The corrective loop of sound perception (aka frequency-weighting) specified in current noise control regulations is indicated as A-weighting. Since the correction of A-weighting for low-frequency noises is larger, it is necessary to make a correction to the helicopter (low-frequency) noise in order to make it closer to the true perception of the helicopter (low-frequency) noise felt by the public. According to Article 4 of the Airport Vicinity Aircraft Noise Control Regulations (revised on June 8th, 2009), the aircraft noise control zones are classified into 3 levels. The difference value of the Day-Night Level (DNL) for jet aircrafts, propeller airplanes, and helicopters is determined to be 8 dB. Given that whether the noise levels of the newly introduced AH-64 Apaches and UH-60 Black Hawks similar to those of our existing helicopter models is yet to be determined and the principles for noise control zone delimitation have been adopted for many years, it is necessary to review those principles and make necessary revision to them based on measurements. Through the implementation of this Research Project, research data relating to studies on helicopter noise control conducted in recent years at home and abroad have been collected and compiled and the development trends in the international arena identified. The results of related analysis and assessment might be used for making recommendations on the development of measurement techniques for helicopter noises, as well as assessment indicators and models used for low-frequency aircraft noises. In addition, the knowledge about weighting methods through actual measurement or correction based on noise assessment indicators for fixed-wing aircrafts might serve as a reference for delimitation of helicopter noise control zones and correction of noise contours. Therefore, the Environment Protection Administration (EPA) proposed the 2016 Research Project for “Study on Low-frequency Noise Indicators and Measurement Techniques for Aircraft Noise Control Zone Delimitation” in hope that the results might serve as a reference for correction of regulations and legal process relating to helicopter noise control in the future. The achievements of the Research Project include: 1. Collected and analyzed the measurement methods and assessment indicators for low-frequency aircraft noises currently adopted by various countries. 2. Collected studies on the perception by the public and impact assessment of low-frequency noises. 3. Analyzed the impact characteristics of low-frequency aircraft noises and investigated and planned forward the assessment indicators and measurement techniques for low-frequency aircraft noises in our country. 4. Investigated and analyzed the measurement data of the low-frequency noises at existing heliports and acquired knowledge on the actual impact situation of them on adjacent communities.