Acoustic Isolation & Sound Control
H-O Products die-cuts and converts the resilient, barrier, and sealing layers that let a building's rated wall and floor-ceiling assemblies perform: isolation pads and gaskets under partitions and floors, resilient isolation-clip and hanger pads, perimeter isolation gaskets, mass-loaded barrier layers, acoustic sealing gaskets at penetrations, door and perimeter acoustic seals, and floor-underlayment die-cuts, cut to your drawing from closed-cell foams, EPDM and neoprene sponge, cork-rubber, and felt.
Built for: resilient breaks under partitions and floating floors, perimeter isolation around slabs and columns, gaskets that close the flanking air paths at penetrations and door perimeters, and the underlayment die-cuts that cut footfall, all as the converter-side ingredients of an assembly rated for airborne Sound Transmission Class (STC) per ASTM E90 / E413 and impact Impact Insulation Class (IIC) per ASTM E492 / E989.
This guide is for acoustic consultants, architects, and structural, mechanical, and building engineers specifying the resilient, barrier, and sealing parts inside partitions, floating floors, decoupled ceilings, and equipment interfaces, and for the procurement and sourcing teams qualifying those parts as made-to-order components. It covers what each converted part does, the failure modes you design against, the standards that rate the assembly (never the part), and what to send H-O for a quote.
Acoustic requirement → strategy (decouple / mass / seal) → material selection → part → production supply.
- 1Define the acoustic jobReduce transmission between spaces (isolation), close flanking gaps (sealing), or cut reverberation in a room (absorption). Name the assembly and its STC/IIC target.
- 2Pick the strategyDecoupling (a resilient break), added mass (barrier layer), damping, and sealing at every air path. Most assemblies use more than one.
- 3Select the material classResilient sponge or PU for the break, dense rebond or cork-rubber for load, felt or foam underlayment for impact, EPDM or neoprene gasket for sealing.
- 4Size by load, not gaugeSet the resilient pad by its compression-deflection class against the bearing load so it stays in its working range; thickness and durometer fall out.
- 5Die-cut to drawingPads, perimeter strips, penetration gaskets, and underlayment with sealed, accurate edges, with adhesive, liner, or pull-tab as the detail needs.
- 6Quote prototype or productionSend the assembly detail and part footprint; H-O returns a manufacturable part, the TDS, and the standards language framed to the assembly.
To control sound in a building, first name the job, because absorption, isolation, and sealing are different. Isolation (reducing sound between spaces) combines decoupling, mass, damping, and sealing, and is rated STC for airborne (ASTM E90 lab data to E413) and IIC for impact (ASTM E492 to E989), always at the assembly level. The remaining zones and duties are mapped in the When-to-spec list on this page. Values are per the TDS on file; see the material reference below for ordering details.
Assembly ratings, by designation (the rating belongs to the tested assembly): ASTM E90 (lab airborne transmission loss) · ASTM E413 (Sound Transmission Class, STC) · ASTM E336 (field airborne isolation, ASTC) · ASTM E492 (lab impact via tapping machine) · ASTM E989 (Impact Insulation Class, IIC). Absorption, distinct from isolation: ASTM C423 (sound absorption, NRC/SAA) · ASTM C522 (airflow resistance of porous absorbers).
Material-level, per the maker TDS: ASTM D1056 (flexible cellular sponge/expanded rubber Type/Class/Grade) · ASTM D3574 (flexible PU foam CFD and compression set) · ASTM D2240 (durometer) · ASTM E84 (surface burning, by designation).
- Resilient break (light load): neoprene sponge / vinyl-nitrile foam
- Resilient break (heavy load): rebonded neoprene / PORON® PU
- Perimeter isolation gasket: EPDM foam / RE-series closed-cell
- Penetration & door sealing: EPDM / neoprene sponge gaskets
- Floor underlayment (impact/IIC): cork / cork-rubber / felt
- Underlayment (foam): crosslinked PE / EVA foam
- Temperature / flame duty: BISCO® A2 sound-barrier silicone
- Mass / barrier layer: mass-loaded vinyl (limp barrier; per product TDS)
Where are you in the spec process?
This page serves engineers who already know the resilient, barrier, or sealing part they want and engineers still deciding which acoustic job they are solving. Pick the path that matches where you are; you don't have to read the rest.
Send a drawing, get a quote
A neoprene or EPDM sponge gasket, a resilient isolation pad, a perimeter isolation strip, a penetration seal, a door-perimeter seal, or a floor-underlayment on your drawing.
Skip to the quote form →Work from the acoustic job outward
Six selection factors (job, decoupling, mass, sealing, load, environment), a resilient-and-sealing layer checklist, and ten material families with TDS-cited methods and by-designation standards language.
Start with selection factors →
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1Send drawingUpload a DXF, DWG, or PDF of the partition or floor detail, or describe the joint. A sample part works too.
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2Material reviewEngineering reviews the bearing load, the gap and closure at perimeters and penetrations, and the resilient-break detail against the maker TDSs, and frames the standards language correctly: material classes (ASTM D1056 / D3574) per TDS, and STC/IIC by designation with the rating belonging to the tested assembly.
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3PrototypeSamples typically ship in 3–5 business days for common configurations on materials we keep on hand. Standard production 2 weeks; special orders run custom lead times. Made-to-order; MOQ varies by material and part.
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4ProductionStandard production runs ship about 2 weeks after drawing approval, on flatbed die-cutting, CNC knife cutting for pad and underlayment sets, and kitting for multi-part joint kits. Ongoing parts run with material traceability and lot-code TDS records.
Which acoustic job are you solving?
Application Zones
Eight converted-part roles define acoustic isolation and sealing in a building. They fall into three jobs the honest spec keeps separate: decoupling (a resilient break in the structure-borne path), mass and damping (a barrier layer), and sealing (a gasket that closes the airborne flanking gap). The diagram below shows why the two paths need two different answers; the tabs then walk each role, the controlling property, and the families H-O converts for it.
Throughout, one rule holds: the STC and IIC numbers belong to the tested assembly, not to any single part.
Partition & floor isolation: the resilient break
The decoupling job starts here. A resilient isolation pad or strip, to the track or slab-edge footprint, sits between a partition's bottom track (or a floated slab) and the structural deck, so the structure-borne path is broken by a compliant layer instead of a rigid contact.
The pad is a spring: it works only when its working compression range brackets the bearing load, which is why closed-cell neoprene sponge and the SCE by-density grades (Type 2 closed-cell classes per ASTM D1056) carry the light-to-moderate loads, rebonded neoprene and PORON® microcellular PU (compression-force-deflection per ASTM D3574) carry the heavier bearing loads under floated slabs, and vinyl-nitrile foam handles gentler duty.
One sentence governs all of it: the isolation shows up only as an improvement in the tested assembly's STC/IIC, never as a rating on the pad.
Resilient clip & hanger pads: the decoupling insert
Sound-isolation clips and resilient hangers decouple drywall and ceilings from framing, and the acoustic work is done by a resilient element inside the clip. H-O converts that resilient pad or insert, not the stamped-steel clip body: a PORON® microcellular PU pad specified by its compression-force-deflection curve (ASTM D3574) where the insert must hold its spring rate for decades, a closed-cell neoprene or cork-rubber pad where the load and geometry suit it, with durometer reported per ASTM D2240 on the grade TDS.
The insert's job is the same as every resilient element on this page: introduce compliance so the connection's structure-borne path is broken, and let the improvement land on the tested assembly's rating.
Perimeter isolation: keep the decoupled element off the structure
A floating floor or an isolated partition only stays decoupled if nothing bridges the break, and the perimeter is where bridging happens: grout, mortar, or a hard edge that lets the slab touch the surrounding wall or column re-couples the structure-borne path around the whole edge. Continuous resilient perimeter strips, from closed-cell EPDM or neoprene sponge (compression classes per ASTM D1056), keep the floated element off the structure and absorb the edge movement.
EPDM earns its place where the edge sees moisture or an exterior-adjacent condition; neoprene where general resilience and load range govern. The strip is drawn as part of the decoupling detail, not caulked in as an afterthought.
Mass & barrier layers: raise the transmission loss
Where the airborne transmission loss needs to come up, one lever is mass: a heavy, limp barrier layer added to the wall, floor, or ceiling raises the assembly's transmission loss. Mass-loaded vinyl (a high-density, limp loaded-PVC barrier) is the common construction, specified by areal density (surface weight, commonly around 1 lb/ft² with lighter and heavier variants), not by thickness, with the exact areal density and any assembly contribution taken from the specific product's TDS.
Two honest cautions belong on the drawing: it is a mass strategy, not an absorber (it does not cut reverberation within a room), and it performs best as a limp mass, decoupled rather than bonded rigidly. H-O and slits barrier sheet to the panel and penetration geometry; H-O does not stock a mass-loaded-vinyl catalog line, so the grade is specified from the product data you supply.
Penetration & door sealing: close the flanking air paths
An enclosure leaks at its worst aperture, not through the wall, and in acoustics the apertures are the unsealed air paths: the gap under a track, an outlet box, a service penetration, a door perimeter. Field isolation (ASTM E336) measures direct plus flanking transmission, which is exactly why an unsealed gap drags the field ASTC below the lab STC.
Die-cut acoustic sealing gaskets close those paths: EPDM and neoprene sponge gaskets and collars sized to the real gap and closure at penetrations and boxes, and resilient compression seals at door perimeters and meeting stiles. Sealing is drawn as part of the rated design; extruded or mechanical door-bottom hardware, where a job needs it, is coordinated through H-O's partner network, not in-house.
Floor underlayment: cut the footfall (impact/IIC)
Footfall is an impact problem, and the resilient underlayment under a floating floor or slab is the layer that cuts it, contributing to the tested floor-ceiling assembly's IIC (best expressed as the assembly rating or a ΔIIC improvement, never as an underlayment "IIC").
The material is chosen by the finish, the load, and the impact target: cork and technical rubberized cork give damping and isolation with a long service history under floors; pressed felt gives a high-damping resilient separator; crosslinked polyethylene and EVA foams give economical resilient underlayment by density.
All are thickness-, density-, and load-dependent, so the numbers come from the specific grade's TDS, and the underlayment is to the pad or sheet layout the floor detail calls for.
Equipment interface: specified on the mechanical page
Where mechanical equipment, pipe, and duct meet the structure, the resilient pads, washers, and wraps that blunt structure-borne vibration are specified on the mechanical equipment isolation page — the deep playbook for isolation pads, grommets, and washers under building equipment, argued once in one place. Duct and pipe thermal wrap at supports is on the duct, pipe & thermal insulation page.
This acoustic page owns the room-side assembly — partitions, floating floors, decoupled ceilings, perimeter sealing, and underlayment; when the noise source is a running machine, start on the mechanical page and come back here for the assembly it sits in.
Six decisions that drive your acoustic material spec
An acoustic assembly is a stack of single-purpose layers, and each has one controlling property. Miss one and the failure is rarely dramatic: a gap left unsealed, a resilient break bridged, a pad picked by thickness, an absorber specified where isolation was needed. The result is a wall that tests below its target and a review that stalls on a component asked to carry a rating.
Materials carry classes; assemblies carry ratings. A compression-deflection class (ASTM D1056) or a CFD curve (ASTM D3574) belongs to a material grade per its TDS. STC and IIC belong to the tested wall or floor-ceiling assembly per ASTM E413 and E989. Write material classes on the part callouts, cite STC/IIC by designation, express a component's effect as a delta (for example, a ΔIIC improvement), and never let a drawing imply that a gasket, pad, underlayment, or barrier sheet is itself "rated STC 50."
STC (airborne) and IIC (impact) are single-number ratings of a specific lab-tested build: a whole wall, a whole floor-ceiling. The resilient pads, perimeter strips, sealing gaskets, and underlayment on this page are the converter-side ingredients of that build; the rating belongs to the tested assembly, which is why this page cites the designation and never assigns a number to a part.
Read the six factors below in order. The first three name the job and the two isolation levers (decoupling, mass); the next two close the flanking gaps and size the resilient part by load; the last one matches the material to the environment. Every factor names its test method, because in this application the documentation is part of the part, and the rating is never the part's to carry.
Show all 6 selection factors tap to expand
Name the job first: absorption, isolation, or sealing
Rule — decide whether you are cutting reverberation within a room (absorption), reducing sound between spaces (isolation), or closing an air path (sealing), because the material classes do not cross over. A porous open-cell absorber earns a high NRC (ASTM C423, with airflow resistance per ASTM C522 a governing property [7]) and does little to stop transmission; a dense limp barrier raises transmission loss and does little for reverberation; a resilient break decouples structure-borne sound; a gasket closes flanking.
Write the job on the drawing before the material, and let each layer answer exactly one of the three. [6]
Decoupling: draw the resilient break as a continuous layer
Rule — isolation's first lever is a resilient element inserted into the structure-borne path: an isolation pad under a track or slab, a perimeter strip around a floated element, a resilient insert in a clip or hanger. It works only if the break is continuous and nothing rigid bridges it. Specify the resilient family by load (neoprene/EPDM sponge and vinyl-nitrile for light-to-moderate, rebonded neoprene and PORON® PU for heavy), and detail fasteners and edges so they do not short-circuit the break.
Continuity is the spec: a decoupled assembly with one rigid contact is a coupled assembly. [8]
Mass: add limp barrier where transmission loss must rise
Rule — the second isolation lever is mass: a heavy, limp barrier layer raises the assembly's airborne transmission loss. Mass-loaded vinyl is the common construction, specified by areal density (surface weight, per the product TDS), not thickness, and it works best as a limp mass, decoupled rather than bonded rigidly. It is a mass strategy, not an absorber. State the areal density from the product data and keep the layer limp; H-O and slits barrier sheet to the panel and penetration geometry from the grade you supply. [1]
Sealing: close every flanking air path with a gasket
Rule — a well-built assembly still leaks at its worst aperture, so seal the gap under the track, the penetrations, the boxes, and the door perimeter with gaskets sized to the real gap and closure. Field isolation (ASTM E336) captures direct plus flanking transmission, which is why the field ASTC reads below the lab STC when a path is left open.
Specify EPDM or neoprene sponge gaskets by compression class (ASTM D1056) to the joint. Treat sealing as part of the rated design, not a finishing step, and let edges remove the field-trimming that starts most flanking failures. [3]
Size the resilient part by load, not by gauge
Rule — a resilient isolation pad is a spring specified by its load-deflection behavior, not its thickness. Picked by footprint alone, it either bottoms out (transmitting vibration straight through) or never compresses into its working range (no isolation).
Specify the bearing load and the compression-deflection class (ASTM D1056 for sponge, CFD per ASTM D3574 for PU foam), and let thickness and durometer (per ASTM D2240 on the grade TDS [10]) fall out of the load; PORON®'s compression-set resistance is what keeps the spec valid over building life.
Get the bearing stress onto the drawing and the pad's working range brackets it. [9]
Match the material to the environment
Rule — the resilient/sealing family is picked by the location as much as the load. Neoprene sponge for general interior duty and moisture tolerance; EPDM for weather, ozone, UV, and exterior-adjacent or below-grade edges; cork and felt for underlayment damping; and BISCO® A2 silicone where the location adds temperature endurance or a flame class, with UL 94 listings and surface-burning (ASTM E84) cited by designation on the grade TDS.
Name the exposure, temperature, and any flame-spread requirement on the drawing, and let it pick between the EPDM, neoprene, cork/felt, and silicone tracks before cost does. [11]
Specification Tools
Two tools to take you from "we're isolating a partition" to here's the resilient-and-sealing part list for the drawing set: a requirement-driven checklist that assembles the layer list with its citations, and a side-by-side comparison of every resilient, barrier, and sealing family on this page.
1. Resilient & sealing layer checklist builder
Check the requirements your assembly carries. The builder assembles the corresponding resilient, mass, and sealing layers into a checklist with the family, what to send with the drawing, and the citation language (material classes per TDS; STC/IIC by designation, the rating belonging to the tested assembly). The default selection below is pre-built for a typical isolated partition; every layer is also printed in the material reference section, so nothing here exists only behind a script.
Resilient & sealing layer checklist: 3 layers selected
Each checked requirement adds its layer below. The list is the starting bill of materials for the engineering review, not a rating: material classes (ASTM D1056 / D3574) come from the grade TDS, and STC/IIC are cited by designation with the rating belonging to the tested assembly.
2. Side-by-side: resilient, barrier & sealing family comparison matrix
Every family called out on this page, with construction, the property that drives its selection, the standards its TDS cites, and the job it serves. Click a column header to sort. Click any material name to jump to its accordion entry.
| Material | Construction | Selection property | Standards on the TDS / by designation | Job | |
|---|---|---|---|---|---|
| Resilient isolation families | |||||
| Closed-Cell Neoprene Sponge + SCE by-densityClosed-cell sponge | Closed-cell neoprene sponge | Compression-deflection class | ASTM D1056 (per TDS) | Isolation, sealing | |
| Closed-Cell EPDM Foam + RE-seriesClosed-cell sponge | Closed-cell EPDM sponge | Weather/ozone + compression class | ASTM D1056 (per TDS) | Perimeter, sealing | |
| Rebonded NeopreneDense rebond | High-density rebonded foam | Static bearing stress (working range) | ASTM D1056 (per TDS) | Heavy-load isolation | |
| PORON® Industrial Microcellular PUMicrocellular urethane | Microcellular PU foam | Compression-force-deflection (CFD) | ASTM D3574; D2240 (per TDS) | Resilient pads, clip inserts | |
| Vinyl-Nitrile FoamClosed-cell VN | Closed-cell vinyl-nitrile | Compression-deflection class | ASTM D1056 (per TDS) | Light-load isolation, seals | |
| Cork + Technical Rubberized CorkCork / cork-rubber | Cork & cork-rubber composite | Damping + isolation (per grade) | Per maker TDS | Underlayment, inserts | |
| Underlayment & damping families | |||||
| SAE Pressed FeltPressed felt | Pressed wool/synthetic felt | Damping factor (thickness/density) | Per maker TDS | Underlayment, separators | |
| Crosslinked PE + EVA FoamClosed-cell foam | Crosslinked PE / EVA foam | Density-based resilience | Per maker TDS | Economical underlayment | |
| Mass / barrier & specialty families | |||||
| BISCO® A2 Sound-Barrier SiliconeSilicone sponge | Cellular silicone (barrier grade) | Temperature / flame class | UL 94; ASTM E84 (per TDS) | Barrier, seals (hot/flame) | |
| Mass-Loaded Vinyl (limp barrier)Loaded-PVC barrier | High-density limp PVC sheet | Areal density (surface weight) | Per product TDS | Added mass (barrier) | |
Skip ahead and request your material-selection review now
If your drawing set already calls out a resilient isolation pad, a perimeter strip, a sealing gasket, or a floor-underlayment die-cut, send it over for engineering review against the TDSs and the standards language.
Acoustic failures you can prevent at spec
Acoustic assemblies fail quietly first: a gap nobody sealed, a resilient break a screw bridged, an absorber bought where isolation was needed, a pad picked by thickness, a component asked to carry a rating it never had. Five patterns cover most of what goes wrong, and each is a specification decision made before the first part is cut.
In acoustics, the field number is the honest number. Lab STC/IIC assume a perfect build with no flanking; the field ASTC (ASTM E336) includes every path you left open. A correct assembly with one unsealed penetration, or a drawing that claims an STC for a gasket, costs more at review and in the field than any cutting error. Cite material classes per TDS and STC/IIC by designation at the assembly.
Show all 5 failure modes tap to expand
1. A good wall, defeated by an unsealed gap (flanking)
Fix — close every air path (perimeter, penetration, box, door edge) with a gasket sized to the real gap, and treat sealing as part of the rated design. The single most common acoustic failure is not a weak partition but sound bypassing a strong one through an unsealed opening. Field isolation (ASTM E336) captures direct plus flanking transmission, so the field ASTC reads below the lab STC exactly when a path is left open, and a small gap can dominate the result.
EPDM or neoprene sponge gaskets (compression class per ASTM D1056) at the track, penetrations, and door perimeter close the flanking paths; edges remove the field-trimming that starts most of these leaks. [3]
2. The resilient break, bridged into a rigid short-circuit
Fix — draw the break as a continuous resilient layer or perimeter, size the pad so it stays in its working range, and detail fasteners and edges so nothing rigid crosses it. A floating floor, decoupled ceiling, or isolated partition only works if the two sides never touch rigidly; a screw through the resilient layer, grout in the perimeter gap, or a pad compressed solid re-couples the structure-borne path and erases the isolation.
Specify the resilient family by load (neoprene/EPDM sponge and vinyl-nitrile for light-to-moderate, rebonded neoprene and PORON® PU for heavy) and keep the break continuous; a decoupled assembly with one rigid contact is a coupled assembly. [8]
3. Absorption specified where isolation was needed
Fix — name the job first: reduce reverberation within a room (absorption, NRC per ASTM C423) versus reduce transmission between spaces (isolation: decoupling, mass, damping, sealing), then pick the class that answers it. A porous open-cell "soundproofing" foam earns a high NRC and does little to stop sound passing between rooms; a dense limp barrier raises transmission loss and does little for reverberation.
Confusing the two, the most common SERP-level error, spends budget on the wrong material and leaves the complaint unsolved. Write the goal on the drawing before the material, and let each layer answer exactly one of the three jobs. [6]
4. A resilient pad picked by thickness, not by load
Fix — specify the bearing load and the compression-deflection class (ASTM D1056 for sponge, CFD per ASTM D3574 for PU), and let thickness and durometer fall out of the load. A resilient isolation pad is a spring, and picked by footprint alone it either bottoms out (transmitting vibration straight through) or never compresses into its working range (no isolation).
The pad that fits on day one can be the wrong spring, and if it takes a compression set the decoupling quietly expires; PORON®'s compression-set resistance is what keeps the spec valid over building life. Get the bearing stress onto the drawing and the working range brackets it. [9]
5. A component sold or drawn as having "an STC or IIC"
Fix — cite the material's own methods and classes by designation (ASTM D1056/D3574 classes; ASTM E84 flame-spread), express a component's acoustic contribution as a delta or as the tested assembly's rating, and never let the part carry the assembly's number. A drawing note that assigns an STC or IIC to a gasket, underlayment, mass-loaded-vinyl sheet, or clip stalls at review, because those single-number ratings exist only for a lab-tested wall or floor-ceiling build (ASTM E413 / E989).
The mass-loaded-vinyl bare-sheet number is not the wall number; the underlayment ΔIIC is not an underlayment "IIC". Keep the rating with the tested assembly and the classes with the material. [2]
Material reference
Detailed notes for the resilient, barrier, and sealing families referenced on this page: the resilient isolation set (closed-cell neoprene and EPDM sponge, rebonded neoprene, PORON® PU, vinyl-nitrile, cork and cork-rubber), the underlayment and damping set (pressed felt, crosslinked PE and EVA foam), and the specialty layers (BISCO® A2 sound-barrier silicone; mass-loaded vinyl as a supplied-grade concept).
Values are per the maker TDS on file for each grade with the method named; STC and IIC are cited by designation only, with the rating belonging to the tested assembly.
H-O die-cuts, kiss-cuts, slits, and kits every family to drawing.
Closed-Cell Neoprene Sponge (SCE by-density)Isolation pads, perimeter strips & sealing gaskets · ASTM D1056 Type/Class/Grade
Specify the bearing load and the ASTM D1056 compression class, not just thickness. The rating stays with the tested assembly; the sponge carries its material class.
Closed-Cell EPDM Foam (RE-series)Perimeter isolation & weather-facing sealing · ASTM D1056 classes
Match the compression class to the real closure force, and let the exposure pick EPDM over neoprene where weather and ozone govern. The material carries its class; the assembly carries the rating.
Rebonded NeopreneHeavy-load resilient pads under floated slabs & equipment · ASTM D1056
Size by bearing area and mass, not footprint alone. The isolation improvement lands on the tested assembly's rating; the pad holds its D1056 class.
PORON® Industrial Microcellular Urethane (4701 / 4790 series)Resilient isolation pads & clip inserts · ASTM D3574 CFD & compression set
Specify the load and the CFD window (per ASTM D3574), not thickness alone. Compression-set resistance is what keeps the decoupling detail alive; the rating stays with the tested assembly. Values per the maker TDS on file. [12]
Vinyl-Nitrile FoamLight-load isolation pads & seals · ASTM D1056 classes
Use where the load is light and conformability matters; step up to neoprene or rebond as the bearing load rises. Material class per D1056; rating with the assembly.
Cork & Technical Rubberized CorkUnderlayment & resilient inserts · per maker TDS
Take the isolation and damping numbers from the grade TDS; the underlayment contributes to the tested floor-ceiling assembly's IIC, expressed as the assembly rating or a ΔIIC, not as a cork “IIC”. Values per the maker TDS on file. [14]
SAE Pressed FeltResilient underlayment & separators · per maker TDS
Distinguish felt's isolation role (thin resilient separator, this page) from its absorptive role in acoustic felt panels; the two are tuned to different densities. Values per the grade TDS.
Crosslinked Polyethylene & EVA FoamEconomical resilient underlayment by density · per maker TDS
Pick the density to the load and impact target; the underlayment's contribution shows up as the tested assembly's IIC or a ΔIIC. Values per the grade TDS.
BISCO® A2 Sound-Barrier Silicone SpongeBarrier & seals where temperature or flame duty is added · UL 94; ASTM E84
Cite UL 94 and ASTM E84 by designation from the grade TDS; the material carries its class, and any fire or acoustic rating belongs to the tested assembly. This is the catalog line named for a sound-barrier role. Values per the maker TDS on file. [13]
Mass-Loaded Vinyl (limp barrier — supplied grade)Added mass to raise transmission loss · areal density per product TDS
Note: H-O does not carry a mass-loaded-vinyl catalog line, so the grade is specified from the product data you supply; H-O and converts the sheet you name. Its contribution is to the tested assembly's STC, not a sheet STC.
Polyether PU FoamPolyether PU Foam (low-force seals)
Acoustic isolation materials: engineer-grade FAQ
Twelve of the questions we hear most from acoustic consultants, architects, and building engineers. If your question isn't here, send a drawing or call, engineering picks up.
Does a gasket, underlayment, or isolation clip have an STC or IIC rating?
No, and no honest supplier will claim it does. STC (airborne, ASTM E413 from E90 data) and IIC (impact, ASTM E989 from E492 data) are single-number ratings of a specific lab-tested wall or floor-ceiling assembly. A gasket, pad, underlayment, mass-loaded-vinyl sheet, or clip contributes to that rating; it does not carry one. The honest way to state a component's effect is as the tested assembly's rating or as a delta (for example, a ΔIIC improvement from an underlayment).
What the material carries is its own class, compression-deflection per ASTM D1056 or CFD per D3574, plus its documentation and lot traceability. [2]
Absorption vs isolation vs sealing: which do I actually need?
Name the problem first. If a room is reverberant (echoey, hard to hear in), you need absorption, porous open-cell materials that cut reflections within the room, rated NRC per ASTM C423. If sound passes between two spaces, you need isolation, decoupling plus mass plus damping plus sealing, rated STC/IIC at the assembly. If a well-built wall still leaks, you need sealing, gaskets that close the air gaps at perimeters, penetrations, and doors.
They do not substitute for each other: an absorber barely reduces transmission, and a barrier barely reduces reverberation. Write the job on the drawing before the material. [6]
What goes under a floating floor to cut footfall (IIC)?
A resilient underlayment: cork or technical rubberized cork (damping plus isolation), pressed felt (high-damping separator), or crosslinked polyethylene and EVA foam (economical, by density). The choice follows the finish, the load, and the impact target, and every option is thickness-, density-, and load-dependent, so the numbers come from the grade TDS.
The underlayment's benefit is measured as the tested floor-ceiling assembly's IIC (ASTM E492/E989) or as a ΔIIC improvement, never as the underlayment's own "IIC". H-O the underlayment to the pad or sheet layout the floor detail calls for. [4]
How do I stop sound flanking around a good wall?
Close every air path with a gasket sized to the real gap and closure: the gap under the track, service penetrations, outlet and junction boxes, and the door perimeter. Flanking is why field isolation (ASTM E336, which captures direct plus flanking transmission) reads below the lab STC when a path is open, and even a small unsealed gap can dominate the result.
EPDM or neoprene sponge gaskets (compression class per ASTM D1056) are the usual answer, and edges remove the field-trimming that starts most leaks. Treat sealing as part of the rated design, not a finishing step. [3]
How do I pick and size a resilient isolation pad?
By load, not by gauge. A resilient pad is a spring: specify the bearing load and the compression-deflection class (ASTM D1056 for sponge rubber, compression-force-deflection per ASTM D3574 for PU foam), and let thickness and durometer fall out. Sized right, the pad works inside its range; sized by footprint alone, it either bottoms out (transmitting vibration straight through) or never compresses (no isolation).
Neoprene/EPDM sponge and vinyl-nitrile cover light-to-moderate loads; rebonded neoprene and PORON® PU cover heavier bearing loads, and PORON's compression-set resistance keeps the spring rate valid over building life. [9]
What is a resilient (decoupled) break, and how does it get bridged?
A resilient break is a compliant layer, a rubber, PORON® PU, cork-rubber, or felt pad or strip, inserted into the structure-borne path to decouple two rigid components (a floating floor from the slab, drywall from framing, a partition from the deck). By introducing compliance, it keeps impact and vibration energy from being rigidly conducted across. It gets bridged, and defeated, by anything rigid that crosses it: a screw through the layer, grout or mortar in a perimeter gap, or a pad compressed solid so it no longer acts as a spring.
The rule is continuity: a decoupled assembly with one rigid contact is a coupled assembly. [8]
Is mass-loaded vinyl an absorber, and how is it specified?
No, mass-loaded vinyl is a mass/barrier material, not an absorber. It is a high-density, limp loaded-PVC sheet that adds mass to a wall, floor, or ceiling to raise its airborne transmission loss, and it is specified by areal density (surface weight, commonly around 1 lb/ft² with lighter and heavier variants), not by thickness, with the exact value from the product TDS.
It does nothing for reverberation within a room, and it works best as a limp mass, decoupled rather than bonded rigidly. Its bare-sheet lab number is modest and is not the wall number; the contribution belongs to the tested assembly. H-O and slits the barrier sheet you supply. [1]
Will these materials make a partition "soundproof"?
"Soundproof" overstates what any assembly does; the honest target is a measured level of sound isolation, an STC and IIC for the assembly, achieved by combining decoupling, mass, damping, and sealing. The converted parts on this page (resilient pads, perimeter strips, sealing gaskets, underlayment) are ingredients of that assembly and raise its rating; they do not make a wall absolute. The right conversation is a target STC/IIC for the specific build, and a design that keeps the resilient breaks continuous and every air path sealed. [2]
What is the difference between STC and IIC?
STC (Sound Transmission Class) rates airborne sound isolation, computed per ASTM E413 from the laboratory transmission-loss data of ASTM E90; it answers "how well does this wall block voices and music between rooms." IIC (Impact Insulation Class) rates impact sound, computed per ASTM E989 from the tapping-machine data of ASTM E492; it answers "how well does this floor block footfall to the room below."
Both are single-number ratings of a tested assembly. A floor needs both; a wall is usually an STC question. In the field, apparent ratings (ASTC per ASTM E336) include flanking and typically read lower. [5]
Neoprene, EPDM, or silicone: which resilient/sealing family for my location?
By environment. Closed-cell neoprene sponge is the general interior workhorse with good moisture tolerance and load range. EPDM (including the RE-series) steps in where weather, ozone, UV, or an exterior-adjacent or below-grade edge would age a lesser foam.
BISCO® A2 cellular silicone is the choice where the location adds temperature endurance or a flame-class requirement, with UL 94 listings and surface burning (ASTM E84) cited by designation on the grade TDS. Vinyl-nitrile suits soft, light-load seals. Name the exposure, temperature, and any flame-spread requirement on the drawing, and it picks the track. [11]
What does H-O for acoustic sealing at penetrations?
Die-cut gaskets, collars, and washers sized to the real opening and closure where conduit, pipe, duct, cable, and service pass-throughs pierce a rated partition or floor, plus outlet-box and junction-box gaskets and door-perimeter seals. Closed-cell EPDM and neoprene sponge (compression classes per ASTM D1056) are the usual materials; silicone where the location adds temperature or flame duty. The point is to close the air path so the penetration does not become the assembly's worst aperture, with sealed, accurate edges that remove field-trimming.
Extruded or mechanical door-bottom hardware is coordinated through H-O's partner network, not in-house. [8]
What should I send so the quote comes back right the first time?
The assembly detail (partition or floor-ceiling section), the acoustic job and any STC/IIC target, the bearing load or mass for resilient pads, the gap and closure at perimeters and penetrations, the part footprint or drawing, adhesive/liner needs, the environment (interior/exterior/below-grade, temperature, moisture), any flame-spread requirement, and prototype plus annual volumes. "Recommend the resilient or sealing layer" is a valid callout: that is what the engineering review is for, and the standards language on the paperwork stays honest (material classes per TDS; STC/IIC by designation at the assembly).
Glossary: terms used on this page
Quick reference for the acoustic isolation, sealing, and material terminology used throughout. Each entry links to the relevant standard or test method where applicable.
STC (Sound Transmission Class)
The single-number airborne sound-isolation rating of a wall or floor-ceiling assembly, computed per ASTM E413 [2] from the laboratory transmission-loss data of ASTM E90 [1]. It rates the tested assembly, not any single component.
IIC (Impact Insulation Class)
The single-number impact-sound rating of a floor-ceiling assembly, computed per ASTM E989 [5] from the tapping-machine data of ASTM E492 [4]. An underlayment's effect is expressed as the assembly's IIC or a ΔIIC, never as the underlayment's own IIC.
ASTC / field isolation
Apparent Sound Transmission Class: the field airborne isolation of a finished assembly, measured per ASTM E336 [3] and rated with E413. Because it includes flanking (paths around the partition), it typically reads below the lab STC.
Decoupling / resilient break
Inserting a compliant (resilient) layer into a structural path to break the direct structure-borne transmission of vibration and impact, so the two sides do not rigidly conduct sound. The isolation pad, perimeter strip, and clip insert on this page are resilient breaks.
Flanking
Sound bypassing an assembly through paths other than straight through it: unsealed perimeters, penetrations, boxes, gaps under tracks, and connected structure. Sealing gaskets close the airborne flanking paths; field measurement (ASTM E336) includes them.
Structure-borne vs airborne
Two transmission paths. Airborne sound travels through air and any gap (answered by mass and sealing); structure-borne sound (impact, vibration) travels through solid connections (answered by decoupling with a resilient break). A floor design must address both.
Absorption & NRC
Absorption dissipates sound energy at a surface, reducing reverberation within a room; it is measured by ASTM C423 [6] and summarized as NRC. It is a different job from isolation: an absorber does little to stop sound passing between spaces.
Compression-force-deflection (CFD)
The pressure a cellular material exerts at a given compression, the curve that turns a resilient foam pad into a specifiable spring. Reported per ASTM D3574 [9] on PU foam TDSs; resilient pads are specified by their CFD against the load, not by thickness.
Compression set
Permanent thickness loss after sustained compression, per ASTM D3574 [9]. It is the long-game number for a resilient pad: a pad that takes a set relaxes out of its working range, and the decoupling detail quietly expires.
ASTM D1056 (Type / Class / Grade)
The specification for flexible cellular sponge/expanded rubber, per ASTM D1056 [8]. It classes neoprene, EPDM, and vinyl-nitrile sponge by Type (open/closed cell), Class (fluid resistance), and Grade (compression-deflection), the language on the gasket and pad TDSs.
Mass-loaded vinyl (MLV)
A high-density, limp loaded-PVC barrier that adds mass to raise an assembly's airborne transmission loss, specified by areal density (surface weight) per the product TDS. A mass strategy, not an absorber; best used as a limp, decoupled layer. Its contribution is to the tested assembly's STC.
Resilient underlayment
A resilient layer (cork, cork-rubber, felt, PE/EVA foam) under a floating floor or slab that reduces impact (footfall) transmission, contributing to the tested floor-ceiling assembly's IIC [4] or a ΔIIC. Thickness-, density-, and load-dependent per the grade TDS.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and maker technical data sheets cited throughout this page. Acoustic ratings (STC, IIC, ASTC, NRC) are cited by designation: they are single-number ratings of a tested assembly or material, and the rating belongs to the tested build. Standards editions current as of July 2026; verify against the publishing body before final spec. H-O materials are aligned to these standards through the source manufacturer's TDS, not independently certified by H-O unless explicitly stated on the quote.
[1] ASTM E90
Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements (current edition E90-23). The laboratory transmission-loss test whose one-third-octave data STC is computed from. store.astm.org (ASTM E90)
[2] ASTM E413
Classification for Rating Sound Insulation (current edition E413-22): defines the Sound Transmission Class (STC) single-number rating computed from one-third-octave sound-attenuation data (e.g. E90 lab data). The rating attaches to the tested assembly. store.astm.org (ASTM E413)
[3] ASTM E336
Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings (current edition E336-25a): the field method that captures direct plus flanking transmission; applying E413 to its data yields the Apparent Sound Transmission Class (ASTC). store.astm.org (ASTM E336)
[4] ASTM E492
Standard Test Method for Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine (current edition E492-25). The laboratory impact test whose data IIC is computed from. store.astm.org (ASTM E492)
[5] ASTM E989
Standard Classification for Determination of Single-Number Metrics for Impact Noise (current edition E989-21; the standard that defines the Impact Insulation Class, IIC, from E492 data). The rating attaches to the tested floor-ceiling assembly. store.astm.org (ASTM E989)
[6] ASTM C423
Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method (current edition C423-23). The absorption test (NRC/SAA), distinct from transmission-loss and impact testing. store.astm.org (ASTM C423)
[7] ASTM C522
Standard Test Method for Airflow Resistance of Acoustical Materials (current edition C522-03(2022)). Airflow resistance/resistivity is a governing property of a porous sound-absorbing material. astm.org (ASTM C522)
[8] ASTM D1056
Standard Specification for Flexible Cellular Materials—Sponge or Expanded Rubber (current edition D1056-20): classes sponge rubber by Type (open/closed cell), Class (fluid resistance), and Grade (compression-deflection). The language neoprene, EPDM, and vinyl-nitrile sponge TDSs cite. store.astm.org (ASTM D1056)
[9] ASTM D3574
Standard Test Methods for Flexible Cellular Materials—Slab, Bonded, and Molded Polyurethane Foams (current edition D3574-25): the compression-force-deflection (CFD) and compression-set methods PORON®-type microcellular PU TDSs cite. store.astm.org (ASTM D3574)
[10] ASTM D2240
Standard Test Method for Rubber Property—Durometer Hardness. The durometer method reported on resilient elastomer and foam TDSs where hardness is specified. store.astm.org (ASTM D2240)
[11] ASTM E84
Standard Test Method for Surface Burning Characteristics of Building Materials (current edition E84-25). Cited by designation for flame-spread / finish context; the rating belongs to the tested material or assembly, not to a converted part in isolation. store.astm.org (ASTM E84)
[12] Rogers PORON® Industrial Microcellular Urethane (TDS)
Technical data for the PORON® industrial microcellular polyurethane line (4701 / 4790 series): compression-force-deflection and compression-set data reported per ASTM D3574. Source manufacturer TDS for the resilient PU pads on this page. rogerscorp.com (PORON industrial)
[13] Rogers BISCO® Silicones incl. A2 sound-barrier (TDS)
Technical data for the BISCO® cellular silicone line, including the A2 sound-barrier / sound-attenuation grade: UL 94 flammability and surface-burning (ASTM E84) data by grade. Source manufacturer TDS for the silicone barrier/sealing layer on this page. rogerscorp.com (BISCO silicones)
[14] Amorim Cork Composites — Acousticork (TDS)
Technical data for cork and cork-rubber vibration-isolation and acoustic-underlayment materials: thickness-, density-, and load-dependent isolation and damping properties. Source manufacturer data for the cork/cork-rubber underlayment on this page. amorimcorksolutions.com (Acousticork)
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O materials are “aligned to” the standards cited through the source maker's TDS; H-O does not certify acoustic assemblies. Lot-specific documentation available on request.
To review your acoustic isolation or sealing part, send:
- Assembly detail (partition / floor-ceiling section)
- Acoustic job + any STC / IIC target
- Bearing load or mass (for resilient pads)
- Gap and closure at perimeters / penetrations
- Part footprint or drawing (DXF / DWG / PDF)
- Adhesive / liner / pull-tab requirements
- Environment (interior / exterior / below-grade, temperature, moisture)
- Any flame-spread requirement (ASTM E84 context)
- Prototype and annual volume
Get an acoustic materials engineering quote
Send an assembly detail, part drawing, or description. We typically respond within one business day with a material recommendation, prototype lead time, and TDS verification against your loads, gaps, and standards language (material classes per TDS; STC/IIC by designation at the assembly).
See also: related H-O application pages
Engineering content for the adjacent general-construction sub-applications and the parent hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Sibling sub-application
Mechanical equipment isolation
The deep isolation-pad, spring-mount interface, and inertia-base material playbook for building mechanical equipment, the load-bearing companion to this page's equipment zone.
Read the page
Sibling sub-application
Building envelope sealing
Weather, air, and water sealing gaskets at the envelope, where the same closed-cell EPDM and sponge families do the sealing job in a different duty.
Read the page
Sibling sub-application
Duct, pipe & thermal insulation
Thermal and isolation wrap, gaskets, and pads where duct and pipe meet structure, the companion to this page's pipe/duct isolation callouts.
Read the page
Industry hub
General construction
The full general-construction application family: envelope sealing, expansion joints, acoustic isolation, equipment isolation, fire and life safety, and more.
Read the page
Material data & standards. All compression, density, and material values on this page are taken from the source maker's technical data sheets with the method named (ASTM D1056, D3574, D2240; UL 94 and ASTM E84 classes per the listed grade TDSs). Acoustic ratings (STC, IIC, ASTC, NRC) are cited by designation only: they are single-number ratings of a tested wall, floor-ceiling assembly, or material (ASTM E90/E413, E492/E989, E336, C423), the rating belongs to the tested build, and the materials on this page contribute to it.
H-O converts materials; H-O does not design acoustic assemblies or certify their STC/IIC, and does not independently certify materials against the standards unless explicitly stated on the quote. Verify against the maker TDS and your assembly-level test plan.
Conversion scope. H-O and converts sheet, roll, and slab stock to drawing in Winsted, Connecticut: die-cut and kiss-cut pads, strips, gaskets, and underlayment, slit barrier and roll stock, waterjet-cut thick sections, laminations, and kitted joint sets, with material traceability and lot-code TDS records.
H-O does not run in-house molding or profile extrusion; molded parts and extruded profiles (including mechanical door-bottom hardware) are coordinated through a partner network. Lead-time and MOQ details are in the process strip and the quote form above.