{'fraction_non_alphanumeric': 0.01039119804400978, 'fraction_numerical': 0.0, 'mean_word_length': 5.600806451612903, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
AN EXPERIMENTAL ANALYSIS OF FREQUENCY EMISSION AND NOISE DIAGNOSIS OF COMMERCIAL AIRCRAFT ON APPROACH

Simple noise level monitoring systems, which are currently used around airports to create a noise map in residential areas, are unable to identify source frequencies and their impact on the environment. This article presents dominant frequencies during aircraft approaches of the SaintExupéry Lyon International Airport (France), and analyzes the evidence of impact on the environment. The main objective is the characterization of the most dominant frequencies emitted during approach operations, and the diagnosis of frequencies having a negative impact on populations living around the airport. A detailed analysis of signal processing concerns for measuring aircraft flyover noise is presented. A study of the emission angle has been completed and a classification period depending on the noise level has been achieved. Development of a deDopplerization scheme for both corrected time history and spectral data is discussed along with an analysis of motion effects on measured spectra. It is shown that correcting for Doppler amplitude and frequency can give some idea about source directivity. The obtained results provide additional information placing the results of theoretical models in their context, and will help validate and extend certain methods of calculating the propagation of aircraft noise. They have the potential to quantify environmental quality around the airports. The precise measured frequencies during the operations can be treated by passive or active control systems developed by aircraft manufacturers.