Ravi Umadi M.Tech

TUM School of Life Sciences
Technische Universität München
Freising, Germany

Connect with me

I am a behavioural bioacoustician and experimentalist, fascinated by how animals interact with their environment through sound. My doctoral research at the Technical University of Munich focused on echolocation dynamics in bats, particularly how they adapt their sonar system during active foraging and pursuit. I combined theoretical modelling, laboratory experiments with real-time virtual acoustic environments, and field studies to explore how bats modulate sound production, ear movements, and flight behaviour to optimise prey detection and capture.

A key part of my work has been developing new experimental and computational methods to study these processes, including ways to model and simulate acoustic interactions with dynamic morphology—such as moving ears or noseleaves—that shape auditory perception. This has allowed me to uncover new insights into emitter-receiver coordination and the sensory strategies bats use in complex environments.

Beyond my core work on bats, I am deeply interested in applying generative simulation and AI-based modelling to broader questions in sensory biology. I enjoy building tools that bridge biology, physics, and computation, and I am constantly driven by the challenge of understanding how living systems exploit physical laws to navigate and survive in the world.

Selected Work

Doctoral dissertation

• 1.

  Umadi, Ravi (2025). Echolocation Dynamics in Active Foraging and Pursuit. TUM School of Life Sciences. Submitted.

  Abstract

  Echolocating bats rely on self-generated biosonar signals to perceive and navigate their environments. While traditional models treat echolocation as a rigid, reflexive behaviour with fixed emitter and receiver geometries, empirical evidence suggests a high degree of plasticity in both signal generation and spatial sampling. This thesis explores the dynamic sonar strategies employed by the omnivorous bat Phyllostomus discolor, focusing on how emitter-receiver decoupling, deformable noseleaf morphology, and context-sensitive signal timing enhance acoustic sensing flexibility. I first present measured beam geometric and a computational beam model that treats the bat's noseleaf as a two-point source rather than a conventional piston emitter. This approach reveals that small deformations in the noseleaf can result in substantial changes to the spatial profile of the sonar beam, including shifts in beam direction and width. My results show that such modulation is functionally significant, allowing the bat to alter its acoustic gaze without body reorientation. Subsequently, I examine the degree of coordination between emission and reception axes during fixed-ears and free-moving conditions. Using high-resolution motion capture and stereo microphone arrays, I demonstrate that P. discolor exhibits fast, independent pinna movements that enable acoustic sampling across a wide spatial field. This emitter-receiver decoupling enhances spatial resolution and increases the likelihood of detecting novel or peripheral targets, supporting a broader sensory field during foraging and navigation. In the final study, I analyse changes in sonar signal structure during target approach. I show that bats regulate their call rate and duration based not only on distance to target but also on task urgency and context variability. The terminal buzz, traditionally viewed as a motor constraint, is instead framed here as a responsive sensory strategy that modulates information update rate dynamically. Together, these findings reveal a sophisticated system of acoustic sensing grounded in morphological flexibility, sensorimotor coordination, and adaptive control. By integrating physical modelling, behavioural experiments, and signal analysis, my work contributes to a growing view of echolocation as an active and embodied perceptual process. These insights have implications for the evolution of biosonar systems and offer promising design principles for artificial sensing technologies, particularly in robotics and autonomous navigation.

Research

• 1.

  Umadi, Ravi and Firzlaff, Uwe (2025). Biosonar Responsivity Sets the Stage for the Terminal Buzz. bioarxiv. https://doi.org/10.1101/2025.06.16.659925

  Abstract

  Echolocating bats must continuously adapt their sonar output to meet the increasing demands of prey pursuit. While call rate and duration modulations have been extensively described, the underlying control thresholds governing these transitions remain poorly understood. Here, we present a predictive framework based on a novel metric responsivity, defined as the inverse change in interpulse interval (IPI), to quantify moment-to-moment temporal precision in sonar control. This metric reveals a critical transition point---buzz readiness---where fine-scale IPI adjustments peak prior to the onset of the terminal buzz. By integrating biologically plausible reaction time constraints with echo-acoustic feedback loops, our model predicts how increasing relative velocity compresses the time available for sonar adaptation. Simulations incorporating prey motion and bat flight kinematics reproduce a consistent sublinear tradeoff between call rate and relative velocity. High-resolution field recordings from a portable, custom-built microphone array validate the model predictions, demonstrating that buzz readiness thresholds reliably align with behavioural transitions in natural prey interception. The framework further explains why shortened or absent buzzes occur at high velocities, when reaction constraints prevent full transition into the buzz phase. This work introduces a generalised, predictive model linking sensory-motor control, kinematics, and temporal adaptation in bat biosonar. The responsivity approach offers new tools to quantify control dynamics in natural behaviour and provides a foundation for biologically inspired sensing systems operating under real-time constraints.

• 2.

  Umadi, Ravi (2025). Temporal Precision Necessitates Wingbeat-Call Asynchrony in Actively Echolocating Bats. bioarxiv. https://doi.org/10.1101/2025.06.18.660328

  Abstract

  I present a unified theory and empirical analysis showing that temporal precision, rather than energetic efficiency or mechanical synchrony, is the primary axis guiding echolocation call timing in flying bats. While classic hypotheses posited that coupling call emission to wingbeat and respiration cycles is optimal, my field data and mathematical modelling demonstrate that such synchrony is only maintained when sensory-motor demands are minimal. As bats approach a target or encounter complex, dynamic environments, synchrony is frequently and necessarily broken(:) I show that the strict temporal constraints imposed by the call-echo-response loop require bats to decouple vocal output from wing motion whenever echo delays become short or as circumstantial demands for information updates dictate. Using a simulation framework grounded in first principles, I reveal that wingbeat-call synchrony is possible only within a narrow physiological window, bounded by wingbeat frequency and amplitude. When these limits are exceeded, asynchrony reliably emerges as the only viable strategy to maintain real-time sensory feedback. Both my empirical data and theoretical model predict and explain the universal emergence of a hyperbolic relationship between interpulse interval and call rate-across all behavioural and environmental contexts-demonstrating that closed-loop, echo-guided timing is a fundamental, conserved feature of bat biosonar. Patterns such as sonar sound groups arise not as discrete modules, but as visible signatures of the feedback-driven system flexibly adapting to heightened uncertainty or unpredictability. I further discuss how species-specific morphological and aerodynamic constraints set the boundaries for synchrony flexibility, explaining interspecific diversity in echolocation behaviour. Altogether, these findings demonstrate that wingbeat-call asynchrony is an adaptive, mathematically inevitable solution for temporal precision in active echolocation, unifying previously disparate empirical observations and providing a predictive foundation for future research in sensory-motor coordination, flight control, and biosonar.

• 3.

  Umadi, Ravi (2025). Oscillating Ears Dynamically Transform Echoes in Constant-Frequency Bats. bioarxiv. https://doi.org/10.1101/2025.06.14.659613

  Abstract

  The oscillatory movements of the pinnae in constant-frequency (CF) bats have long been documented, yet their role in actively transforming echo signals has remained underexplored. Inspired by Perrine's foundational description of Doppler effects in oscillating receivers, I hypothesised that bat ear oscillations could serve as dynamic signal modulators, introducing time-varying Doppler shifts to received echoes. I tested this hypothesis using both computational simulations and controlled experiments. In the simulations, each ear was modelled as an angularly oscillating structure receiving echoes from a CF pulse, with motion parameters systematically varied across frequency (5-50 Hz) and excursion angle (15-45 degrees). The received echoes were synthesised as composite signals comprising delayed, Doppler-shifted components based on instantaneous ear segment velocities. Results showed pronounced spectral broadening, instantaneous frequency fluctuations, and binaural disparities that scaled with tip velocity. These effects were then validated using a subwoofer-driven oscillating reflector that emulated the ear's motion while reflecting a stable 80 kHz tone. Recordings showed consistent bandwidth expansion to over 1.2 kHz at 30 Hz, with phase warping evident in the time-domain waveforms. These findings confirm that oscillatory motion alone, without source modulation or target motion, can dynamically restructure the spectral and temporal profile of echoes. I argue that in CF bats, such echo transformations represent an active encoding strategy, enabling spatial and temporal contrast enhancement within the auditory fovea. This reconceptualises ear motion not as passive filtering, but as a means of dynamically enriching incoming sensory information.

• 4.

  Umadi, Ravi (2025). Widefield Acoustics Heuristic - Advancing Microphone Array Design for Accurate Spatial Tracking of Echolocating Bats. bioarxiv. https://doi.org/10.1101/2025.06.03.657701

  Abstract

  Accurate three-dimensional localisation of high-frequency ultrasonic bat calls is essential for advancing behavioural and ecological bioacoustic studies. Here, I present a novel, comprehensive simulation framework that enables the design, characterisation, and optimisation of microphone arrays tailored to specific localisation requirements -- named Array WAH. This tool integrates realistic signal generation, frequency-dependent propagation effects, and advanced time difference of arrival (TDOA) localisation algorithms. I evaluate and compare three four-microphone array geometries -- tetrahedral, planar square, and pyramid, and one with six, the Octahedron configuration -- across a volumetric spatial grid, generating detailed positional and angular error maps. My results demonstrate that the tetrahedral array offers the best balance between positional and angular accuracy, while the octahedral configuration excels in angular precision but with increased positional variability. Planar arrays perform less robustly, especially in angular localisation. My results demonstrate the critical influence of array geometry on localisation robustness and highlight the advantages of three-dimensional microphone arrangements for near- and mid-field echolocation monitoring. By providing a versatile, user-friendly software package, this framework facilitates informed microphone array design decisions for a range of bioacoustic and other ultrasonic sensing applications. Ultimately, it supports improved localisation accuracy in real-world settings, aiding the deployment of compact and effective acoustic monitoring systems.