Computation of flow induced sound in DVD drives - Effects of turbulence noise

This paper presents the numerical prediction of airflow-induced sound in digital versatile disk (DVD) drives. Computational fluid dynamics (CFD) is first conducted to evaluate flow field characteristics due to the high-speed disk rotation, and to support the acoustic analysis. Acoustic analogy based on Ffowcs Williams-Hawkings (FW-H) equation is adopted to predict aeroacoustic noise patterns. The integral solution for quadritpole volume source is included to identify the turbulence noise generated inside the DVD tray. The strength of the sound pressure level with respect to rotation speed shows a tendency of increasing thickness noise at a high-disk rotation speed. Nearfield noise is strongly affected by the flow field characteristic, which is caused by the complex shape of the tray. For a midfield, as a result of the combination of three noise sources, different sound noise patterns appear in comparison with those in the near field. Especially the quadrupole noise plays as a counterpart of thickness noise or loading noise depending on rotation speed. Because each of the three source terms in the FW-H equation have physical meanings, their physical basis provide information that can be used when designing quieter devices.