Introduction: An acoustic analysis was conducted of the voice of 25 patients with Parkinson's disease (PD) subjected to deep brain stimulation (DBS) to assess the impact of therapy. Materials and Methods: We examined 25 patients with advanced PD under four different conditions: deprived of medical treatment, under medical treatment, and one week and one month after the implant of the DBS electrodes. At the four time points, the patients produced a sustained /a/ and a standard sentence in Spanish, and microphone and electroglottographic recordings were digitally analyzed using the Computerized Speech Lab program. Results: Waveform analysis of the sustained /a/ captured by the microphone indicated a higher fundamental frequency (F0) when the patients were under levodopa treatment. The frequency perturbation (jitter) decreased remarkably after the three treatments. Shimmer also fell, but differences were not significant. Conclusions: Nearly all acoustic analysis parameters during phonation of a sustained /a/ improved after DBS, but the factor that was most sensitive to the impact of both surgical and medical therapy was jitter.