An interesting Read on DOLBY

http://web.archive.org/web/20090521052914/http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/212_Dolby_B,_C_and_S_Noise_Reduction_Systems.pdf

I think anytime you apply a filter,IT CAN MAKE IT WORSE!!!!!

The cassette player in our car for example had a button to ENABLE OR DISABLE NR -- I always left it disabled AS IT SOUNDS WORSE WITH IT ON!!