Structural and acoustic noise radiated by CD drives

ABSTRACT Optical drives inside PCs operate at high speed, which may result in significant noise. These drives function both as airborne and structural vibration sources. Three main paths can be distinguished through which noise is emitted to the surroundings: (1) the vibrations of the front of the drive emit noise directly into the far field, (2) the sound waves induced by the vibrations of the faces of the drive inside the enclosure excite the PC enclosure and (3) the structural vibrations of the drive excite the PC enclosure at its mounting points causing the enclosure to radiate sound. The techniques used to determine the contribution of each path are described and preliminary results of an experimental setup are presented in this paper. The contribution of the structural path is determined by comparing the results of a normal setup with the result of a setup for which the structural path is eliminated by mounting the CD-drive on a support that is structurally uncoupled from the PC. Direct measurements of the pressure with a scanning microphone were made. Also, a reconstruction of the pressure field using the Boundary Element Method based on the measured surface velocities of the main radiating surfaces was performed.