inglés al español Ciencias Ingeniería (general) Acoustics

Rayleigh derived an asymptotic formula for the number of characteristic frequencies or eigentones, N, up to a given frequency, , and the derivative form which gives the number of eigentones in the range to +d. This dN form was applied successfully to quantum radiation laws. In acoustic terminology the equations are: N = (4V/3c3)3 and: dN = (4V/c3)2 d where V is the volume of the room and c is the velocity of sound. It is shown that these simple formulae do not apply accurately to sound waves, especially in small rooms and at low frequencies. The discrepancy is attributable to the comparatively small number of eigentones involved, compared to the number of characteristic frequencies usually concerned in the case of electromagnetic radiation. More accurate expressions have been derived, for a rectangular room, from a consideration of the density of characteristic points in frequency space.