Causes of pump noise

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Our company’s gear pumps are fed from a vacuum vessel, with the pressure in the feed tank being -0.095 MPa (gauge pressure). The container is located 0.4 m above the pump; the saturated vapor pressure of the liquid fed into it is -0.1 MPa. The flow resistance associated with this liquid is 0.2 m, and its density is 850 kg/m³. Under these operating conditions, the pump generates extremely loud noise – to the point where operators cannot hear each other speaking. The noise level is estimated to be around 90 decibels. In my opinion, cavitation is occurring in the gear pump due to an insufficient installation height. But the chief engineer in charge of consultations said it’s not the case. He told me that for any type of pump, if there is no throttling, then no large pressure difference will be generated, nor will cavitation occur. In most cases, cavitation happens after throttling at the inlet – that is, when the inlet size decreases or when there is a strong gravitational force acting in the opposite direction. Other than these two conditions, cavitation is practically impossible to occur. So, isn’t it necessary to calculate the installation height for gear pumps? What are the prerequisites for the occurrence of cavitation? Thank you for helping as soon as possible