  Usual modal analysis techniques are based on the Fourier transform. Due to
the Delta T . Delta f limitation, they perform poorly when the modal overlap mu
exceeds 30%. A technique based on a high-resolution analysis algorithm and an
order-detection method is presented here, with the aim of filling the gap
between the low- and the high-frequency domains (30%<mu<100%). A pseudo-impulse
force is applied at points of interests of a structure and the response is
measured at a given point. For each pair of measurements, the impulse response
of the structure is retrieved by deconvolving the pseudo-impulse force and
filtering the response with the result. Following conditioning treatments, the
reconstructed impulse response is analysed in different frequency-bands. In
each frequency-band, the number of modes is evaluated, the frequencies and
damping factors are estimated, and the complex amplitudes are finally
extracted. As examples of application, the separation of the twin modes of a
square plate and the partial modal analyses of aluminium plates up to a modal
overlap of 70% are presented. Results measured with this new method and those
calculated with an improved Rayleigh method match closely.
