International sound expert and TED Talk Speaker Julian Treasure reveals the need for quality acoustics in schools, offices, hotels and healthcare facilities. Explore the unintended consequences when sound isn’t managed well. A must see webinar for architects, designers, facility managers, contractors, distributors, and acousticians.

The Impact of Sound

Everyday our ears are met with a barrage of sounds. Sounds can be pleasant, like music or laughter. But they can also be disruptive, like construction or traffic, or even just the people in the cubicle next door. At a certain point sound becomes noise and we look for ways to control it. Sound control is especially important in classrooms, hospitals, hotels and offices, as it impacts our ability to learn, heal, sleep and think. The U.S. Green Building Council recognizes the importance of acoustical control by including LEED Indoor Environment Quality (IEQ) credits for acoustics.

Basic Acoustics

Sound transmission reduction relies on two main principles:

Sound Absorption - Removing sound energy from within a room by using materials such as acoustic tiles or open cell foam to soak up sound.

Sound Insulation - Preventing the transmission of sound waves by introducing a barrier. Examples include brick, concrete, metal, heavy doors, etc.


Sound waves will travel the path of least resistance. A high performing door will not compensate for less performing materials in the walls around it. In order to reduce the transmission of sound, materials are added between the source room and the receiving room. The resulting change in decibel level is the sound transmission loss and is given a Sound Transmission Class (STC) rating. The higher the rating number, the lower the transmission of sound. The STC rating is roughly the decibel reduction a partition can provide. For instance, if a 100 dB noise is reduced to 55 dB, that product roughly has a STC 45 rating.

Acoustic Door Testing

Acoustic Door Testing is done on “sealed-in-place” (fully caulked) doors for door STC ratings, as well as on assemblies (with gasketing and door bottoms) for operable STC ratings. Operable STC ratings are always equal to or lower than the sealed-in-place ratings. The best performance rating on the operable test is a 'zero drop' in the assembly's STC rating. For example, a door with a STC 45 rating can only achieve an operable STC of 45 at its very best; it can never achieve a STC 50.

Also, since sound waves travel the path of least resistance, a high performing door will not compensate for elements like improperly installed seals around doors, the lack of a threshold under the door, a non-insulated frame, louvered doors, or poor seals at the wall/ceiling/floor/mullion connections. When STC ratings are determined, normal human speech and hearing are used. In most cases the level of reduction does not totally eliminate but rather muffles the sound to an unintelligible level. The chart shown on the left compares the level of speech that would be heard through a door system with the indicated operable STC rating.