Noise level estimation in weakly nonlinear slowly time-varying systems

J. Aerts, John Lataire, Rik Pintelon, J.j.j. Dirckx

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Recently, a method using multisine excitation was proposed for estimating the frequency response, the nonlinear distortions and the distrubin noise of weakly nonlinear time-invariant systems. This method has been demonstrated on the measurement of nonlinear distortions in the vibration of acoustically driven systems such as a latex membrane, which is a good example of a time-invariant system. However, not all systems are perfectly time invariant, e.g. biomechanical systems. This time variation can be misinterpreted as an elevated noise floor, and the classical noise estimation method gives a wrong result. Two improved methods to retrieve the correct noise information from the measurements are presented. Both of them make use of multisine excitations. First, it is demonstrated that the improved methods give the same results as the classical noise estimation method when applied to a time-invariant system (high-quality microphone membrane). Next, it is demonstrated that the new methods clearly give an improved estimate of the noise level on time-varying systems. As an application example results for the vibration response of an eardrum are shown.
Original languageEnglish
Number of pages10
JournalMeasurement Science and Technology
Publication statusPublished - 1 Aug 2008


  • Noise
  • time-varying
  • non-stationary
  • multisine
  • nonlinear
  • heterodyne interferometry
  • vibrometry


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