简介：Proceedingfromtheeigenvalueequationofthenormalmodeinhomogeneousshallowwater,wederiveseveralformulaecalculatingthemodeattenuationandgroupvelocity,andcomparetheiraccu-racybymeansofnumericalresults.Thepaperespeciallydiscussestheattenuationandthegroupve-locityofcriticalmodeinaPekerischannelandshowsthatingeneral,theattenuationandthegroupvelocityofthecriticalmoderespectivelyarelessthantheabsorptionandthesoundspeedinthebot-tom.Therefore.theKornhauser,Raney,WestonTindle‘sconclusionsaremodifiedthattheattenuationandthegroupvelocityofthecriticalmodeareexactlyequaltotheabsorptionandthesoundspeedinthebottom,respectively.

简介：Thegrouptimedelaysandamplitudesofthenormalmodearederivedusingthenormalmodefilter.Theseabottomsoundspeed,densityandattenuationareinverselydeducedbymatchingthegrouptimedelaysandtheamplitudeofthenormalmode.Ageneticalgorithm(GA)isusedforoptimizationsearchintheparameterspace.Theinvertedattenuationhasthenonlinearfrequencyrelationshipa=0.29f1.91dB/m(theunitoffrequencyiskHz)inthefrequencyrange200-500Hz.Thetheoreticaltransmissionlosscalculatedusingthededucedparametersmatchestheexperimentdataverywell.