The Atomic Force Microscope (AFM) is a powerful tool for the measurement of forces at the micro/nano scale when calibrated cantilevers are used. Besides many existing calibration techniques, the thermal calibration is one of the simplest and fastest methods for the dynamic characterization of an AFM cantilever. This method is e cient provided that the Brownian motion (thermal noise) is the most important source of excitation during the calibration process. Otherwise, the value of the spring constant is underestimated. This paper investigates noise interference ranges in low sti ness AFM cantilevers taking into account thermal uctuations and acoustic pressures as two main sources of noise. As a result, a preliminary knowledge about the conditions in which thermal uctuations and acoustic pressures have closely the same e ect on the AFM cantilever (noise interference) is provided with both theoretical and experimental arguments. Consequently, beyond the noise interference range, commercial low sti ness AFM cantilevers are calibrated in two ways: using the thermal noise (in a wide temperature range) and acoustic pressures generated by a loudspeaker. We then demonstrate that acoustic noises can also be used for an e cient characterization and calibration of low sti ness AFM cantilevers. The accuracy of the acoustic characterization is evaluated by comparison with results from the thermal calibration.