Author Topic: Traffic Noise Sound Blocking with Plywood.  (Read 10008 times)

Andrew Baker

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Traffic Noise Sound Blocking with Plywood.
« on: September 02, 2005, 11:10:11 PM »
One big Q. Any experts please pitch in.

The scoop: Bought a great house on a busy street. (Topanga Canyon Blvd) The lot is approx 6 feet+  above the street, and the house about 30 feet back from the street.

The front of the lot is very wide, much wider than the living space, which is house and adjacent outdoor room.  

Currently:
Along the front: from ground 6 feet up to lot is riverrock wall.
Along front of lot: standard issue 6ft wood split rail fence that is obviously very porous to sound.

Questions:
1. If I screw 6ft talll sheets of plywood on the back of the fence, flush with the ground, and seal any open seams, will this drop the dBs?
My understanding is I need a material density of at least 200kg/m3. And I think wood, say pine, is about 500.?

The distance from the pavement to the top of the fence would be about 12 feet, and the line of sight to the pavement completely blocked.

I am not freaking out by the noise, it's ok. Just curious if I can make an improvement.

All info/thoughts/recommends apprecaited hugely. And big thanks for this site supersoundproofing. I am definitely gonna call you guys and look into other options as well. -AB

AB

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Re: Traffic Noise Sound Blocking with Plywood.
« Reply #1 on: September 05, 2005, 11:13:20 PM »
 Found the answer to my own question.

PDF:

www.fpl.fs.fed.us/documnts/pdf1996/booth96a.pdf

(on page 4, which is 161 of the document)

Bottom line: Massive study by highway finds that plywood and "glued" plywood both offer the same noise blocking as concrete. And, way easier to construct.

Sweet! Off to get a hammer, nails and some sheets of exterior plywood.

Good luck all.

from the PDF...

...here are significant differences in the estimated insertion losses for the two plywood barriers; the losses for the barrier on I-95 range from 17 to 12 dBA at 3.1m and 7.6m, where the losses for the barrier on I-83 range from 7 to 6 dBA at 3.lm and 7.6m. This is partly due to the differing distance of these two barriers from the roadway the barrier on I-95 was 2.4m from the roadway and the barrier on I-83 was 24.4 meters from the roadway, almost twice the distance for any of the other barriers tested in the program. This, along with clearly observable leaks in the barrier produced the low estimated losses presented in Table 2. However, the I-95 barrier does show losses that fall within the range of the losses for the concrete barriers, except for the transmission loss, which is lower than any of the transmission losses for the concrete barriers. The estimated insertion losses and transmission losses for the glued-laminated barriers are within the range of both the estimated losses for the concrete barriers. The only estimated insertion loss that falls below 10 dBA is for the barrier on I-495 at 15.3m. Because this barrier was very close to the four one-way lanes of I-495, an accurate equivalent source location was difficult to provide, and the sensitivity to the normalization factor is higher for smaller barrier-to-roadway distances. The lower estimated insertion loss for the I-95 barrier at 5.3m may be partly due to the inability to provide an accurate normalization. All of the concrete barriers had much greater roadway to barrier distances (see Table 1). The high value of transmission loss (21 dBA) indicates that the acoustic performance for thisglued laminated barrier is similar to the concrete barriers with estimated transmission losses of 19 to 22 dBA. The post & panel barriers, on the other hand offered the most divergent set of estimated insertion losses. Two reasons can account for the variable results. Background noise masked some of the 1/3 octave band levels for the 1.9 meter high Hutchinson River Parkway barrier, providing incomplete results. At the same time, both of the Hutchinson River Parkway barriers were influenced by high correction factors in the normalization process, since the barrier was low, and the distance from the roadway was large. The attenuation results should, consequently, not be used to make final decisions about post & panel barriers. The only remaining barrier, the one on the Long Island Expressway, had insertion loss values of 18 dBA at 3.1 m, 11 dBA at 7.6 m, and 7 dBA at 15.3 dBA and a transmission loss of 15 dBA. Public Acceptance Selection of Design Types Computer edited images, presented in 35 mm slides, were designed for subjects to make evaluations on the general appearance of the barriers rather than the appearance of specific barrier design types. Thus, the slides presented images that vary in barrier layout and panel orientation rather than finish or detail. Barrier layout considered variations in the plans of the

skip

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Re: Traffic Noise Sound Blocking with Plywood.
« Reply #2 on: September 13, 2005, 11:33:58 PM »
Andrew:



Over the years, it has been our experience that highway and road noise is much like a child blowing a "Soap Bubble". Even though a wall along the highway may stop or impair the sound being made, the sound just expands and goes right up over the wall and then dive bombs into any buildings in its path. To stop highway sound from entering a nearby building, one would have to soundproof-encapsulate the area where one does not want the sound to interfere.

AB

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Re: Traffic Noise Sound Blocking with Plywood.
« Reply #3 on: September 14, 2005, 12:19:30 AM »
 Hey Skip



Thanks for the reply. While I understand the "soap bubble" analogy, click on the link below for a more in depth explaination from a massive government study.



http://www.fhwa.dot.gov/environment/noise/3.htm#3.5.2



(See 3.4 and 3.5)



Bottom line from this study is that depending on both where the receiever is in relation to the road and what frequencies are transmitting from the pavement, high or mid or low, dramatically affects the receiver's drop in decibels from a sound blocking wall. Low decibels refract more while high decibels, like wind noise from spinning tires/wheels, remain on their upward and deflected path. But, the refraction of the low decibels is such that if you're close enough to a wall that is high enough, they still pass over your house/living space.



Which looks to be the case for me.




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Re: Traffic Noise Sound Blocking with Plywood.
« Reply #4 on: September 29, 2005, 10:28:01 PM »
Wood is said to transmit sound 1200 times better than air

BJ
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