hi, Usually, 3D-noesy use 2D plane to correlate two nuclei attached together (correlation through bonds) and a third dimension to correlate nuclei through space (dipolar coupling). So, 3D CCH-noesy is composed by a plane that correlates a carbon and its attached proton (correlation based on interaction of two nuclear spin mediate by electronic orbital) and a third dimension that correlates this latest carbon with other carbon that are closed in space (interaction of two magnetic moment, through space). Thus, you have to know assignment (resonance of each proton and carbon) of your compound (I guess a protein ?), and with this 3D spectra, you can know which carbon is near your H-C couple. This information is also used as a constraint for structure calculation by restraint molecular dynamic.