Acoustic emission (AE) has emerged as a reliable technique for detecting wire breaks from stress corrosion cracking (SCC) in prestressed concrete structures. The relationship between mechanical boundary conditions at the fracture location and the characteristics of the AE signal is of significant interest for monitoring applications because the released energy influences the sensor layout design. However, this relationship has not been thoroughly examined to date. This study addressed this gap by conducting controlled tensile tests on individual wire samples. A comprehensive dataset encompassing various wire lengths and stress levels was generated. The wire samples were obtained from a demolished prestressed concrete bridge susceptible to stress corrosion cracking. Following fracture mechanics theories, the findings reveal that higher applied stresses correlate with higher peak-amplitudes and energy of the AE signals. Additionally, the wire length affected AE signal characteristics, with shorter samples exhibiting more significant signal scattering. The influence in intensity was less pronounced, but longer samples showed increased frequency content. No direct superimposition of stress and wire length effects was observed, as these factors appear to act independently, likely due to different impacts on either the wave pressure or the frequency content. These findings form a baseline for transferring results from artificially induced wire breaks, e.g. under a laboratory environment or during material sampling at bridges, to spontaneous events caused by SCC in monitoring applications.