Speech reinforcement needs 70–80 dBA; music reinforcement requires 85–100 dBA with 10–20 dB headroom

The program material (speech vs. music style) determines a sound system’s required SPL capability and frequency response. Speech reinforcement requires only 100–150 Hz minimum low-end response and 5 kHz high-end for intelligibility; average SPL of 70–80 dBA with ~10 dB headroom is adequate. Acoustic music reinforcement needs 40–50 Hz low-end and 16 kHz high-end; 80–85 dBA average with 10–20 dB headroom. Rock music reinforcement requires 30–40 Hz low-end, 10–16 kHz high-end, up to 100 dBA average with 15–20 dB headroom. System design must match these requirements: the same SPL specification becomes a system design target that drives amplifier power, loudspeaker sensitivity, and acoustic coverage calculations.

Examples

A conference hall speech PA system needs only modest amplification (70 dBA average, 80 dBA peak at the back row). A rock concert venue system might need 105 dBA average at the front with 20 dB headroom reserve, requiring an order of magnitude more amplifier power.

Assessment

Why does a speech system not need to reproduce 30 Hz, and what problem would result from providing that capability in a speech-only system?