How to Soundproof Windows: 8 Best Methods

Soundproofing windows is essential when developing a home soundproofing system because most outdoor noise comes through the windows. Windows are the weakest point in the building's acoustic envelope and can easily let in noise pollution (any sound above 65 decibels) from traffic, animals, neighbors, or construction.

The best way to soundproof is by adding mass. Mass is dense, heavy, and usually opaque—qualities not conducive to soundproofing windows. But there are a number of ways to soundproof windows that permit light, are easy to install, and are cost-effective.

Learn how to soundproof windows with simple methods like adding caulk or weatherstripping, plus other methods that dampen sound like window inserts or acoustic curtains.

Acoustic Caulk

Gaps and cracks in and around windows transmit sound from the outside to the inside. Sealing those openings is an important step in window soundproofing.

Using interior-grade, paintable caulk ($3 to $10 per tube) is always better than leaving the gaps open. But acoustic caulk (or acoustical sound sealant or noise-proofing sealant) works better because it is latex-based and will remain flexible, rather than hardening over time. Acoustic caulk will not shrink and create new gaps.

At around $10 per tube, acoustic caulk's cost is comparable with ordinary painter's caulk. Two beads of acoustic caulk can more than triple the soundproofing ability of an uncaulked area.

Tip

Use acoustic caulk on other gaps in the wall that allow sound to enter: around electrical boxes, pipe inserts, ducts, or around doors.

Custom Window Inserts

Add more layers of glass or other translucent materials to soundproof the window. One way to do this is with a window insert, a layer of clear material on the interior side of the window.

Also known as an indoor storm window, window inserts are custom-made acrylic or Plexiglas panels that fit snugly on the inside of the window frame, forming an air space between the insert and the window. This layer of air dampens sound vibrations.

A standard custom-made window insert for a 40-inch by 30-inch window costs $260 to $300. An acoustic window insert of the same size costs $335 to $360.

Tip

Window inserts reduce exterior noise by 70 percent when used with single-pane windows and 50 percent when used with double-pane windows.

DIY Window Inserts

Make your own window insert from a Plexiglas or acrylic panel purchased from a home improvement or hardware store.

Cut the sheet with an acrylic cutter to fit the outer edges of the window trim. Drill pilot holes through the sheet and screw the material to the window trim.

Because the sheet is attached to the face of the trim, it's more visible than a compression-fit, custom window insert. But a DIY insert is less expensive. A 36-inch by 48-inch by 3/32-inch clear acrylic sheet costs $60 to $70. A plastic sheet-cutting tool costs $5 to $10.

Storm Windows

Storm windows are meant to protect a window from damage during storms, preserve the window, and save energy. Storm windows can also help soundproof a window by adding another layer of air and by preventing air infiltration.

An improvement on seasonal storm windows that are installed and removed annually are permanent storm windows. Permanent storm windows remain in place all year, blend in better with the home's exterior, and have low-e (UV-blocking) capabilities. Permanent storm windows can be fixed or operable, for easier maintenance.

The cost of storm windows is from $250 to $625 per vinyl framed, low-e storm window, installed.

Tip

Adding Energy Star-certified storm windows can help you save $350 per year in heating or cooling bills.

Sound-Absorbing Curtains

Soundproofing a window effectively at night or when a view is not desired is made easier by using solid, opaque materials like curtains or blinds. Any type of window curtain will add some soundproofing, even thin mini-blinds. Heavier, thicker curtains that stretch across the entire window improve soundproofing.

Blackout curtains: Blackout curtains are thick curtains with a liner to block light. A set of two 42-inch by 45-inch 100-percent blackout panels is $28.
Velvet curtains: Velvet curtains are usually made from cotton or polyester and come in solid colors. Two velvet curtain panels, each panel 55 inches by 84 inches, are $65.
Acoustic curtains: Acoustic curtains dampen both indoor and outdoor sound, while also controlling heat and cold, and help block out light. Acoustic curtains have up to three layers to maximize the material's sound-blocking ability. Acoustic curtains begin at around $175.

Weatherstripping

If the area between the window frame and the window sash is gapped and allows drafts, it also allows noise into the room. The fix is to apply self-stick vinyl foam weatherstripping or foam weatherseal to that gap.

With double-hung windows, raise the lower sash. Add the weatherstripping to the window bottom. If the window is intended to remain shut, stuff foam weatherseal into the window stops and to the top of the window sash.

Ten feet of adhesive-backed foam weatherstripping costs $5 to $10. Forty inches of foam weatherseal costs less than $5.

Heavy Furniture

Move heavy furniture like bookcases, armoires, sofas, and sectionals in front of and around windows to dampen noise. The dense mass of these pieces will absorb some sound and create a quieter room.

It's not necessary to block the window. Even arranging the pieces around the window can help.

Warning

If furniture fully blocks a window, keep egress requirements in mind. Local building codes have egress or emergency exit requirements for finished spaces. If the room doesn't have alternative egress points already, the window may need to remain unblocked to fulfill this requirement.

Double-Glazing

Whether you add glazing to current windows or install double-glazed new windows, double-glazing can reduce noise by up to 35 decibels. Double-glazing helps to reduce vibrations, dissipate sound waves, and prevent gaps that could otherwise allow noise to come through.

Tips for Soundproofing Windows

Remove window-unit air conditioners, as sound can easily pass through these units.
Single-pane windows should be replaced with double-pane windows, now standard in most climates.
Soundproof against annoying low-frequency noise with bass traps: large pieces of insulating materials placed at strategic points in the room.
For windows that can be blocked, add sheets of mass-loaded vinyl (MLV). Mass-loaded vinyl is effective at dampening sounds and can be layered to improve soundproofing.
Use large plants and plush rugs to further dampen noise that enters the room from the outside.

How Soundproof Windows Work

Soundproof windows slow the transmission of sound waves into a room, making it quieter overall. Soundproof windows are made of a variety of materials that can absorb, reflect, or dissipate sound. They can also vary in thickness to help reduce noise.

Installing new soundproof windows can vary in cost depending on the material and labor/material costs where you live, but you can expect to spend between $500 and $2000 per window.