#Underlayment sound code#
Without the addition of sound isolation products, the IIC rating of basic wood structures will rate better than concrete structures because they are naturally more resilient.Īn IIC rating of 50 and above is most common in building code and HOA requirements. The IIC ratings for basic wood structure with no resilient underlayment is around 40 to 45 IIC. The IIC ratings for basic concrete sub-floor with no resilient underlayment is around 28 to 35 IIC. Nor does it account for low frequency footfall noise or structural deflection.
The IIC rating does not account for any squeaking or rattling caused by loose wood frame construction. A higher number shows better performance. The engineer plots the results of each tap on a graph, compares the results to the reference assembly, and determines the IIC rating from comparing these two tests. The impact creates vibrations that travel through the floor into the receiving side (the room below). These hammers strike a test floor material generating sounds between 125 to 4,000 Hz. IIC stands for impact insulation classĪcoustic labs conduct the IIC test using a tapping machine with steel faced hammers. These two frequencies are now more commonplace thanks to high quality speakers and sub-woofers. This is because of the inclusion of the 80 and 100 Hz frequencies in the OITC calculation. When planning an isolation project, the OITC rating is often more crucial than the STC rating. As a result, OITC ratings are typically much lower than STC ratings. A higher number shows better performance.Įxtreme mass and decoupling are requirements to isolate low frequencies. The results express in decibels as opposed to the point system used to determine STC ratings and with weighting more towards low frequency performance. The OITC rating represents transmission loss results from 80 to 4,000 Hz using a different mathematical equation than the STC rating. We also use the OITC rating to determine a product’s value for use in low frequency sensitive areas such as home theaters and recording studios. The original purpose of the OITC rating was to determine performance of products in relation to exterior noise, which is often heavy in low frequencies. OITC stands for outside inside transmission class
#Underlayment sound plus#
A high level of isolation for walls is STC 60 plus with ceilings at STC 50 plus. The STC rating for a six inch concrete sub-floor is 52-55.Ī good level of isolation for walls and ceilings is STC 50 plus. The STC rating for a basic wood structure floor/ceiling is 40-43.
This rating increases to STC 42-45 with steel studs. The STC rating for a basic insulated 2×4 wall with a single layer of drywall on each side is 35-38. The performance in relation to the STC contour line will reveal the consistency of the product over the most common frequencies. Sort through the misleading ratings by gaining access to actual sound test data showing the STC contour line on the transmission loss graph. This is a pretty common occurrence that should not be ignored when comparing products. However, the rating is essentially an average over the 16 frequency points tested.īecause of this, a product can perform exceptionally well in one range, poorly in another, and still end up with a better STC rating than a competing product that may have performed better in a frequency range more relevant to your project requirements. A higher STC rating often shows improved performance. This range covers the majority of common noises we hear including speech, television, music, dogs barking, and other similar annoyances. This is the most common rating used in North America for determining airborne sound transmission loss between 125 and 4,000 Hz.
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