A growing number of homeowners and property managers are turning to interior window soundproofing systems as an alternative to full window replacement, according to Soundproof USA, which installs products such as CitiQuiet in cities including Florida, Seattle, Las Vegas, Philadelphia, Los Angeles, Boston, Atlanta, Austin, San Francisco, Dallas, New Jersey, and Washington, D.C.
The systems work by adding a laminated glass panel a few inches inside an existing window frame, creating an air gap that acts as a sound barrier, without requiring construction or, in most cases, a permit. According to the company, a standard wood-frame window typically has a Sound Transmission Class (STC) rating of around 13; adding an insert can raise that rating to roughly 35, reducing outside noise by up to 95 percent depending on the building and noise source.
Demand varies by region. Coastal traffic and construction noise are common concerns in Florida and Los Angeles, while dense urban construction drives interest in Boston, Philadelphia, and Washington, D.C. In fast-growing metro areas such as Austin, Dallas, and Las Vegas, ongoing development is a primary noise source. Each insert is custom manufactured to fit the specific window opening, allowing installation in both older buildings and new construction.
Beyond noise reduction, the added glass panel and air layer can improve insulation, which may lower energy costs — a benefit the company says is particularly relevant in cities like San Francisco and Seattle, where older windows are often less energy-efficient.
Installation involves measuring the existing window and custom-building an insert to fit, regardless of window type or shape. Single-room installations are typically completed in a day, while larger multi-window projects can take up to a week. The original window remains unaltered, and the insert operates independently on its own track.
The systems are used most commonly in homes near busy roads, apartments and condominiums in dense urban areas, office spaces requiring quiet for calls or meetings, and recording studios. Inserts are removable and can be serviced or replaced without affecting the original window.
Soundproof USA has installed the systems nationwide since the mid-2000s.
