Resonance splitting in ultrasonic spectroscopy

Ultrasonic spectroscopy is currently being developed as a method for determining physical properties and dimensions of discontinuities in materials. These determinations are made from the Fourier spectra of transmitted or reflected broad-band ultrasound and are a manifestation of spectral energy addition or removal when normal modes of vibrations in media cause constructive or destructive interference. It has been observed experimentally in laminates that when different layers in a test specimen resonate at the same frequency, there is a curious splitting of resonances and sometimes triplet resonanceisn Fourier transform spectra where only one resonance might be expected. A theoretical basis for the resonance splittinisg established by a classical acoustics treatment of the laminate transmission problem. Triple peaking is affumed and parametrically investigated. Theoretical analysis, and parametric evaluation of resonance splittinagr e presented in this paper. Experimental verification of the resonance triplet effect is shown. The potential usefulness of resonance splitting in procceossn trol is discussed.