Speech evaluation apparatus and speech evaluation method

A speech evaluation apparatus comprising:

• a memory;
• and
• a processor coupled to the memory and configured to:
• calculate an autocorrelation value of a first signal that is a signal of a first period;
• determine whether the calculated autocorrelation value is no less than a threshold;
• generate, when the calculated autocorrelation value is no less than a threshold, a first input spectrum obtained by frequency transforming the first signal;
• generate a second input spectrum obtained by frequency transforming a second signal that is the signal of a second period earlier than the first period;
• generate a processed spectrum obtained by transforming the second input spectrum in accordance with a coefficient;
• calculate a correlation value between the first input spectrum and the processed spectrum;
• and
• determine a change amount of pitch frequency between the first signal and the second signal in accordance with the coefficient and the correlation value.