Understanding Noise and How it Relates to Flooring
In the last few years noise has become a hot topic. One of the reasons for this change is that people are moving away from carpets to hard surface floors, such as
hardwood and
laminate flooring. It seems like every place you go there is "the newest and
best underlayment". All these new products and product claims can be quite overwhelming and misleading. The purpose of this article is to provide a better understanding of noise and how it relates to flooring.
Complaints from condo owners about noisy neighbors are a constant issue. Some of these involve airborne sound sources (talking, music, plumbing), but many are due to the reverberation of footfall (people walking, running, to tap dancing!) or structure-borne noise that differs from its airborne counterpart.
The most commonly used terms in multi-family residential construction are the sound transmission class (STC) and the impact insulation class (IIC). These describe different types of noise, but are often interchanged or misunderstood.
What is noise?There are two basic types of noise and measurements used to rate the acoustical performance of the floor-ceiling assembly. They are airborne noise and stucture-borne noise. The measurements used to determine the acoustical performance of airborne and structure-borne noise is the Sound Transmission Class (STC) and the Impact Insulation Class (IIC).
- The STC measures the performance of the floor-ceiling assembly to stop or isolate airborne noise such as voices, radio, televisions, etc.
- The IIC measures the performance of the floor-ceiling assembly to reduce or isolate impact noise (footfall) people walking, dropping objects, furniture being moved, etc.
Building codes
Building codes have established standards for minimum noise performances of partitions between residences. Most states use the International Building Code (IBC) which calls for a minimum IIC & STC rating for multi-family dwellings for new construction at 50 (or 45 if field tested). The minimum IIC rating of 50 would be considered low or an affordable housing rating, while a 55 would be considered more of an average or mid range rating and a 60+ would be considered a luxury or high-end rating.
One of the most common mistakes in selecting a floor underlayment is to look at a product IIC rating and think that it will perform to the same rating in your building. An IIC rating is determined on the complete floor-ceiling assembly, not just the floor underlayment. When comparing floor underlayments it is important to request the official IIC report from the company. The test report should come from an accredited lab and should detail what the floor-ceiling assembly was tested at. In recent years there have been some companies that advertise IIC rating of 72 without explaining how the product was tested, leaving many uneducated builders thinking that's all they need.
Whenever architects, builders and contractors are concerned with impact noise they should take the time to evaluate what underlayment will be installed and have an experienced acoustical consultant review their plans.
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