A method of estimating natural frequencies and damping ratios from noisy impulse responses is considered. Parameter evaluations are carried out, in the time domain, from the instantaneous envelope and the total phase, which can be derived from the complex signal formed by the autocorrelation function and its Hilbert transform. This approach enables modal parameter estimates to be obtained with acceptable errors even when the level of the random noise, added to the impulse response, is very high.

by ASL