Acoustic emissions (AE) induced by electric fields have been investigated on Rochelle salt single crystal in the temperature range 240K-310K under uni-axial pressuresup to10.5 MPa. Square shaped samples (45°X-cut) are used for measurement. The uni-axial pressure and the electric field are applied along the direction to make an angle of 45°to the c-axis in the a-plane and along the polar a-axis, respectively. As the pressure increases, the AE signal due to domain reorientation disappears while it due to piezoelectric deformation increases its intensity at around the phase transition temperatures. Some discussions are made about the generation mechanism of these AE signals.