Talk:Particle velocity

Does anybody mind if I move this page to Particle velocity and change the content to describe the general case of particle velocity in waves i.e. Not all particles are air molecules and not all waves are sound. But, since it is a good concrete example of particle velocity, I'll put the part that applies to sound in a section of the article titled "Application to Acoustics" or something similar. I might also merge the content of Sound velocity level and Particle velocity level in with this as well, their content is exactly the same and they are relatively short.

Proposed move: Sound particle velocity -> Particle velocity and generalize content.
 * Danny Beardsley 08:05, 16 Nov 2004 (UTC)

Sound particle velocity
The definition in the present article refers to a 'particle (real or imagined).' Can anyone give an example of a wave in which the vibrating 'particles' are real? For sound waves, the particles are described as 'air molecules'. But these are not molecules in the usual physical or chemical sense. In the absence of sound the particle velocity is zero but the molecular velocity certainly is not! The rms molecular speed $$c_m$$ is related to the speed of sound by

$$c_m^2=\frac{3c^2}{\gamma}=\frac{3P}{\rho_o}$$ where c is the speed of sound, P is atmospheric pressure, $$\rho_o$$ is the density of air and $$\gamma$$ is the ratio of the principal specific heats (approx 1.40).

PeterHaughton 08:57, 1 September 2006 (UTC)

Sound particle velocity answer
'Particle' in particle velocity is here defined as a small acoustic volume, the term 'particle velocity' is representing the average speed of this volume due to sound waves. Doekle —Preceding unsigned comment added by 130.89.19.162 (talk) 09:37, 6 May 2008 (UTC)

Changed introduction
I added a paragraph about the fact that particle velocity has nothing to do with molecules, the speed of sound or dust. I copied it from the dissertation of Doekle Yntema and added the reference. Hope you all agree, Jelmer Wind. —Preceding unsigned comment added by 130.89.67.43 (talk) 10:18, 9 October 2008 (UTC)

ISO 80000 standards
ISO 80000 standards recommend using δ for sound particle displacement, not ξ. — Preceding unsigned comment added by 74.71.29.139 (talk) 14:09, 2 August 2015 (UTC)