GHD: Electro acoustics test

Challenge

GHD designed a bespoke loudspeaker system and required measurement of the spatial directivity conformity in accordance with ISO 16283-3:2016 and ISO 3382-1:2009.

Solution

The anechoic chamber at UTS Tech Lab is a box within a box with an air gap in between, which allows it to be acoustically isolated from the rest of the building and adjacent rooms. The whole inner chamber is mounted on a set of springs to reduce structure-borne sound. The inner chamber’s walls, floor, and ceiling are made of heavy brick and concrete to prevent sound from getting into the room. The inside of the chamber is lined with 1300 foam wedges to absorb sound and remove reflections from the chamber walls.

The sound pressure levels were measured around the loudspeaker at a distance of 1.5 m from the centre of the loudspeaker, time-averaged over 10 seconds in each measurement. The loudspeaker rotated with 5° intervals and driven with a broadband noise signal (pink noise).

The test was delivered in 3 hours using a Brüel & Kjær Electroacoustics testing system to scan sound radiation per direction of the bespoke loudspeaker with a controllable turntable in the UTS anechoic chamber.