How to use MFCC (or any other tool/method/algorithm) for speech verification
This is not an easy task since its a classification problem. A while back at work I used time-frequency-domain transformations like STFT (Short Time Fourier Transformation), IWT (Integral Wavelet Transformation), DWT (Discrete Wavelet Transformation) STCEP (Short Time Cepstrum), WVD (Wigner Ville Distribution) to create images/matrices from voice recordings which were then classified using a convolutional neural network as classifier. This is a common approach for this task. You could try that or you could try setting certain limits, e.g. if in a certain frequency range a certain energy is exceeded for a certain time, the file is classified as a speech file.