In this paper, a kind of active noise barrier (ANB) using active noise control (ANC) technique to improve noise attenuation in low frequencies is proposed. The ANB consists of an ordinary noise barrier, three active noise control units (ANCU) and a DSP (TMS 320C6713 DSK). Feedback ANC system is used in the ANCUs. In order to achieve higher noise attenuation, fast transversal filter adaptive algorithm is introduced into the feedback ANC system. An investigation into the acoustic boundary generated by an ANCU is conducted. It is shown that the acoustic power flow around the surface of an ANCU reduced when control is turned on. Also, numerical and experimental study on an active noise barrier is conducted. As a result, the active noise barrier shows better noise attenuation performance in low frequencies.