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How do sound-level meters account for differences in human hearing at different frequencies?

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Sound-level meters account for the human ear's varying sensitivity to different frequencies by using electronic frequency filters that apply specific weighting scales to the measured sound. Because human hearing does not perceive all frequencies with equal loudness—generally finding high-frequency sounds louder than low-frequency sounds of the same amplitude—these filters adjust the meter's response to better correlate with subjective human perception.12

The most common method is A-frequency-weighting, which is used internationally to describe how complex noises affect people and to help prevent hearing loss in work environments. Measurements taken with this filter are expressed in A-weighted decibels (dBA). Other weighting scales include:12

C-weighting (dBC): Often used for impact noises, such as gunfire, as it is more accurate for sounds with significant low-frequency components.2
B, D, and Z-weightings: Additional scales available for specific measurement needs.1

By applying these frequency-dependent weighting factors, sound-level meters provide objective data that more closely align with the human ear's actual sensitivity to different pitches.12