[danbence]

I would like some understanding of what features of turbulence create the noise we can hear at a distance. To simplify, lets pick one frequency in the audible range, say 1000hz. I imagine there are two cases of hearing turbulence.


1) The listener in inside the turbulent stream and is subject to the pressure variation of the turbulence. Inside a vortex, there is a pressure difference between the center of the vortex and the extremities due to the difference in velocity. If a vortex moves past the listener in 1/1000th second, the listener would hear noise at 1000hz


2) The listener is outside of the turbulent stream and a longitudinal sound wave radiates from the turbulent volume. I imagine that a stable vortex produces no sound. With a stable pressure distribution, no sound will radiate out. However, turbulent vortexes have the urge to break up into N smaller vortexes. Is it the rapid division of a vortex in 1/1000th second that radiates sound at 1000hz ?



I can’t find any clear explanation on the web, so would be grateful for any insights.