简介：ThisintroductoryarticledescribeshowtypicallyanISOIntemationalStandardismadeandtheactivityofthetechnicalcommittee(TC24/SC4)responsibletoestablishIntemationalStandardsrelatedtoparticlesizingmethods.

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

简介：BasedonthenoisesurveyinChina,theformula（H′=H+N-HN/120）ofISO/DIS1999.2（"Acous-tics-DeterminationofOccupationalnoiseexposureandestimationofnoise-inducedhearingimpairment,1985）wasappliedtothecalculationofthehearingthresholdlevelassociatedwithageandnoise（HTLAN）ofthenoise-impairedpeople.AccordingtotheGaussciandistribution,whenthenoise-exposurelevelLEX8hwas85,90,95,100dBandthehearingthresholdfrequencyisfrom0.5kto6kHz,theHTLANofnoise-exposedpeoplewithdifferentdurationofexposureanditsrelationvaluestothehearingthresholdfrequencyassociatedwithage（HTLA）wereobtained.TheISO/DIS1999.2hasbeenprovedtobeapplicableinChina.