  The transition angles are defined to describe the vowel-to-vowel transitions
in the acoustic space of the Spectral Subband Centroids, and the findings show
that they are similar among speakers and speaking rates. In this paper, we
propose to investigate the usage of polar coordinates in favor of angles to
describe a speech signal by characterizing its acoustic trajectory and using
them in Automatic Speech Recognition. According to the experimental results
evaluated on the BRAF100 dataset, the polar coordinates achieved significantly
higher accuracy than the angles in the mixed and cross-gender speech
recognitions, demonstrating that these representations are superior at defining
the acoustic trajectory of the speech signal. Furthermore, the accuracy was
significantly improved when they were utilized with their first and
second-order derivatives ($\Delta$, $\Delta$$\Delta$), especially in
cross-female recognition. However, the results showed they were not much more
gender-independent than the conventional Mel-frequency Cepstral Coefficients
(MFCCs).
