C-Weighting

Published: | Updated: November 9, 2020

Definition - What does C-Weighting mean?

C-weighting is a type of frequency weighting that is used when measuring the amount of noise in an environment. It is primarily used for measuring noise above 100 decibels (dB).

Modern noise measurements provide a measurement of the amount of noise that is present at discrete frequencies; however, these objective noise measurements do not necessarily reflect how humans will hear noises, as human ears are less sensitive to very high and very low-frequency noises. C-weighting, then, alters the results of unweighted noise measurements so that they more accurately represent the amount of noise in the environment as humans would perceive it.

Safeopedia explains C-Weighting

Frequency weighting is an important aspect of modern approaches to occupational noise measurements. In high-noise environments (+100 dB), the human ear is about 10 dB less responsive to very high-frequency and very low-frequency noises than it is to mid-frequency noises. When a noise measurement is C-weighted, its measurements are altered to reflect this difference. C-weighted noise measurement is recorded as dBC or dB(C).

The use of C-weighted measurements allows OHS experts to accurately understand how much noise workers will be exposed to in the workplace; for instance, exposure to a 100 dB sound at a frequency of 1000 Hz is more dangerous than a 100 dB sound at 16000 Hz, because the ear is less responsive to the latter. C-weighting is not useful for noises below 100 dB; the differences in how the human ear responds to different frequencies are larger below that point, which means that a different weighting system (A-weighting) is needed to understand noise exposures in that context.

The use of C-weighting (for measuring noises above 100 dB) and A-weighting (for measuring noises below 100 dB) are both important for determining the effectiveness of specific hearing protection PPE.

When determining the effectiveness of hearing protection in a given environment, the amount of noise that the protector absorbs can be measured using both C- and A-Weighted measurements. For example, the difference between C- and A-rated measurements of the same hearing-protected noise source can be used to evaluate whether the hearing protection is less efficient at blocking low frequencies than high frequencies. If this lack of efficiency is detected, the protective equipment will receive a lower Noise Reduction Rating than it otherwise would.

The use of C-weighting in noise measurements is recognized by all OHS agencies as well as all standards organizations that deal with audiometry.

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