Abstract: An acoustic emission technique and apparatus that determines the take-off velocity of a slider based upon a quantitative measurement of slider velocity without internal access to the file. The system includes a vibration detector for detecting contact energy, and for producing an output signal; and a logic circuit coupled to the vibration detector, for processing the output signal from the vibration detector to identify a slider take-off velocity. The slider take-off velocity is derived by multiplying lambda by the characteristic frequency, where lambda is the spacing between bumps in a circumferential direction. The output signal of the vibration detector disappears when the slider clears the landing zone. The vibration detector is attached to the actuator screw or other vibration transfer features accessible from outside the disk drive.