Underwater acoustics – Simulation tools

In 2012 and 2013, MAREE has designed simulations tools concerning underwater acoustic propagation, reverberation and ambient noise. Applications concerns sonar performance prediction, help for new Modem design, mapping of expected noise …

Ambient noise:

Simulation can be used to predict ambient noise by means of models that take in account with environmental features of a given area. It is therefore possible  to evaluate noise variability versus input parameters .

Sensibilité de 4 paramètres environnementaux (hauteur d'eau, vitesse du vent, vitesse du courant et trafic) sur un spectre de bruit ambiant

Ambient noise spectrum sensitivity versus four parameters (Water depth, wind speed, current speed and trafic)

Propagation:

Propagation features of an acoustic waveguide are given by the impulse response. In general, this is done by means of  ray theory. In practice, a dichotomic method is used to compute eigenraies. A spectrum is associated with each ray and the complete temporal signal is then given by inverse Fourier transform. It is therefore necessary to  provide an environment, a geometry and the signal specifications to establish the impulse response.

Réponse impulsionnelle du canal acoustique. En haut, rayons propres. En bas à gauche, spectre reçu. En bas à droite, signal temporel reçu.

Acoustic channel impulse response. Top, plot of eigenraies. Bottom left, received spectrum. Bottom right, received signal versus time.

Reverberation:

Reverberation prediction is necessary to simulate the signal received by a Sonar. It consist in computing parameters of the ray tube. Volume, surface and bottom functions are then calculated along each ray tube. It is therefore possible to evaluate the response corresponding to a particular emitted signal.

Exemple de signal réverbéré pour un environnement grand fond.

Reverberation intensity versus time for a deep water environment.

Signal processing:

From these calculus, it is possible to generate a simulated signal corresponding to the signal that would be recorded in real conditions.

Analyse du fichier .wav généré par le simulateur.

Analysis of a .wav file generated by the simulator.

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