Assessment of cabin noise contributing factors of a turbo-propeller airplane using EMD and SSA signal decomposition methods

Abstract

The acoustic signals throughout the cabin of a regional turbo-propeller driven airplane were measured during a cruise flight. To that end, the noise power at the front and rear of the cabin are obtained in the scale of one-third octave-band. Furthermore, the sound pressure signals are acquired at 5 positions within the cabin. In order to determine the noise characteristics and key contributing factors to the noise, the sound pressure signals are decomposed. For the first time, the signal decomposition methods of the Empirical Mode Decomposition (EMD) and Singular Spectrum Analysis (SSA) are implemented to the cabin noise signals. An attempt is made to recognize the physical sources of the noise components. The signal decomposition results show that the propellers generate the most significant part of the cabin noise. In addition to the base frequency of the propellers, their harmonics also play major roles in the acoustic signals. Some other components caused by the unbalanced propellers, and the structural and acoustic resonance are discovered in the noise signal. Finally, the noise level is studied throughout the cabin. The results demonstrate that the base frequency of the propellers and their harmonics have the highest noise pressures at the front of the cabin while the other components are high at the rear.