Decibel Level
A pdf version of this information can be found here.
The depreciation of sound vs distance assumes that measurements are taken in still air 'open field' conditions and that the sound will not be interrupted by buildings, bills or other objects.
The sound level emitted by a sounder is usually measured in dB at 1 metre. As the distance from the sounder increases the audible level of the sounder reduces. The rate of reduction, normally known as attenuation, is approximately 6dB as the distance doubles. Eg. For a sounder with an output of 100dB at one metre: -At two metres the audible level will be 94dB. -At four metres the audible level will be 88dB -At eight metres the audible level will be 82dB. From the following table you can calculate the dB level required from a sounder to achieve a given alarm sound level at a known distance from the sounder. It can be seen on the table that to achieve 84dB at 128 metres a sounder with an output of 126dB must be used.
The sound level emitted by a sounder is usually measured in dB at 1 metre. As the distance from the sounder increases the audible level of the sounder reduces. The rate of reduction, normally known as attenuation, is approximately 6dB as the distance doubles. Eg. For a sounder with an output of 100dB at one metre: -At two metres the audible level will be 94dB. -At four metres the audible level will be 88dB -At eight metres the audible level will be 82dB. From the following table you can calculate the dB level required from a sounder to achieve a given alarm sound level at a known distance from the sounder. It can be seen on the table that to achieve 84dB at 128 metres a sounder with an output of 126dB must be used.
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