Exposure, hearing protection and the crew's day

The SPL tab answers the questions the crew asks and nobody has the table for: how long can we stand at this level, how much does this plug actually help, and how does the whole day add up.

Run the damage timer

1. Open the SPL tab and find Hearing Damage Timer.
2. Choose the weighting of your reading: dBA (what most meters report) or dBC. A dB(C) reading is converted with the programme's C − A difference — 2 dB by default, a conservative value for amplified music; put in your own if you know it. The card shows the conversion.
3. Enter the Current SPL level.
4. Read the two results — permissible time until the daily dose is used up:
   • NIOSH (3 dB) — 85 dB(A) for 8 hours, 3 dB exchange rate: every 3 dB more halves the time. A US recommendation.
   • OSHA (5 dB) — 90 dB(A) for 8 hours, 5 dB exchange rate, and never above 115 dB(A). US law.

Times are rounded down and show seconds below a minute.

Check hearing protection

The Hearing Protection card estimates the level behind a plug or muff.

1. Pick the HPD type: foam plug, earmuff, IEM, ACS Pro 15 / 20, or Custom with attenuation per octave band.
2. Read Effective SPL (dBA) behind the device and the protected exposure times.

The rating is derated the NIOSH way — the lab value is first reduced for real-world fit (earmuffs keep 75 %, formable plugs 50 %, others 30 %) and then 7 dB come off for the A-weighting — so the protection is lower than the number on the box. In Custom mode the per-band attenuation is summed as energy over a live-music spectrum, which is why strong treble attenuation does little when the bass is loud; the lab result and the derated field estimate are shown side by side.

The crew's day (EU)

Crew day — EU noise at work adds up a working day in segments — load-in, soundcheck, show, or your own — each with a level, its minutes and the hearing protection worn. It reports the daily exposure LEX,8h:

• without protection against the action values — 80 dB(A) (the employer offers hearing protection and information) and 85 dB(A) (protection must be worn, the area is marked, a noise-reduction plan is made);
• with protection against the exposure limit of 87 dB(A), which must never be exceeded.

These are the values of Directive 2003/10/EC — in Germany the LärmVibrationsArbSchV, in the UK the Control of Noise at Work Regulations.

The other SPL cards

• Distance — level at a new distance: a point source loses 6 dB per doubling, a line array in its near field about 3 dB.
• Back-Row Level — the same for the last row.
• Source Combiner — two sources: different signals add by energy (+3 dB), the same signal in phase — stacked subs — by pressure (+6 dB).
• Audience — the rule where you play: see The rule where you play, the correction value and the protocol.