Acoustic Source Localization in Shallow Water Environments

Acoustic source localization in shallow water seeks to determine the position of sound-emitting objects—such as vessels, marine mammals or underwater disturbances—within environments typically less than 200 m deep. In these settings, the sea surface and seabed form a complex waveguide that generates multiple propagation paths, characterised by reflections, refractions and modal interference. Accurate localisation must therefore contend with rapid spatial and temporal variability in sound speed, sediment properties and ambient noise. Common strategies include time difference of arrival (TDoA), beamforming and matched-field processing (MFP), each relying on arrays of hydrophones to extract bearing, range and depth information. Recent advances in environmental inversion, signal processing and embedded sensing have markedly enhanced localisation accuracy, enabling real-time operation on compact platforms. These developments have broad applications in naval surveillance, environmental monitoring, marine biology and offshore industry operations, where precise, robust and low-footprint solutions are essential.

Research from Nature Portfolio

Recent studies have demonstrated high-resolution recovery of seabed geoacoustic properties through a semi-automated inversion framework applied to autonomous underwater vehicle data. By employing parallelised trans-dimensional Bayesian inference, seabed sound speed, attenuation, density and porosity are estimated along survey tracks with centimetre-scale vertical precision. Quantified parameter uncertainties and close agreement with core samples enhance predictive models of the shallow water waveguide. Integrating these refined seabed characterisations into matched-field and beamforming algorithms has reduced localisation errors in environments with complex layering, thereby improving the reliability of range and bearing estimates under heterogeneous sediment conditions.

Research from all publishers

A compact passive localisation system has been realised by combining TDoA for impulsive sources with a low-complexity MFP implementation for broadband emissions, all executed on a System-on-Chip embedded platform. Trials across varied shallow sea conditions showed angular errors below one degree and range errors on the order of metres, affirming real-time performance on small autonomous vessels. Concurrently, a novel approach using the waveguide invariant has been applied to blind deconvolution of Green’s functions for moving sources. By exploiting striation patterns in the frequency–range domain, individual channel responses are coherently combined across adjacent ranges, substantially boosting signal-to-noise ratio without prior environmental knowledge. Moreover, foundational work on horizontal line array matched-mode processing has been extended: modal amplitudes are extracted via frequency–wavenumber transforms, enabling robust source depth estimation even under environmental mismatches and moderate noise levels.

Acoustic Source Localization in Shallow Water Environments publication trend

The graph below shows the total number of articles in acoustic source localization in shallow water environments across all publications each year (not limited to Nature Index journals).

Technical terms

Shallow water waveguide: A water column bounded by surface and seabed layers, where acoustic energy propagates through discrete modes and multipath reflections.

Matched-field processing (MFP): A localisation method that matches measured acoustic fields to predicted fields from environmental models to infer source location.

Time difference of arrival (TDoA): A technique that computes source direction by measuring differences in signal arrival times at spatially separated sensors.

Waveguide invariant: A parameter that characterises the rate at which interference fringes shift in frequency with range, used for coherent integration in waveguide propagation.

Geoacoustic inversion: The process of inferring seabed properties—such as sound speed and attenuation—from acoustic reflection or transmission data to improve propagation models.

References

1. Meso-scale seabed quantification with geoacoustic inversion. Communications Engineering (2024).
2. Real-time passive underwater localization using a compact acoustic sensor array. Computer Networks (2024).
3. Improvement of a Green’s Function Estimation for a Moving Source Using the Waveguide Invariant Theory. Sensors (2024).
4. Source Depth Estimation Using a Horizontal Array by Matched-Mode Processing in the Frequency-Wavenumber Domain. EURASIP Journal on Advances in Signal Processing (2006).