Abstract: In order to verify the acoustic character of the standing wave field between the noise source and the secondary source in ducts under the control of the active noise attenuation system, the authors made the single frequency noise cancellation experiment in low frequency bands on the adaptive active noise control experimental system designed by their own. After achieving the maximum noise cancellation result at each frequency point, the duct acoustic characters under the control of the active noise attenuation system are measured and analyzed by the standing wave separation method. The experimental results show that the reflection coefficient's module of standing wave field between the noise source and the secondary source is close to 1 while reaching the maximum noise cancellation effect, i.e., most of sound energy transmitted from the advanced of ducts is reflected back.