Operational transfer path analysis: Comparison with conventional methods

Abstract

Transfer Path Analysis describes how sound and vibration propagates through complex structures. The correct determination of transfer coefficients between sources and receivers is essential for a high quality analysis. Conventional methods use artificial excitations (forces or volume velocities) to evaluate transfer functions. Therefore, they do not consider the influence of different load conditions on the transfer function behaviour of complex structures. In a second step, operational data (vibrations or sound pressures) are applied to the transfer functions to calculate the different path contributions. In order to overcome these restrictions, transfer coefficients can be evaluated directly from operational data. Thus, the actual load conditions are taken into account and the quality of transfer characteristics is improved. The relation between simultaneously measured data of sources and receivers can be derived by statistical methods. Principal Component Analysis is used to separate the total signal into individual path contributions, while operating on airborne and structure-borne contributions simultaneously. Operating in the time-domain gives direct access to auralisation and in-depth analysis of dominant path contributions. This new single-step approach has been proven to generate more precise analysis results within a much shorter testing time.

Time-domain two-substructure transfer path analysis of transient dynamic response in mechanical systems with weak nonlinear couplings

“…(13) and (14), represents the convolution as described earlier, m is the response coordinate and n corresponds to the excitation coordi- nate. Note that the impulse response function h͑t͒ is analogous to the frequency domain transfer function H͑͒ but operates in time domain.…”

“…The analysis of vibration energy transmission also yields results of controlling parameters, components and structural paths that can be treated to alleviate the response. Over the last two decades, a variety of TPA approaches has been developed to improve the automotive structure design and NVH performances [5][6][7][8][9][10][11][12][13] . However, those current TPA approaches that are performed in frequency domain inherently assume that the system behaves linearly.…”

Contribution analysis of vehicle exterior noise with operational transfer path analysis

“…constant speed measurements with varying load, can also be used for the transfer function estimation. However, it is important for the OTPA to cover all operating conditions of interest, which has been shown by Lohrmann (2008) and Putner et al (2012).…”

Obtaining method of high contributing whole body principal component mode by separated measurements

“…For carrying out effective countermeasure to vehicle interior noise, finding out the contribution of each sound or vibration source and part to the interior noise and measuring the part intensively is essential. Transfer path analysis (TPA) has been proposed to obtain the contribution quantitatively and several methods were developed until now (Plunt, 1998;Noumura, 2006;Brandl, 2008;Lohrmann, 2008;Klerk, D., 2010;Putner, 2012). Operational TPA (OTPA) is one of the methods recently developed and the method calculates the contribution using only the sound and vibration signals at the operational condition (Noumura, 2006;Lohrmann, 2008;Klerk, D., 2010;Putner, 2012).…”