Valve noise due to cavitation has frequently posed serious problems with the increase of operating oil pressure. For different electroproportional relief and flow control valves, we have carried out noise tests and numerically simulated oil flows under the assumption of noncavitating conditions in various configurations of the valves by a finite difference method. In addition, we have performed pressure measurements at two locations in a valve chamber, and flow visualization, employing two-dimensional models. By comparing measured and computed results, some design criteria can be set up for low-noise valves.