Strangest of questions

Hi there
I'm new here, been a conventional sound engineer for the past 18 years but am now starting to produce experimental sound installations.

I am trying to build a speaker that makes no audible sound...kinda weird concept I know but let me explain.
I want to use infrasonics to move air with little or no audible result. So I,m looking at frequencies below 20hz with a very tight Q to literally just shift air.
Can anyone suggest a design that may be suitable. My current thinking is a closed back long thin tube like affair (albeit square in profile) with an infinite baffle 1/3 of the way along. I'm not a physicist or mathematician so forgive me if this sounds nonsense, in my head it works.

I'd be grateful for any advice other than 'give up now, you're an eejut'

Thanks
Pete

Maybe a rotary infrasonic? That is the fan type. I have never worked with those, as I need a more audible and musical low end, but they operate at ridiculously low frequencies. I can't refer you to a specific product or design, but if you have not researched those, you might want to.

thank you bgrade.
its a thought but i fear the motor would be too noisy.

I suppose it might, but I think the problem with using cone drivers with this would be that all of them I have ever seen have a rising response above your desired point, so you would need to use a lot of processing to eliminate the audible frequencies and the excursion would always be a concern with any power when you are going so low. The calculation of a box that has a pass band that low should not be hard in theory.

I did forget to say that the source tones will be generated in Max/msp which will effectively become my processor.

I.ll build some prototypes and see what happens,

Will report back.
Thanks