For the purpose of controlling reverberation time in the low-frequency range in a room, the variable system of sound absorption power by the chairs in the low-frequency range by the experiments in a scale model was examined. As the results of scale model experiments (1/10 scale) in the reverberation room, the absorption power was controlled in the low-frequency range by the opening and closing of holes of the resonator. Because of the achievement of the variable system of sound absorption of the actual chairs, an experiment on sound absorption power characteristics was made in the reverberation room of the chair with resonators given a variable with the quantity and the diameter of holes, a neck's length, and a cavity volume of the seat. The result was obtained that variable characteristics of the sound absorption power of the chairs with the resonator (four holes, 30 mm diameter of the hole, and neck length 10 mm) is 0.2 m[sup 2] each for 125 or 250 Hz by changing the cavity volume of the seat in the experiment. The characteristics under the occupancy condition are nearly equal to it under nonoccupancy conditions.