In this study, the experimental open-tube and close-tube thermoacoustic apparatuses were constructed. In order to determine the optimum length of resonant tube, frequency and the optimum length of stack, the resonant characteristics of thermoacoustic apparatuses were investigated, The length of resonant tube varies from 400mm to 850 mm. The experimental frequency varies from 100 Hz to 1000 Hz. In case of first harmonic, the maximum temperature difference of the open-tube thermoacoustic apparatus is 41$^{circ}C$)resonator length: 500 mm), and the maximum temperature difference of the close-tube thermoacoustic apparatus is 42$^{circ}C$ (resonator length : 850 mm).