Abstract: A method for controlling the abrasive machining, especially abrasive flow machining of a part which includes measuring any acoustic emission signal caused by the abrasive machining of such part; thereafter comparing a high frequency, e.g. greater than 100 kHz, component of said signal with a low frequency, e.g. less than 100 kHz, component of said signal to generate a control ratio. When the control ratio reaches a predetermined ratio, or predetermined change in the ratio over time, a control action of the machining process is effected, such as termination of the flow of abrasive.