Which statement about siren effectiveness and speed is correct?

• A. The siren effectiveness decreases around 50 mph
• B. The siren effectiveness is the same at all speeds
• C. The siren is only effective above 60 mph
• D. The siren is most effective below 20 mph

Answer: (A)

Speed affects how well a siren gets the warning across. As you approach around fifty miles per hour, wind and road noise rise, and the siren’s sound energy is carried away more quickly, making it harder for drivers nearby to hear and react. This combination means the siren becomes less effective at that speed, which is why the statement about effectiveness decreasing around 50 mph best fits real-life conditions. The other ideas—siren effectiveness being constant at all speeds, only being effective above sixty mph, or being most effective below twenty mph—don’t reflect how increasing speed changes ambient noise and how sound travels from a moving vehicle.