The wavenumber-frequency filtering characteristics of compliant layers

Techniques for the measurements of the wavenumber-frequency filtering characteristics of compliant layers mounted on an elastic structure and subject to unsteady pressures were developed. In order to measure the performance of the layer at arbitrary wavenumbers and frequencies, an array of shakers was fabricated and used to generate a standing wave pattern of the input forces where the maximum spectrum levels of the input forces could be concentrated at selected wavenumbers independent of the selected frequency. The wavenumber-frequency admittances of a coated and uncoated beam were measured and used to determine the effectiveness of compliant layers in reducing the vibration response of the beam as a function of wavenumber and frequency. Arrays of thin-film transducers were designed, fabricated, and used to measure the wavenumber-frequency pressure spectra above and below compliant layers. The measured wavenumber-frequency pressure spectra were then used to determine the wavenumber-frequency transmission loss of compliant layers as a function of wavenumber and frequency.