Foam insulation plays a key role in reducing unwanted noise inside homes. Both open-cell and closed-cell spray foam can improve sound attenuation, but their effectiveness depends on their physical properties and how they interact with sound waves. Open-cell foam is softer and more porous, making it better at absorbing airborne sounds like voices, televisions, and appliances. Closed-cell foam is denser and stiffer, which helps block structural vibrations and impact noise but is less effective for absorbing airborne sound.
Understanding these differences helps homeowners and builders choose the right foam system for soundproofing domestic spaces. This article breaks down how foam systems affect sound attenuation, technical performance data, and what to consider before making a choice.
Foam Types and Their Acoustic Performance
Spray foam insulation comes mainly in two types: open-cell and closed-cell. Each type affects sound transmission differently because of its structure and density.
Open-cell foam has a sponge-like texture. Its cells are not completely closed, which traps sound waves inside the foam’s porous structure. This reduces airborne noise by converting sound energy into heat within the foam. Open-cell foam generally has a low density, about 0.5 pounds per cubic foot, which allows it to compress slightly and absorb vibrations effectively.
Closed-cell foam has tightly packed cells filled with gas, making it much denser—around 2 pounds per cubic foot. Its rigidity helps block sound waves from passing through but does not absorb sound well because the foam’s surface is harder and less porous. Closed-cell foam acts more as a barrier to sound transmission caused by impact or vibration rather than muffling airborne noise.
Choosing between the two depends on the primary noise sources you want to control and your building conditions. Open-cell is usually better for interior walls where conversations and general household noise are the concern. Closed-cell suits exterior walls or areas with moisture issues but requires supplementary soundproofing measures to address airborne noise.
Comparison Table of Foam Systems for Domestic Sound Attenuation
| Feature | Open-cell Foam | Closed-cell Foam |
| Density | ~0.5 lb/ft³ | ~2.0 lb/ft³ |
| Sound Absorption Coefficient* | 0.70–0.85 (high absorption) | 0.20–0.40 (low absorption) |
| Airborne Noise Reduction | Effective | Moderate |
| Structure-borne Noise Control | Limited | Strong |
| Vapor Permeability | Permeable | Acts as a vapor barrier |
| R-value per inch | ~3.6 | ~6.5 |
| Typical Application Thickness | 3–5 inches | 1–2 inches |
*Measured in frequencies between 500–2000 Hz, common for residential noise.
Technical Specifications Affecting Sound Attenuation
Spray foam affects several acoustic and physical properties that influence how sound behaves in a home. Two key measurements are the Noise Reduction Coefficient (NRC) and the Sound Transmission Class (STC).
NRC measures how much sound a material absorbs. Open-cell foam has an NRC between 0.7 and 0.85, making it a strong absorber. Closed-cell foam’s NRC is much lower, around 0.2 to 0.4, so it does not absorb sound well.
STC rates a wall assembly’s ability to block sound transmission. Adding open-cell foam to a standard drywall wall can raise STC ratings by 3 to 7 points, improving the wall’s ability to block airborne sound. Closed-cell foam improves STC by about 2 to 4 points, mostly by reducing vibration and impact noise transmission rather than airborne sound.
The foam’s thickness also matters. Open-cell foam needs more thickness—typically 3 to 5 inches—to achieve effective sound absorption and insulation. Closed-cell foam achieves higher thermal resistance in thinner layers but does not significantly improve airborne noise reduction at low thickness.
| Property | Open-cell Foam | Closed-cell Foam |
| NRC (Noise Reduction Coefficient) | 0.70–0.85 | 0.20–0.40 |
| STC Increase | +3 to +7 points | +2 to +4 points |
| Vapor Permeability (perms) | 10–15 | ≤1 |
| Compressive Strength (psi) | 1–2 | 25–35 |
| Typical Installed Thickness | 3–5 inches | 1–2 inches |
The vapor permeability difference makes closed-cell foam a good choice for damp areas but requires care in interior walls to prevent moisture trapping.
Market Trends in Foam Use for Sound Attenuation
The spray foam insulation market in the United States continues to grow steadily. Market data shows that the sector expands about 4.6% annually, driven by builders and homeowners looking for combined thermal and acoustic performance.
Open-cell foam is favored in domestic interior applications because of its superior noise absorption and cost-effectiveness. Closed-cell foam sees more use in basements, garages, and external walls due to its moisture resistance and structural support.
As awareness of sound quality in homes rises, combining foam insulation with other soundproofing materials, such as double drywall layers and acoustic sealants, becomes a common practice.
Factors to Weigh Before Selecting a Foam System
Choosing the right foam for sound attenuation depends on the noise type, space conditions, and installation environment.
First, identify the noise source. Airborne noise—like talking, music, or TV—is best reduced by open-cell foam. If vibration or impact noise travels through structure elements, closed-cell foam may be more effective.
The thickness and space available inside wall cavities matter. Open-cell foam needs more room to perform well. If walls are thin or retrofitting, closed-cell foam might fit better but won’t absorb airborne sound as effectively.
Moisture levels influence foam choice. Closed-cell foam blocks moisture and prevents mold growth in humid spaces. Open-cell foam, being vapor permeable, risks trapping moisture unless paired with proper vapor barriers.
Budget and long-term goals also affect the decision. Open-cell foam tends to cost less per board foot and offers good acoustic benefits. Closed-cell foam costs more but adds structural strength and moisture protection.
Finally, consider future changes. Professional foam insulation installation forms a hard barrier, complicating repairs or upgrades inside walls. Open-cell foam remains softer and easier to work with after installation.
Bonus Tip: Combining both types in one project can balance acoustic and moisture control needs. Use open-cell foam where sound absorption is a priority and closed-cell in moisture-prone zones.
Common Questions About Foam and Sound Attenuation
Spray foam is often misunderstood regarding its soundproofing capacity. It’s important to clarify common points:
Can spray foam alone soundproof a room? Spray foam improves sound reduction but usually doesn’t fully soundproof a space on its own. For best results, combine foam with dense drywall, sealing gaps, and adding decoupling materials.
Does foam block all noise types? Open-cell foam excels with airborne noise but has limited impact noise control. Closed-cell foam controls impact noise better but doesn’t absorb airborne noise well.
Is it possible to mix foam types in one home? Yes. Many homes use open-cell foam on interior walls and closed-cell foam in basements or exterior walls, optimizing both moisture control and sound reduction.
How thick should foam be to improve sound attenuation? For open-cell foam, at least 3 inches is recommended for sound absorption. Closed-cell foam provides some benefit at thinner layers but is less effective for airborne noise.
Will foam insulation reduce echo inside rooms? Open-cell foam reduces echo by absorbing sound waves inside the cavity and room. Closed-cell foam’s rigidity makes it less effective at reducing echo.
Make the Right Decision
To effectively reduce domestic noise, evaluate the primary sound problems you face and your building conditions. Open-cell foam offers strong airborne sound absorption, making it ideal for interior walls where quiet living spaces are needed. Closed-cell foam protects against moisture and vibration but falls short on muffling voices or general household noise.
Consider wall thickness, moisture risk, budget, and future flexibility. Use technical data on NRC and STC as guides to how foam impacts sound performance. Combining foam with other soundproofing materials enhances results and can meet strict building codes or homeowner expectations.
Evaluate your needs carefully before investing in a foam system. Sound attenuation results depend on proper product selection, installation quality, and the surrounding wall assembly.
Bonus Tip: Check local building codes for soundproofing requirements and vapor barrier regulations. Compliance avoids future problems and ensures effective, lasting insulation.
Foam System Influence on Domestic Sound Attenuation FAQ
Does open-cell foam outperform fiberglass for sound control?
Open-cell foam absorbs sound more effectively across residential frequency ranges than fiberglass batts, offering improved noise reduction.
Which foam type best blocks conversation noise?
Open-cell foam absorbs mid-frequency sounds, including human speech, better than closed-cell foam.
Is closed-cell foam necessary for interior walls?
Not typically. Closed-cell foam is best for structural support and moisture resistance, less for airborne noise control inside living spaces.
Can foam insulation make a room completely soundproof?
No. Foam reduces noise but full soundproofing needs additional materials like extra drywall layers or sound-dampening panels.
How much foam thickness improves soundproofing?
At least 3 inches of open-cell foam is needed for noticeable sound attenuation. Closed-cell foam can contribute at thinner layers but is less effective overall.
Reviewer: With 11 years in the spray foam field, Aiden Baker reviewed this content and provided advice on building steady growth through practical, honest communication.