[en] Steady cross-flow over tube-arrays can induce both unsteady forces on tubes and acoustic standing waves. These facts become all the more dangerous for the structures as heavy fluid exchangers are developed (e.g. steam generators for pressurized water reactors) and flow velocities increased, specially with the working safety notion which is above the structural failure problems, particularly for nuclear power units. In addition of the three sorts of vibration (due to flow turbulence, vortex shedding and instabilities phenomena) one can have an excited acoustic standing wave, these phenomena coming together or interacting. In this first step, this study analyses the vortex-shedding phenomena, the excitation of an acoustic standing wave and its locking-in, and the unsteady flow induced forces on the tubes. The paper points out results obtained on thirteen test-rig arrangements (in-line or staggered, with unfinned or finned tubes). The study shows that the risks are more important in arrangements with small spacing ratios: acoustic standing waves occur at lower flow speeds, because of the jump in frequency of the Strouhal frequency; in addition, the shedding vortices being perfectly correlated over the whole array, the flow induced forces on the tubes are more severe. (Auth.)