In hazardous industrial spaces, alarms and voice announcements must do two things: be heard and be understood. It’s easy to crank volume and still fail at intelligibility. Reverberation, distance, background machinery, and hearing protection all reduce clarity.
A flameproof speaker solves the ignition-risk side (its enclosure contains no internal ignition), but you still need the right acoustic design so messages land clearly across bays, corridors, and yards. This guide walks you through the specs that matter, simple coverage math, mounting/wiring best practices, and a maintenance plan you can actually follow.
Quick reference: full range at Flameproof Speaker →
SPL (Sound Pressure Level): Catalogue SPL is given at 1 m (e.g., 110 dB @1 m). Because sound decays with distance, that headline figure must be translated into listener-position SPL. In most open areas, a quick rule of thumb is ~6 dB loss each time you double the distance.
Frequency response: Speech intelligibility lives mainly between 500 Hz and 4 kHz. Choose speakers voiced for speech rather than music; a slightly “forward” midrange improves consonant clarity.
Directivity/dispersion: Horns with controlled dispersion throw intelligible sound farther. In shorter corridors, a wider dispersion avoids hot spots and dead zones; in high bays, a narrower pattern focuses energy where people stand.
Line type (100V vs 8Ω):
Mechanical & ingress: In corrosive or dusty areas, prioritize robust housings, stainless fasteners, quality gaskets, and rated cable glands. Good mechanics preserve acoustic performance over time.
Target: Aim for +10–15 dB above ambient at ear height where people actually stand. Suppose the packing hall averages 88 dB at peak. Your target is ~100–103 dB at listener positions.
One 110 dB horn at 12 m, will it work?
From 1 m to 12 m: 1→2 m (−6 dB), 2→4 m (−6), 4→8 m (−6), 8→16 m (−6). At ~12 m, you’re in the 89–92 dB range, below target. Solution: shorten throw distance by adding devices and spacing them so no listener is more than 6–8 m from a source, or step up to a higher-output horn (often less comfortable than adding units). In most plants, several moderate sources deliver better clarity than one “cannon.”
Height: 2.5–4 m in production bays; 2.2–2.7 m in corridors so the horn “sees” people, not the floor.
Aim: Slight toe-in toward the listener plane reduces wall reflections. Avoid firing directly at reflective sheets or open stairwells.
Zoning: Split PA into logical zones (line A/B, tank farm, utilities). Independent gain per zone adapts to different ambient noise levels.
Outdoors: Angle down a touch; position out of the prevailing wind path; keep clear of flashing beacons that could mask the horn’s visual line.
Considering visual reinforcement where hearing protection is common? Pair audio with Flameproof Hooter with Jumbo Flasher 110 dB.
Quarterly: Check brackets, re-torque glands, wipe grilles, and confirm screws haven’t loosened with vibration.
Half-yearly: Re-aim after any machine relocations; re-balance taps if the acoustic environment has changed.
Yearly: Full drill with shift teams; document audibility feedback and refine as needed.
Q1. 100V or 8Ω, how do I decide?
If you have long runs and multiple speakers, 100V is simpler and scalable. For small rooms with short cable, 8Ω is fine.
Q2. How loud is “loud enough”?
As a rule, +10–15 dB above ambient at the listener’s ear. Measure during real production.
Q3. Can we mix horn types in one zone?
Yes, but keep dispersion patterns similar so coverage feels even.
Q4. Do we need different tones for different alarms?
Keep tones consistent plant-wide; use cadence or duration changes to distinguish events.
Designing or fixing PA/GA coverage? Send a quick bay sketch and a peak-noise reading, and we’ll suggest spacing, taps, and counts tailored to your layout. Explore options on the Flameproof Speaker page or contact us to review your map today.
