12.1.2.5-5 Noise Distractions

Noise distractions generated either inside or outside the control room should be minimized.

Additional Information: One method to control both ambient noise and noise distractions emanating from outside the control room is to acoustically insulate the control room from surrounding building enclosures. Transmission of excessive noise into the control room should be attenuated by means of

high-density and multilayer sound-attenuating materials (e.g., concrete, gypsum board, and high-density sound-absorbing ceiling tiles). Transmission of noise should be further attenuated by sound reducing construction techniques (e.g., staggered seams in walls, acoustic caulking of walls to the hard structure of the floor and ceiling but not to a suspended ceiling, acoustic attenuators placed in HVAC supply and return ducts, sound-absorbing doors, and multipaned windows. Wherever possible, these materials and building systems should be rated by sound transmission class (STC). Many manufacturers of

sound-attenuating barriers specify the STC rating of their products or systems. The STC measures the sound transmission loss (TL) of an acoustic barrier in 1/3 octave bands from 125 Hz to 4,000 Hz. The TL spectrum is then compared to a reference STC curve and the STC rating of the barrier is read as the

500-Hz value of the appropriate STC curve. The STC is designed primarily to correlate with the perception of oral communication through acoustic materials or systems. For example, with an STC = 25– 35, conversation can generally be heard and understood through the barrier, whereas with an STC = 55– 65, most external noise sources are rendered inaudible. American Society for Testing and Materials (ASTM) E90 (2009) contains more information on the STC method. 0700, 1472G