in very general terms acoustic emission (AEs) signals are generated by the spontaneous release of stored strain energy in the form of transient elastic waves. In other words AEs are pulses with a defined amplitude in a broad frequency range (from kHz to GHz). As a consequence amplitude of AEs can be expressed in terms of displacement, velocity or acceleration.
In first analysis and with the due caution, if force measurements are available, you can estimate the acceleration of your acoustic emission signals (rms or peak, it depends on force measurement you have) simply from a=F/m, where m is the mass of your tested object.