Sound Pressure Levels - Why ??!!

[David Rooney]

1. How did the figure of 65db come to be?

2. Why was was 60db adopted for "smaller" rooms etc in 2002?

3. If 60db is acceptible in smaller rooms why not larger rooms?

4. Typical office environment - corridor with lots of offices .... the offices are being measured at anywhere between 50db to 60db+. Contractor want to install over 100 more sounders in the offices - big extra to client - As the human ear can't differentiate between 3db either way, would it be reasonable to accept an alarm level down to 57db in the offices??

As the alarm levels are "arbitrary" (16.2.1 note 5) - "a term given to choices and actions which are considered to be done not by means of any underlying principle or logic, but by whim or some decidedly illogical formula" .... could the figure of 57db (or any other figure) be adopted as an agreed variation if the rooms are assessed as being particulary quiet and the likely occupant healthy and with good hearing?

[Allen Higginson]

You no work on or something??
The drop from 65dB to 60 is certain applications allows for the differential,to drop to 57dB would mean a drop of 8dB over the desired figure.
Would increasing the number of sounders in the corridors not achieve what they need (or are they those dopey sounder base type?).

[David Rooney]

Am in the midst of our BAFE inspection....!!

...just having a sandwich..... !

All the detectors in the corridors already have base sounders installed....(Notifier) this is a typical scenario we come across a lot due to the noise insulating properties of modern materials....

[Allen Higginson]

Am in the midst of our BAFE inspection....!!

...just having a sandwich..... !

All the detectors in the corridors already have base sounders installed....(Notifier) this is a typical scenario we come across a lot due to the noise insulating properties of modern materials....

Hate sounder bases - only really good for offices or single rooms.Anyway of adding "proper" loop powered sounders in the corridors?

[Benzerari]

We had been in similar situation a while ago, the designer looks, he knew about BAFE involvement..., he suggested a sounder base with every single detector..., to guaranty the sound pressure, but in case it's too loud, it would be then easy to turn down or isolate it... etc. This found to be much secure, then getting struggled if say, the sound pressure hasn't been achieved in certain area... etc

More is always secure

[Benzerari]

1. How did the figure of 65db come to be?

2. Why was was 60db adopted for "smaller" rooms etc in 2002?

3. If 60db is acceptible in smaller rooms why not larger rooms?

Definitely BS researcher have a reason behind that, I think 65db came through a series of research and analysis in regards to testing the human's intention while awaking or their ability to wake if sleeping.... etc

Obviously, there is a min and max in this issue, above I think 120db, it may perforate the human’s ear or (membrane), and below 40db it may be overridden with the existing noises... etc

Regarding the noise level in small room, it shouldn't have the same sound pressure, if produced in bigger room, it will be dropped down, due to the size of the room, sound waves propagate like any other sort of waves, the longer they propagate the less pressure sound is detected... etc

[Allen Higginson]

We had been in similar situation a while ago, the designer looks he knew about BAFE involvement..., he suggested a sounder base with every single detector..., to the sound pressure, but in case it's too loud, it would be easy to turn down or isolate it... etc. This found to be much secure, then getting struggled if say the sound pressure hasn't been achieved... etc

More is always secure

Sounds more like someone who doesn't know how to design a fire alarm system to me by throwing devices in just in case!

[colin todd]

1. Prior to 1980, CP 1019 simply called for the fire alarm signal to be adequately audible above background noise throughout the building. This was considered by the Home Office not to be objective enough so they asked for the revision in the form of BS 5839-1 to give a figure. The 65 was based on very subjective listening plus two forms of logic. Firstly, people think sound is twice as loud if it increases by 10dB. Normal conversation is around 55dB, (unless you are asking Messeys chums why they want things and then the conversation is about 120 dB). So 65dB is about twice as loud as normal conversation. Also, the answer was reverse calculated. Typically, it was considered that bells in corridors gave about 65 in non-sleeping rooms off.

2. 60 was adopted as a pragmatic relaxation to make it less likely to need a sounder in every titchy little room.

3. Because it is less of a cost issue.

4. yes possibly but dont push your luck and ask for 54 on the basis that it is like 57.

[Benzerari]

We had been in similar situation a while ago, the designer looks he knew about BAFE involvement..., he suggested a sounder base with every single detector..., to the sound pressure, but in case it's too loud, it would be easy to turn down or isolate it... etc. This found to be much secure, then getting struggled if say the sound pressure hasn't been achieved... etc

More is always secure

Sounds more like someone who doesn't know how to design a fire alarm system to me by throwing devices in just in case!

What you call it throwing devices..., in fact is not throwing detectors but rather maximizing the number of sounders for safety reasons…, that's the correct meaning

Devices = (Detectors , MCPs , Interfaces , Sounders...etc)

You need to specify, before jugging Buzz

[David Rooney]

Regarding the noise level in small room, it shouldn't have the same sound pressure, if produced in bigger room, it will be dropped down, due to the size of the room, sound waves propagate like any other sort of waves, the longer they propagate the less pressure sound is detected... etc

Benz I'm talking about the level acheived by your ear.... not the output from the sounder...  I'm asking why is 60 acceptable in a small office but not, for example, on an escape staircase or even a larger office?

[David Rooney]

4. yes possibly but dont push your luck and ask for 54 on the basis that it is like 57.

Thanks Colin..... as if I would !!!

[Benzerari]

Regarding the noise level in small room, it shouldn't have the same sound pressure, if produced in bigger room, it will be dropped down, due to the size of the room, sound waves propagate like any other sort of waves, the longer they propagate the less pressure sound is detected... etc

Benz I'm talking about the level acheived by your ear.... not the output from the sounder...  I'm asking why is 60 acceptable in a small office but not, for example, on an escape staircase or even a larger office?

Sorry Dave, but I don't see any differences in the way, you exposed this issue, and my answer is as already quoted... etc, other replies may better clarify it.

[messy]

(unless you are asking Messeys chums why they want things and then the conversation is about 120 dB). .

Colin:

I think I know exactly the converstaion that you are referring to!!

[Wiz]

Regarding the noise level in small room, it shouldn't have the same sound pressure, if produced in bigger room, it will be dropped down, due to the size of the room, sound waves propagate like any other sort of waves, the longer they propagate the less pressure sound is detected... etc

Benz I'm talking about the level acheived by your ear.... not the output from the sounder...  I'm asking why is 60 acceptable in a small office but not, for example, on an escape staircase or even a larger office?

David, I would guess it is because a larger office is likely to be more noisy (with ambient noise from occupants, office machines etc) than smaller offices. This is why even 60 is acceptable in areas of limited extent in larger offices, since someone in a larger office is likely to be in the areas of 65 and react even if someone else was in the 60 area (and possibly didn't react)

[Allen Higginson]

We had been in similar situation a while ago, the designer looks he knew about BAFE involvement..., he suggested a sounder base with every single detector..., to the sound pressure, but in case it's too loud, it would be easy to turn down or isolate it... etc. This found to be much secure, then getting struggled if say the sound pressure hasn't been achieved... etc

More is always secure

Sounds more like someone who doesn't know how to design a fire alarm system to me by throwing devices in just in case!

What you call it throwing devices..., in fact is not throwing detectors but rather maximizing the number of sounders for safety reasons…, that's the correct meaning

Devices = (Detectors , MCPs , Interfaces , Sounders...etc)

You need to specify, before jugging Buzz

Sorry Benz but in what you are referring to you are talking a sounder base every 10 metres - why charge the client more than is needed when you can design a system to achieve the correct sound levels?