Structure-borne noise transmission in the propfan test assessment aircraft

Abstract

Estimates of the level of structure-bor ne noise transmission in the Propfan Test Assessment (PTA) aircraft were carried out for the first three blade passage frequencies. The procedure used combined the frequency response functions of cabin sound pressure level to wing strain response obtained during ground test of the PTA aircraft with in-flight measured wing strain response data. The estimated structure-borne noise levels varied from 64 to 84 dB showing very little dependence on engine/propel ler power, flight altitude, or flight Mach number. In general, the bare cabin in-flight noise levels decreased with increasing propeller tone frequency, giving rise to a plausible structure-borne noise transmission problem at the higher frequency blade passage tones. Without knowledge of the effects of a high insertion loss sidewall treatment on structure-bor ne noise transmission of the bare cabin no quantitative conclusions could be made on the level of structure-borne noise transmission in a treated production aircraft.