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This paper introduces the continuous wavelet transform method to analyze different multiple tonal phenomena of the high-lift configurations, aiming at revealing the time-frequency information of these multiple tones simultaneously. Two types of multiple tones can be respectively observed in the far-field noise spectra at landing and cruise configurations, but their inherent physical mechanisms are different. Two wavelet functions are applied in this paper. The Morlet function as a complex wavelet function returns both amplitude and phase information for capturing oscillatory behaviors, so that it can clearly distinguish the mode switching mechanism and the amplitude modulation mechanism of different multiple tonal phenomena. While the Mexihat function as a real wavelet function returns only amplitude information, so that it is usually to isolate peaks or discontinuities of signals and cannot reveal the mechanisms of different multiple tonal phenomena. In summary, the Morlet function is more appropriate to analyze the periodical oscillatory acoustic tonal signals from multiple tonal phenomena. [ABSTRACT FROM AUTHOR]

• Aeroacoustic experiment and wavelet analysis are conductedon the 30P30N model. • Time-frequency characteristicsof differentslat and flap configurations. • Multiple tonesof flap noiseis satisfied withamplitude modulation phenomenon. • Multiple tones of slat noise is satisfied withmode switching phenomenon. High-lift device installed on modern large aircraft is a major noise source during the approach and landing phases. For high-lift device, slat and flap parameters such as gap, overlap and deflection angle have strong effect on aerodynamic and aeroacoustic characteristics. However, the research about time–frequency characteristics of high-lift device noise affected by slat and flap parameters is lacking. This paper presents an investigation on 30P30N model to reveal the effect of different slat and flap geometrical configurations on the aeroacoustic time–frequency characteristics with experimental measurement and wavelet analysis. The results show that the multiple tones at small flap and slat deflection angles are mainly generated from the flap gap region. The time–frequency characteristic of the tones is satisfied with the amplitude modulation phenomenon, namely that the acoustic energy concentrates on the primary tone and the other tones are generated from the modulation process of the primary tone. While the multiple tones at large slat deflection angles are generated from the slat cove and slat gap regions. The time–frequency characteristic of the tones is satisfied with the mode switching phenomenon, namely that the dominant noise energy temporally switches from one mode to another in time and these multiple tones cannot coexist independent of one another. [ABSTRACT FROM AUTHOR]