**2.3 Software interface**

Speech signal processing plays an important role within the digital processing projects and investigations. Within this field, the esophageal voices are being objective of analysis and transformation [2],[3] but these have the limitation of measuring their quality only with subjective criteria as hearing tests. This is because an evaluation based on the calculation of objective parameters like pitch, jitter, shimmer or the harmonic to noise ratio HNR demands a high precision in the definition of the beginnings and ends of cycle in the voice signal.

The oesophageal voice is generated using the air pass across the oesophagus but without the modulation possibility by the vocal fold because they have been removed due to, generally, a larynx cancer. Because of this their time-spectral characteristics are atypical and include levels of noise, fundamental frequency asymmetry and formant unstructuration. This leads to wrong measures in commercial applications and therefore is impossible to assess the quality of oesophageal voices. The same is applicable to voices with severe pathologies.

In this sense, it is necessary to develop an algorithm for the exact calculation of the marks that correspond to each cycle of the signal of oesophageal or pathological voices so that the calculation of pitch is exact and, with it, the measures of jitter, shimmer or signal to noise ratio. This algorithm has been included in a software interface for allowing users to measure and to plot in a graph the results of the acoustic parameters of the speech signal. This is suitable for evaluating and comparing the results between original oesophageal speech signal and the processed one after applying the wavelet transform.
