▁ ν 2 ▁are ▁two ▁spectral ▁channels ▁y ν ▁is ▁the ▁vector ▁composed ▁of ▁the ▁signal ▁intens ities ▁in ▁E ▁in ▁column ▁ ν ▁n ▁the ▁number ▁of ▁signals ▁in ▁the ▁original ▁dataset ▁N ▁the ▁N oda - H il bert ▁transform ▁matrix ▁ ▁The ▁values ▁of ▁N , ▁N j , ▁k ▁are ▁determined ▁as ▁follows : ▁ 0 ▁if ▁j ▁= ▁k ▁ ▁if ▁j ▁ ≠ ▁k ▁ ▁where : ▁j ▁the ▁row ▁number ▁k ▁the ▁column ▁number ▁ ▁Inter pret ation ▁Inter pret ation ▁of ▁two - dimensional ▁correlation ▁spect ra ▁can ▁be ▁considered ▁to ▁consist ▁of ▁several ▁stages . ▁ ▁D ete ction ▁of ▁pe aks ▁of ▁which ▁the ▁intensity ▁changes ▁in ▁the ▁original ▁dataset ▁As ▁real ▁measurement ▁signals ▁contain ▁a ▁certain ▁level ▁of ▁noise , ▁the ▁derived ▁ 2 D ▁spect ra ▁are ▁influenced ▁and ▁de grad ed ▁with ▁substantial ▁higher ▁amounts ▁of ▁noise . ▁Hence , ▁interpretation ▁begins ▁with ▁studying ▁the ▁aut oc or relation ▁spectrum ▁on ▁the ▁main ▁diagonal ▁of ▁the ▁ 2 D ▁synchron ous ▁spectrum . ▁In ▁the ▁ 2 D ▁synchron ous ▁main ▁diagonal ▁signal ▁on ▁the ▁right ▁ 4 ▁pe aks ▁are ▁visible ▁at ▁ 1 0 , ▁ 2 0 , ▁ 3 0 , ▁and ▁ 4 0 ▁( see ▁also ▁the ▁ 4 ▁corresponding ▁positive ▁aut ope aks ▁in ▁the ▁ 2 D ▁synchron ous ▁spectrum ▁on ▁the ▁right ). ▁This ▁indicates ▁that ▁in ▁the ▁original ▁dataset ▁ 4 ▁pe aks ▁of ▁changing ▁intensity ▁are ▁present . ▁The