Serbian term (edited): изван чујности сирена

Списак помоћних средстава за узбуњивање изван чујности сирена
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what is meant is here is:

what other/auxiliary means can be used in places/zones that are too far away from sirens - so far away that you can't hear clearly enough the sirens.

see:

https://www.e2s.com/product-advice/advice-alarm-sounders

How do I calculate the effective distance and coverage of an alarm sounder?

Loudness decreases as the listener gets further from the source of the sound, mainly due to “divergence”. The intensity decreases because the energy is spread over a larger area. It decreases inversely with the square of the distance from the source at a rate of 6dB for each doubling of the distance. So the sound output from an alarm rated at 106dBA) will travel twice as far as a sounder rated at 100dB(A). If a sounder is rated at 100dB(A) at 1 metre, at two metres it will be 94dB(A), at 4 metres it will be 88dB(A) and so on.


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Note added at 3 days 1 hr (2020-06-08 11:42:38 GMT)
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The "audibility" of a siren has two components:

- How loud is the sound emitted by the siren (decibels at the source of sound)

- How far you can clearly hear the siren (a distance)

In this text when they talk of "изван чујности сирена" the ONLY aspect that is relevant / could make sense is about the distance from the siren.