustness, and compact profile.

Characterization of Underwater Acoustic Pentamode Materials

 Friday, April 9, 2021, 4:00 p.m. Central Time

Colby W. Cushing
Applied Research Laboratories
The University of Texas at Austin
https://www.arlut.utexas.edu/

Three-dimensional Pentamode materials (PM) are a subset of acoustic metamaterials that use engineered periodic elastic structures to mimic the acoustic properties of fluids. For this reason, they are often referred to as “metal water” or “metafluids.” Pentamode materials achieve fluid-like behavior through sub-wavelength structure that yields negligible shear moduli in the static limit and thus PM materials only support compressional wave motion over large frequency ranges while maintaining structural integrity for static loading. The unit cells also have the important ability to be impedance-matched to the surrounding fluid thereby minimizing reflections. Pentamode structures can be designed to achieve highly anisotropic stiffness, which is useful for the implementation of metamaterial designs predicted by transformation acoustics. PMs were originally theorized in 1995 by Milton and Cherkaev [Milton & Cherkaev, J. Eng. Mater. Technol., 117 (4) (1995)] but have been limited in use by fabrication technology due to the intricate structures involved. Recent advances in additive manufacturing have allowed larger, more stable structures to be physically realized for improved experimentation. This seminar will explore the development of functional underwater PM by examining the modeled behavior of designed unit cells and impacts of fabrication constraints through experimental data. First, a 2D analogy to the PM material, known as a bimode material, was used to create an underwater gradient index focusing lens as a proof of concept for this type of unit cell. Success in 2D modeling and experiments supported growth into highly anisotropic 3D materials from which current challenges in acoustical characterization will be presented and discussed. 

Atlantic Deepwater Ecosystem Observatory Network (ADEON):
An Integrated Acoustic Observation System on the U.S. Southeastern Atlantic Outer Continental Shelf

 Friday, March 26, 2021, 4:00 p.m. Central Time

Dr. Jennifer L. Miksis-Olds
Center for Coastal & Ocean Mapping
The University of New Hampshire
https://ccom.unh.edu/user/jmiksisolds

A seven-node Atlantic Deepwater Ecosystem Observatory Network (ADEON) for the U.S. Mid- and South Atlantic Outer Continental Shelf (OCS) was established in November 2017. ADEON is generating long term measurements of the natural and human factors that describe the ecology and soundscape of the OCS.  Ocean processes, marine life dynamics, and human ocean use are each inherently three-dimensional and time-dependent, and each occur at many spatial and temporal scales. No single measurement system (in situ or remote) is sufficient for describing any of the ocean state variables, and a “multi-platform, multi-variable” observational approach integrated with models is required. The ADEON network combines acoustic information with contextual data from space-based remote sensing, hydrographic sensors, and mobile platforms to fully comprehend how human, biologic, and natural abiotic components create the soundscape and influence ecosystem dynamics of the OCS. Measurements made within this research program will serve as a baseline for pattern and trend analyses of ambient sound and the ecosystem components contributing to the OCS soundscapes. Study concept, oversight, and funding were provided by the U.S. Department of the Interior, Bureau of Ocean Energy Management, Environmental Studies Program, Washington, DC under contract Number M16PC00003, in partnership with other NOPP funding agencies.  Funding for ship time was provided under separate contracts by ONR, Code 32.

Design of Metamaterial Acoustic Leaky Wave Antennas for Air and Water Environments

 Friday, March 12, 2021, 4:00 p.m. Central Time

Dr. Christina J. Naify
Applied Research Laboratories
The University of Texas at Austin
https://www.arlut.utexas.edu/

Acoustic direction-finding is commonly performed using arrays of microphones in air or hydrophones in water. These arrays can be both costly and bulky, making them non-ideal for applications where weight, size or cost are critical design parameters. Leaky wave antennas, which utilize an analog dispersive structure to couple frequency and directionality, promise a lightweight, compact solution to direction finding and steering with minimal active transducer requirement. This seminar will review the basic physics of acoustic leaky wave antennas and explore design options for air-acoustic and water-acoustic environments. Specifically, designs which incorporate metamaterial elements for air-acoustic and elastic wave-water coupled waveguides will be demonstrated. The chosen metamaterial elements, which are designed to have simultaneous negative effective bulk modulus and negative effective mass density, enable full forward to backward steering with frequency of acoustic energy using a single transducer coupled to the analog antenna, saving electronics processing and space. Several other design variations will be presented, including for two-dimensional sensing and for generation of acoustic vortex waves.

Acoustic Sensing on Earth, Titan, Mars, and Venus

 Friday, March 5, 2021, 4:00 p.m. Central Time

Professor Andi Petculescu
Department of Physics
University of Louisiana at Lafayette
https://physics.louisiana.edu/node/100

I will give an overview of my work in acoustic sensing predictions in planetary atmospheres. The focus so far has been on Earth, Titan, Mars, and Venus. I use a physics-based model to calculate the sound speed and attenuation coefficient hence the wavenumber as a function of altitude and frequency. The ambient inputs to the model are obtained from mission data and/or general circulation models. At the outset, the fluid dynamics equations have to account for the ratio between the mean-free-path and wavelength (acoustic Knudsen number, Kn). If the “typical’’ Navier-Stokes-Fourier equations can be applied in a planet’s low/middle atmosphere, they lose significance at higher elevations where the Knudsen number increases, depending on the wavelength of interest. I will show the results of a simple model of infrasonic attenuation in Earth’s lower thermosphere (~90–160 km) based on the so-called Burnett equations; the results show a loss reduction consistent with observed thermospheric arrivals. Next, the choice of equation of state (EoS) dictates how pressure, density, and temperature are related in the environment. The ideal-gas EoS is generally applicable to Earth, Mars, and, possibly, higher altitudes on Titan and Venus. For generally denser atmospheres (e.g. Titan, Venus), real-gas EoS must be used. In a 2012 study, we showed that using the Van Der Waals and Dieterici EoS for Titan’s lower atmosphere, we were able to reproduce the sound speed measured during the Huygens lander’s descent. We have also used the Van Der Waals equation to predict the acoustic wavenumber through Venus’s main cloud layer. The goal is to set the stage for Venus aerial infrasonic seismology i.e. detecting venusquakes by their infrasound signatures received by freely drifting balloons at ~55 km. Time-permitting, I will also present simple simulations of thunder on Titan, and the results of a preliminary study on the efficacy of using easily deployable porous domes as wind-noise filters on Mars.

Sonoluminescence in Stars:
Wave-driven Shocks as the Source of Stellar Outbursts

 Friday, February 26, 2021, 4:00 p.m. Central Time

Professor Christopher D. Matzner
David A. Dunlap Department of Astronomy & Astrophysics
University of Toronto
https://www.astro.utoronto.ca/people/faculty/name/chris-matzner/

Massive stars succumb to core collapse at the ends of their lives, often producing a brilliant supernova explosion.   But before they do, many stars are now observed to undergo dramatic eruptions and outbursts,  in which matter is ejected at high speeds.   Sound waves and shocks are very likely to play a leading role in the transport of energy outward from the star’s core during one of these outbursts.   This process is similar to a classic problem in nonlinear acoustics; however, drastic changes in the environment demand a tailored approach.   I will introduce a set of modified Riemann invariants for this purpose, and use these to predict the creation and evolution of shocks. Two branches of shock behavior emerge: one deposits heat deep within the star, while the other preserves energy to drive strong flows near the star’s surface.

A Field Study of Underwater Acoustics at Challenger Deep

 Friday, February 19, 2021, 4:00 p.m. Central Time [Postponed]

Dr. Ying-Tsong Lin
Woods Hole Oceanographic Institution
Woods Hole, Massachusetts
https://www.whoi.edu/profile/ytlin/

An underwater acoustic experiment was conducted at the Challenger Deep of the Mariana Trench on a scientific expedition cruise sponsored by the Caladan Oceanic LLC in June 2020.  The experiment was set to study ambient sound and acoustic signal propagation in the hadal zone, the deepest region of the ocean.  Specifically, one of the experiment objectives, taking the advantage of reduced marine traffic during the COVID-19 pandemic, was to measure how quiet the ocean can be with minimum influence of acoustic emissions from container ships.  The experiment was also focused on characterization of underwater sound propagation and seabed geoacoustic properties at these extreme depths.  State-of-the-art equipment was utilized for measuring and estimating ocean environment variables including seafloor bathymetry and water column sound speed profiles.  High-fidelity numerical models of sound propagation were also employed to aid acoustic data analyses and provide insights for better understanding the hadal zone acoustics.  Lastly, a full field acoustic model was established to calculate passive acoustic listening coverage from the bottom of Challenger Deep to the sea surface and validated with measured data.

The Detection of Signals from Large Explosions on Networks of Infrasound Sensor Arrays

Friday, February 12 2021, 4:00 p.m.

Dr. Roger Waxler
National Center for Physical Acoustics and
Department of Physics and Astronomy
University of Mississippi
https://physics.olemiss.edu/waxler/

Infrasound is one of the technologies used in the verification regime for the Nuclear Weapon Test Ban Treaty and is also used for forensic analysis of large explosive events. Last decade, a series of experiments using large chemical explosions as nuclear weapon surrogates were performed. The goal was to provide ground truth data sets for studies related to signal propagation and characterization. In this context, an overview of infrasound signal propagation and detection using networks of sensor arrays will be presented with particular attention on the role of the atmosphere. Rationale for the design of the networks deployed for these experiments will be discussed and results of the data collection and analysis will be presented.

Light and Sound: Integrating Photonics with Ultrasonics

Friday, February 5 2021, 4:00 p.m.

Professor Matthew O’Donnell
Frank and Julie Jungers Dean Emeritus, College of Engineering
Department of Bioengineering
University of Washington
https://bioe.uw.edu/portfolio-items/odonnell/

Coherent light and sound have become essential tools in modern medicine. Lasers are routinely used for both therapeutic and diagnostic applications, and real-time ultrasound scanning has become the dominant biomedical imaging modality in the world. Starting over thirty years ago, scientists and engineers have combined these modalities for applications ranging from non-contact sensing to novel molecular imaging techniques. In this talk, I will explore the history of integrated photonic-ultrasonic systems, focusing on examples where light generates sound, light detects sound, and sound “tickles” light. I will also present specific applications of integrated photonic-ultrasonic techniques, including photoacoustics for molecular imaging, non-contact laser ultrasound systems for medical and non-medical applications, and optical coherence elastography (OCE) in which air-coupled ultrasound stimulates propagating shear waves in the eye and skin tracked with real-time, 3-D optical coherence tomography (OCT). The talk will conclude by discussing current barriers to clinical translation of these systems and possible ways to overcome the obstacles.

Acoustical Oceanography with a Single Hydrophone:
Propagation, Physics-based Processing and Applications

Friday, January 29 2021, 4:00 p.m.

Dr. Julien Bonnel
Woods Hole Oceanographic Institution
Woods Hole, Massachusetts
https://www2.whoi.edu/staff/jbonnel/

Lobsters, whales and submarines have little in common, except that they produce low-frequency sounds, like many other ocean inhabitants that use sound for communication, foraging, navigation and other purposes. However, unraveling and using the underwater cacophony is not at all simple. This is particularly true for low-frequency (f < 500 Hz) propagation in coastal water (water depth D < 200 m), because the environment acts as a dispersive waveguide: the acoustic field is described by a set of modes that propagate with frequency-dependent speeds. In this context, to extract relevant information from acoustic recordings, one needs to understand the propagation and to use physics-based processing. In this tutorial-like presentation, we will show how to analyze low-frequency data recorded on a single hydrophone. We will review modal propagation and time-frequency analysis. We will then show how those can be combined into a non-linear signal processing method dedicated to extracting modal information from single receiver, and how such information can be used to localize sound sources and/or characterize the oceanic environment. The method will be illustrated on several experimental examples, including geoacoustic inversion on the New England Mud Patch and baleen whale localization in the Arctic.