NFPA 72 - Sound Calcs

[BlaineVT]

I am short on time and need help going in the right direction.

The AHJ wants the sound levels in each room without a horn/strobe. I indicate horn/strobes in the corridors and common spaces.

I know the output for each horn/strobe: 98dBA

The distance from each room to the horn/strobe varies, but I plan on basing the calculation to the center of the room. For this example, we can use 12feet.

The walls for each room is double 5/8" GWB with STC of 40.

The sound levels needs to be 15dB above the average ambient sound of 54dBA.

I have found a lot of calculations for sound. But what am I missing?

 

[chicopee]

About giving us a sketch showing the locations of and the distance between the horns and the placement of a typical room in relation to a corridor with horns. I have never analyzed sound level in the type of setting that you are involved but I have done sound level analysis in heavy structural steel plants, concrete batch plants, cast concrete plants and industrial garages, so I am offering some suggestions that I would personally use if I were in your shoes. Since a typical room will probably have a UL fire rated door, contact the door manufacturer who may provide a sound level attenuation curve for a typical door; if the door manufacturer is not able to do so, such information may be available from one of the UL pamphlets (I don't recall the name of these pamphlets so you may have to research) that list all the UL products with info on construction, fire rating and other relevant info. Such door will also have a UL tag showing fire rating and UL number that you'll need. Also research other catalogs on fire rated doors as sound attenuation may be provided. Since you may be familiar with sound calculations you should be able to combine (that is adding) the sound level of each horn at particular distances from the horns, calculate sound levels at different distances from sound sources and subtract sound levels between sources and any interference such as doors. Sound absorption from the walls and sound travelling around corners could complicate the situation but initially I would discount their interferences for some preliminary work for the AHJ, then you adjust.