Audio Fundamentals
A-weighted refers to a frequency weighting curve used in audio measurement that approximates the sensitivity of human hearing. It de-emphasises low and very high frequencies, providing a more perceptually accurate representation of noise and sound levels.
The A-weighting curve is a standardised filter applied to sound level measurements to reflect how the human ear perceives loudness at moderate listening levels. Human hearing is less sensitive to very low and very high frequencies, so the A-weighting curve attenuates these regions — reducing low frequencies below 500 Hz and slightly rolling off above 10 kHz — while leaving the midrange (around 2–5 kHz) relatively unaffected, where our hearing is most sensitive.
Sound level meters and measurement systems often express results as dB(A), indicating that the reading has been A-weighted. This approach is especially useful when evaluating background noise, electronic noise, or acoustic environments in a way that correlates with human perception.
In professional audio, A-weighted noise measurements are commonly used to specify equipment performance, such as the signal-to-noise ratio (SNR) or dynamic range of preamplifiers, converters, and other audio devices. For example, a noise floor of –100 dB(A) means the measurement has been filtered according to the A-weighted curve, giving a more realistic indication of how quiet the device sounds to the human ear.
Other weighting curves, such as B-weighting, C-weighting, and Z-weighting, exist for different purposes, but A-weighting remains the most widely adopted standard for general noise evaluation and equipment specification.
By aligning measurements with auditory perception, A-weighted readings provide a meaningful, real-world assessment of audio performance and environmental noise.
