## 4 Discussion
On the other hand, when there is a loudness or phonatory system rigidity increase, the subglottic pressure also increases to start phonation, making the closed phase of the glottal cycle longer [23] and increasing vocal strain. This situation also leads to a less steep spectral slope [23, 28, 42]. Our finds corroborate this information as we observed positive correlation (weak) of the alpha ratio and strain inVHG, indicating that the increase of vocal strain (even with a normal variation of voice quality) also leads to a less steep spectral slope. Even though participants in DG have behavioral dysphonia, characterized by increased loudness and closed phase of the glottal cycle, there were no significant correlations of the alpha ratio with breathiness and strain. However, for continuous speech, there was a negative correlation between the alpha ratio and roughness. We believe that the vocal quality aperiodicity of frequency and amplitude reduced the intensity of the harmonics above 1 kHz, thus decreasing alpha ratio values. As previously described [23; 28; 42], the alpha ratio can indicate a less steep spectral slope in two situations: higher vocal projection and increased vocal strain. This fact was found in the complementary analysis of the current study. There was no significant difference between both groups, VHG and DG, for alpha ratio. We believe that people with behavioral dysphonia have vocal strain to compensate for other deviations of vocal quality and the inefficiency of the phonatory system. The absence of a significant difference between groups was also observed for L1-L0. L1-L0 measure provides information on the phonation mode and is the difference between the F1 intensity level (L1) and the F0 intensity level (L0) [31]. According to the non-linear source-filter coupling theory [50], the various filter configurations influence in vocal fold vibrations and emphasize different harmonics. Thus, the formants represent the mode that supraglottal airflow is molded by the filer [51]. Hence, the F1 intensity is determined by the mandibular lowering [51] and by the emission intensity [25]. At last, previous studies found that, when L0 is near or just below L1, the source has an efficient vibratory pattern due to the reactive vocal tract, and there is an improved vocal economy [52; 53; 32]. The significant correlations with L1-L0 were negative, which indicates that when that measure has lower values, there is a high auditory-perceptual parameter deviation. This could be seen in the current study regarding general degree and breathiness in both groups and roughness for DG. Breathy vocal patterns reduce L1-L0 [23], which was expected and corroborated our findings. [PERSON] and [PERSON] [28] suggest that the spectrum of voices with high glottal adduction L0 has lower energy than L1, however, the spectrum of voices with insufficient glottal adduction L0 has higher energy than L1. It is important to highlight that normal voices can also be breathy as a normal variation of voice quality. The negative correlation of L1-L0 with roughness in DG was a surprising finding. We believe that roughness, a perceptual-auditory parameter generated from differences in muscle tone and mass in vocal folds (benign mass lesion; condition of DG), may have affected the phonation mode, making it less efficient with lower values of L1-L0. Although continuous speech better represents the daily vocal use [54; 55], this voice sample may have higher variability on its auditory-perceptual analysis due to the influences of each individual's articulation, prosody, and accent [4; 34]. However, a sustained vowel, which is not biased in that way, has its auditory-perceptual parameter easily analyzed and may provide more information about the source. Thus, we think that was the reason for the weakest correlation degree with acoustic measures and auditory-perceptual analysis in continuous speech. We encourage future studies to analyze the correlations of voice intensity with CPPs and LTAS measures. Thus, a complete and objective analysis will be possible.