Acoustic glazing — what actually stops sound at the window.
STC vs. OITC, laminated glass and asymmetric IGU makeups, and why the perimeter gasket and sealant detail decides as much as the glass package does. Written for hospitality, multifamily, and airport-corridor projects in Florida and Tennessee — not a sales sheet.
STC and OITC aren't the same test, and specs mix them up.
Sound Transmission Class (STC) and Outdoor-Indoor Transmission Class (OITC) are both single-number ratings for how much a wall or window assembly reduces airborne sound, and both come out of laboratory testing on the assembly — not the glass alone. They diverge in what noise spectrum they're weighted toward. STC is weighted toward the frequency range of interior speech and typical building-to-building noise. OITC is weighted toward lower-frequency, higher-energy noise — aircraft, highway traffic, rail — the kind of exterior noise that a hotel next to an airport or a tower on an arterial road actually has to deal with.
That distinction matters at the spec-writing stage. A glazing package that tests well for STC can still underperform against real aircraft or traffic noise if OITC wasn't the controlling number in the design. On hospitality and multifamily work near airports, highways, or elevated transit, the acoustic consultant should be specifying to OITC, or to both — and the sub needs to know which one the assembly was actually tested against before it's ordered.
What raises an assembly's acoustic rating.
This is a qualitative reference, not a numeric guarantee. Actual STC/OITC values are assembly-specific, lab-tested, and belong on the acoustic consultant's schedule and the manufacturer's test report — not a web page. What follows is the direction each variable moves the rating, not a target number.
The glass package gets the spec attention. The gasket gets the field failures.
Acoustic consultants spend most of a spec's word count on the glass makeup — lite thickness, interlayer, airspace. That's the easy part to get right, because it's a purchased assembly with a lab test behind it. What determines whether the installed opening actually hits the rated performance is almost always the perimeter: continuous compression seal around the full frame perimeter, no direct metal-to-metal telegraphing path from exterior frame to interior trim, and sealant joints built to the depth the acoustic detail calls for, not the standard weathertightness detail.
Two field realities worth flagging before bid:
- A single gap in the perimeter seal — a missed gasket segment, a sealant joint that wasn't tooled to depth — can measurably drag down the field-tested performance of an otherwise correctly specified assembly. Acoustic paths are unforgiving about small gaps in a way that weathertightness details generally aren't.
- Where the acoustic glazing meets an adjacent wall assembly — spandrel, mullion cover, or interior finish — the acoustic detail needs to carry through that transition. A high-performing window in a wall that isn't detailed to the same standard won't deliver the room-level result the owner is expecting.
The controlling numbers on any given project are always in the acoustic consultant's test report and the project's specific STC/OITC targets — not a generic figure. If your project has an acoustic consultant's schedule, send it with the Division 08 package and we'll price to it directly.
Hospitality, multifamily, and airport-corridor demand.
Acoustic glazing shows up most often on projects where exterior noise is a known, named problem at the design stage rather than an afterthought: hotels near airports or highways, multifamily and condo towers on urban arterials, and healthcare or education buildings where interior sound isolation is part of the program. Nashville's BNA airport expansion is a regional example of the demand — the on-site Hilton at BNA was specified with triple-pane acoustical windows and an STC 45/OITC 40-rated curtain wall to address aircraft noise, a publicly documented market data point for the category, not an ACG project.
In South Florida's condo and high-rise market, brokers and buyers are increasingly discussing STC and IIC performance as a selling point in supertall towers, which signals acoustic glazing moving from a niche spec item to a market differentiator in that segment. Occupied-building acoustic retrofits also intersect with local construction-noise rules — Miami-Dade County and the City of Miami Beach both enforce construction-noise ordinances that affect scheduling and jobsite sequencing on retrofit projects near sensitive neighbors (Miami-Dade notice), (Miami Beach noise rules). ACG Nashville, opening Q3 2026, positions the company to bid airport-corridor and hospitality acoustic scopes directly in that market.
Common acoustic-glazing spec traps.
STC specified where OITC should control
Near airports, highways, or rail, OITC is the more relevant rating because it weights low-frequency noise. A spec that only calls out STC may not actually address the noise source the building faces.
Airspace width conflicts with the thermal spec
The cavity width that helps acoustic performance isn't always the cavity width the energy code path assumes. Confirm both targets are reconciled in the submittal before the IGU is fabricated.
Perimeter detail left generic
A weathertightness-grade perimeter seal isn't automatically an acoustic-grade perimeter seal. If the acoustic rating matters, the gasket and sealant detail needs its own callout, not a assumption that standard glazing practice covers it.
No lab test behind the number
A quoted STC or OITC figure without a lab test report behind the specific assembly is a marketing number, not a spec number. Ask for the test report before you build a design around the figure.
Acoustic and impact requirements stacked without checking compatibility
On Florida coastal sites, an acoustic assembly may also need to meet HVHZ impact requirements. Laminated glass often satisfies both, but the specific makeup needs to be checked against both test regimes, not assumed to carry over.
What we do about it
We flag rating-mismatch and perimeter-detail gaps in writing at the RFI stage on acoustic scopes we price — before we quote, not after award.
Laminated glazing experience that carries into acoustic scopes.
ACG installs laminated glass and IGU assemblies across storefront, curtain wall, and punched-opening systems as part of its core Division 08 scope — the same laminated-glazing and perimeter-sealant discipline that acoustic assemblies require. Our verified public-sector past performance includes laminated storefront and punched-opening glazing at the Haines City Public Safety Complex & EOC (25,443 SF, GC Pirtle Construction, completed 2025), the Cudjoe Key fire station for Monroe County, and the Martin County Fire Training facility.
Acoustic glazing questions GCs and architects ask.
What's the difference between STC and OITC ratings?
Both are single-number lab ratings for sound reduction through an assembly. STC weights the frequency range of interior speech and typical building noise. OITC weights lower-frequency, higher-energy exterior noise — aircraft, highway, and rail. Airport-corridor and highway-adjacent projects should specify to OITC, or to both, since STC alone may not reflect real exterior noise exposure.
Does laminated glass improve acoustic performance?
Generally yes. The interlayer in laminated glass damps vibration passing through the lite, which typically improves acoustic performance over monolithic glass of similar thickness. It's also why laminated makeups often serve double duty across acoustic, impact, and forced-entry glazing scopes on the same project.
Can ACG deliver a specific STC or OITC rating?
ACG prices and installs glazing assemblies to the acoustic consultant's specified rating and test report as a Division 08 subcontractor. We don't publish a standalone STC/OITC number on this page because the controlling figure is always assembly- and project-specific — send the acoustic schedule with your plans and we'll price to it directly. FL CGC #1531993.
Why does perimeter sealant matter as much as the glass package?
A lab-tested acoustic rating assumes a continuous, gap-free perimeter seal. In the field, a missed gasket segment or an under-depth sealant joint can measurably drag down the installed performance of an otherwise correctly specified assembly — acoustic paths are far less forgiving of small gaps than weathertightness details are.
Can an acoustic-rated assembly also meet Florida's impact glazing requirements?
Often, yes — laminated glass frequently satisfies both acoustic and HVHZ impact test regimes, but the specific interlayer and lite makeup needs to be checked against both sets of requirements rather than assumed to carry over from one to the other. That verification belongs in the sealed glazing submittal.
Related pages
Sending an acoustic glazing scope to bid?
Send Division 08 and the acoustic consultant's schedule to [email protected]. We'll price to the specified STC/OITC target and flag any perimeter-detail or rating-mismatch risks in writing before we quote.