VO-BB - 20 YEARS OLD!

[tackerman]

We're looking at a house with a finished basement and an 6 X 8 room that would be perfect for a booth. Problem is there is a radon mitigation system in the utility room and a low level hum is detectable from the blower.
Any advice from the audio pros here on a good way to deaden that room and cut the hum? Since soundproofing/deadening material is so expensive I'm wondering if I throw another thin layer of sheetrock on the walls before soundproofing if this would help.

[todd ellis]

not an expert - but if you're going to throw up another wall - add a few more 2x4s and create an air space between, failing that ... how bad could radon REALLY be???
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[tackerman]

LOL, I was looking for a toggle switch on the blower then realized that forgetting to turn it back on might be a bit of an issue.

[Frank F]

In a last ditch effort, move the detector. Or depending upon whether the hum is electrical (i.e.: in the wires) where one could get isolation transformers and put eh detector ion a different unique circuit or a buzz from the components... you might isolate the detector from the wall (rubber mouse mat or similar product between the wall/detector coupling), build a new all with with de-coupling materials to separate and isolate the "studio room wall from other components of the house, or check the actual detector unit to see if it is faulty and replace or repair as needed.

Good luck.

Frank F
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[Gp]

If it's fan noise, build a box around it. Like a soffit so that it goes the whole length of the room. Or even build it on an angle spanning the wall and ceiling. Would even help acoustics in the room that way. You can make a door in it to get to the radon detector if you need to.
You'll want to cut some slits in the structure so the air has an escape. This idea would work whether it was electical or fan hum I would think.
You can even line the structure with some insulation like they use in the heat duct stuff...maybe even build it out of that heat duct stuff?

Hope that helps some.

I am no expert either, nor have I played one on radio or tv. I did sleep at a Holiday Inn once though...but that was years ago.

[georgethetech]

Is it structure or airborn noise from the fan?
Does it vibrate the wall or do you hear the rushing of the air through the vent?
They are different problems with unique solutions.
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[Mike Sommer]

You say it's coming from the blower?? So is the blow in the same room or
in the attic? And because you can hear it I'll venture to guess they used
4" PVC or ABS pipe. Pictures will help a great deal here!
I will assume you have something like this:
http://www.indoor-air-health-advisor.com/radon-mitigation-system-photos.html

If the blower is in the basement, move it outside or to the attic. Then
replace the plastic pipe in the basement in the room with cast iron piping.
Plastic pipe will resonate like you would not believe.

The next trick is to build a chase wall ( this is a soffit wall that is vertical)
around the tube with inside dimensions 16X16" -24X24" would be better -
floor to ceiling. I would build it with steel stud, filling the space with 703
and cover it with 5/8" drywall, then cover that with lead sheeting and
another layer of 5/8 drywall. Caulk the top and bottom seams with Green Glue Acoustic Caulk.

That should kill any hum resonating from the tube.
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Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong.

[tackerman]

Wow, thanks for the advice folks!

Yes, it is in a utility room in the basement and constructed from PVC. I never realized how much noise those things make, I'm planning on going back for another look with pics.

[Ed Gambill]

I would approach this problem in another manner. I would turn the fan off with a timer circuit.

I found this timer module on line http://www.cablegiant.com/Default.aspx?p_id=4&Product_id=1064&utm_campaign=GBase&utm_medium=GBase&utm_source=GBase&utm_content=1&source=googlebase

I would purchase a timer module similar to the one displayed. I would use the module to turn off the fan. At the end of a predetermined time say 15 min- 60min the timer would turn the fan back on.

A fail safe can be had by using another timer module to trigger a sounder device like a back up alarm used in autos and trucks in the event the first module fails to turn the fan on again.

Some years ago I built 20 modules to restart DVD players in a hotel installation that played traveler/visitor information. They were 555 ICs with some switching circuit.

Disclaimer: This is what I would do for myself. I do not purpose or suggest that any one employ this method with out first consulting with there electrical advisor.
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[Mike Sommer]

Moving the blower up or out and replacing the section of PVC pipe in the room with cast iron and rubber boot unions should kill the hum.

Building the chase wall is the next and last resort.

Turning off the blower for intermittent periods of time would greatly reduce
the system's efficiency; since it is working on the position of a continues vacuum.
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Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong.

[Ed Gambill]

Mike

I suspect you know that difference between empirical and theoretical statements. And as previously stated I do appreciate you acumen regarding sound.

This reply is not to cause an argument but to discuss respectfully the potential for other operation scenarios for a Radon Extraction System. In fact when proffering my own idea for noise abatement I had not given much thought to how intermittent operation or cessation of the fan rotation would affect the overall operation of the extraction system.

On first blush your statement on continues negative pressure in the substrate of the floor in question seems very accurate; it caused me to want to know more. My key word search was “intermittent fan radon system” and it reported this PFD http://arcas.nuclear.ntua.gr/apache2-default/erricca/erricca2/Topic_4/CS_GS/ERSD_gs_CZ_005.pdf from the NATIONAL TECHNICAL UNIVERSITY OF ATHENS Nuclear Engineering Section. I would like to know what information is available from ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) on this point as well.

Looking at page 3 of the aforesaid F, near the bottom there is a paragraph regarding system enhancement. In this case the intermittent operation of the fan in the extraction system was put forth as an enhancement to the system. As I read this statement it appears that continues negative pressure is not an absolute in the proper operation of an extraction system.

This implies that there may be the opportunity to manually discontinue the fan operation from time to time with out negatively impacting the successful operation of the system.

Granted a means to properly monitor the Radon level in the living space would be a best practice to insure that occasional disruption of the negative pressure in the substrate would not abrogate the totality of the system.

After doing a cost comparative, I might go with the interruption of the fan method. I have not yet taken the time to cost the cast iron pipe alteration or building a barrier wall. Nor am I sure that there would be an equal noise reduction compared with cutting off the fan.

Ed Gambill

PS My back ground in these matters include, commercial and residential construction, emergency tunnel ventilation fan construction-testing & maintenance (not a member of ASHRAE).



S This post is for discussion purposes only and not to be considers or construed as a basis in fact for any alteration, adjustment, or modification to any established Radon Abatement &Extraction System. Always consult a certified technician before making any change, alteration or adjustment to your Radon Abatement & Extraction System.
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[Bruce]

I'm not a radon expert, but I've done a commercial for a radon abatement company! Really. I'm also a bit of a science nut and here's what I'm thinking on radon...

Radon is a gas that seeps up from the ground in very small quantities. The amount leaking into the atmosphere where you live is clearly not dangerous when standing, working or playing outside or they wouldn't allow you to even be there, let alone build a house. A house does however trap the gas and over a period of time it can accumulate to possibly unhealthful levels, but this is something that takes days or even weeks to reach those levels. It also takes years of exposure to see any possible health effects. Shutting off the fan for a few hours here and there seems quite logical and inexpensive. Just be sure to have a failsafe way to turn the fan back on, or remind yourself to do so, when you're through.

B
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VO-BB Member #31 Enlisted June, 2005

I'm not a Zoo, but over the years I've played one on radio/TV. .

[Hart]

[Mike Sommer]

Wonderful information Ed, based on your research a timer indeed would be the preferable solution.
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The Blog:
http://voiceoveraudio.blogspot.com/

Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong.

[Living Culture]