Which arrangement would produce louder output when wiring two sirens—parallel or series?

• A. Depends on model
• B. Equal loudness
• C. Quieter
• D. Louder

Answer: (D)

Loudness comes from how much electrical power is delivered to the sirens. Wiring two sirens in parallel keeps the full supply voltage across each siren, so each one can operate at its rated power, and the total sound produced is the sum of both units. If the sirens are identical with resistance R and the supply is V, the total power in parallel is 2V^2/R, which is louder than using just one siren.

Wiring in series, on the other hand, shares the supply voltage between the two sirens, so each gets only about V/2. The current is V/(2R), and the total power becomes V^2/(2R), which is half the power of a single siren at full voltage. That reduced power means quieter output overall.

So, wiring two sirens in parallel produces louder output. In practice, exact loudness also depends on the devices and enclosure, but the parallel arrangement provides more power and thus more sound.