This paper provides a new interpretation of the so-called ''delta-ceps
trum'' and extends the formulation of the conventional delta-cepstrum
towards an optimal design of the filter, which extracts important spec
tral dynamics from a cepstrum sequence. The algorithm to obtain new fe
ature parameters is unified to a formulation using a matrix coefficien
t filter and is tested through Japanese speech recognition experiments
. The average recognition error rate in a Japanese 24 phoneme recognit
ion experiment for four speakers was reduced from 12.2% to 10.3%.