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. Studies in shallow waters pointed out that the acoustic wave interference patterns have potential application in a broad range of problems in underwater acoustics such as: passive sonar, active sonar, array processing, time-reverse mirrors and geoacoustic inversion. For shallow waters underwater sound waveguides, the main features of this research is interference pattern or “striations” obtained by means of Frequency-time or Frequency-distance spectrograms. This work aims to characterize these interference pattern or striations related to “invariant” parameter β. The theory is developed based on real underwater waveguide. The present results confirm that the parameter β is frequency dependent and at high frequencies it tends to the unity. In another words, far from the waveguide cut-off frequency the present real waveguides could be treated by an ideal waveguide. Besides, in this approximation it is possible to make source-receiver passive distance predictions based on the related interference pattern. Keywords: underwater acoustic, waveguide, interference pattern. RESUMO. Estudos em aguas rasas apontam que os padroes de interferencia de ondas acusticas tem aplicacao potencial em uma ampla gama de problemas de acustica submarina, tais como: sonar passivo, sonar ativo, processamento de arrays, espelhos de reversao temporal e inversao geoacustica. O foco principal desta pesquisa e o padrao de interferencia ou estrias obtidas por meio de espectrogramas e graficos no plano de Frequencias e Distâncias. Este trabalho tem como objetivo caracterizar estes padroes de interferencia ou estrias com o parâmetro invariante β. A teoria e desenvolvida com base em um guia de onda real. Os resultados deste estudo confirmam que o parâmetro β e dependente da frequencia e, em altas frequencias, tende a unidade. Em outras palavras, longe da frequencia de corte, o comportamento do guia de onda real e semelhante ao guia de onda ideal. Alem disso, nesta aproximacao, e possivel fazer previsoes de distância passiva entre o receptor e a fonte com base no padrao de interferencia. Palavras-chave: acustica submarina, guia de ondas, padrao de interferencia.

SHALLOW WATERS INTERFERENCE PATTERN FEATURES AND APPLICATIONS