When people speak in a loud voice, or give a long lecture, their throats get sore and their voices become hoarse. This phenomenon is due to the fatigue of the vocal cords that causes its disturbed function after using it too much or too long. When the voice becomes cracked or weaker, the frequency spectrum shows not only the high frequency range more narrowed but also the amplitude of the sound waveform lowered than usual. In this paper, we propose a new method to improve voice hoarseness by massaging the inner skin of the mouth by generating resonance of the vocal cords by using a sound-reflection cup in front of the mouth. The paper first examines the sound characteristics of hoarse voices and suggests how to use a sound-reflection cup to relieve the fatigue of vocal cords. In the experiment of applying the proposed method, we obtained about 94% of voice quality recovered when compared to the original voice. We also acquired a successful result that the clarity of voice after the elimination of hoarseness became more improved when compared to the voice quality even before the lecture. The result will be positively applied to those who are supposed to speak for a long time.