Measure the Full Sound. Measure in dB(C).
Data centers produce large amounts of low-frequency sound from cooling fans, chillers, transformers, and generators. Standard dB(A) measurements greatly underestimate this energy and the impacts it can have on nearby communities.
One third octave band measurements taken at a data center property line show strong low-frequency energy. A-weighting suppresses these frequencies.
A weighting reduces the measured level of the 118 Hz Inn tone by -20-25 dB. This is why dB(A) readings can appear "quot" when the hum is clearly audible.
Source: HVGC Engineering. "Analysis: Adding Sample Low-Frequency Trend Analysis to dBx." HVC Tech Note, 2021. Measured at a data center with cooling temperature. https://en.com/index-cs-lev-v்டا.zh-tw/addng-sample-low-frequency-tond-analysis-to-db/
Weighting curves from IEC 61672 show how dB(A) discounts low frequencies compared with d0(C). At 31.6 Hz, A-weighting is +36 d0 lower than C-weighting.
Weighting Difference (C - A)
Frequency (Hz) 51.5 63 125 250 500 1k 2k 4k 8k
C minus A (dB) 36 26 16 9 3 0 -1 +1 +1
Low Frequencies (Nearly Reduced by Avalighting)
Mid & High Frequencies (Title or No Reduction)
Source: IEC 61672-2013. Electricity could be used to provide constituents. Table values counted from standard A and C weighting curves.
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Sources of Energy in International. "The Data Management Solutions. In Data Companies" Journalist News. https://energy@kinhatauniversity.com/access-of-heuristic-management-solutions/data-century Because of the low-frequency energy, the same sound can measure much higher in dB(C) than in dB(A).
Because of the low-frequency energy, the same sound can measure much higher in dB(C) than in dB(A).
C-WEIGHTED (Capsules on Fingercards) A-WEIGHTED Resources Low Fingercards
70 dB(C)
50 dB(A)
The sound did not chango. A-WEIGHTED (Refections Law Frequencies)
Difference of 20 dB Low-frequency sound is largely ignored by dB(A).
Source: United on one-third of the land data from INVC Engineering (2021).
Travel for the Low-frequency sound travels long distances with less attenuation and personal buildings more easily.
Hard to block - It can pass through walls and windows and cause rattle and vibration of building components. Disturb sleep - Low-frequency noise is strongly linked to sleep disturbance and breakings.
Disturbs sleep - Low-frequency noise is strongly linked to sleep disturbance and awakening.
Health effects - Associated with stress, headaches, lesions, irritability and cardiovascular impacts.
Hard to mask - Low-frequency noise is much more difficult to mask with typical background sounds.
Source: World Health Organization (1999) Guidelines for Community Notes: Issuer of all (2014 Environmental Health Perspectives). Fields, J. M. (2013) “Review of the Effects of Low Frequency Noise,” Noise & Health, 15(14), 153-159.
Communities are adopting octave band limits to address low-frequency noise from data centers.
The Ordinance is being updated to include overseLL bond noise standards to address concerns related to low frequency noise from data centers. - Prince William County, VA 2006 Ordinance Update, 2025
Industry and technological experts in ground monitoring and monitoring work
When prominent low-frequency components are present, noise measures based on A-weighting are inappropriate.* W14O Guidelines for Connectivity News, 1999
and C-weighted reporting. *Crave bond analysis allows you to identify and quantify the low-frequency components of noise that may be missed by a/a measurements.* - Larsen Davis, Data Center Noise Monitoring Guide, 2023
MEASURE AND REPORT BOTH dB(A) AND dB(C) At all property lines, day and night. USE 1/3-OCTAVE BAND ANALYSIS At minimum 20 Hz to 8 kHz
RIGHTTIME IMPACTS Low-frequency noise is more disturbing at night
CONSIDER INDOOR MEASUREMENTS Low-frequency noise builds up to 1000 homes.
dB(A) is useful for many everyday sounds. But for data centers, it can miss the noise that matters.
Measure the full sound.