According to siplab, the equation to calculate wave particle velocity is w = c/f. For the calculation, use v = w*f to figure out the velocity, where w is the wavelength, f is the frequency of the source, c is the constant speed of sound and v is the particle velocity.
The constant c, or the speed of sound, in air, is 3 * 10^8 meters per second. The variable f is based on the cycles per second in a unit of hertz, and this variable can be found in an appendix or other source document.
After you calculate the variable w, which is the wavelength, using the equation c/f, then find the velocity. If, for example, f is 15 megahertz, then w is 20 meters. To then calculate the particle wave velocity, insert the wavelength (20 meters) and the frequency (15 megahertz) to get 300 * 10^6 meters per second.
Fifteen megahertz is actually 15 * 10^6, instead of just 15, as frequency is measured in hertz and not megahertz. A wavelength is calculated in meters not in kilometers. Without interference and under normal conditions, the velocity of a wave particle is equal to the speed of sound constant, 3 * 10^8 meters per second.