Uncertainties in Acoustical Transfer Functions

Pascal Dietrich

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Pascal Dietrich, Uncertainties in Acoustical Transfer Functions (2013), Logos Verlag, Berlin, ISBN: 9783832596057

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Beschreibung / Abstract

Measured transfer functions of acoustic systems are often used to derive single-number parameters. The uncertainty analysis is commonly focused on the derived parameters but not on the transfer function as the primary quantity. This thesis presents an approach to assess the uncertainty contributions in these transfer functions by using analytic models. Uncertainties caused by the measurement method are analyzed with a focus on the underlying signal processing. In particular, the influence of nonlinearities in the acoustic measurement chain are modeled to predict artifacts in the measured signals and hence the calculated acoustic transfer function. Secondly, characterization methods commonly applied in the field of signal processing are linked to the acoustic scenarios and the main influencing parameters. Acoustic parameters are then derived analytically and by means of Monte Carlo simulations considering the uncertainty of these input parameters.

In order to provide airborne applications, analytic models for sound barrier and room acoustic measurements are developed incorporating the directivity and the orientation of the sound source as well as the positions of sources and receivers. The simulated uncertainty contributions are validated by measurements. The same approach is also applied to structure-borne sound applications.

Inhaltsverzeichnis

  • BEGINN
  • 1 Introduction
  • 2 Fundamentals
  • 2.1 Physical and Acoustical Quantities – Conventions
  • 2.2 Basics in Signal Processing
  • 2.3 Parametric Transfer Function Models
  • 2.4 Uncertainty Modeling Techniques
  • 3 Measurement of Acoustic Systems
  • 3.1 Characterization of LTI Systems
  • 3.2 The Acoustic Measurement Chain
  • 3.3 Nonlinear Systems
  • 3.4 Implementation and Emulation of the Measurement Chain
  • 3.5 Dealing with Nonlinear Systems
  • 3.6 Post-processing of Measurement Data
  • 3.7 Application†”Uncertainties in Room Acoustic Parameters
  • 3.8 Summary and Scientific Contribution
  • 4 Uncertainties in Airborne Transfer Paths
  • 4.1 Modeling Sound Sources and Receiver
  • 4.2 Application I†”Reflection Index of Sound Barriers
  • 4.3 Room Modes and Modal Superposition
  • 4.4 Application II†”Microphone Position and Source Orientation
  • 4.5 Measurement of Transfer Functions for Variable Source Directivities
  • 4.6 Application III†”Directivity and Room Acoustic Parameters
  • 4.7 Summary and Scientific Contribution
  • 5 Uncertainties in Structure-borne Transfer Paths
  • 5.1 Remark on Structure-borne Uncertainty Analysis
  • 5.2 Source, Receiver and their Interaction
  • 5.3 TPA Methods in Matrix Notation
  • 5.4 Characterization of Vibration Isolators
  • 5.5 Application I†”Uncertainty in Sensor Position
  • 5.6 Application II†”Modeling of Typical Simplifications
  • 5.7 Summary and Scientific Contribution
  • 6 Conclusion and Outlook
  • A Appendix
  • A.1 The ITA-Toolbox for MATLAB
  • A.2 Rotation of Physical Multipoles
  • A.3 Room Acoustic Parameters and Modal Superposition
  • A.4 Changes in Temperature and Room Transfer Function
  • A.5 Influence of the Size of the Scan Grid
  • A.6 Influence of the Number of Modes
  • A.7 Implementation of OTPA Simulator
  • Bibliography

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