Air Rush Howling Noise

[8911101]

Hello,

Has anyone known the air rush noise caused by Helholtz resonator? I have a resonator (500Hz) closed to inlet opening. The chassis dyno testing shows that We are getting quite an adverse affect from the 500 Hz resonator. The thing howls. We don't see it in white-noise tests (no air flow) - only when air is rushing over it.

Do you have any ideas as to why exactly this happens and how to alleviate it?

Thanks,

LL

 

[GregLocock]

You are blowing air over a sidebranch. You are generating turbulence at the lip of the tube.

Radius the lip of the tube.

Mount the resonator away from the maximum stream velocity. Cheers

Greg Locock

 

[Rob45]

Or change the angle of the Helmholtz opening with respect to the flow.
Angling it into the flow stream, you might well find you've improved the effectiveness as well.
(PS: 500 Hz is a rather high frequency to be using a Helmholtz tuner for air intake, don't you think? Might you not have better results using some form of broad-band attenuator?)