Analytical formulations for annular disk sound radiation using structural modes

Sound radiation characteristics of an annular disk with application to the computer disk are examined analytically. The far‐field and the radiation impedance approaches are employed to calculate radiated sound of a disk vibrating at its elastic or rigid body modes. Modal sound power is formulated by approximating the structural modal functions and is expressed in terms of a power series of the wave number. Predictions show that axisymmetric vibration modes are more efficient radiators compared to those asymmetric disk modes that have the same number of nodal circles. Numerical results obtained by a boundary element program are used to support analytical predictions. Formulations are also extended to include the modal coupling and source rotation effects. The effect of coupling between disk vibration modes on the radiated sound is found to be significant if multimodes are excited. A simple empirical equation has been developed to predict the modal sound radiation efficiency of a rotating disk for selected ...