# Spectral Envelope Transformation in Singing Voice for Advanced Pitch Shifting
## 6 Results and Discussion
### Subjective Evaluation  
As the objective evaluation, the subjective evaluation provided other interesting results. A total of 23 anonymous subjects participated and fully completed the survey. Most of the participants had some musical background. There were six female and 17 male participants. The survey informed the participant that the differences between the audio samples might be subtle and recommended the usage of good quality headphones. Figure 14 shows the results of the survey; five different participant categories have been identified to interpret the results. The figures show the 95% confidence interval of the scores with a notch placed at the median value. The evaluation of the three transformations considered was done for isolated notes and melodies, separately. In Figure 14a, the global results including all of the participants are shown. Our approach achieved a mean quality of 61.4%, whereas Logic Pro X and PSOLA attained 60.8% and 60.0%, respectively, in the case of isolated notes. In the case of the melodies, the three schemes achieved very similar results; although our scheme is skewed towards a higher score. Figure 14b shows the values obtained from the participants using headphones/earphones (as recommended) for the test; they were 73% of the total number of participants. For isolated notes, the mean score of FDPS and Logic was 60.4% and 58.7%, respectively. The mean score of PSOLA was 58.2%. In the case of melodies, FDPS obtained a 52.6% mean quality score while Logic and PSOLA attained lower scores, 47.3% and 47.9%, respectively. Figure 14c shows the result of the survey considering only the participants with professional music studies or professional music production background using headphones (30% of the total). In this case, FDPS achieved 65.2% of mean quality score in the case of isolated notes, while Logic and PSOLA obtained 58.0% and 54.7%, respectively. Regarding the melodies, our FDPS scheme achieved a 55.9% mean quality, whereas Logic Pro X and PSOLA attained mean scores of 46.5% and 43.9%, respectively. As in the previous cases analyzed, our algorithm attained better results than the other two schemes, but in this case, in which the participants have significant musical background and do the survey in good listening conditions (according to their answers), the difference in the performance between our scheme and the others is larger. In Figure 14d, the participants with no more than elementary musical background using headphones were considered. FDPS, Logic and PSOLA achieved a mean score of 53.9%, 58.6% and 58.8% in isolated notes and 47.0%, 45.2% and 49.2% in melodies, respectively. Somehow, curiously, the results for the musically untrained subjects do not follow the trend of the results attained by trained subjects. The latter reveals rather clearly the better performance of our scheme, whereas untrained subjects do not show the same difference in performance. This can be due to the combination of two factors: the lack of musical knowledge and the inadequate listening conditions (subjects in this group are using speakers instead of headphones/earphones). The latter seems corroborated by the results shown in Figure 14e. Figure 14e shows the results of the participants using speakers during the test (26%). In this case, the mean score for notes was 64.2%, 66.7% and 65.0% for FDPS, Logic Pro X and PSOLA, respectively. The mean score attained for the melodies was 60.1%, 56.7% and 56.5% for FDPS, Logic Pro X and PSOLA, respectively. Considering all of the results analyzed above, it can bee seen that our FDPS approach achieved better quality according to the assessment of the participants doing the survey with a professional musical background. More specifically, the FDPS score in the case of the notes evaluated achieved greater differences of quality with regard to PSOLA and Logic Pro X. Furthermore, in the case of melodies, FPPS performance was perceived more clearly better when listening in good conditions (using headphones).