Two sirens wired in parallel compared to series will be louder.

• A. Louder
• B. Quieter
• C. The same loudness
• D. Unpredictable

Answer: (A)

When you connect two identical sirens to the same power source, how they’re wired changes how much power each siren gets. In parallel, each siren is across the full supply voltage, so both run at their rated loudness and their sounds add together, making the overall output louder (roughly a 3 dB gain over one siren). In series, the same current flows through both but the voltage is split, so each siren only gets about half the supply. That reduces the power to each unit, and the combined sound is quieter than when they’re wired in parallel. Since loudness increases only modestly with additional sources, parallel wiring is the louder arrangement.