Measuring Loudness

Equal-loudness curves are useful for quantifying sound impact on hearing.

Various standards attempt to account for relative loudness perceived by human ear.

Most common of a family of curves is A-weighting:

• originally intended for the measurement of low-level sounds as it is based on the 40 phon Fletcher-Munson curve;
• adds values, listed by octave or third-octave bands, to the measured SPL in dB to produce dB(A);
• now used at all sound levels (though less suited for this purpose) and is mandated for environmental sound-level meters;
• based on single-frequency measurements.
• doesn't address ``annoyance'' or damage from broad spectrum sound, yet remains the standard.