“…Murthy and her colleagues have recently used GDF-based features for ASR (Murthy and Gadde, 2003;Hegde et al, 2004b,c;Alsteris and Paliwal, 2005). The time-derivative of the phase spectrum, most often referred to as the instantaneous frequency distribution (IFD), has been used in the past for pitch extraction (Abe et al, 1995;Charpentier, 1986;Nakatani et al, 2003) and formant extraction (Potamianos and Maragos, 1996;Friedman, 1985). Potamianos and Maragos (2001), Dimitriadis and Maragos (2003), Paliwal and Atal (2003) and Wang et al (2003) have recently investigated IFD-based features for ASR.…”