Basketballs as spherical acoustic cavities

The sound field resulting from striking a basketball is found to be rich in frequency content, with over 50 partials in the frequency range of 0–12 kHz. The frequencies are found to closely match theoretical expectations for standing wave patterns inside a spherical cavity. Because of the degenerate nature of the mode shapes, explicit identification of the modes is not possible without internal investigation with a microphone probe. A basketball proves to be an interesting application of a boundary value problem involving spherical coordinates.