KSTR
Major Contributor
Velocity field means particle velocity field here, as @René - Acculution.com has already pointed out (IIRC). The complete sound field at a point in space is described by a 3D velocity field vector and a scalar pressure componentBut I am pretty sure that there is no velocity field, and that it is only a pressure field… with the speed of propagation being a constant at any temperature.
And it can be directly measured with a hot wire microphone, besides the indirect method of measuring pressure gradients. The "wind" from the particles in motion removes heat from a hot wire by convection cooling, which in turn can be measured via the resistance change of the wire. Requires very small/thin wires to get to high enough frequecies, though. The technology is more than 100 years old.