Soundproof Window Inserts

STC (Sound Transmission Class) rates the entire frequency range. Single-pane glass: STC 26-29. Standard double-pane: STC 28-31. Acoustic laminated IGU (Cardinal Loe-i89 or comparable): STC 35-37. Window insert added to existing double-pane: STC 42-50. Premium insert (1/4 laminated, sealed airspace, perimeter gasket): STC 48-52.

STC is a single number. Real-world noise is frequency-dependent. Aircraft noise concentrates in 100-500 Hz; truck and train rumble is 50-200 Hz; emergency sirens are 1,000-3,000 Hz. Inserts perform best at mid and high frequencies (above 500 Hz) and somewhat less at low frequencies (below 100 Hz). For pure low-frequency noise (heavy diesel locomotive at distance), even an STC 50 insert can leave residual rumble — though it'll cut speech and high-frequency noise dramatically.

dBA reduction translation: STC 30 to STC 45 is roughly a 15 dBA reduction at most speech frequencies. 15 dBA is perceived as about 1/3 the original loudness — a 747 takeoff at distance going from 'loud and clear' to 'noticeably present but background.' That's the typical experience our clients report after install.

We measure baseline noise at the site when the homeowner reports specific sources (aircraft, train, highway). A simple dBA reading on a calibrated SPL meter at the existing window vs at the back of the house tells us how much we're starting from and what STC we need to target. We don't sell on speculation — we measure.

Newark Liberty operates roughly 1,200 flights per day — the third-busiest in the NYC metro area. Runways 4L/22R and 11/29 generate departure and approach corridors that cover large parts of Essex County (Newark, East Orange, Maplewood, South Orange, Irvington), Hudson County (Bayonne, Jersey City, Hoboken — especially on west-flow days), and Union County (Elizabeth, Linden, Roselle Park, Cranford). On north-flow days, parts of Hudson and southern Bergen are under the departure corridor.

Teterboro is the busiest general aviation airport in the country. Heavy corporate and private jet traffic — Gulfstreams, Falcons, occasional 737-BBJs. Approach to runways 6, 24, 19, and 1 covers parts of Bergen County (Teterboro, Carlstadt, Moonachie, Wood-Ridge, Hasbrouck Heights, Hackensack) and Hudson County (Secaucus, North Bergen). The peak noise events are heavy jets during early-morning departures and late-evening arrivals.

Both EWR and TEB have FAA-approved noise abatement procedures but the residual impact on residential neighborhoods is significant. Cities in the affected zones (Maplewood, South Orange, Carlstadt, Hasbrouck Heights, Hackensack) sometimes have sound insulation programs funded by FAA Part 150 grants that subsidize window upgrades for qualifying homes. We work with these programs when applicable and complete installs to the program's spec.

For homes in EWR or TEB flight paths, we typically spec 1/4 inch laminated glass inserts with 3-4 inch airspace from the existing window. Target STC 45+. That delivers the speech-frequency reduction that makes overnight sleep possible and TV/conversation audible at normal volume during overflight.

The NJ Turnpike runs 122 miles from the Delaware Memorial Bridge to the George Washington Bridge. Within roughly 1,000 feet of the centerline, residential properties experience constant truck noise — peaks of 80-85 dBA during heavy traffic periods, baseline 65-70 dBA day and night. The Garden State Parkway adds similar coverage along the eastern part of the state. I-78 (Newark to PA border), I-80 (across northern NJ), and I-287 (around the Bergen/Morris loop) generate similar profiles.

Highway noise is broadband — engine, tire, wind, brake noise spanning the full frequency range. Window inserts perform well across this profile because the airspace decoupling works regardless of frequency. We've installed inserts in homes along the Turnpike in East Brunswick, Edison, Carteret, and Linden that brought interior nighttime levels from 55-60 dBA (noticeably loud) to 30-35 dBA (comparable to a quiet suburban interior).

Concrete sound walls along the highways are state DOT infrastructure that help with ground-level noise but do nothing for second-floor and above bedrooms. Window inserts are the practical fix for upstairs bedrooms in homes that already have sound walls protecting the ground floor.

The NEC runs through Newark, Elizabeth, Linden, Rahway, Edison, New Brunswick, Princeton Junction, and Trenton. NJ Transit commuter trains run roughly 200 trains per day in each direction during peak periods. Amtrak operates Acela and Northeast Regional service, including freight Conrail and NS operations overnight. Freight is the loudest — heavy diesel locomotives, long consists, and overnight operations from 10 p.m. to 5 a.m.

Rail noise has a distinct profile: high-frequency wheel squeal on curves, low-frequency engine rumble, repetitive low-frequency thumping from rail joints (less now that welded rail is standard). Horn blowing at grade crossings is the loudest single event — 110+ dBA at the source, 80-90 dBA at residential distances.

For homes within 500 feet of the NEC or major freight lines (Conrail Bayonne Branch, NS Lehigh Line through Morris County), we recommend 1/4 inch laminated inserts with deeper airspace (4-5 inches) to address the low-frequency rumble. Bedroom installs are the priority — most homeowners report the relentless overnight freight operations as the source of complaint, not the daytime commuter trains.

Indow Windows (Portland, OR) — the dominant US insert brand. Compression-fit silicone gasket around a clear acrylic or glass panel. Custom-measured to fit the existing interior window stop. No screws, no permanent modification to the existing window. STC 41-44 with standard glass, STC 45-48 with their acoustic glass option. We install Indow regularly in residential applications.

CitiQuiet (NY-based) — premium acoustic insert system with framed inserts and laminated glass. Higher STC than Indow (45-50 range), higher cost, more visible from interior (the framed insert has a visible aluminum or wood frame). We spec CitiQuiet for the most demanding applications — homes directly under flight paths or adjacent to freight rail.

Soundproof Windows Inc (Reno, NV) — comparable to CitiQuiet, slightly different mounting hardware. Strong product, good warranty.

DIY-grade plastic acoustic film products — we don't install these. They claim STC improvements but don't deliver in any of our field tests. Compression-fit silicone or framed laminated glass are the only insert types that perform.

Beyond inserts: for the highest acoustic performance, we recommend full window replacement to acoustic IGU (laminated tempered with acoustic PVB on both lites of a dual-pane). STC 42-45 in the window itself. Combine with an insert for STC 50-55 — recording studio territory in a residential context.