Research on acoustic noise in hard disk drive spindle motors at Chulalongkorn University

Abstract

This paper aims to give an overview of the on-going research on acoustic noise in fluid dynamic
bearing spindle motors in hard disk drives at the mechanical engineering department, Chulalongkorn University.
The main objective of this research is to seek ways to reduce the level of the spinning motor’s emitted
acoustic noise. Vibro-acoustic investigations on the source of noise and vibration to noise transmission were
carried out. The primary source of noise and the range of frequencies that deemed important to the noise
problem for the hard disk drive spindle motor are identified. The influence of supply waveform from the driver
is then studied. It is found that the noise can be reduced through reducing the electromagnetic source especially
from imperfect supply waveform. In addition, it is known that the motor structure and its resonances affect the
acoustic noise level as the path for vibration transmission. Hence, the structural resonances of the motor and
vibro-acoustic modes are experimentally investigated. If the harmonics composition in the electromagnetic
excitation is close to the structural resonance frequency, it will result in the amplified vibration and hence the
high level of sound at that frequency. Reduction of noise can also be done by shifting the resonances or the
excitation frequency and reducing vibration transmitted to the motor surface.