According to NFPA 72, when using a decibel meter to test proper audible notification levels, what must the state of the door to a sleeping room be?

In accordance with NFPA 72, the proper state of the door to a sleeping room when testing audible notification levels with a decibel meter must be closed. This is crucial because the closed door serves to simulate realistic conditions in which the alarm system will be experienced during an emergency situation.

When the door is closed, it allows for an accurate assessment of how sound travels through the environment as it would during an actual event. Testing in this manner helps ensure that the audible alarms can be heard effectively by occupants who may be asleep or in other rooms, providing a better gauge of the system's effectiveness in alerting individuals in a confidential manner.

If the door were to be open or ajar, it could lead to sound measurements that do not reflect actual conditions, thereby influencing the reliability of the test results.