Sound Deading?

Old 06-11-08, 07:45 PM
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Sound Deading?

Am just about ready to buy some windows.

Considering Peachtree w/Sound-Controlled Laminated Glass.

Anyone familiar as to whether the sound control is substantial, minimal or in-between. Peachtree's web site has no particulars, regardless, still would appreciate some personal experience from someone.
Old 06-12-08, 04:00 AM
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As far as I know, there is nothing special about sound control with windows. All windows with a dead air space(insulated glass panels) reduce transmitted sound. But to advertise it as such is bunk, IMHO.
Old 06-12-08, 04:06 AM
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I agree with Bill, the space between the panes would have to be too great in order to "deaden" sound as their advertising may indicate. Normal IGU's reduce sound to a degree naturally, but "deadening", not likely.
Old 06-12-08, 06:24 AM
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Ahh..well, some windows do have a higher STC. I got this info when I had to help a customer who was building in a high noise area (Air Force base landing path), and codes required him to have a certain STC on all his windows.

It's less about the air space, and more to do with the type of glass and seals the window used. He had to go with Andersen 400 series and almost all of them had to have laminated glass, IIRC.

Casements as a rule have a higher STC than an equivalent sized DH, and a fixed casement is even higher. Then when you get to a certain size, the STC drops due to the larger glass area.

Peachtree should have those numbers, but you may have to call their technical people.

Heres a link to a pretty good explanation, but its a manufacturers link, so grain of salt is indicated.
Old 06-13-08, 07:07 PM
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Windows, doors, walls, whatever, are all rated as to their ability to deaden or attenuate sound based on the STC or Sound Transmission Class.

STC is an average of an object’s ability to attenuate sound across a fixed frequency spectrum of approximately 100hz-5000hz. An STC average (what you will be quoted if asking about STC of a specific product) does not provide specific frequency-deadening information which may be what is needed if you want to block a specific type of unwanted noise – for example traffic noise – and while the attenuation characteristics of certain products at particular frequencies do exist, they are often not generally available to the consumer.

Sound Transmission Class is a laboratory rating based on some very specific criteria within a very specific frequency range. STC was designed to test the frequency range where the human voice will be the predominant consideration.

Unfortunately, this does tend to minimize the effectiveness of STC as a tool for helping to block sound outside of that range.

While using STC to compare the sound-blocking ability of different window styles or brands is certainly not a bad idea since, generally speaking, a window with an STC of 40 should outperform a window with an STC of 35 – STC is sort of like mileage ratings on a new car – not always as useful as one might hope and that 40 versus 35 is for an overall rating – it does not say which of those products would perform best at specific frequencies – again blocking traffic noise for an example.

STC is a rating that is independent of the conditions under which the window will be used – meaning that it does not take into account the actual field conditions of the assembly. These conditions might include background noise, window area, even the level of sensitivity to noise of the occupants. Noise reduction requirements are affected by these conditions so that windows with the same STC might have very different NR requirements when used in different situations.

But, at the basic level there are three primary issues to consider when dealing with unwanted "noise" – the frequency, the level, and the duration of said noise.

Sound frequency and sound level are combined into what is called a "dBA" – or A-filtered decibel value – in order to quantify the sound in relation to the human perception or ability to hear it. In other words, we all “hear” (no pun intended – really!) about the specific dB level at a rock concert or at the airport, but we don’t hear “evenly” across the whole sound spectrum. For example, we may hear a sound at a relatively low decibel (or sound pressure) level at one specific frequency and yet be unable to hear an even louder sound at a different frequency - which is why frequency response is weighted.

Sound duration is added into the mix because even a relatively quiet sound can become annoying when it persists for a certain time. Using figures derived from these three descriptors, a sound professional can determine what is required to attenuate (opposite of amplify) the inappropriate sounds.

Sounds like a lot of trouble (again, no pun intended!), right? Well, it actually is and unless you live next to an airport or train crossing it is usually not worth the trouble to go there. But, I pointed it out to give you some idea of how in depth fighting unwanted sound can be.

As humans we are born with the ability to hear from approximately 20 to 20,000 hertz.

Hertz, or Hz, is how sound frequency is measured - like electricity is measured in volts. By the time we are teenagers we have generally lost the ability to hear above about 13,000hz. Since the human voice tends to fall between 500hz and 5000hz, the loss of higher frequency sounds is not usually a big deal.

Generally, low frequencies are much harder to attenuate (opposite of amplify) or block than are higher frequencies - just think how often you hear the bass sounds from the neighborhood kid's car stereo and not the higher pitch tunes when he is coming down the street.

When considering glass sound performance, there are four primary considerations to take into account for maximum possible attenuation – or blocking.

First is laminated glass.
Second is a wider airspace between the lites.
Third is different thickness lites within the IGU or Insulating Glass Unit.
Fourth would be a combination of all three.

Airport windows, as an example, often will have laminated glass on both sides of an IGU in an aluminum frame and with a maximum airspace between the lites. In an airport the primary concern is sound attenuation and energy efficiency is secondary. I mention this because the width of the airspace and the choice of window framing material affects both sound and energy efficiency.

Some folks will suggest triple pane glass for its sound deadening ability, and while triple pane may be a slight improvement over standard double pane at certain frequencies due to the additional density of the extra lite, overall there is no major difference in STC rating between triple and double pane provided that the overall airspace between the panes is constant between the two constructions.

In other words, a triple pane with two 1/4" airspaces and a dual pane with a 1/2" airspace – both using 1/8" glass – will have the same overall STC assuming that windows are otherwise the same.

Using one thicker and one thinner - different thickness - lites in an IG construction may also help deaden sound because each lite is transparent to a different frequency and each lite will then attenuate the frequency that passed thru the other lite.

As a very general rule, different thickness lites in an IG configuration (for example 1/8” and 3/16”) contributes more to lower frequency noise attenuation than it does to higher frequency attenuation, yet oddly, using different thickness lites does not contribute significantly to overall STC performance as well as the other options – such as using a wider airspace or laminated glass in the IG unit - and the wider the airspace between the lites, the more potential for limiting unwanted sound thru that space.

Unfortunately, for significant sound attenuation, it may be necessary to have an airspace approaching two inches or more – although lesser width airspace can make a difference as well – possibly depending on the frequency and amplitude of the unwanted sounds.

Minimizing unwanted sound thru any material is determined by three things – mass, stiffness, and damping of the material. Increasing the mass of a window by using thicker glass will increase sound attenuation and the change from a single pane window to dual pane or triple pane IGU to a window will add glazing mass and thus improve sound performance thru the window; but often not as much as might seem obvious based on the given criteria.

So why do folks with new dual pane windows, after living with single pane, often comment on the improvement in blocking unwanted outside noise with their new windows?

Often, this is due to the replacement window being tighter than the previous older window, but also the addition of the airspace between the lites of a dual pane – rather than to the effect of the additional lite, unless as mentioned the lites are different thicknesses – can have an effect on sound propagation.

So in that sense, the additional lite in a standard dual pane window improves performance over a single pane by the formation of the airspace. But this doesn’t always apply when adding triple pane due to the decrease in the airspace between the lites overriding the potential advantage of the additional lite (as mentioned earlier in this really long post...)

And, going back to mass, stiffness and damping; since increasing the stiffness of glass isn't really practical, what about damping?

Inherently, glass has very little damping ability, but when putting a layer of a more viscous material between two of lites of glass we substantially increase the unit’s ability to dampen sound – thus the advantage of laminated glass which just so happens to be a product that has a layer of more viscous material between two lites of glass – cool how that works right into the explanation!

A single pane of 1/4" laminated glass consisting of two 1/8" lites with the plastic interlayer actually has just about as much sound blocking ability as a 1/2" lite of monolithic glass. The monolithic glass tends to do better at mid to higher frequencies while at the lower frequencies the performance of ” laminated and ” monolithic tend to be about the same as well as the overall STC rating.

A fixed, versus an operating, window is usually going to give you much better sound attenuation. However, having a house-full of windows that can't be opened is not very appealing to most people, so again we come back to the earlier comment that the window MUST be tight when closed.

Old 06-13-08, 10:41 PM
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I don't think anyone can beat the info provided by the previous post. Just an added note, many of the hgtv shows feature soundproof windows in homes near heavy traffic. If noise is a problem, then exploring sound reduction windows tends to be a recommendation. For outdoors, fencing and plantings of layers of trees and shrubbery can also reduce sound.

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