In the field of helicopter acoustic detection, a primary concern is the identification of rotor noise emissions. One challenge is that, over long transmission distances, rotor noise is often masked by ambient noise, making its detection nearly impossible. To achieve long-range helicopter noise detection, it is crucial to restore the frequency characteristics of the received rotor noise signal. This study proposes the use of an adaptive filter to precisely isolate and process this signal. Through this method, we aim to establish an effective long-range helicopter noise detection system. The results presented in this paper demonstrate the adaptive filter's ability to accurately recover the frequency features unique to helicopter rotor noise, confirming the feasibility of a potent long-range helicopter acoustic detection system.