why not just use soapy water to find the leak?

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A member of the PI-100 Club:
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On Tue, 29 Jun 1999, Graeme Smith wrote:

> Now this might seem low tech....
>
> But air leaks are high frequency noise.
>
> add to this the fact that they tend to be fairly localized, and the answer
> turns out to be a long tube not too dissimilar to a straw...
>
> Kind a reminds me of ballancing two venturi carbs....
>
> You feed the microphone into the straw, blocking side noise, to create
> a sort of directional pickup. Then you monitor loudness of high frequency
> noise components.... (High pass filter?) as volume increases, led scale
> advances...
>
> The neat thing about this is you can set the zero point to near to a place
> that doesn't leak, and then trace the seals etc, with the sensor tip, and
> actually pick out the place where the seal is leaking. Not only that, but
> it saves on thickening of eardrums because you are not exposing the
> workers ears to focussed high frequency sound.
>
> Getting the sensitivity/frequency cut-offs will require some work, but
> then, I don't get any money for the idea....;)
>
>                                 Grey
>
> GRAEME SMITH                         email: grysmith@freenet.edmonton.ab.ca
> YMCA Edmonton
>
> Address has changed with little warning!
> (I moved across the hall! :) )
>
> Email will remain constant... at least for now.
>
>
> On Tue, 29 Jun 1999, Roger, in Bangkok wrote:
>
> > I have a customer having problems with vacuum leaks (-50 kpa or so
> > range) in equipment that they manufacture.  I expect their
> > problem is with connectors and seals, and they have asked for help to
> > locate and correct the problem.  Seems simple enough to sniff around
> > with a tiny microphone.
> >
> > Thought...why not develop a simple handheld field
> > tester...PIC...active filtering...LED bargraph...etc
> >
> > Unknowns...are there audio signatures that would allow this...has it
> > already been cheaply and efficiently done...
> >
> > Appreciate any input.
> >
> > Regards/Roger, in Bangkok
> > Roger N. Shane
> > Suncolor Co., Ltd.
> > P.O. Box 11-303
> > Prakanong, Bangkok 10110
> > Thailand
> > Email:  roger@wnet.net.th
> > FAX:    +1 (707) 276-1170
> >         +66 (2) 291-3826
> > ICQ     2152164
> >
> > SAHA GROUP...Thailand's Best!
> >
>