Decibel A Scale (dBA)

Last Updated: June 15, 2018

Definition - What does Decibel A Scale (dBA) mean?

The Decibel A Scale (dBA) is a logarithmic system of measuring sound as the human ear experiences it. The scale assigns a weight to the decibel value of sound based on the sensitivity of the ear at a particular frequency. The scale is calibrated in units called A-weighted decibels or dBA for short. This provides an easy way to compare sound levels of different noises and their potential for causing hearing harm. For example, a jet taking off is measured around 150 dBA while bird calls average around 44 dBA.

WorkplaceTesting explains Decibel A Scale (dBA)

The human ear is not as sensitive to very low or very high frequency sound pressures and this is what the Decibel A Scale is premised on. The decibel scale rating of zero is the smallest sound audible to the human ear. The World Health Organization recommends a daily maximum noise exposure of 85 dBA over an 8 hour period to prevent hearing loss. This is important for the acoustic design of the workplace and the scheduling of employees who are exposed to high noise levels for long periods of time.

There is also a Decibel B Scale and Decibel C Scale, however the Decibel A Scale is the most commonly used system of measurement because of its indication of hearing loss risk.

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