Interior Noise Predictions in the Preliminary Design of the Large Civil Tiltrotor (LCTR2)

摘要

A prediction scheme was established to compute sound pressure levels in the interior of a simplified cabin model ofrnthe second generation Large Civil Tiltrotor (LCTR2) during cruise conditions, while being excited by turbulentrnboundary layer flow over the fuselage, and tiltrotor blade loading and thickness noise. Finite element models of therncabin structure, interior acoustic space, and acoustically absorbent (poro-elastic) materials in the fuselage wererngenerated and combined into a coupled structural-acoustic model. Fluctuating power spectral densities wererncomputed according to the Efimtsov turbulent boundary layer excitation model. Noise associated with the tiltrotorrnblades was predicted in the time domain as fluctuating surface pressures and converted to power spectral densities atrnthe fuselage skin finite element nodes. A hybrid finite element (FE) approach was used to compute the lowrnfrequency acoustic cabin response over the frequency range 6–141 Hz with a 1 Hz bandwidth, and the StatisticalrnEnergy Analysis (SEA) approach was used to predict the interior noise for the 125–8000 Hz one-third octave bands.