Perceptual Weighting Filter in AMR-WB
I have a question regarding the "perceptual weighting filter" used in the AMR-WB (also in the AMR-WB+) codec that is standardized in 3GPP and ITU.
Please check the 2002 Journal article from the developers of AMR-WB, where they present the perceptual filter (pages 8-10, and Figures 3 and 4).
Is this the best that one can achieve?
I would like to know if there are any recent research efforts made to improve this perceptual weighting filter to improve the quality of wideband speech. If so, any pointers in that direction will be highly appreciated.
Thanks in advance.