System damping for a single mode in resonance is often estimated from a measurement of the bandwidth of the frequency response function. While the bandwidth is customarily measured between the half-power frequencies, it is also possible to choose any other fraction of the maximum amplitude. If the damping is linear, i.e., if the loss factor is independent of amplitude, the same damping will be found with any such choice. While intuition might suggest that the damping of a nonlinear system would be better estimated from a bandwidth taken closer to the maximum amplitude, this is shown to be false.

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Lazan, B. J., 1968, Damping of Materials and Members in Structural Mechanics, Pergamon Press, Oxford, UK, p. 135.
Plunkett, R., 1979, “Measurement of Damping,” Structural Damping, ASME, New York, p. 119.
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