The most common mutational voice disorder is the mutational falsetto. The voices of four young male patients with mutational falsetto were acoustically and auditory-perceptively analyzed in pre-and post-therapy situations to verify the result of speech-language intervention. For data collection, the patients were asked to say the days of the week. Four speech-language pathologists performed auditory assessment of these emissions using auditory-perceptual parameters: overall grade of dysphonia, roughness, breathiness, strain, instability, and pitch. The emissions of each patient corresponding to pre-and post-therapy were randomly presented to the evaluators, who did not have prior knowledge of the condition being analyzed. The assessment was performed by comparison, and the evaluators should inform whether the second emission was better, worse or unchanged when compared to the first. When change was observed, they should select three auditory-perceptual parameters regarding the expressive modification. The evaluators were informed only about subjects' age and gender. Mean, maximum and minimum fundamental frequencies were extracted from each emission of the patients using the Praat Program (version 5132). Semitone values were also extracted and analyzed. Data was statistically analyzed. In the post-therapy condition, the evaluators found an improvement in the vocal quality of all patients, as well as a decrease in the mean, minimum and maximum fundamental frequencies and in the semitones, resulting in a deeper and more stable vocal pattern.