André, Michel

Delory, Eric

Mas, Alex

Van der Schaar, Mike Connor Roger Malcolm

UPCommons. Portal del coneixement obert de la UPC

INSTRUMENTATION VIEWPOINTSessions103BIO-SONAR SIGNAL PROPAGATION MODELLING IN HETEROGENEOUS MEDIA WITH FDTD METHODSAlex Mas, Mike van der Schaar, Eric Delory and Michel André.Laboratori d’Aplicacions BioacústiquesUniversitat Politécnica de Catalunya (UPC)alex.mas@lab.upc.edu, http://www.lab.upc.esCentre Tecnológic de Vilanova i la GeltrúAvda. Rambla Exposició, s/n 08800 Vilanova i la GeltrúBarcelona, EspanyaModelling of acoustic waves in heterogeneous media with fi nite dif-ferences is a useful tool for a number of disciplines providing a com-plete description of the acoustic fi eld. However, these models are lim-ited by their accuracy, stability, dispersion and grid dimension. These parameters depend mostly on the order and the dispersion proper-ties of the chosen method. However, there are no specifi c guidelines to choose the right method in advance; therefore prior analysis is often needed. is paper, we focused on the behaviour of an acoustic wave passing trough heterogeneous media simulating biological tissues and stud-ied the response of this wave depending on the angle of incidence from one medium to another. We also compared the results of 4th and 2nd order fi nite diff erence schemes simulating this scenario. In-terestingly, the latter was never tested in a similar environment, while the fi rst brought successful results.RANGE DETECTION OF SPERM WHALE SONARAndré, M., Johansson, T., Delory, E., van der Schaar, M. and Morell, M.Laboratori d’Aplicacions BioacústiquesUniversitat Politécnica de Catalunya (UPC)michel.andre@upc.edu, http://www.lab.upc.esCentre Tecnológic de Vilanova i la GeltrúAvda. Rambla Exposició, s/n 08800 Vilanova i la GeltrúBarcelona, EspanyaThere has been much speculation about the sperm whale sonar ca-pabilities. While the usual clicks of this species are considered to sup-port the mid-range echolocation, no physical characteristics of the signal have clearly confi rmed this assumption nor have explained how sperm whales forage on squids. The recent data on sperm whale on-axis recordings have allowed us to simulate the propagation of a 15kHz pulse as well as its received echoes from diff erent targets tak-ing into account the refl ections from the bottom and the sea surface. The analysis was performed in a controlled environment where the oceanographic parameters and the acoustic background could be modifi ed. We also conducted experimental measurements of squid target strength (Loligo vulgaris and Sepia offi  cinalis) to further inves-tigate and confi rm the TS predictions from the geometric scattering equations. Based on the results of the computer simulations and the TS experimental measurements, we were able to determine the sperm whale sonar minimum requirements, i.e. range and directional hearing, to locate a single 24,5cm long squid, considered from stom-ach contents to be the major component of its diet. Here, we present the development of the analysis which confi rms that sperm whale usual clicks are appropriate to serve a mid-range sonar function al-lowing them to forage on individual low sound-refl ective organisms. M12

Bio-sonar signal propagation modelling in heterogeneous media with FDTD methods

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