This work contributes to the overall goal of identifying and reducing noise sources and propagation in hydraulic systems. This is a general problem and a primary design concern for all fluid power applications. The need for new methods for identification of noise sources and transmission is evident in order to direct future modeling and experimental efforts aimed at reducing noise emissions of current fluid power machines. In this paper, this goal is accomplished through the formulation of noise functions used to identify contributions and transfer paths from different components of the system.An experimental method for noise transfer path analysis was developed and tested on a simple hydraulic system composed of a reference external gear pump, attached lines, and loading valve. Pressure oscillations in the working fluid are measured at the outlet of the pump. Surface vibrations are measured at multiple locations on the pump and connected system. Finally, the radiated air-borne noise is measured at a fixed distance from the pump. A post-processing algorithm was developed to identify key frequency features present in each domain as well as the transmission between different physical domains. The main outcomes of this research consists of a method to separate the contributions of fluid-borne noise or structure-borne noise to the overall air-borne noise emissions of the unit or system. The method has general applicability to many different fields, and results allow for separation of the different noise contributions and better understanding of the overall noise emissions.