Analysis: Origin, and Prevention of Whistles

To create a whistle there appear four principles that all need to be fullfilled to create a whistle (for the insiders; they all have a strengtened Reynolds vortex shedding). Only whistles (> 500Hz, no humming) are taken into account.

laminar flow

area, surroundings

amplify

repetition

multiple regular vortex sheddings

slits, cavities, sharp edges

audible

air velocity

whistle risk

To create a whistle all 4 of these principles are needed. Taking away one of the four principles results in the disappearance of the whistle. A principle is taken away (or avoided) by one of the following changes:

changing the facing direction
roughing the surface
irregular repetition
disturbing the up- or downstream
increasing the slit or bar diameter

More information is available in the background information page.