Higher frequency components estimating method using codebooks based on formants

A talk with communication device, such as a cell phone, loses information of language because of a limited frequency range. Currently, we research algorithm estimating higher frequency components from the limited signal. We propose method to estimate codebooks using formants based on Hilbert transform. Firstly we prepare temporary limited signals from the original signals from raw voice sound sources. And then we derive the estimated signals from limited signal using proposed method. The experimental results successfully demonstrate that the method restores a part in higher frequency. As shown in the characteristic frequency, the proposed method is better than only using Hilbert transform, comparing to formant of the based signal. The estimated signal can be heard clearly when the formant in the original signal becomes closer.