A study of rotorcraft structure-borne noise isolation using empirical component coupling

Control of component excitation generated structure-borne noise transmissio n into a rotorcraft cabin, such as from rotor vibration imbalance, transmis sion excitations or auxiliary equipment induced vibrations, can be studied empirically via accelerance characterization of the system components and a pplication of appropriate component coupling procedures. The present study was aimed at demonstrating the usefulness of such accelerance modeling tech niques as applied to a Bell 206B rotorcraft. Simulated rotor excitations we re applied to the assembled rotorcraft system to provide baseline structure -borne noise transmission data. Thereafter, accelerance tests of the system components were carried out to provide a data base from which system compo nent coupling studies were carried out. Results presented demonstrate the l evel of expected accuracy in predicted structure-borne noise transmission f rom the component coupled model. Compliance was then analytically introduce d at attachments between system components to evaluate the level of expecte d structure-borne noise isolation for a given level of joint compliance.