Have you ever had a quiet evening ruined by heavy footsteps overhead or been kept awake by a neighbor’s music? Noise is one of the most common complaints in multi-story buildings and flooring plays a major role in how sound travels between spaces.
Acoustics matter when hard surface floors are installed since they don’t absorb sound the way carpet does. There are ways to reduce sound transmission, but measuring performance can be tricky since acoustical ratings are often misunderstood, misrepresented, and misapplied. This blog explains the basics, why the numbers can be misleading, and how you can protect yourself from noise complaints or disputes.
Key Ratings (IIC & STC)
Two numerical rating systems measure how floors and underlayment handle sound transmission. Ratings usually fall between 50–74 (higher = better performance):
- Impact Insulation Class (IIC): Measures how well a floor reduces impact noise—footsteps, dropped objects, chairs sliding, etc. Some manufacturers also publish a Delta IIC (ΔIIC), which shows how much a floor or underlayment improves the baseline rating of a bare floor.
- Sound Transmission Class (STC): Measures how well a floor reduces airborne noise—voices, music, or TV sound traveling through walls, ceilings, or floors.
Why Ratings Can Be Misleading
While that might seem straightforward, the problem is inconsistency. Acoustical tests are conducted in specialized labs and while the test procedure is standardized, the floor assemblies are not. A product might be generally tested:
- On concrete with a suspended drop ceiling (common in commercial offices).
- On a bare concrete slab (typical in condos).
- On wood frame construction (common in homes).
Suspended acoustical drop-ceiling
Results can vary significantly. A bare concrete slab typically tests in the 50’s, while adding a drop ceiling can raise ratings to the high 60’s or low 70’s. Variations also arise from differences in test assembly thickness, insulation, and construction. When adding an underlayment to a floor, each combination has a unique sound rating and must be tested together - you cannot simply add the underlayment rating to the floor rating. The only way to know exactly how your floor will perform in your unit is through a costly in-situ test by an acoustical engineer.
Some manufacturers will provide results for multiple assemblies so you can identify the one that applies to your situation:
Example 1: Silencer LVT Universal Luxury Vinyl Underlayment Spec Sheet
But often, only the highest results are listed, usually from the most favorable test that includes a drop ceiling, sometimes without disclosing how the test was done:
Example 2: Platinum LVT Underlayment Spec Sheet
Why This Matters for Condos & HOA’s/AOAO’s
Acoustical requirements vary widely depending on the building and specifiers, associations, and CC&R authors sometimes don’t always understand how IIC/STC ratings work. Some buildings provide a short list of pre-approved underlayments, which can directly affect flooring choices since whatever floor you select must be compatible.
Most associations write IIC/STC limits in the low 50’s that are realistic for “no-drop ceiling” construction and generally achievable. However, it’s not uncommon to see standards in the 60’s or 70’s which are only possible with a suspended ceiling, which most Hawaii condos do not have.
Here's an example of the acoustical requirements from a residential condo in Honolulu:
The problem arises when a reviewer sees acoustical tests that reflect the correct condition (a slab without a drop ceiling) and denies the application because the results fall in the 50’s. In doing so, they’re comparing apples to oranges by measuring a “no drop ceiling” performance value against a “with drop ceiling” requirement.
This puts both homeowners and reviewers in a tough spot. Reviewers are tasked with enforcing inapplicable requirements, while homeowners must either forgo hard-surface flooring or submit a spec sheet showing only drop-ceiling results. While inconsistent, many other units in the same building probably already have hard-surface floors approved under similar circumstances, making this a systemic, building-wide issue rather than the fault of any single owner.
The best solution is for AOAO’s to work with an acoustical engineer to establish realistic, building-specific standards, instead of relying on inapplicable requirements. Meanwhile, Owners should protect themselves by keeping spec sheets, highlighting test conditions, and documenting correspondence and approvals.
3 ways to Make Your Floor Quieter
- Choose Carpet Where Possible: Carpet with a quality cushion pad is the quietest flooring option.
- Add an Underlayment: Rubberized underlayments are top performers and come in different thicknesses. Foam, cork and felt underlayments are also available, but check compatibility and avoid “double padding” a pad-attached floor. For hardwood, certain adhesives also provide sound-dampening benefits.
- Add Rugs: Runners and area rugs absorb impact noise in High-Traffic Areas.
Bottom Line
Flooring acoustics is a complicated inexact science and numbers on a spec sheet don’t always tell the whole story. The key is understanding the limits of what flooring can do under what conditions, documenting everything carefully, and setting realistic expectations from the start. At Paradise Flooring, we don’t just sell floors — we help you navigate the fine print so you can enjoy your new floor and peace of mind.
Disclaimer: Paradise Flooring provides only the product specifications supplied by the manufacturer and makes no representations or warranties as to their accuracy, applicability, or performance in any specific building. This blog is for educational purposes only and is not intended to guide compliance. We do not encourage or condone deceptive practices. It is the Owner’s sole responsibility to confirm compliance with all applicable rules, regulations, and association requirements before proceeding with any installation.
