It has been done an experimental study of the use of two stacks 1 and 2 in a straight resonance tube of a thermoacoustic cooling system. We used a half-wavelength straight resonance tube at which the one end is closed by rigid plug and the other end is closed by a plastic diaphragm which can vibrate axially due to sound wave produced by a loudspeaker facing to it. The tube is PVC pipe and filled by free air at atmospheric pressure and has 112 cm of length so it gives a calculated operating frequency around 152 Hz. The stacks are parallel plates type, which have plates thickness of 0.3 mm, and the plates spacing of 0.85 mm which is around four times of the thermal penetration depth. The diameter of stack is the same as the inner diameter of the tube, i.e. 46 mm, while the length of stack is 100 mm. We varied the sound frequency in the range of 130 - 160 Hz, the input electric power of loudspeaker from 40 W until 160 W, and stacks center position in the range of 8 - 25 cm measured from each end of the tube, to investigate the their influences to the temperature decrease which can be achieved. It is found that the temperature decreases of the two cooling points 1 and 2 reached maximum at sound frequency of 147 Hz and when the two stacks were placed near to the ends of the tube. It is also found that a higher electric power tends to produce a larger temperature decrease. At 90 W of the input electric power, the maximum temperature decrease around 9.8 ↓C was obtained at cooling point 1 when the center of the stack 1 was placed at 80 mm from the rigid closed end of the tube.