The general problems of AE sensors are overviewed. The effects of mounting conditions of sensors on the sensitivity are discussed. then the sensitivity measurement methods are compared. The results of a sensor's sensitivity, obtained by NBS and by the Hatano method show that there is very little difference between them.

The convenient calibration method for sensor sensitivities, especially the “acoustic pressure method” and the “pencil lead fracture method” are discuss ed. The characteristics of lead, specially standard pencil lead from JAEWG which produce very stable reproducible AE signals, was demonstrated. The characteristics of the lead is quite similar to the lead produced in 1975. Then sensor sensitivities were obtained by the standard lead and are compared with the results of the reciprocal method.