In the modern engine of both small and large size, the acoustic emission is a very important matter increasingly studied as per specific international standards.This paper presents the study of the acoustic emission of a hydraulic rotary oil pump by means of measurement techniques and numerical approaches. This activity aims at showing a complete test-case in which both methods are used to face a noise issue and highlighting also the “weight” of the hydraulic excitation in both cases. In particular, an oil pump has been completely characterized on a test bench to verify the hydraulic performances and the noise radiation. A structural modification has been suggested with the target of altering the noise spectrum of the pump, achieving an optimization of the noise generation. From this assumption, experimental and numerical activities have started in parallel. Measurements have been carried out by means of the intensimetric method and supported also by conventional acquisitions performed with hydraulic pressure transducers, accelerometers and microphones. The numerical model is the result of the interaction of a high sample frequency Computational Fluid Dynamic (CFD) simulation and a modal analysis that has been previously correlated with some experimental tests.The same numerical and experimental methodology, has confirmed that the sound spectrum reduces the noise emission following the same trend, increasing the accuracy of the CFD input pressure signal.In this way, our work presents a combined methodology to face the acoustic issue generated by a Volumetric Vane Oil Pump (VVOP). Fluid-dynamic and structural aspects are treated from both numerical and experimental sides; in particular the hydraulic excitation, in terms of fluid dynamic load, has been studied inside the test bench (the experimental fluid dynamic) and improved inside the pump volume (the calculated fluid dynamic). The forcing load and the structural properties have been completely characterized and combined together by means of tests and calculation to obtain the level of sound power emitted from the source.