There is a plethora of acoustical laboratory test data published by manufacturers of building products and systems. Why do we need it? Why do building code representatives and acoustical consultants require certain levels of acoustical performance? Because they are concerned with the quality of people's soundscapes in their living environment. They want to make sure that from the acoustical standpoint, the space created by these materials provides an acceptable acoustical environment in which to work, live, and recreate. By measuring and evaluating laboratory-collected data, spaces can be designed in ways that make living easier and more enjoyable.
Sound Absorption
We want an environment in which speech is intelligible but not muffled. There are guidelines in the acoustical technology that can predict this acceptability. Correlation between room sound absorption (as measured for noise reduction coefficient, or NRC) and speech intelligibility exists. The greater the sound absorption in a room, the less reverberant the room, which increases the intelligibility of speech communication in that room.
Sound Transmission Class
Sound transmission class (STC) measured data will indicate how well a wall or floor/ceiling structure acoustically insulates neighbors. Outdoor/indoor transmission class (OITC) measures how well a window reduces outside noise. The higher the measured STC/OITC, the less noise that will be transmitted into a room from a source outside that room.
Impact Insulation Class
Impact insulation class (IIC) measures and characterizes noise from a room directly over another room, such as the annoyance of hearing high-heeled shoes or boots. The higher the measured IIC, the less the vibrational noise levels that will be transmitted to a room directly below the source room, making footfall/impact noise less annoying.
Ceiling grid panels in both open office and normal office environments must be effective from both a sound absorption and sound attenuating context. Therefore, a measure of a ceiling panel's ceiling attenuation class (CAC), sound absorption (NRC) and articulation class (AC) are all required to ensure a productive work environment.
The sound power that is emitted by an operating piece of equipment needs to be measured and characterized prior to introducing that equipment into an existing acoustical environment. A work or living area with noise levels that are too high can be distracting and even ear damaging.
An acoustical engineer must take all of these issues into consideration when designing a work or living environment. An objective yardstick is imperative to predict the acceptability of a room's soundscape, and these are the ratings that can assign an objective number for the acoustical quality of an environment. To quote the Riehle Axiom, "One test is worth a thousand expert opinions."
These are the types of acoustical testing that NGC Testing Services provides to the building products industry. With nine test chambers, we are the largest laboratory and most comprehensive in North America for a wide range of building acoustical testing. It is a service that we are quite proud to provide for the industry!