What it actually decides.
A sound level meter can report a level flat, or report it through a filter that follows the ear’s reduced sensitivity to low frequencies at moderate levels. That filter is A-weighting, and a level read through it is written dBA. Florida municipal noise codes are written in dBA almost without exception, so the number an officer reads at the property line already has the filter applied.
The size of the discount is published. Pulsar Instruments’ weighting table gives A-weighting as −26.2 dB at 63 Hz and −16.1 dB at 125 Hz, 0 dB at 1 kHz and +1.2 dB at 2 kHz. C-weighting across the same span is close to flat, −0.8 dB at 63 Hz. The part of a festival PA that travels furthest into a neighbourhood is the part the measurement takes 26 dB off.
Meters are graded as well. IEC 61672-1:2013 is the performance specification for sound level meters and sets two classes, with class 2 acceptance limits equal to or wider than class 1. Two conforming meters can disagree at the edges of the band, which matters when a reading is taken to settle a dispute rather than to steer a mix.
The exposure limits use the same unit and do not agree with each other. OSHA publishes a permissible exposure limit of 90 dBA over an eight-hour day on a 5 dBA exchange rate. NIOSH publishes a recommended exposure limit of 85 dBA over eight hours on a 3 dBA exchange rate. Both describe a crew working a full day, not an audience standing through a ninety-minute set.
We own this equipment.
Event audio production — owned inventory, our own crew, and a site survey before anything is specified.