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Blog Post - What is Noise Control?

What is Noise Control?

A simple definition of "noise control" is the reduction or mitigation of unwanted sound. Sound is a physical phenomenon; more specifically, sound is pressure fluctuations in the atmosphere (or any fluid). Noise is unwanted sound, which relies on someone's perception of sound. A good way to remember the difference is to think of the age-old question, "if a tree falls in the woods, does it make a sound?" The answer is yes, it does make a sound; however, it may not make noise, depending on whether someone is there to hear it and be bothered by it.

A more specific definition of noise control was given by the late Prof. Cyril Harris, in his classic handbook: "Noise control is the [process and implementation] of obtaining an acceptable noise environment, consistent with economic and operational considerations."

In other words, noise control is the endeavor to
• achieve the right sound parameters (e.g., level, frequency content, harshness, etc.),
• to fit the required conditions (e.g., a specific regulatory requirement, performance parameters of a theater, etc.),
• for a given environment (e.g., classroom, workshop, neighborhood, etc.),
• at an acceptable cost,
• without adversely affecting
  ◦ the function of the noise generator (e.g., gas compressor, petrochemical facility, lawnmower, etc.),
  ◦ the people who use it (e.g., factory workers, tractor drivers, etc.),
  ◦ the people who are exposed to it (e.g., neighbors, hikers, etc.) or
  ◦ the business that relies on it (e.g., oil & gas company, power plant, petrochemical plant, manufacturer, etc.)

If one wants to control (mitigate) noise, he/she must consider one or more of three things:
1) the source of noise, that is, the machine or process causing the noise,
2) the receiver/listener or receiver location of noise, that is, where the noise is a problem or potential problem, and
3) the path between the source and the receiver.

It is always best to control the source of noise, because the less noise that is generated in the first place, the less there is to control. This can be impractical sometimes, because changing aspects of the noise source can bring up a host of issues such as operation, warranty, maintenance, and safety. If noise cannot be controlled at the source, or all has already been achieved, then the path should be considered next. Controlling noise at the receiver/listener or at a specific location is usually a last resort.

USSI 3D animation that explores acoustical Compressor Building applications

About the Author - Tim Simmons, Ph.D. - USSI Director of Industrial Acoustics
Dr. Tim Simmons manages USSI's Industrial Acoustics Department. Tim comes to USSI with a wealth of Acoustical and Noise Control knowledge and real-world experience. Tim holds a Ph.D. in Physics from the University of Mississippi and a B.S. in Engineering Physics from the University of Tennessee.