voiced/unvoiced detector

the voiced/unvoiced detector elektor february 1981 — 2-17 the finishing touch to the Elektor vocoder On the face of it, the detector may seem superfluous. However, when the block diagram of the complete vocoder in figure 1 is considered and the proposed additions are momentarily forgotten, their necessity will be readily apparent. In the upper section the speech signal is divided and split into control voltages to feed the VCA"s in the synthesis section. The VCA"s are thus provided with an input signal consisting of the carrier signal chopped into identical bits and pieces. Fair enough. In practice how- ever, the synthesised result proves to be less satisfactory than expected. The fault lies with the carrier signal which is far from ideal. remedy for this was the inclusion of the "high frequency blend" provided by P17 shown in the dotted area in figure 1. Part of the "high frequency" in the speech signal is taken from the high pass filter in the analysis section and is blended d...