Window Manufacturers

Understanding Noise

At the basic level there are three primary issues to consider when dealing with unwanted "noise" – the frequency, the sound pressure level, and the duration.

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 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 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, 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 13,000 Hz. 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, such as traffic noise, are much harder to attenuate or block than are higher frequencies - just think how often you hear the bass sounds from the neighbourhood 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 and may not be the best solution for the average home.

While 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. However switching to a 1” overall compared to a 1/4" will defiantly improve the overall STC, and will greatly increase your overall insulating value.

Using one thicker and one thinner - different thickness - lites in an IG construction may also help deaden the sound because each lite is transparent to a different frequency and each lite will then attenuate the frequency that passes 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, such as using a wider airspace or laminated glass in the IG unit - 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 air space 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.

While mass is a given based on your existing windows and increasing the stiffness of glass isn't really practical, what about damping?

Inherently, glass has very little damping ability unless laminated, but no matter what you do you must ensure that any window MUST be tight when closed to achieve both maximum energy performance as well as for deadening sound.

• Ducana Windows & Doors products are energy star high efficiency
• Ducana Windows & Doors products are CSA approved
• Ducana Windows & Doors are made in Tilbury Ontario, Canada

• HOME
• RESOURCES
• NEWSROOM
• SITEMAP
• PRIVACY
• CONTACT