Instructions for Territory Day fireworks assessors – Sound level testing

The Northern Territory Government banned the sale of all shopgoods fireworks with a sound level of over 115 decibels (dB) in 2014. The ban includes shopgoods fireworks known as ‘Salutes’.

To ensure consistency of assessment, and to meet the required sound level reductions, the following requirements are to be met:

• a type 1 sound level meter is to be used; meeting the Australian standard, within current calibration
• the sound level meter is to be set up with a direct line of sight to the fireworks being tested, and is to be clear of any obstructions that may interfere with accurate sound recordings (e.g. Vehicles, buildings, trees etc
• the sound level meter is to be positioned 1m above the ground, with the microphone facing towards the firework being tested
• a 'windscreen' (sponge like material designed to fit over the microphone), as supplied by the manufacturer of the sound level meter, may be used where conditions require (e.g. If the wind is interfering with test results)
• refer to the instruction manual provided with the sound level meter for further guidance
• accurate records, including data logging if available, are to be kept and made available to NT WorkSafe on request.

Sound level meter settings

Settings for the sound level meter are to be as follows:

• sound Level Weighting: C type dB(C)
• measurement type: Max
• measurement timing: Fast (125ms, usually denoted by "F" symbol)

Explanation of settings

The C type sound level weighting is a standard feature on most sound level meters. The C type weighting is designed to give a response similar to human perception at higher noise levels.

The A type weighting is not to be used, as its primary function is for the measurement of lower level sound levels below 100 dB. A Z weighting (close to the linear unweighted scale) could also be used, but is not available on many brands of sound level meters.

The 'Max' measurement type is to give the best measurement that equates to a bystanders perception of the noise level.

The Fast measurement timing is also to give the best measurement that equates to a bystanders perception of the noise level, and ensure that the loud noise levels are accurately recorded. 'Peak' noise is not to be used as it is highly affected by wind and deemed to be not as accurately a measurement of human noise perception for fireworks.