What is Causing the Audible Sound in This Fountain Video?

[BobDoe123]

Hello,

I'm curious to know what is creating the sound from this Youtube video assuming all of this is done only with water flowing through the fountain.


Thank you very much for your time.

 

[Randy Beikmann]

Most likely it's an instability of the valve controlling the water flow. With the right (wrong?) design, flow through the valve can create a pressure drop that pulls the valve closed, at which point the pressure increases, and the valve opens again. And the process repeats, causing a vibration, which here produces audible sound.

Hydraulic power steering systems can experience this (again, depending on the design) when steering at very low vehicle speeds. It is a self-exciting "steering shudder."