Soundproofing Materials: What Works, What Doesn't, and Where Each One Goes

Every week someone arrives at a Hush consultation with a product already in mind: a roll of mass loaded vinyl, a case of soundproofing foam, a tube of green glue, a can of soundproofing paint. Some of those materials are excellent. However, some do nothing at all. None of them works on its own, because soundproofing is an assembly, not a product. So this guide explains what each soundproofing material does, where it belongs, and which ones we actually use in New York City apartments and offices.

Choosing a Soundproofing Material: Blocking vs. Absorbing

The single most common mistake in choosing a soundproofing material is confusing two different jobs.

Sound blocking (isolation) stops sound from travelling between rooms. It is measured in STC for airborne sound and IIC for footsteps. In practice, blocking requires mass, airtightness, and decoupling. Materials: drywall, mass loaded vinyl, damping compound, isolation clips, sealant.

Sound absorbing (treatment) reduces echo and reverberation inside a room. It is measured in NRC. Absorbing, by contrast, requires soft, porous, thick material. That is, it needs fibre, not weight. Materials: mineral wool panels, felt, fabric-wrapped panels, acoustic foam.

Acoustic foam glued to a shared wall will make your room sound less echoey and will do nothing about your neighbour. Similarly, mass loaded vinyl behind drywall will quiet your neighbour and do nothing about echo. Therefore, pick the material for the job you have. Our sound absorbing material guide covers the treatment side in depth; this page is about blocking.

The Four Jobs Every Soundproofing Material Does

Every material below does one of four jobs. As a rule, a wall, ceiling or floor needs all four to reach a meaningful STC.

1. Mass — heavy layers that resist being set in motion by sound.
2. Decoupling — breaking the rigid connection between the noisy side and the quiet side so vibration cannot cross.
3. Damping — converting vibration in rigid panels into heat so they do not ring. Damping compound raises a drywall sandwich’s loss factor, the share of vibration energy turned into heat each cycle.
4. Absorption — filling the cavity so it does not resonate.

And underneath all four: airtight sealing. In fact, even a small gap can cost a large share of the performance.

Two pieces of physics explain why. First, the mass law. Doubling a single layer’s weight adds only about 5–6 dB of transmission loss, the decibels a wall removes. So mass alone runs into diminishing returns quickly: each extra pound buys less sound reduction. Second, a two-layer wall behaves like a mass–spring–mass system. The two leaves and the air cavity resonate at a low frequency, where isolation is poor. Insulation, a deeper cavity and heavier leaves push that resonance below the range that matters.

Soundproofing Insulation: Mineral Wool, Rockwool and Fiberglass

Soundproofing insulation (also sold as soundproof insulation, acoustic insulation or sound attenuation batts) is the absorption layer inside the cavity. It is not what blocks the sound; it stops the empty cavity from behaving like a drum.

Mineral wool (Rockwool, Roxul Safe’n’Sound, Thermafiber) is what we specify. It is dense, so it holds its shape in a vertical cavity without sagging, is fire-resistant, and absorbs across a wide band of frequencies. Rockwool sound insulation is the standard for party walls and ceilings. So it’s our default insulation for soundproofing in NYC.

Fiberglass batts work nearly as well acoustically in a sealed wall, and they are also already in many cavities. Where fiberglass is present and well fitted, we usually leave it.

Cellulose and spray foam are thermal products. Closed-cell soundproofing spray foam actually hurts, because it rigidly bridges the two sides of the wall and transmits vibration. Soundproofing spray foam is for sealing penetrations, not filling cavities.

The best soundproofing insulation is whichever dense batt fits the cavity with full contact and no voids. In most cases, the difference between brands is small; the difference between a full cavity and a half-filled one is large. Insulation alone moves a bare stud wall from roughly STC 33 to the high 30s. After that, everything above comes from mass, decoupling and damping.

Mass Loaded Vinyl (MLV) as a Soundproofing Material

What is mass loaded vinyl? A flexible acoustic barrier: a sheet of vinyl loaded with heavy mineral filler, typically one pound per square foot at one-eighth inch thick. It adds mass without adding thickness, and because it is limp it does not resonate the way a rigid panel does.

Where MLV belongs. Inside an assembly, as one mass layer among several: stapled to studs or joists before drywall, hung behind a new ceiling, or laid under a floated floor. In a wall it typically adds 4 to 6 STC points when properly installed and sealed. MLV soundproofing works well in two situations in particular: thin cavities where there is no room for a second layer of drywall, and ceilings where every inch of height matters.

Where MLV disappoints. When it is used on its own. A sheet of mass loaded vinyl stapled to the face of an existing wall and left exposed, or hung as a curtain, adds a little mass and seals nothing. As a result, it will not stop a conversation and will do almost nothing for footsteps or bass. Similarly, transparent and clear MLV products are marketed for windows; they are too light to make a meaningful difference against a window that leaks at the frame.

Where Mass Loaded Vinyl Came From

MLV is a modern take on an old idea. For decades, sound insulation work relied on lead sheet, the classic limp-mass barrier: heavy, flexible and airtight. By the early 1970s, engineers were mixing fine lead particles into PVC. A 1972 SAE technical paper called the result a “limp high mass sound barrier material.”

Lead’s toxicity ended that era. Early lead-free MLV used barium as the heavy filler, and most sheets today use calcium carbonate instead. We came back to MLV for the same reason acousticians first reached for lead. A limp layer has very low bending stiffness, which pushes its coincidence frequency high, above the range that matters for voices. As a result, it adds mass without the coincidence dip a stiff board suffers. In other words, it gets close to the ideal M. David Egan describes in Architectural Acoustics: “heavy, limp, and airtight.”

Installing Mass Loaded Vinyl

How to install mass loaded vinyl so it performs: overlap or butt the seams and tape them with MLV seam tape, seal the perimeter with acoustical sealant, cover it with drywall, and do not let it bridge rigidly from one side of a decoupled assembly to the other. Mass loaded vinyl STC ratings printed on packaging (often STC 26 to 27) are for the sheet alone in a lab frame; what matters is the rating of the full wall it goes into.

Generally, MLV is safe for interior residential use. Follow the manufacturer’s handling guidance, and buy it by weight per square foot rather than by brand.

Soundproof Drywall and Damping Compound (Green Glue)

Soundproof drywall (QuietRock, SilentFX and similar) is two layers of gypsum laminated around a viscoelastic damping core. It also does two jobs in one board: mass and damping. A single layer of soundproof drywall performs roughly like two layers of standard drywall with damping compound between them, in less thickness. For this reason, it is the right choice when depth is limited.

Green Glue and other damping compounds are the soundproofing material you apply yourself, between two layers of ordinary drywall. The compound then converts the vibration in the boards into a small amount of heat. Two layers of five-eighths-inch Type X drywall with damping compound between them is the finish layer on most Hush walls and ceilings. The compound needs the full recommended coverage to work and takes weeks to fully cure; results measured in the first week understate the final performance.

Acousticians call this constrained-layer damping: a viscoelastic layer sandwiched between two rigid ones. It also reduces the coincidence dip, the frequency where a board’s bending waves line up with sound in the air. For five-eighths-inch gypsum, that dip falls around 2,500–3,000 Hz. Two properties set that frequency: the board’s weight per square foot and its bending stiffness, how hard it resists flexing.

Either approach, then, reaches the same place. Soundproof drywall costs more per sheet and saves labour; standard drywall plus compound costs less and adds a step. Neither one does anything useful screwed directly to the existing wall without decoupling, which is why “I added a layer of drywall and it did nothing” is the most common story we hear.

Soundproofing board, sound insulation board, and fibreboard products (Homasote, SoundStop and similar) are lightweight, so they add very little mass. They are not a substitute for drywall in a blocking assembly.

Resilient Channel and Sound Isolation Clips

These are the decoupling layer. In fact, no soundproofing material does more to separate a good result from a great one.

Resilient channel is a thin, springy metal strip screwed across the studs or joists; drywall hangs from the channel rather than from the framing. It is an inexpensive and effective soundproofing material. Still, it is fragile: a single screw driven through the channel into a stud short-circuits it, and heavy double-layer drywall can bottom it out.

Sound isolation clips with hat channel (Whisper Clips, RSIC, Genie Clips) are the heavier-duty version. Rubber-isolated clips attach to the framing, hat channel snaps into the clips, and drywall hangs from the channel. Clips carry more weight and are far harder to short-circuit, so they are what we install on party walls and ceilings. With insulation, damping and two layers of drywall, a clip-and-channel assembly is how a wall gets from STC 33 to STC 55-60+.

For ceilings under a noisy upstairs neighbour, clips are the material that addresses footsteps. In contrast, nothing you add to the ceiling surface without decoupling will.

Sealing Materials: Acoustical Sealant, Putty Pads and Gaskets

These are the least glamorous soundproofing materials, and therefore the ones most often skipped.

• Acoustical sealant stays flexible permanently and goes at every perimeter joint, around every penetration, and behind every piece of trim where the frame meets the wall. Ordinary caulk, however, hardens and cracks.
• Putty pads wrap electrical boxes. That matters because back-to-back outlets sharing a stud bay are a classic leak in NYC party walls.
• Isolation gaskets go under bottom plates and around pipes and ducts so they do not couple the assembly to the structure.

For example, a wall built with every material above and no sealant will underperform a sealed wall built with half of them.

Soundproofing Materials That Don’t Work

We would rather you hear this from us before you spend money on the wrong soundproofing material.

• Soundproofing paint. Marketed as a soundproof material that adds mass. A coat of paint weighs a fraction of a single layer of drywall. As a result, it does nothing measurable.
• Acoustic foam and soundproof foam panels. Excellent at absorbing echo inside a room. However, they have zero effect on sound passing through a wall. “Soundproof foam” is a contradiction.
• Egg cartons. No.
• Peel and stick soundproofing. Thin adhesive foam or vinyl sheets add almost no mass and seal nothing. So they may soften echo, but the wall’s STC stays about where it was.
• Soundproof curtains and acoustic blankets. Useful for echo and a small amount of high-frequency attenuation at a window. However, they do not seal and do not block speech.
• MLV, drywall or anything else added to one side of a wall without decoupling and sealing. Adds a few points at best. See the drywall story above.

Which Soundproofing Material Should You Use?

Problem	Materials that solve it
Neighbour’s voices or TV through a shared wall	Isolation clips + mineral wool + two layers drywall with damping compound + acoustical sealant
Footsteps from above	Decoupled ceiling on isolation clips; MLV as an extra mass layer if height is tight
Your footsteps bothering the neighbour below	Acoustic underlayment under a floated subfloor; see floor soundproofing
Hallway or street noise through a door or window	Perimeter seals, automatic door bottom, window inserts; see door and window soundproofing
Echo in a conference room or living room	Mineral wool or felt acoustic panels; see acoustic panels
Bass from a bar or music studio	Mass + decoupling on every surface; the hardest problem and the one where single materials fail completely

The best soundproofing material is the complete assembly, specified for the noise you actually have. That is what an assessment is for, after all.

Soundproofing Materials FAQ

What is the best soundproofing material for walls?

There is no single one. A decoupled assembly of isolation clips, mineral wool insulation, and two layers of drywall with damping compound, sealed airtight, outperforms any individual product by a wide margin.

Is mass loaded vinyl worth it?

Inside a wall or ceiling, as one mass layer among several, yes, especially where depth is limited. Hung on the surface or used alone, no.

Does soundproofing insulation block sound?

It absorbs the sound inside the cavity so the wall does not resonate. On its own, however, it adds a few STC points. It is necessary but not sufficient.

Rockwool or fiberglass for soundproofing?

Both perform similarly when the cavity is full. Rockwool is denser, fire-resistant and does not sag, so it is what we specify in new assemblies.

Does green glue work?

Yes, between two rigid layers, at full coverage, given time to cure. It does not work as a glue to stick drywall to an existing wall.

Does soundproof paint work?

No.

Where can I buy soundproofing materials in NYC?

Most of the effective soundproofing materials above are available through building-supply and acoustic distributors. However, the harder part is specifying and installing them correctly, which is the work we do.

Get the Right Assembly, Not the Right Product

Hush is a licensed New York City soundproofing contractor with an in-house acoustic consulting team. Every project starts with identifying the noise type and the path it takes, and only then choosing materials. Book a consultation and we will tell you what to use and, just as often, what not to bother buying.

Related: Wall Soundproofing · Ceiling Soundproofing · Floor Soundproofing · Door and Window Soundproofing · Acoustic Panels · Sound Absorbing Material · STC and IIC Ratings · Soundproofing Cost NYC