1. A method for the noise reduction of CT image data comprising: scanning an examination object; generating at least two CT image data records, each generated on the basis of a different x-ray energy spectrum, as input image data records; breaking down the input image data records into at least two broken down image data records, each with different local frequency bands; determining local and band-dependent correlations between the broken-down image data records having the same but not a relatively lowest local frequency band; calculating at least one newly broken-down image data record by using the local and band-dependent correlations of the broken down image data records, with: a weighted average value of a pixel being formed from at least two pixel values of the broken-down image data records in the case of a relatively weak local band-dependent correlation of a pixel, and the pixel value of the originally broken-down image data record being used as a new pixel value in the case of a relatively strong local correlation; and calculating at least one new final image data record for at least one x-ray energy spectrum from the broken-down image data record with the relatively lowest local frequency band and the at least one newly broken-down image data record of the same c-ray energy spectrum with the at least one relatively higher local frequency band.