Abstract

In the present effort, a series of experimental investigations was conducted to ascertain noise generation mechanisms involved in 3.5 inch and 5.25 inch disk drives with the ultimate objective to improve the acoustic performance. The acoustic performance of selected samples was characterized in terms of sound pressure and power in a frequency range of up to 8 KHz. The acoustic and structural response of the disk drive were examined using an impact hammer and sinusoidal excitation at the spindle motor. In addition, motor torque characteristics data was collected. A sound intensity measurement technique was employed for the delineation of the acoustic directionality. Two major contributors were identified through the acoustic characterization measurement: (1) broad band noise and (2) prominent discrete tone (PDT). It was shown that the major feature extant in the disk drive acoustic frequency spectrum can be reconstructed from the data obtained from sinusoidal excitation and acoustic response data. Based on the data collected, a series of modifications were evaluated including changes to the spindle motor design, application of dampers, and introduction of vibration isolators. These modifications yielded an acoustic level reduction of 3 to 5dB. Additionally, the parts, process, and operating condition tolerances were found to have a measurable effect on the acoustic performance of disk drive.

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