perform a long or a full seek operation i e to move the head 67 to the outer diameter of the disk 40 this results in a mechanical excitation of the head gimbal assembly which leads to oscillation the amplitude and or angular velocity of the oscillation performed by the head gimbal assembly is measured by means of the laser beam 56 which is directed on the side of slider 53 further a fourier transformation of the measured oscillation is performed and inputted into comparator 57 from the laser measurement system 55 comparator 57 compares the mechanical frequency response curve provided by the laser measurement system 55 to the master frequency response stored in storage 58 in case of a discrepancy between the mechanical frequency response as measured and the master frequency response a required adjustment of the head gimbal assembly is determined and outputted from the comparator 57 to trimming device 59 0041 fig4 shows a master frequency response curve 61 which is stored in storage 58 the master frequency response curve is shown in an x y coordinate system where x is the mechanical oscillation frequency in hz and the y axis shows the angular velocity of the mechanical oscillation the master frequency response curve.