Complex Resonance in Acoustics

A complex spectroscopy principle is extended to the bending vibration analysis. We considered the complex spectrum of attenuated Lamb waves for simply supported rectangular plate. The spectral analysis of real and imaginary parts of the vibration frequency enhances the acoustic spectroscopy as well as in optics. The complex spectrum allows one to distinguish two normal modes with identical frequencies and different attenuation coefficients, besides the resonance curve's width along the imaginary axis could be less than one along the real axis. This method can be applied to the investigation of non-linear interaction of magnetic, electromagnetic and acoustic waves in limited medium. The complex spectral analysis can also be used for non-destructive testing and in seismology.