Wavelet transformation was applied to filter synchrotron IR spectra collected from Alzheimer's infected tissue. db1 wavelet function was used to remove possible noise. Calculation indicated that the extracted portion contained about 3% of the original on the average when db1 was applied to a relatively smoother spectra. Second derivatives were then derived from filtered spectra. Second derivatives and local changes in error were discussed in relation to each other. (c) 2006 Elsevier B.V. All rights reserved.