Operational transfer path analysis: Practical considerations for selecting sensor positions

Operational transfer path analysis (OTPA) is an alternative to classical transfer path analysis (TPA) as a method used to predict the noise or vibration source and/or path contributions to the response of a system. Both methods are based on the assumption that there is a linear relationship between input (reference) and response positions; however, while the classical TPA mehtod uses a known input force to compute the transfer functions as FRF's, which are then multiplied by a known input force to compute the contributions to the response at the reciever position, the OTPA method uses operational measureable quantities to compute both the transfer functions (in this case transmissibilities) and the response to the receiver. Although OTPA is currently used predominantly for vehicle noise, vibraiton and harshness (NVH) assessment, the method is useful for any noise/vibration assessment where a ranking of the source and/or path contributions at the reciver position(s) is desired, e.g. industrial installations, building HVAC installations, complex machinery and appliances, trains, aircraft, ships, construction equipment. The goal of this paper is to introduce the underlying theory behind the OTPA method, as well as to highlight some practical considerations for selecting sensor positions and the OTPA post-processing. The practical considerations are highlighted through the description of a case study and by recreating the results of the case study via a simple numerical model. © 2017, Canadian Acoustical Association. All rights reserved.