Description 
Implements triangular filterbank given in [1]. Returns matrix of M triangular filters (one per row), each K coefficients long. The triangular filters are between limits given in R (Hz) and are uniformly spaced on a warped scale defined by forward (h2w) and backward (w2h) warping functions. For example, h2w and w2h can be hz2mel and mel2hz functions, respectively, in which case trifbank returns a mel filterbank, i.e., a filterbank of triangular filters uniformly spaced on the mel scale. Other forward and backward warping functions can be specified to arrive at arbitrary warped triangular filterbanks.
[1] Huang, X., Acero, A., Hon, H., 2001. Spoken Language Processing: A guide to theory, algorithm, and system development. Prentice Hall, Upper Saddle River, NJ, USA (pp. 314315).
