| F.P. Mechel, Formulas of Acoustics, Berlin 2002
Chapter S, Nonlinear Acoustics by O.V. Rudenko:
"The strength of an acoustic field can be characterised by an acoustic Mach number:
M= v/c0 = d1/d0 = p1/p0 [we really need a formula editor, d is actually ro]
Parameters of the equlibirum state of the medium are: c0 = adiabatic sound speed, d0 = density and p0 = c0²ro0 = internal static pressure. The acoustic wave leads to variations of density d1 = d - d0 and and pressure p1 = p - p0, as well as to the appearance of nonzero particle velocity v. The limit M -> 0 corresponds to linear acoustics. Nonlinear acoustics deals with small, but finite values of M."
So Ethan is right, non-linear acoustics happen at M >> 0. Not the situation we deal with in normal rooms. |