Sound Reduction Is Not Soundproofing

“Soundproof” suggests that sound will no longer enter the room. That is an unrealistic promise for most residential window projects.

Sound can travel through the window, exterior wall, roof, vents, doors, electrical penetrations and gaps around the construction. It can also travel through the building structure as vibration.

Even when a new window substantially improves the window opening, another portion of the building envelope can become the dominant sound path. The homeowner may notice improvement without experiencing silence.

What Is an STC Rating?

Sound Transmission Class, or STC, is a single-number classification derived from laboratory sound-transmission measurements across a range of frequencies. A higher STC generally indicates better resistance to the types of sound emphasized by that classification.

STC is widely used for building components and is often helpful when discussing speech and other mid-frequency sounds. It does not communicate performance at every frequency equally.

A small numerical increase should not be translated into a fixed percentage reduction in what a homeowner will hear. Human perception, frequency content, background sound and installation conditions complicate that comparison.

What Is an OITC Rating?

Outdoor-Indoor Transmission Class, or OITC, is intended to characterize how an exterior building component reduces outdoor sound entering a building. Its frequency emphasis makes it particularly relevant to environmental noise such as roadway, rail and aircraft activity.

OITC ratings are commonly lower than STC ratings for the same product. That does not mean the OITC test is weaker. The two classifications use different evaluation methods and should not be compared as if they were the same scale.

When the homeowner’s complaint involves traffic, trucks, trains or aircraft, OITC will often be the more relevant number to review. A project specification may still require one or both classifications.

STC and OITC Compared

What Gentek’s 1900 Series Sound Chart Shows

Gentek’s published 1900 Series sound-transmission chart covers single-hung, double-hung, sliding, picture and factory-combination models with several glass constructions.

Across the configurations shown, the published values range from approximately STC 23 to STC 32 and OITC 20 to OITC 28. These are not blanket ratings for the series. Each value belongs to the product and glass configuration represented in the chart.

The chart includes conventional single-strength and double-strength glass, glass constructions using different pane thicknesses and laminated options. In the published results, certain upgraded constructions receive higher classifications than the basic configurations.

Contractors should obtain the current chart and match the exact row to the ordered window. Do not quote the highest STC or OITC shown unless that exact model and glass construction are being supplied.

Why Different Glass Thicknesses Can Help

Two glass panes with identical thicknesses can respond similarly at certain frequencies. Using panes of different thicknesses can alter those response patterns and improve performance across parts of the sound spectrum.

That does not mean that every unequal-glass construction will outperform every other option. Pane thickness, spacing, laminated interlayers, frame design, sash seals and test-unit construction all influence the result.

The tested whole-window rating is more reliable than a sales assumption based only on the words “different glass thickness.”

How Laminated Glass Can Affect Sound Performance

Laminated glass uses an interlayer bonded between pieces of glass. That construction can help damp certain vibrations and may improve sound transmission ratings when incorporated into a properly tested window system.

Laminated glass also has applications involving security, safety glazing and impact performance, but those claims are separate. A laminated glass option shown in a sound chart should not automatically be represented as safety glazing, forced-entry protection or hurricane-impact glazing.

Each required performance claim must be supported by documentation for the exact assembly.

Double-Pane and Triple-Pane Do Not Tell the Whole Story

Homeowners often assume that adding a pane of glass automatically produces the best acoustic result. Additional panes can help, but pane count by itself is not enough information.

Glass thickness, the differences between pane thicknesses, air-space width, laminated interlayers and the window’s operating construction can matter as much as—or more than—the simple number of panes.

Triple-pane glass may be selected primarily for thermal performance. Do not promise superior noise control unless the proposed configuration has documented acoustic data supporting that conclusion.

Fixed Windows and Operating Windows

Fixed windows have no operable sash joint. This can help reduce air and sound paths compared with an operating design, but only an applicable test result establishes the rating for the exact unit.

Single-hung, double-hung and sliding windows require weatherstripped joints so their sashes can move. Casement and awning windows use compression seals when closed and locked. These design differences can influence acoustic performance.

The best style is not determined by acoustics alone. Ventilation, emergency escape, cleaning, appearance, hardware access and budget still matter.

Air Leakage and Sound Leakage Are Related but Not Identical

An uncontrolled air gap can provide an easy path for sound. Correct sash adjustment, intact weatherstripping and a well-sealed installation perimeter can therefore support acoustic performance.

However, an air-leakage rating is not an acoustic rating. Sound can pass through solid materials and sealed assemblies as vibration. A window with strong air performance should not be assigned an STC or OITC value that has not been documented.

The Entire Wall Controls the Result

A room’s final sound level is limited by its weakest significant path. Upgrading the window may produce disappointing results if substantial noise continues through another component.

• Exterior doors and their perimeter seals
• Wall cavities and lightweight exterior construction
• Roof and ceiling assemblies
• Bathroom, kitchen and mechanical vents
• Wall-mounted air conditioners
• Electrical, plumbing and utility penetrations
• Unsealed window and door installation gaps
• Structural vibration transmitted through the building

For severe airport, highway, industrial or rail noise, recommend evaluation by a qualified acoustical consultant. Product sales literature is not a substitute for a project-specific acoustic design.

AAMA Gold Label Certification Versus Acoustic Ratings

The AAMA Gold Label Certification Program provides third-party verification for qualifying fenestration products under applicable performance standards. FGIA explains that certified samples undergo independent testing and that ongoing manufacturing inspections help verify continued compliance.

The Gold Label supports documented product quality and performance, but it should not be presented as an acoustic rating. STC and OITC values must come from applicable sound-transmission testing for the relevant configuration.

Installation Details That Can Affect Noise Reduction

Laboratory data describes a tested specimen. Field installation introduces the rough opening, shims, fasteners, insulation, interior air seal, exterior flashing and surrounding wall.

A narrow, continuous gap can allow noticeable sound transmission. The window should be installed plumb, level and square so that the sash, locks and weatherstripping function as designed.

The FGIA InstallationMasters program provides professional education related to window and exterior glass-door installation. Contractors should combine sound installation practices with the current Gentek instructions, local code and project specifications.

Do not fill an installation cavity with an improvised material simply because it appears dense. Compatibility, expansion pressure, drainage, air sealing and manufacturer requirements still matter.

Sales Questions That Identify the Real Noise Problem

1. 1. What is the sound source? Speech, barking dogs, motorcycles, truck traffic, trains and aircraft have different frequency characteristics.
2. 2. When does the problem occur? Intermittent nighttime events may be more disruptive than steady daytime background sound.
3. 3. Which rooms are affected? Bedrooms, offices and nurseries may justify different priorities from kitchens or utility areas.
4. 4. What windows are installed now? An old single-pane window with poor perimeter sealing presents a different opportunity from a recently installed insulated unit.
5. 5. Are other sound paths obvious? Inspect doors, vents, wall penetrations and through-wall equipment.
6. 6. Is there a required specification? Multifamily, institutional and commercial projects may specify a minimum laboratory rating rather than a general homeowner preference.

Popular Homeowner Questions

Contractor Preorder Checklist

• Identify the noise source and affected rooms.
• Determine whether STC, OITC or both are relevant.
• Confirm whether the project has a written acoustic specification.
• Select the exact Gentek 1900 Series style and model.
• Specify the exact tested glass construction.
• Match the quoted rating to the manufacturer’s current sound chart.
• Do not transfer a rating between different window styles.
• Inspect doors, vents and other likely sound paths.
• Plan a continuous, compatible perimeter air seal.
• Verify sash operation and locking after installation.
• Document the rating without promising a final room sound level.

Get Help Comparing Gentek 1900 Series Glass Options

Suburban Wholesale & Supply helps contractors and builders compare Gentek window configurations for projects throughout the Quad Cities. Share the window styles, dimensions, glass requirements and customer’s noise concerns so the team can help prepare an accurate product quotation.

Acoustic ratings and glass availability vary by product style and configuration. Laboratory ratings do not predict an exact indoor sound level. Verify current manufacturer data for the ordered unit and involve a qualified acoustical professional when the project has demanding noise-control goals.