Monitoring the sea environment using acoustics the role of the acoustical observatories

The presentation deals with theoretical factors and technical specifications pertinent to the design of an acoustical observatory for the monitoring of the marine environment. Two types of observatories are mentioned, namely active and passive. Among the various cases of active observatories, the ones related to ocean acoustic tomography are presented in some detail and the inverse problem of retrieving information from measured acoustic data is explained. Some basic issues related to the type of measurements that should be made for optimal use of the acoustic field are also given with related references. Finally, the basic features of passive observatories are underlined without going into details

Inversions of statistical parameters of an acoustic signal in range-dependent environments with applications in ocean acoustic tomography

The paper presents an application of a method for the characterization of underwater acoustic signals based on the statistics of their wavelet transform sub-band coefficients in range-dependent environments. As it was illustrated in previous works, this statistical characterization scheme is a very efficient tool for obtaining observables to be exploited in problems of ocean acoustic tomography and geoacoustic inversion, when range-independent environments are considered. Now the scheme is applied in range-dependent environments for the estimation of range-dependent features in shallow water. A simple denoising strategy, also presented in the paper, is shown to enhance the quality of the inversion results, as it helps to keep the signal characterization to the energy significant part of it. The results presented for typical test cases are encouraging and indicative of the potential of the method for the treatment of inverse problems in acoustical oceanography

Inversion of acoustical data from the SW06 experiment, using a statistical method for signal characterization

his paper presents an application of an acoustic signal characterization scheme for ocean acoustic tomography and geoacoustic inversions proposed by Taroudakis et al., using real data. The work is the first attempt to validate the proposed scheme with data taken from sea experiments. The data have been collected during the SW06 experiment held in the New Jersey Continental Shelf and the inversion results (sea-bed geoacoustic parameters and source range) are compared with those reported by Bonnel and Chapman. The comparison and the signal reconstruction using estimated values of the model parameters is satisfactory being an indication that the new signal characterization method can be used in practical applications of acoustical oceanography

Verso un ambiente marino silenzioso: il ruolo degli osservatori acustici passivi - Towards a silent marine environment: the role of passive acoustic observatories

Il suono è ampiamente impiegato nelle osservazioni marine come strumento alternativo per ottenere informazioni su dati ambientali nella zona marina oggetto di monitoraggio. L’idea originaria di utilizzare specifiche sorgenti sonore artificiali per inviare segnali nell’ambiente marino ha dato origine alla tomografia acustica oceanica e numerosi metodi alternativi sono stati sviluppati per poter utilizzare le onde sonore come mezzo di raccolta di dati ambientali. Per contro vi è la necessità di ridurre al minimo il rumore generato da sorgenti non naturali per preservare l’ambiente marino e le sue caratteristiche acustiche. Per questo motivo, l’idea di poter utilizzare misure ottenute sorgenti sonore occasionali o anche il rumore ambientale per l’attuazione di analisi inverse sta costantemente guadagnando l’attenzione dei ricercatori. ------ The sound is widely used in marine observatories as an alternative means to retrieve information about environmental data in the sea area under surveillance. The original idea of using specifically man-made sound sources to send signals in the marine environment triggered the idea of ocean acoustic tomography and many alternative methods have been developed to exploit the acoustic measurements towards the retrieval of the environmental data. It is however desirable to reduce the noise originated from not natural sources in the marine environment to obtain a more silent marine environment. Thus the idea of using measurements of signals due to acoustic sources of opportunity or even the ambient noise for inversion purposes is continuously gaining the attention of the scientist