Projects in Sonar

Whilst most of the projects that I have been involved in for sonar signal processing are classified, here are some references to the types of processing systems that I was building and testing at sea.

Custom audio analysis software

By creating custom audio analysis suites, the user is not limited to the predefined detection criteria and can concentrate on the tools and frequency range required for the job. I created several analysis and calibration software tools over my time in the sonar community with diverse goals.

Example of a typical analysis plot from Tyack et al, 2011, https://www.researchgate.net/publication/50597241_Beaked_Whales_ Respond_to_Simulated_and_Actual_Navy_Sonar

Beam shape due to dropouts

A typical beam pattern when using phased array beam forming. Image credits Comiso et al 2019 https://www.mdpi.com/2079-9292/8/6/656

When using a transducer array to perform phased array beam forming, the sensitivity pattern of the beam is complex. This is even more extreme for more complex array shapes. If some of these transducers are defective, the beam shape is affected and may not be steered in the direction that it is supposed to be directed. Systems which model these beam patterns using the true repair state of the array can provide the user with insight into the change in pattern of his beam compared to the theoretical steered direction, as well as the peak beam sensitivity.

Towed array shape and left-right ambiguity

A towed linear hydrophone array (towed array) is a one-dimensional hydrophone array, typically up to several hundred meters long, which can be towed at large distances from the towing platform e.g. 100s m to 1 km, such that the self-noise of the towing platform is minimised. Data from a towed array is normally only used when the array is known to be straight, which can take a while following a manoeuvre due to the length of the array. Physical real-time models of the array shape can provide the towing platform with a better picture of when the data is usable and prevent unintended damage to the array. Such information could also theoretically be used to correct previously unusable array data.

The problem of 'Left-Right Ambiguity' and some solutions to this problem are described in Yang et al. 2015. Whilst modelling the array shape based on sensors in the array, this ambiguity can also be resolved, providing the operators with a clearer operational picture.

The shape of a towed array during an extreme maneuver. Image credits: Yang et al. 2015 https://www.extrica.com/article/16427

Training and reference websites

Whilst in the sonar community I was constructing and contributing to reference and training material including an intranet site (raw html/css).