Technology Integration: Audio

Jan. 1, 2008

The Critical Sound

By Chuck Wilson

If video is the science, then audio is the art. In many cases, audio is just as important as video imagery. With proper planning, architects can design buildings that incorporate superior acoustics.

When constructing or retrofitting acoustical spaces, there are three critical factors to consider:

  1. The quality of the input source - whether it's from teachers, pastors, opera singers, politicians, rock bands, or other sources 
  2. The quality of the electronic system in place 
  3. The level of background noise and acoustical properties of the room.

To create an intelligible listening environment, you must address all three ratios equally, not just the system or the ambient noise.

First, ensure that the acoustical properties align with the purpose of the venue. That's where the RT60 measurement comes into play. Acoustical pioneer Wallace Sabine created a formula to determine how long it takes an audio signal to decay -60db (decibels). Predicting this measurement allows architects to create the perfect listening environment for different applications.

Ambient sound is the level of unwanted noise in a given location. In a college lecture hall, for example, students typing notes on laptops create distracting sounds. Multiply their noise by 50, 100, or more and you have real audio issues. Proper acoustics and sound systems are crucial to allow the message to be heard above the inherent noise floor.

According to the Acoustical Society of America, many classrooms have "speech intelligibility ratings" of under 75 percent. That means only three-fourths of people with normal hearing can hear words read from a list. HVAC systems often cause major noise disturbances that should be considered during design, and shiny tile floors don't absorb sound. Select floor, wall, and ceiling materials carefully so they work together to provide the proper RT60. It's also important to consider the size, shape, and physical location of the classroom for optimal acoustical results. Refer to the American National Standards Institute S12.60 Classroom Acoustics Standard for additional best practices when constructing classroom spaces.

Audio quality considerations affect more than just classrooms, though. Performing arts halls, in order to create the best listening environment, are usually long and narrow. That's because, as Music Acoustics and Architecture author Leo Beranek found, the impact of sound intensifies when reflecting surfaces are closer to the listener. Similarly, concert halls typically are designed with very little absorbent materials, whereas smaller recording booths produce better results with more absorption. In many business settings, the installation of diffusion panels will create sound isolation barriers and lower the reverberation in the room. Acoustical ceiling tiles serve dual purposes: They can reduce noise transmission and improve the quality of the room audio. Houses of worship depend on crisp, audible, spoken words as they share the message through both speech and song.

Finally, audio intelligibility plays an important role in life-safety issues. Today's mass notification systems use prerecorded messages with clear, well-articulated phrases, allowing important messages to be heard during stressful situations. Further, today's technology allows one person to make one phone call to communicate with thousands of people anywhere using simultaneous communication devices. There are many examples of panicked people who, under duress, have produced garbled and confusing evacuation messages or failed to provide them at all - such as the London Kings Cross subway station fire, Columbine, or, more recently, Virginia Tech. Imagine how much more effective a mass notification system could have been in these situations.

Designing interconnected, audio-rich intelligent buildings not only sounds good, but can also provide better learning environments, more meaningful worship experiences, clearer business meetings, and life-saving opportunities.

Chuck Wilson ([email protected]) is executive director of the National Systems Contractors Association (NSCA).

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