## 5pSA4. Methods of isolation of modal resonances (a review).

### Session: Friday Afternoon, May 17

### Time: 2:50

**Author: Naum Veksler**

**Location: Inst. of Cybernetics, Akadeemia 21, EE-0026 Tallinn, Estonia**

**Author: Jean-Mark Conoir**

**Author: Jean-Louis Izbicki**

**Author: Pascal Rembert**

**Location: Univ. Havre, 76610 Le Havre, France**

**Abstract:**

The analytical methods of isolation and description of the resonance
components of partial modes in scattering problems of acoustic, elastic, and
electromagnetic waves are set forth. The results of these methods' applications
are presented and their effectiveness is discussed. For some particular cases
the exactness of the results obtained can be estimated as well. The following
methods are considered: gradient of the phase, utilization of impedance type
intermediate backgrounds, Argand diagram method, and pole evaluation on the
frequency complex plane for a fixed mode order. The methods can be even used for
rather complicated situations: for very narrow and rather broad resonances, near
the point of intersection of the dispersion curves of phase velocities, and for
very close situated resonances. The illustrative examples are given for the
problems of scattering of bodies of spherical and cylindrical shape. The
resonances are isolated for waves of different physical nature: diffracted
(Franz type), normal (Lamb type), shear, Rayleigh type, and whispering gallery.
With the properly computed modal resonances one can immediately obtain the
dispersion curves of the phase and group velocities of every wave, and construct
the acoustic spectrogram of the scatterer. Jointly with the well-known
experimental methods, the described ones form the basis for ultrasonic
spectroscopy.

from ASA 131st Meeting, Indianapolis, May 1996