The first thing to settle is the source. Noise from a road, a railway, a business and a neighbour are four different problems. Brisbane City Council's noise restrictions cover nuisance noise from premises and devices, and Council states that where it has approved specific emissions for a business, the conditions of that approval apply instead. Council's restrictions do not cover road traffic noise or railway noise. So the same fence can be a private owner's only practical lever on one boundary and a small part of a regulated answer on another.
The second is what a fence can physically do. The Queensland Department of Transport and Main Roads describes noise barriers as working by interrupting the path of sound waves. A fence helps most when it sits between the source and the people hearing it, is continuous, and has no gaps at the base or the joins. It helps least when the source is above it, such as a road on an embankment or structure, or when the noise arrives over a length of boundary the fence does not cover. That is a question of geometry at your address, and it is why the site visit comes before the height.
The third is the rules for the fence itself. Height, position on the lot and whether an approval is needed depend on the site, and Brisbane City Council publishes guidance on acoustic fence heights. Guidance is not an entitlement to build to a height, and a fence built to it has not satisfied any approval by doing so. Check what applies to your own address with Council before a height is designed.
The fourth is whose line it is. The fence may sit on a boundary shared with a neighbour, a body corporate, a landlord or a business, and the person hearing the noise is not always the one who owns the line. Settling ownership first saves a quote aimed at the wrong party.