Estimating longer modal functions using shorter vertical arrays in a closed-form manner

H. Gazzah, houssem.gazzah@isen-ouest.yncrea.fr
ISEN Yncrea Ouest, L@bisen/SEACOM,
44470 Carquefou, France
S.M. Jesus sjesus@ualg.pt
LARSys, University of Algarve,
Campus de Gambelas, PT-8005-139 Faro, Portugal.

Comments: download (pdf).
Ref.: Forum Acousticum, Torino (Italy), September 2023.

High-resolution estimation of modal functions has been recently demonstrated. Two VLAs collect pressure data due to a monochromatic source, and feed a subspace algorithm that computes, in a fully automatic closed-form manner, modal functions at sensors depths. Estimation accuracy can be improved at will by improving the SNR, using the same limited number of sensors. In this proposal, the apparatus is improved in order to reduce by two the number of required sensors to cover a given portion of the water column, or equivalently, to double the covered portion of the water column using the same number of sensors. This is made possible by allowing the source and the hydrophones to be deployed at different depth locations. The modified algorithm continues to exhibit the same attractive features of the original one, i.e. closed-form and asymptotically (as SNR increases) unbiased estimation. At limited SNR, a moderate degradation of the estimates is observed because the collected data matrices are not symmetric anymore.