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Fire alarm sounder level calculator

Find the sound level a fire alarm system must reach.

NZS 4512

Reads NZS 4512:2010. Tables checked 26 Sept 2026.

Try a job 6

Each job fills in example values. Replace them with your values.

Inputs

Worked example with the default inputs. The live calculator replaces it when the page loads.

Residual sound level (dB)
50
Voice facilities used for evacuation
No
Building provides accommodation
No
Occupiable balcony
No
Ear protectors routinely worn
No

Required level (dB LAFmax)

65

Margin over the residual level (dB)
5
Set by
65 dB floor
Visual alerting device required
No

This result is a design aid. Verify it against the current standard.

Calculation steps

  1. Residual sound level, dB50

    NZS 4512:2010 Cl 406.3

  2. Margin over the residual level, dB5

    NZS 4512:2010 Cl 406.3

  3. Level from the margin, dB LAFmax55

    NZS 4512:2010 Cl 406.3

  4. Lower limit that applies, dB LAFmax65

    NZS 4512:2010 Cl 406.3

  5. Required level, dB LAFmaxResult65

    NZS 4512:2010 Cl 406.3

  6. Upper limit, dB LAFmax100

    NZS 4512:2010 Cl 406.3

  7. Measurement height1.8m

    NZS 4512:2010 Cl 406.3

  8. Visual device trigger level, dB LAeq(10min)90

    NZS 4512:2010 Cl 406.4

  9. Visual alerting device requiredNo

    NZS 4512:2010 Cl 406.4

  10. Care area low level sounder, dB above ambient5

    NZS 4512:2010 Cl 406.7

About this calculator

How this is calculated

The tool finds the sound level a fire alarm sounder must reach. The point is the bed head or the room. It reads NZS 4512:2010 Clause 406.

  1. Residual level. You enter the ambient level in dB. Cl 406.3 uses it as the base.
  2. Margin. The tool adds the margin that Cl 406.3 sets for the room. The margin depends on the system type and on sleeping accommodation.
  3. Lower limit. It reads the floor that applies, such as the floor for sleeping areas. The result is not lower than that floor.
  4. Upper limit. It reads the ceiling level. The result is not higher than that ceiling.
  5. Visual device. Cl 406.4 sets a trigger level. Above it, a visual alerting device is also needed.
  6. Measurement height. The tool gives the height for the reading, from Cl 406.3.

The result is in dB LAFmax.

Worked example

Limits

The tool does not count devices. Check Cl 406.6 for that. It does not give the measurement method. A care area has its own rules in Cl 406.7. The tool reads NZS 4512:2010. NZS 4512:2021 supersedes it, so check the current edition.

The result is a design target. Measure the level on site with the method the standard gives, then record it. A tone sounder and a voice sounder can need different levels. Check the entry you pick against the clause.

See also: Detector spacing calculator, Fire alarm cabling and Fire alarm battery.

Questions

Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.

How loud does a fire alarm sounder have to be?

NZS 4512:2010 Clause 406.3 sets a margin over the residual sound level. The margin is 10 dB with voice facilities for evacuation and 5 dB without them. The level also sits between 65 dB and 100 dB LAFmax. AmpSize reports whichever figure is higher.

What level is needed at a bedhead?

Where a building provides accommodation, Clause 406.3 gives 75 dB LAFmax, measured at the bedhead. Clause 406.5 and Clause 406.7 cover other areas. Turn on the accommodation option to see the bedhead figure.

When are visual alerting devices required?

Clause 406.4 names three cases. AmpSize checks two of them: an ambient level above 90 dB LAeq(10min), and ear protectors worn as a routine. Read Clause 406.4 in full, because it carries a third case that this tool does not check.

How is the level measured?

Clause 406.3 gives the method and the meter standard. AmpSize reports the measurement height of 1.8 m. An occupiable balcony carries its own figure. Read Clause 406.3 in full before you record a level.

Does this tool show that a system complies?

No. AmpSize reports the levels of NZS 4512:2010 Clause 406 for the values you enter. It is a pointer, not a ruling. A fire alarm design is checked against the whole standard and against the building's declared functional requirements.

Clauses and tables this tool reads

Every clause and table, with how each was verified

Tables last checked on 26 Sept 2026.

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