Correlation study and control of mechanical vibration and psychoacoustic parameters in hard disk drive

Abstract

The sound quality of 2.5-inch Hard Disk Drives (HDD) has received an interest in the industry. However, the quantification of human feelings of HDD noise annoyance has rarely been studied. A social survey was conducted to determine how annoying an HDD noise affects people. Jury Test 1 was used to examine the four main classes of annoying HDD noise on the psychoacoustic parameters using multiple regression analysis. The result shows that the Roughness has a significant effect on the annoyance level. The Jury Test 2 using BradleyTerry-Luce model on the proposed subjective sound paired-comparison was performed on thirteen different sounds (from different HDD showing the four main classes of annoying HDD noise) to quantify the degree of HDD noise annoyance level on sound pressure level and the psychoacoustic parameters for young and old age groups. However, the noise from HDD mainly comes from its components such as spindle motor, voice coil motor, and other mechanical components enclosed in a small aluminum mechanical casing. Performing noise control on such a small complex system has been a challenge. The conventional approach of using frequency analysis is not sufficient to identify the noise source from the HDD. In this thesis, a detailed mathematical formulation and a noise source identification were demonstrated. The near field experimental results indicated that near-field acoustic holography is an excellent way to identify noise location, amplitude and frequency content of the HDD. Moreover, using near field velocity, the far field sound pressure can be computed. The computed value is well agreeable with the measured far field sound pressure level.