Since data centers use electrical and mechanical equipment both inside and out, it’s reasonable to wonder what they sound like. Sound is carefully considered during the site selection, building design, construction, and daily operation of a data center. I recently visited a DC BLOX data center in Birmingham, Alabama. When I stood outside its front door, I could hear some mechanical equipment from the building next door whirring, birds chirping, a plane flying overhead, and nothing coming from the data center itself.
Like all industrially zoned facilities, a data center will never be silent, but what can be heard in the surrounding areas depends heavily on facility design, equipment placement, distance from the facility, and specific mitigations implemented at a given site.
How Is Sound Measured?
Life is full of sounds. Some are pleasant, like rain splashing on the roof, ocean waves breaking on the shore, or a breeze rustling the leaves of trees. Others are more disruptive. Phones buzz and beep, cars and trucks whizz by, leaf blowers and lawn mowers whine and roar. Sound is not a bad thing in and of itself. But any sound that is unwanted, or worse, harmful to the health and wellbeing of people, animals, or ecosystems, is considered noise. Noise is monitored and regulated.
Sound Terms to Know
Text description of power terms
- Decibel (dB): A unit used to measure sound levels. Higher decibel levels generally mean louder sounds.
- A-weighted decibels (dBA): A measurement that adjusts sound levels to better approximate the frequencies the human ear is most sensitive to. Most noise ordinances use dBA measurements.
- C-weighted decibels (dBC): Measures a broader range of frequencies more evenly, so low-frequency sound has a greater influence on the reading.
- Frequency: The number of sound wave cycles per second. This characteristic of sound largely determines its pitch. Two sounds at the same decibel level can be perceived very differently depending on their frequency.
- Hertz (Hz): A unit used to measure frequency. Lower frequencies sound deeper, like a rumble, hum, or the low keys on a piano; higher frequencies sound more like a whine or hiss, or the tinkling high keys of a piano.
- Ambient or background sound: The sound present in an environment, such as traffic, wind, insects, HVAC systems, or nearby businesses. Provides context for how noticeable additional sounds might be.
- Sound or acoustic study: An assessment used to measure or predict how sound from a facility or other source may affect the surrounding area. A sound study typically considers existing background sound, potential sources of new sound, distance from the source, and features such as buildings, barriers, and terrain that can affect how sound travels.
One thing to note is that the decibel scale is logarithmic. This means that a sound that is 10 dB higher than another sound is actually twice as loud. A one decibel increase is not like one tick of the volume button on your TV remote; it’s much more noticeable. Keep that in mind when you compare different measurements in decibels.
Sound is impacted by the distance from the source. Every time you double the distance from the source, the level goes down by 6 dB. Put simply, how far away you are from a source of sound affects how loud it is. This is why sound measurements for the purposes of regulation are taken at varying distances from the source, such as right next to the equipment being measured, at the property line, and at nearby residences or businesses. The numbers at each of these locations can be quite different.
Decibel Measurements of Common Sounds
Duration is critical. At 85 dBA over an eight-hour workday, the Occupational Health and Safety Administration (OSHA) requires employers to take steps to protect workers’ hearing. Hearing an 85 dBA lawnmower for a few minutes occasionally is very different from occupational exposure averaging 85 dBA for eight hours.
What Is Infrasound?
Infrasound is very low-frequency sound (measured in hertz) that is below the range most people can hear. Low-frequency sound exists throughout everyday environments, produced by sources including traffic, wind, HVAC and refrigeration equipment, storms, and industrial machinery.
Wind turbines are one well-known industrial source of infrasound because their large blades create very low-frequency pressure waves as they move through the air. Mechanical equipment used at data centers and other places of business, including cooling fans, HVAC systems, generators, and transformers, can possibly produce sound that extends into low-frequency and infrasonic ranges. But while data centers have been around for decades, infrasound has only recently begun being discussed, and it’s unclear whether data centers are a source of infrasound. Research measuring these frequencies and their potential effects in communities surrounding data centers remains very limited.
And although infrasound has received significant attention, its presence alone does not tell us whether a sound presents a health risk. Frequency, sound level, duration, and level of exposure all matter. Different sound measurements can help characterize different aspects of noise, while measurements taken over time can provide a more complete picture of overall exposure.
Where Does Data Center Sound Come From?
Like any other building with HVAC, cooling, electrical, and backup power systems, data centers do produce some sound. The main sources of sound from a data center fall into several categories:
- Cooling equipment: Fans, chillers, pumps, cooling towers, dry coolers, air handlers, and other HVAC equipment.
- Electrical equipment: Transformers, Uninterruptible Power Supply (UPS) systems, switchgear, substations, and associated cooling fans.
- Computers and networking equipment: Servers, switches, routers, and cooling fans, primarily located inside the building.
- Backup generators: Engines, cooling fans, and exhaust systems that produce sound during testing, maintenance, or utility outages.
- Ventilation equipment: Exhaust fans, louvers, and air intakes that can produce sound as air moves through them.
Not all of this equipment runs continually, and much of is contained within the four walls of a well-insulated building. Modern facilities are specifically designed to operate quietly and within local standards (more on that below).
What Does a Data Center Actually Sound Like?
Inside the data center, the computer and networking equipment produces a low, consistent hum that is contained by the building’s walls. Outside, HVAC, cooling, and electrical equipment produce low grumbling sounds that diminish quickly across distance. The backup generators are for reliability, not for everyday operations. They are tested once a month for about 30 minutes at a time; otherwise, they only run in the case of an emergency (such as a brownout or blackout).
In short, cooling and some electrical equipment can contribute to the normal, ongoing sound of a facility. Servers are primarily an indoor sound source, and backup generators are louder but only intermittent.
How Data Centers Manage Sound
During normal operations, sound levels from a data center often blend into existing background noise in the area thanks to how they are designed. Unlike facilities with constant outdoor activity, such as a distribution center, most data center equipment operates inside the building, where sound is contained by reinforced concrete walls and insulation. Generators tend to be oriented facing the center of the site, rather than neighboring properties. Physical buffers like vibration isolation systems, insulated enclosures, and natural landscaping further help mitigate and absorb sound. It’s also possible to select quieter equipment in general.
The measurement that matters most is the level of sound that reaches any nearby homes or businesses. At DC BLOX facilities, the level at the property line is usually around 55-60 dBA, in line with the volume of a normal conversation.
Zoning & Regulation
Noise levels are not just estimated; they are measured. A formal sound study is usually required as part of the permitting process, and levels are verified on an ongoing basis once operations have started. Compliance with local noise ordinances is enforceable. These requirements ensure that sound levels remain within established limits over time.
Summing It Up
Data centers are not unique in producing sound. Many common buildings and industrial activities generate equal or greater levels of sound as part of normal operations. Data centers are designed to operate quietly and consistently within community noise standards. Thoughtful architecture, deliberate selection of materials and equipment, appropriate setbacks, sound mitigation, and ongoing monitoring help keep data centers from becoming disruptive neighbors.
Understanding data centers starts with understanding the role they play in everyday life. Explore the rest of our Data Centers 101 series to learn how these facilities are designed, operated, and integrated into the communities they serve.
