Inthispaper,aneffectiveandrobustactivespeechdetectionmethodisproposedbasedonthe1/fprocesstechniqueforsignalsundernon-stationarynoisyenvironments.TheGaussian1/fprocess,amathematicalmodelforstatisticallyself-similarradomprocessesbasedonfractals,isselectedtomodelthespeechandthebackgroundnoise.AnoptimalBayesiantwo-classclassifierisdevelopedtodiscriminatethembytheir1/fwaveletcoefficientswithKarhunen-Loeve-typeproperties.Multipletemplatesaretrainedforthespeechsignal,andtheparametersofthebackgroundnoisecanbedynamicallyadaptedinruntimetomodelthevariationofboththespeechandthenoise.Inourexperiments,a10-minutelongspeechwithdifferenttypesofnoisesrangingfrom20dBto5dBistestedusingthisnewdetectionmethod.Ahighperformancewithover90%detectionaccuracyisachievedwhenaverageSNRisabout10dB.