Why does the frequency matter so much?

Because the mass law gives 6 dB per doubling of the product of mass and frequency. Halving the frequency therefore requires doubling the mass to hold the same transmission loss. A 25 dB requirement at 500 Hz needs about 3 lb/ft²; the same 25 dB at 125 Hz needs about 12. That single relationship explains why low-frequency noise complaints are so much more expensive to fix.

The required mass exceeds my structural capacity. What are the options?

Three real ones. A double-leaf partition with an air gap beats the mass law substantially for the same total weight, and is the standard answer. Treating the source, an enclosure at the machine rather than a barrier at the boundary, reduces the area that needs mass and usually costs far less. Or the requirement itself gets renegotiated once the achievable figure on this page makes the physics concrete. Adding as much mass as the structure allows and hoping is not on the list.

Why use 38.5 rather than 33.5 in the formula?

Those are the field-incidence and normal-incidence constants. Real partitions are struck by sound arriving from all directions, which is the field-incidence case and is about 5 dB less favourable than the normal-incidence idealisation. Using 33.5 would overstate every barrier on this page by 5 dB, which is roughly the difference between a treatment that satisfies a complaint and one that gets torn out and replaced.

Does two layers of one-pound vinyl equal two-pound vinyl?

Acoustically, roughly yes, and that is the problem people expect otherwise. Two limp layers in direct contact behave as a single layer of the combined mass, so you get the mass-law benefit of doubling: about 6 dB, and nothing more. To do better the layers need separating with an air gap or a resilient element, at which point it stops being a mass-law calculation and becomes a double-leaf design.

How does this relate to the Decibel Reduction Estimate?

They are inverses of the same relationship. That page starts from a barrier you have chosen and predicts the decibels, including the ceiling that any open area imposes. This one starts from the decibels you need and returns the barrier. Use this page to size and budget, then that one to check what leakage does to the result, because an unsealed barrier caps out well below whatever mass you bought.

Is the total mass figure what I hang on the structure?

It is the acoustic layer only. Framing, fixings, any facing or protective skin, and the labour access to install it all add to the load the structure sees. Treat the figure as a floor and give the structural engineer the finished construction, not this number.

Acoustic, Noise, Vibration & NVH Products calculator

Acoustic Barrier Mass Loading Calculator

Work out how heavy a barrier has to be to deliver a required noise reduction, and whether the building can carry it. Enter the area to be treated, the transmission loss the specification demands, the frequency it applies at, and the added dead load the structure can accept. The calculator inverts the field-incidence mass law to give the surface density required in pounds per square foot, multiplies it out to a total weight, and compares that against the structural allowance. It also shows what six more decibels would cost in mass and what the best achievable reduction is if the structure is the binding constraint.

What this calculator does

Turn a required transmission loss into the barrier surface density and total mass it demands, and check that mass against what the structure can carry.
Use it for converting a noise-complaint requirement into a barrier specification a supplier can price, checking whether an existing roof or mezzanine can carry the barrier a specification demands, showing a client what six more decibels actually costs in mass and structure, deciding when to abandon a single-layer barrier and design a double-leaf partition instead, screening a low-frequency requirement before committing to a mass-based approach.
Turn a required transmission loss into the barrier surface density and total mass it demands, and check that mass against what the structure can carry.

Formula used

Required surface density = 10^((required TL + 38.5) ÷ 20) ÷ design frequency
Total added mass = required surface density × barrier area
Margin = structural capacity − required surface density
Surface density for 6 dB more = required surface density × 10^(6 ÷ 20) ≈ ×2
Best TL the structure allows = 20 × log10(capacity × frequency) − 38.5

Inputs explained

Barrier area to treat: Total area of wall, ceiling or enclosure that will carry the barrier. Include every surface in the transmission path, not only the one facing the source.
Required transmission loss: The reduction the specification or the complaint demands at the design frequency. This is a single-frequency requirement, not an STC rating.
Design frequency: The frequency the requirement applies at. Mass-law performance improves 6 dB per octave, so the lowest frequency of concern sets the mass.
Structural capacity available: Added dead load the roof, wall or frame can accept, from the structural engineer. Not a guess: hanging barrier is added permanent load.

How to use the result

Best suited to converting a noise-complaint requirement into a barrier specification a supplier can price, checking whether an existing roof or mezzanine can carry the barrier a specification demands, showing a client what six more decibels actually costs in mass and structure, deciding when to abandon a single-layer barrier and design a double-leaf partition instead, screening a low-frequency requirement before committing to a mass-based approach.
Ignores the coincidence dip, where a real panel loses several decibels in a band set by its stiffness and thickness. Ignores flanking: sound around the barrier through structure, ducts, conduit or a shared ceiling void frequently governs the installed result. Says nothing about double-leaf constructions, which beat the mass law substantially and are the right answer whenever this page demands an impossible mass. Not a structural assessment. It compares one number against an allowance somebody else must supply. Laboratory transmission loss is an upper bound. Installed performance is typically several decibels worse even when the construction is right.

Common questions

Why does the frequency matter so much? Because the mass law gives 6 dB per doubling of the product of mass and frequency. Halving the frequency therefore requires doubling the mass to hold the same transmission loss. A 25 dB requirement at 500 Hz needs about 3 lb/ft²; the same 25 dB at 125 Hz needs about 12. That single relationship explains why low-frequency noise complaints are so much more expensive to fix.
The required mass exceeds my structural capacity. What are the options? Three real ones. A double-leaf partition with an air gap beats the mass law substantially for the same total weight, and is the standard answer. Treating the source, an enclosure at the machine rather than a barrier at the boundary, reduces the area that needs mass and usually costs far less. Or the requirement itself gets renegotiated once the achievable figure on this page makes the physics concrete. Adding as much mass as the structure allows and hoping is not on the list.
Why use 38.5 rather than 33.5 in the formula? Those are the field-incidence and normal-incidence constants. Real partitions are struck by sound arriving from all directions, which is the field-incidence case and is about 5 dB less favourable than the normal-incidence idealisation. Using 33.5 would overstate every barrier on this page by 5 dB, which is roughly the difference between a treatment that satisfies a complaint and one that gets torn out and replaced.
Does two layers of one-pound vinyl equal two-pound vinyl? Acoustically, roughly yes, and that is the problem people expect otherwise. Two limp layers in direct contact behave as a single layer of the combined mass, so you get the mass-law benefit of doubling: about 6 dB, and nothing more. To do better the layers need separating with an air gap or a resilient element, at which point it stops being a mass-law calculation and becomes a double-leaf design.
How does this relate to the Decibel Reduction Estimate? They are inverses of the same relationship. That page starts from a barrier you have chosen and predicts the decibels, including the ceiling that any open area imposes. This one starts from the decibels you need and returns the barrier. Use this page to size and budget, then that one to check what leakage does to the result, because an unsealed barrier caps out well below whatever mass you bought.

Last reviewed 2026-08-25.