Which of the following is NOT a requirement for a system arranged to stop or reduce ambient noise?

• A. Provide active noise cancellation
• B. Produce a sound level at least 10 dB above the reduced ambient sound level or 5 dB above the maximum sound level having a duration of at least 60 seconds after reduction of the ambient noise level
• C. Increase acoustic absorption in the space
• D. Limit the system to lower volume

Answer: (B)

The essential idea is to reduce ambient noise through methods that either cancel, absorb, or limit the noise produced by the system. Active noise cancellation uses phase-inverted sound to interfere with and reduce unwanted noise. Increasing acoustic absorption in the space helps by converting sound energy into heat, reducing reflections and overall sound levels. Limiting the system to a lower volume ensures the device itself doesn’t add excessive noise. The statement about producing a sound level at least 10 dB above the reduced ambient level or 5 dB above a sustained maximum after reduction is not a requirement because it would defeat the purpose of noise reduction by intentionally creating louder sound.