ICAN Acoustics can carry out audibility tests in accordance with Irish Standard I.S. 3218:2009.

Image result for fire alarm sounder on ceiling
This standard suggests that a fire alarm/sounder should have a minimum sound level of either 65 dB(A), or 5 dB(A) above any other noise likely to persist for a period longer than 30 s, whichever is the greater, shall be produced by the sounders in all accessible parts of the building except as may be recommended in the standard.

If the fire routine for the premises requires the audible alarm to arouse sleeping persons then the minimum sound level shall be 75 dB(A) at the bed head with all doors shut. This may require sounders in every room. This will not guarantee that every person will be awakened but can reasonably be expected to wake a sleeping person in most circumstances which are defined in the standard.
Generally, a large number of quieter sounders is preferable to a few very loud sounders, as excessive noise levels disorientate and make communication difficult. The maximum sound level from a single sounder shall not be greater than 120 dB(A) at any normally accessible area.
In premises used for public entertainment, retail and similar premises, in which the pressure level of music or sound is likely to be greater than 80 dB(A), the music or sound shall be muted automatically when a fire alarm signal is given.
The sound pressure levels shall be checked using an instrument complying with I.S. EN 61672-1, class 2 (or better) with slow response and “A” weighting. The instrument shall have a valid calibration certificate for the period of the test.
In general (excluding at bed heads) the minimum sound levels recorded shall be taken at the height and location where people are likely to be located (i.e. 1,2 m to 2 m above each floor level).