6. The speech processing device according to claim 5 , comprising a learning output signal recording means for recording the learning output signal of audible whisper input through a prescribed microphone into the learning output signal storing means.
5. A speech processing device for producing an audible speech signal based on and corresponding to an input non-audible speech signal as a non-audible speech signal obtained through an in-vivo conduction microphone, comprising: a learning output signal storing means for storing a prescribed learning output signal of audible whisper, a learning input signal recording means for recording a learning input signal of non-audible speech input through the in-vivo conduction microphone as a signal corresponding to the learning output signal of audible whisper into a prescribed storing means, a calculating means of learning signal feature value for calculating a prescribed feature value of each the learning input signal and the learning output signal, a learning means for conducting learning calculation of a model parameter of a vocal tract feature value conversion model, which, on the basis of a calculation result of the calculating means of learning signal feature value, converts the feature value of a non-audible speech signal into the feature value of a signal of audible whisper, and then storing a learned model parameter in a prescribed storing means, a calculating means of input signal feature value for calculating the feature value of the input non-audible speech signal, a calculating means of output signal feature value for calculating a feature value of a signal of audible whisper corresponding to the input non-audible speech signal, based on a calculation result of the calculating means of input signal feature value and the vocal tract feature value conversion model, with a learned model parameter obtained through the learning means set thereto, and an output signal producing means for producing a signal of audible whisper corresponding to the input non-audible speech signal by employing a signal of a prescribed noise source, on the basis of a calculation result of the calculating means of output signal feature value.