Author Topic: Exterior Polycarbonate Wall - Good for blocking traffic noise?  (Read 1981 times)

millhouse

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Exterior Polycarbonate Wall - Good for blocking traffic noise?
« on: October 14, 2015, 08:39:09 PM »
I have an atrium within my house that has an existing exterior wall that faces a highway.  I am contemplating adding an 8' X 10' polycarbonate wall, on top of the existing wall that already stands 7 feet high (new total height of 15 feet).  The new wall will completely fill the existing space, however the atrium will still be exposed from above (i.e. open air). 

Has anyone had any experience using this material to block sound?  The construction costs are not cheap and I am not sure if the investment will pay off in noise reduction.

The polycarbonate panels are triple wall and 16mm thick.  Additionally, the frame that the panels will attach to will be built with wood studs that are sleeved with aluminum.     

Randy S

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Re: Exterior Polycarbonate Wall - Good for blocking traffic noise?
« Reply #1 on: October 15, 2015, 04:23:54 PM »
Because the top is left open the value of anything you do falls back to diffracted path and shadow zones.
So any value given to the mass of the wall will be greatly reduced due to the sound going over the wall.

In this scenario no one can give you the FSTC Rating for this type of build... Normally for exterior sound walls my experience is around 3-5 decibel change depending on distance to source.

Randy S.


Randy Sieg

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millhouse

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Re: Exterior Polycarbonate Wall - Good for blocking traffic noise?
« Reply #2 on: October 15, 2015, 05:34:39 PM »
Because the top is left open the value of anything you do falls back to diffracted path and shadow zones.
So any value given to the mass of the wall will be greatly reduced due to the sound going over the wall.

In this scenario no one can give you the FSTC Rating for this type of build... Normally for exterior sound walls my experience is around 3-5 decibel change depending on distance to source.

Randy S.

Randy - Thank you for your reply. 

I am getting a little tripped up on your first 2 statements.  To clarify it sounds like the wall will help diffract some sound and create a shadow zone.  However, the thickness of the wall is less of a concern due to the height and the fact that it will still be open aired?

One other thing I noticed is that the decibel rating in the atrium (55 - 58 DBA) compared to the same point on the opposite side of my house (side yard) is around 5 - 7 DBA less.  They are both the same distance to the highway.  Do you think the slope of my roof (see attachment) is causing the noise to be pushed down into the atrium?

Attached are a few screen grabs I took from google earth that highlight the distance to the highway (164 feet), atrium location, and slope of roof.  The proposed wall would almost reach the height of the highest point of the roof line.   

 


Randy S

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Re: Exterior Polycarbonate Wall - Good for blocking traffic noise?
« Reply #3 on: October 15, 2015, 06:14:53 PM »
This is correct, the height of the wall will dictate the shadow zone.
Now based on the screen shots you might have a better chance then most to get good results.

If you can get the wall up past the slope you might be able to shoot the sound over the open top depending on how wide the opening is, if that is the case then the mass of the wall now comes into play.

You could even do a 30* or 45* at the top of the wall to assist in increasing the zone.

From the screen shots it appears to be difficult to get line of sight to determine the needed height to increase the shadow zone.

The difference in Decibel readings most likely due to sound reflecting in the atrium where the side yard sound is not bouncing back from other walls...free path in the side yard, I did not see a wall there.


Randy S.



Randy Sieg

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888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

millhouse

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Re: Exterior Polycarbonate Wall - Good for blocking traffic noise?
« Reply #4 on: October 15, 2015, 06:32:40 PM »
Thanks again for the quick reply - this is promising to hear. 

What exactly do you mean by a 30* or 45*?  That is something that google provided no help with, so I assume its acoustic/construction speak?

I think I might be able to get the wall higher, but I would have to speak with the contractor that is getting the polycarbonate and building the frame.  I assume its possible, just more cost.   

You are correct that there is no wall on the side wall, so your theory about the sound reflecting in the atrium makes perfect sense.   

Randy S

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Re: Exterior Polycarbonate Wall - Good for blocking traffic noise?
« Reply #5 on: October 15, 2015, 06:39:06 PM »
Yes you can angle the top of the wall toward the sound source 30 degrees or 45 degrees to cause the sound to bounce back to source, Which widens the zone.
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040