Technical Bulletin: Sound Rated Luminaires

Minimizing sound transmission between living spaces

Why sound rated downlights are important

We have all stayed in hotels or apartments where the people in the room above are making noise when we are trying to sleep. You can hear the constant tap of footsteps or the television blaring and it is really annoying. That’s why sound rated downlights are an important component in the design of any building: to minimize sound transmission from one room to the next. Minimizing the transmission of noise requires the judicious choice of many building components such as floor topping, floor underlayment, subfloor topping, subfloor underlayment, ceiling insulation, joist size, resilient channel, ceiling finish, construction quality and a sound rated luminaire.

DMF Lighting Sound ratings

What are STC and IIC?

The IBC® (International Building Code) recognizes two values when measuring sound ratings. An object’s STC (sound transmission class) measures air-borne sound while IIC (impact insulation class) determines structure-borne sound. They are tested in accordance with international standards ASTM E 90 and 492, respectively, and require a value of at least 50 to pass.

STC is a numerical rating for evaluating efficiency of construction in isolating airborne sound transmission. The higher the STC rating, the more efficient the construction. The following table illustrates the effectiveness of the rating:

STCSpeech AudibilityRating
15 to 25Normal speech easily understood.Poor
25 to 35Loud speech easily understood. Normal speech 50% understood.Marginal
35 to 45Loud speech 50% understood. Normal speech faintly heard, but not understood.Good
45 to 55Loud speech faintly heard, but not understood. Normal speech inaudible.Very Good
55 and upLoud speech usually inaudible.Excellent


In contrast, IIC is a numerical rating developed to estimate the impact sound isolation performance of floor/ceiling systems. This test helps evaluate the impact of footfall, or a chair dragging on the floor, or other impact sounds.

These requirements apply to multi-family and single-family homes around the country as well as hotels, motels, apartments and condominiums. They are in use in all 50 states, the District of Columbia, the U.S. Virgin Islands, Guam and the Northern Marianas Islands. Local municipalities often adopt their state building code with local additions and amendments. For example, the California Building Code 2013 sources the 2012 IBC®. Most municipalities adopt the IBC® sound transmission requirements unaltered.

DMF’s OneFrame exceeds IIC standards

DMF Lighting provides luminaires, such as the OneFrame system, which have been tested to international standards and have excellent sound rating characteristics: STC of 60 and IIC of 58. These ratings exceed the IBC® requirements of 50 STC and 50 IIC and ensure that that loud speech between rooms and footsteps from above will be inaudible in buildings constructed with this rating.

Technical Bulletin: Sound Rated Luminaire