A room that has an average ambient sound pressure level of 62 dBA and a maximum sound pressure level lasting more than a minute at 68 dBA must have a public mode signal that is at least?.

A fire alarm notification appliance is an active fire protection component of a fire alarm system. The primary function of the notification appliance is to alert persons at risk.

If want the audible public mode signal to be hear clearly then, we need to have a sound level that is at least 15dB above the average ambient sound level or 5dB above the maximum sound level of at least 1minute

In this case the,

The average ambient sound level is 62dB,

And the maximum sound level is 68dB

Then, the public mode signal should be at least

1. 62dB + 15dB=77dB

Or

2. 68dB + 5dB = 73dB.

Then the public mode signal hearing must be at least 77dB.