Home / Blog / Window Film and Outside Noise

Does Window Film Reduce Outside Noise? What the Numbers Say

Window film is sold for heat, glare, UV, privacy and safety, not for noise. Here is what we could and could not find, what the sound standards actually measure, and what glass makers, HUD and airport programs say really quiets a room.

Published October 16, 2026 · Armored Glass Solutions

The Short Answer

Short answer: film is not a noise product, and we found no tested data saying otherwise

We found no tested noise data for window film. LLumar’s architectural film FAQ lists glare, heat, privacy and UV protection and does not mention sound. The National Fenestration Rating Council (NFRC) consumer page on blocking street noise does not mention film, and its page on window film does not mention noise. Solar Gard, Madico and IWFA pages we tried did not load or had no noise wording, and 3M’s page timed out. That is a gap in our search, not proof that no maker says anything.

One film retailer says adding film can cut outside noise by about 5 decibels (dB), attributes that to unnamed manufacturer studies, and calls it not enough to be a true option. No study or standard is named. We found no laboratory test of film on glass from any source.

A note on words: elsewhere on this site, “noise” means the loud sound of someone striking filmed glass. This post is about traffic, aircraft and street noise coming in from outside.

Expect little, if anything, from film alone. Unproven, probably small.
Look at the glass and the gaps first: thickness, air space, laminating and sealing.
Ask any noise claim which test, which glass and which scale it used.
Call a glazier for a true noise fix. We do not replace windows.

The Physics

How sound actually gets into a room

The U.S. Department of Housing and Urban Development’s Noise Guidebook (1985, so use it for principles, not today’s product numbers) says sound enters a building through its acoustically weakest points and that windows are one of the weakest parts of a wall. Its worked example: a wall rated STC 45 with a window rated STC 26 covering 30% of its area comes out at STC 35 overall, a 10 dB reduction. HUD’s first step for reducing unwanted sound is to close and seal the windows.

HUD also explains that glass reduces noise by the mass principle: the thicker the glass, the more noise resistant. It lists a double-glass acoustical window of two 3/16-inch panes with an airspace at STC 51, well above much thicker single glass, and calls proper sealing crucial. NFRC says no window is a complete barrier to sound. It does not rate windows for noise, but says its Air Leakage rating is an accurate measure of sound blocking because sound and air pass through the same leaks.

The Ratings

STC vs. OITC: which number matches traffic and aircraft

Most people have seen STC, the Sound Transmission Class. ASTM E413 defines it, and says the single-number rating correlates in a general way with subjective impressions of sound for speech, radio, television and similar sources in offices and buildings. ASTM also says the classification is not appropriate for sources with different spectra, and names transportation noises such as motor vehicles, aircraft and trains. It points to Classification E1332 for building facade elements.

E1332 defines the Outdoor-Indoor Transmission Class, OITC. ASTM says these ratings are designed to correlate with the ability of building elements to reduce outdoor ground and air transportation noise that contains strong low-frequency sound. The reference spectrum averages aircraft takeoff, road traffic and a diesel locomotive passing. The calculation uses data from 80 to 4000 Hz, though ASTM’s text cites a wider 50 to 5000 Hz for the study behind the correlation, so be careful with anyone quoting one OITC band as the only one. ASTM adds that single numbers should always be used with caution.

Guardian Glass says OITC suits exterior glazing against roadway, rail and aircraft sound, and STC suits interior speech. It says the two are not linearly related, so we give no rule for converting one into the other.

The Numbers

What the numbers look like in glass

Guardian’s 2021 paper says a single pane performs worst, and ratings improve with sealed airspaces, laminated panes, thicker glass and acoustic-grade PVB interlayers. Its lab estimates for the center of the glass, written as OITC / STC:

Single pane, 6 mm: 28 / 30. Single pane, 12 mm: 33 / 36.
Laminated, 6 mm with standard PVB and another 6 mm: 32 / 36. With acoustic PVB: 35 / 40.
Double pane, 6 mm, 1/2-inch air, 6 mm: 29 / 34. Triple pane of the same glass: 29 / 37.

Note that Guardian’s triple pane has the same OITC as its double, while NFRC says multiple panes block more sound. Both can be true: gap, thickness and leaks matter more than pane count. And these are lab estimates of glass, not framed windows. ASTM says E90 lab results are an upper limit for what would be measured in a building, and Guardian says a 6 dB loss between lab specimen and site-installed panel is possible. Treat any product number as a ceiling.

Laminated glass makers add their own claims. Kuraray, an interlayer maker, says a 9 mm laminate with ordinary PVB reaches 34 dB, and 37 dB with its acoustic interlayer, and rates that interlayer up to 3 dB better than standard PVB. Eastman says its Saflex Acoustic interlayer decreases transmitted sound up to 10 decibels versus non-laminated glass in the critical frequency range, with no test glass stated on the page. The baselines differ, and Kuraray’s figures are on its own dB scale, so do not set these side by side or against Guardian’s. For laminated glass versus film, see our comparison of security film, laminated glass and replacement. The “acoustic” in acoustic glass refers to that interlayer inside the glass, not to a film applied afterward.

Thickness

Why a thin film is not expected to do much, and what would settle it

Start with what a decibel change means. Kuraray’s perception scale, a glass maker’s table, calls 0 to 2 dB imperceptible, 3 to 5 dB just perceptible, 6 to 10 dB clearly perceptible, and says 5 dB or more is an audible improvement for building windows. Guardian says every 10 dB is a tenfold increase in sound intensity but roughly a doubling in perceived volume. On that scale, the retailer’s unsourced “about 5 dB” would fall in the just-perceptible band.

Now the thickness, and this part is our own arithmetic and inference, not a source statement. The IWFA inspection guideline groups film by thickness in mils, up to 12 mils for its 8-to-12 band. One mil is 0.0254 mm, so a 4-mil film is about 0.1 mm and a 12-mil film about 0.3 mm. Against a 6 mm pane that is roughly 2% and 5%. Since HUD says glass works by mass, and Kuraray’s own example is that doubling glass from 5 mm to 10 mm moves noise reduction from 30 to 33 dB, we would not expect a layer that thin to add much. No maker states this either way.

What would settle it is a paired laboratory test: the same glass and frame measured under ASTM E90 before and after film. We found none. We also found no source on whether film changes the glass-to-frame joint, so we do not claim film seals gaps.

What Gets Installed

What airport programs and secondary glazing actually use

Programs that have to prove results do not use film. The Los Angeles World Airports residential sound insulation program says it replaces existing windows and doors with new acoustically rated ones. The San Diego County Regional Airport Authority’s Quieter Home Program aims to cut interior noise by at least 5 decibels, lists upgraded doors and windows and ventilation systems as treatments, and tests 10% of homes before and after construction. Neither page lists window film. The 5 dB is that program’s design goal, not a noticeability threshold or a federal rule.

FAA guidance from 2012 says noise insulation projects should be designed to reach 45 dB interior levels to qualify for federal funding; it sets targets, not products.

Secondary glazing, an extra pane mounted inside the existing window, shows the same pattern. Indow’s own commercial page lists a lab table for a storefront window: baseline 1/4-inch tempered glass at STC 29 and an estimated OITC of 25; with a 5/16-inch acoustic laminated insert and a 1.25-inch air gap, STC 43 and OITC 31; with a 4-inch gap, STC 51 and OITC 36. Those are the maker’s own numbers; we could not open the linked reports, so lab, edition and sponsor are unconfirmed. The same assembly gained 14 STC points but 6 OITC points, the STC and OITC gap from above. The vendor credits air gap, mass and an airtight frame. We do not install this product.

Where We Fit

Where film and overglaze fit, and when to call a glazier

We install window film, overglaze polycarbonate and door reglaze. We do not replace windows, and we do not promise noise reduction from any of our products. If traffic, aircraft or a nearby rail line is the problem you are solving, the sources above point to work a glazier or window replacement company does: acoustic or laminated glass, thicker or mixed-thickness panes, an air space, tight sealing, and ventilation so windows can stay closed.

Film suits heat, glare, UV fading, privacy and safety. Our film or new windows guide explains how to tell when replacement is the better answer.

Overglaze polycarbonate is a separate panel installed over existing glass in its own frame; our explainer covers how it works. DefenseLite, whose overglaze we install, describes its panel as creating an air space and an added panel against street noise, but its noise page gives no test standard, no STC or OITC value and no report. Without a lab report showing the glass build-up and air gap, we have no tested noise number for overglaze and will not offer one. If noise is the main reason you are asking, ask for that report first.

Before You Believe a Number

How to compare any noise claim

Sources here use different scales (STC, OITC, Kuraray’s sound-insulation dB, and dBA on Indow’s consumer page), so never subtract one from another. Of the percent claims we read, only Eastman says what its percent means (perceived loudness). These questions are our advice, not a sourced procedure.

Which test? A lab test to ASTM E90, rated by E1332 (OITC) for traffic and aircraft, or an STC figure built for speech?
Which glass? The exact build-up and air gap it was measured on, and whether you have the same.
Which scale? STC, OITC, Rw or dBA, and compared with what baseline.
Lab or field? Lab values are upper limits for real buildings.

What we could not find: film maker noise data, any independent lab test of film on glass, an independent test of polycarbonate panels over existing glass, and a published figure for how much noise leaks through gaps.

Questions

Window film and outside noise: FAQ.

Does window film reduce outside noise?

We found no tested noise data for window film. The film maker pages we could read do not mention noise, and the NFRC page on blocking street noise does not mention film. One film retailer says film can cut outside noise by about 5 decibels, cites unnamed manufacturer studies, and calls that not enough to be a true option. On the glass maker Kuraray's own scale, 3 to 5 dB is just perceptible. We found no paired lab test of film on glass, so the honest reading is unproven and probably small.

What is the difference between STC and OITC?

STC (ASTM E413) is built for sounds like speech, radio and television, and ASTM says it is not appropriate for transportation noise such as motor vehicles, aircraft and trains. OITC (ASTM E1332) is designed for outdoor ground and air transportation noise that contains strong low-frequency sound. Guardian Glass says the two are not linearly related, so a strong STC rating does not necessarily mean a similar OITC rating.

What actually makes a window quieter?

The sources point to the same few things: close and seal the window, because sound and air pass through the same leaks; add mass or an air space; and use laminated glass, with an acoustic interlayer where it is offered. HUD calls proper sealing crucial. In Guardian's lab table, a 6 mm pane with acoustic PVB and another 6 mm pane rates OITC 35, against OITC 28 for a plain 6 mm single pane. Those are lab estimates for the center of the glass, not a framed window in your wall.

Is acoustic laminated glass worth it for traffic noise?

The makers say it helps, and their claims depend on the baseline. Kuraray says its acoustic interlayer is up to 3 dB better than standard PVB in laminated glass. Eastman says its Saflex Acoustic interlayer cuts transmitted sound up to 10 decibels versus non-laminated glass in the critical frequency range, and its page does not state the test glass. Lab values are an upper limit for real buildings. We do not replace windows, so for laminated or acoustic glass talk to a glazier or window replacement company.

What do airports do for homes near flight paths?

The programs we read replace windows and doors. The Los Angeles World Airports sound insulation program replaces existing windows and doors with new acoustically rated ones. San Diego's Quieter Home Program says treatments may include acoustic windows, doors and ventilation systems, and aims for at least 5 decibels of interior reduction, with 10% of homes tested before and after. Neither page lists window film.

Sources

Where these findings came from.

We read these on October 14, 2026. Decibel figures belong to the test, scale and glass each source describes and should not be compared across sources. Maker statements are maker claims. Dated documents carry their dates. ASTM entries are public store-page descriptions; the full standards are paywalled. Use the current document for your own glass.

HUD USER, The Noise Guidebook, 1985, Chapter 4, “Windows.” Dated; used for principles only. PDF.
NFRC Consumer Guide to Windows (efficientwindows.org), “Block Noise” and “Window Film.” Block Noise, Window Film.
Guardian Glass, Expert Series: Glass Acoustic Performance, 2021. Glass maker; lab estimates for center of glass. PDF.
Kuraray / Trosifol, Sound attenuation with laminated safety glass, bulletin rev. 2/2026, and Trosifol SC Monolayer product page. Interlayer maker. PDF, Page.
Eastman, Saflex Acoustic. Interlayer maker marketing page; test glass not stated. Page.
ASTM E90 (store page shows the 2016 edition), E413-22 and E1332-16. Public scope text only. E90, E413, E1332.
LLumar, Architectural Window Film FAQs. One page checked; no mention of noise. Page.
Concord Window Film, Does Window Film Reduce Noise? Film retailer; cited only as an example of an unsourced claim, not as data. Page.
IWFA, Architectural Visual Inspection Guideline for Applied Window Film, film cure times by thickness in mils; used for our thickness arithmetic. PDF.
Indow, Noise Performance Data and IndowPRO Performance for Acoustic Consultants & Engineers. Seller-published; the linked test reports could not be opened, so lab, edition and sponsor are unconfirmed. Consumer page, Commercial page.
DefenseLite, Noise Reduction Windows, Polycarbonate Sound Reduction Barrier. Maker page; no test standard or report on the page. Page.
San Diego County Regional Airport Authority, Quieter Home Program, page dated June 24, 2025. Page.
Los Angeles World Airports, news release 030, July 31, 2023, on residential sound insulation near LAX. Page.
FAA, Program Guidance Letter 12-09, Noise Insulation, August 17, 2012 (rev. November 7, 2012). Historical; dated. PDF.

Keep Reading

Window film or new windows?

When film is enough, when replacement is the right call, and how to tell which one your glass needs.

Read the guide →

Security film vs. laminated glass vs. replacement

What laminated glass is, how it differs from film applied to existing glass, and where each one fits.

Read the guide →

Residential window film

What film does at a home: heat, glare, UV and privacy, and what to ask before you choose.

See residential film →

Noise is the problem you are trying to solve?

Tell us what you hear and where. We will look at the glass and tell you plainly whether film, overglaze or door work can help with heat, glare, privacy or safety, and when a glazier is the right call for the noise.

Get a Free Assessment