A hum removal algorithm used for audio restoration purposes

An automatic hum removal system is presented and characterized in the paper, which could be used in audio restoration applications. Its design starts from hum modeling. Two hum models were proposed, then the importance of high precision hum noise fundamental frequency estimation along with a comparative study of common estimators is presented. The problematic of filter design, represented by the choice of the quality factors depending on the spectral band in which each filter will work, is described afterwards, concluding with objective and subjective test results for the algorithm. The results clearly indicate the strong preference of the listeners for the signals resulted after the hum removal, in the high precision frequency estimation case.