Active Noise Control technology takes on the noise effect head on.

Eliminating Noise Pollution in IT Work Environments

Workers no longer have to be subjected to noise's damaging effects -- or suffer frostbite, for that matter.

The wearing effects of noise pollution are well documented: Workers are put at risk for elevated blood pressure, hearing loss, and stress-related disorders. Even heart attacks have been attributed to chronic exposure to excessive noise. Researchers at Yale University concluded that stress caused by negative noise exposure can increase vulnerability to neuropsychiatric disorders.

While many of the problems from noise exposure are cumulative, short-term effects, such as the inability to concentrate and communicate, significantly affect productivity. The easiest rule of thumb is that noise is excessive when people can't speak in normal conversational tones within a distance of 6 feet, or 2 meters. In an emergency, this inability to communicate can be life threatening.

Some IT workers are exposed to chronic noise pollution because of the fan speeds needed to cool equipment. They also are subjected to working in environments that are hyper-cooled. IT hardware generates a great deal of heat, and thermostats must be set low enough to offset this to prevent equipment burnout.

A recent IDC analyst study found the number one challenge facing data centers is power and cooling. According to a study by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, during a four-year period, the maximum temperature for operating IT equipment went up by 9 degrees Fahrenheit (5 degrees Celsius). A lapse in an IT department's cooling system of only a few minutes can result in server meltdown, a very expensive proposition from both the equipment and lost time and data perspectives.

The resulting cost of overcooling and creating noisy IT environments is high, both in terms of human cost and budgetary outlay. Poor work performance, absenteeism, chronic health problems, and soaring electrical bills are obvious outcomes of IT equipment stored in traditional dedicated storage rooms.

Healthier Workers and an Enhanced Bottom Line
Traditionally, primarily passive techniques have been used for controlling noise pollution, such as baffling. Using acoustic foams to reduce noise passively is highly effective with frequencies above 1.5 kHz. However, baffling does nothing to absorb noise in the low frequencies. It also has no effect whatsoever on the cooling infrastructure required. Sometimes it even requires an increase in cooling efforts due to its highly insulating properties.

Now, however, affordable, active technology is available that not only enhances the work environment, but also contributes significantly to the bottom line. Active Noise Control (ANC) technology takes on the noise effect head on. Active noise control combined with traditional passive treatment ensures greater noise reduction within the IT department than either can provide separately.

ANC theory has existed for more than 70 years. It demonstrates that two waves with equal amplitude and identical phase have an additive effect, resulting in a doubling of the overall amplitude, while two waves with equal amplitude but opposite phase have a subtractive effect, resulting in a decrease in the overall amplitude. ANC, in effect, cancels the noise emitted by IT equipment by producing an opposing signal (anti-noise) with the same amplitude as the noise to be reduced (unwanted noise), but in the opposite phase. Of course, the degree of reduction is highly dependent on the accuracy of the system for producing the amplitude and the phase of the reductive, anti-noise signal.

While in theory building your own ANC sounds simple, the actual application can be quite complex and often requires the services of a professional sound engineer who is equipped with specialized hardware and software.

An ANC system has four major components:

  • Reference microphone: The microphone that receives the noise to be cancelled (unwanted noise), which forwards it to the controller.
  • Error microphone: The microphone that senses the noise at the point at which noise reduction is required and also monitors how well the ANC system performs.
  • Speaker: The device that produces the anti-noise signal.
  • Controller: A signal processor (usually digital) that drives the speaker. In the simplest case, the digital signal processor controller multiplies the reference microphone signal by minus one and sends it to the speaker to produce the anti-noise.

After the reference microphone detects the unwanted noise, the ANC system will generate the correct anti-noise signal to send to the speaker, which will produce the anti-noise.

While setting up an individual ANC system within your own facility can be daunting and cost prohibitive, there is already highly effective equipment on the market, such as enclosed IT equipment racks that essentially act as a "server room in a cabinet." At their highest level, they provide up to 30 dB(A), or a 96 percent, reduction in noise, while actively allowing free air movement and heat exchange with the outside of the unit, dissipating heat output by 8 kilowatts, and ensuring the equipment remains dust free. The benefits in terms of protecting workers, equipment, and the bottom line are clear, all while reducing a company's carbon footprint. It's a matter of researching and choosing the right equipment and vendor that best serves your needs.

This article originally appeared in the March 2011 issue of Occupational Health & Safety.

About the Author

Yoel Naor is Director of Product for Silentium (, a design and manufacturing company of Active Noise Control-based equipment, including the AcoustiRACK™ACTIVE, a "server room in a box." The technology reduces server noise and dissipates heat, allowing for the elimination of dedicated server rooms. The company announced in September 2010 that US Rack Distributors Inc. would distribute this and other Silentium products in North America.

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