Hi SG,

there is no doubt that having two panes of unequal thickness does help block unwanted sound from passing thru your windows.

When the two lites are the same they each allow sound at the resonant frequency of the sheet to pass with little propagation loss. This is known as coincident dip.

Having two unequal panes works because they resonate at different frequencies and attenuate the wavelength of the other lite - nice and neat.

There have been questions when dealing with laminated glass if using two unequal panes makes a difference in sound blocking. Everything that I am aware of leans towards the idea that unequal lites in a laminate does not make a significant difference in sound blocking. In laminated glass there is no advantage to using different thickness lites.

However, that really wasn't your question.

Like the question about uneven lites in the laminate, a lot of people have wondered if the three sheets of glass used in a laminated/annealed (heat strengthening or tempering glass does not affect sound performance and neither does adding argon/kryton, despite some claims that they do), should be counted as two offset lites or three of the same.

I don't know, and I don't know anyone who does for certain.

My personal opinion is that if I had the choice I would opt for 1/8" for the two lami lites and 3/16" for the other lite, simply because it can't hurt, so why not.

However, if there was no choice and the three lites were the same thickness I wouldn't worry about it because I don't believe that it would make a significant difference. I suspect that the interlayer in the laminate affects sound wave propagation enough to limit the potential advantage of the offset lites.

I am not convinced that using 3/16" in all three lits might not be a better solution than using 3/16" over the two lami 1/8" lites. In fact, I am going to say that would be my first choice if available.

I know it's contradictory, but really I am simply offering my opinion and I just don't have hard data to back it up. I do believe that in almost all cases as long as you use laminated you will be fine - per glass make-up.

What style windows are you getting? Fixed or casement are good for sound control, gliders and sliders (vertical or horizontal) are not.

And never forget install. if they are installed poorly then everything else that you did is for naught.

Do you have other questions about laminated glass (...anyone has experience with the laminated...)? Or just about laminated and sound performance?

Oberon, thank you for responding. I really appreciate your input. FYI - The Andersen rep and customer
service both tell me that the thickness of their lites is proprietary
information.

Laminated windows are a strain on the budget with a price almost twice that
of standard windows, but it appears that I have no choice if I want to reduce
noise. Would a triple pane window, with
EVEN panes, take the place or even come close to the noise reduction of a
double pane anealed/laminated window?

I am wondering if it is possible to make an educated guess as to the STC/OITC
that I need. Here is my story: My house, built in early 1050s,
is 200-300 feet from a local 4-lane highway.
The hwy has a posted speed limit of 40 MPH (plenty of cars go 50 MPH)
and has lights which slow traffic down.
There are bushes between us, and a neighbor's house partially
blocks the hwy side. My windows are the originals and they do a minimally acceptable job of blocking the traffic noise
from my sensitive ears. Most of the
windows are wood, double hung, single pane, covered by storm windows that are
closed all year. The den, which is the
most exposed room, has a wall of single pane casement windows in steel frames. Each sash is a steel frame/grill that divides the
glass into individual rectangles of approx 10" x 12". The den casements are painted shut and covered
by storm windows all year. In the winter,
there is a draft coming through and they are often wet from
condensation. As part of a major home renovation, I am replacing all the
original windows with casements and would like to reduce the noise more. Can you take an educated guess as to a minimum
STC/OITC rating that I should look for?

I am considering Anderson 400 Series or A series casements, and using the
laminated windows in the more sensitive rooms - den and master bedroom. I am leaning strongly toward the A Series for
two reasons: 1) The STC/OITC ratings of the A Series standard IGU are 27/23 vs the 400 Series 26/22. The ratings of the A Series .060 lami is
33/29 vs the 400 Series 31/27. 2) I visited
my neighbor’s house and stood in front of his standard 400 Series casements
to get a “feel” for the noise reduction and, while I did not pick up individual
car noise, there was a non-stop whirring sound. I
visited a friend who lives further down the same highway to get a feel
for his 400 Series casements. The same
whirring sound. There was once a discussion in this forum about an increase of sound in windows with equal
lites. See http://ths.gardenweb.com/discussions/2586644/noisy-andersen-windows. I suspect that my friends are having
exactly this problem. I am hoping that the A Series, with a different
construction and a higher STC/OITC rating, will provide better noise reduction and
no whirring.

Oberon, other readers, please share your thoughts and experiences. Thank you.

Call Andersen directly and ask for someone in the engineering department. There is nothing "proprietary" about their STC glass. You can ask for the NFRC CPD number and that should be able to tell you what the glass is like as well. That is horse hockey that they fed you.

What window glass did your friends opt for? Low frequency ranges are tough to get out so that whoosh noise is some of the last to go.

I am wondering if in this case "proprietary" may be a euphemism for "I don't know and I am not going to ask"?

In any case, triple pane isn't necessarily an improvement over dual pane (without laminated). With the same glass thickness, provided the combined airspace width of the triple is the same as the airspace between the two lites of the dual, sound attenuation is going to be pretty much the same.

Unless you have noise data, trying to estimate required STC/OITC is not going to be a winning proposition.

Thank you Oberon and WOW for responding. See the following link. Andersen really does not provide the pane thickness. A person in the escalation team at Andersen said that she is almost sure that the panes are unequal. But she could not back it up with anything in writing. Please copy and paste this link. Hopefully it will work. If not, tell me and I will try something else. Thank you. http://help.andersenwindows.com/system/selfservice.controller?CONFIGURATION=1000&PARTITION_ID=1&USERTYPE=1&CMD=VIEW_ARTICLE&ARTICLE_ID=11145