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Natural Science Forum / Physics / Acoustics / May 2007Maximum level for a fire alarm
We had our monthly fire drill today, so I pulled out my B&K 2232 and measured the (A-weighted) sound level to be 110dB at about 4 feet, mike perpendicular to sound source in the hallway and 108dB just outside my office. Can somebody point me to regulations about acceptable sound levels for fire alarms? Would OSHA regulate State of Maryland facilities? People complain of transient ear pain when we have one of these exercises. TIA! >We had our monthly fire drill today, so I pulled out my B&K 2232 and >measured the (A-weighted) sound level to be 110dB at about 4 feet, [quoted text clipped - 6 lines] > >TIA! It used to be 120dBA, but now it is 110dBA, so your system is just compliant. http://www.aes.org/e-lib/browse.cfm?elib=13597 d  SignaturePearce Consulting http://www.pearce.uk.com As you see from the first response there are two sides of this issue. you were concerned that OSHA or someone would limit the loudness so as to protect your ears. The other side of the issue is to make them loud enough that they are heard. The basic problem with these warnings appears to be that no one wants to spend the money on enough signal devices that good coverage could be provided without very loud levels near the individual devices. Thus, they use a few very loud devices to assure the most distant listener probably through a few doors and walls will hear them, resulting in those closer to the device getting far more sound than is necessary. With a warning device in every room, it should not have to be so loud. > We had our monthly fire drill today, so I pulled out my B&K 2232 and > measured the (A-weighted) sound level to be 110dB at about 4 feet, [quoted text clipped - 6 lines] > > TIA! > The basic problem with these warnings appears to be that no one wants to > spend the money on enough signal devices that good coverage could be [quoted text clipped - 3 lines] > the device getting far more sound than is necessary. With a warning > device in every room, it should not have to be so loud. I think this must be a universal problem, I have found exactly the same in the UK. Because the exposure to high sound level from walking past a sounder doesn't normally last very long, and hopefully only happens occasionally, normal calculations would show that there is no risk to hearing, so no-one is likely to do anything about it. However the noise could well cause temporary loss of hearing and is likely to set off a tinnitus attack in some people who are prone to noise induced tinnitus. SignatureTony W My e-mail address has no hyphen - but please don't use it, reply to the group. > > The basic problem with these warnings appears to be that no one wants to > > spend the money on enough signal devices that good coverage could be [quoted text clipped - 16 lines] > My e-mail address has no hyphen > - but please don't use it, reply to the group. In the US the required sound levels are set by NFPA 13, the Fire Alarm Code. Most states adopt this by reference. The code says that the audible notification device sound level is to be a minimum of 75 dBA and at least 15 above the average ambient noise level. The maximum permissible SPL is 120 dB. In this area (upstate NY), these systems are design either by electrical engineers or the fire alarm system rep. It is a rare project indeed when anyone does any calculations. Mark |
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