dBA

dBA is a unit of sound level that applies the A-weighting filter to the decibel scale. It expresses the sound pressure level in decibels after weighting the frequency content to reflect the roughly human ear sensitivity. The A-weighting filter attenuates very low and very high frequencies, producing a single value that correlates, for many steady and broadband sounds, with perceived loudness.

Measurement uses a sound level meter with an integrated A-weighting network. The reference sound pressure is 20 μPa in air, and the result is written as dBA. Because the decibel scale is logarithmic, a 10 dB increase represents a tenfold increase in sound pressure, while a 3 dB or 5 dB exchange rate is used in some exposure calculations to reflect doubling of perceived loudness over time.

A-weighted measurements are widely used for regulatory compliance and environmental and occupational noise assessments. They are commonly used to estimate potential hearing risk for workers and to assess community noise from machinery, traffic, and urban sources.

Limitations include that dBA approximates loudness for steady broadband sounds but can be misleading for impulsive or tonal noises, very low-frequency content, or highly variable noise. It does not capture all psychological aspects of loudness and is sensitive to measurement conditions such as microphone placement and integration time. For these reasons, additional metrics (such as dBZ, dBC, or unweighted measurements, Lp, Leq, or Lden) may be used alongside dBA depending on the application.