Central Station Sydney gets Duran Audio solution
AUSTRALIA: The majority of the external areas of Sydney’s’ Central Station were recently equipped with new sound reinforcement systems that were specifically installed for situations where crowd management is required, such as train-movement announcements, emergency situations or large community events.
Acoustic consultant, Acoustic Directions undertook the acoustic design and commissioning of these systems to optimise speech intelligibility and sound quality for the various areas, which included the Light Rail Concourse and platform area. New Era installed the equipment and loudspeakers, with Open Access taking care of the manufacture and commissioning the new Netspire system.
The heart of the sound system is the Netspire system designed and manufactured by Open Access in Australia, and provides the station with signal processing, routing, transport and remote health monitoring of signals on fibre optic and Cat-5e cables using the Dante signal transport protocol. Dante is the preferred protocol for the digital signal transport of Transport NSW, which operates the Sydney trains. The loudspeakers are customised versions of Duran Audio’s Intellivox DSX280 and DSX430 line arrays. Electrical contractor New Era Group installed all the equipment and the 700m long fibre and cable runs from the announcement source to the loudspeakers.
Discussing challenges the teams faced on this project, Acoustic Directions’ Glenn Leembruggen noted: ‘The primary challenges with this project were acoustic and heritage; each coverage area had a very high ratio of near-to-far listener-distances and high reverberation times in the covered areas. In particular, the Light Rail platform area has a mid-band RT of around three seconds. Normally, high reverberation environments with heritage requirements are addressed by using long, slim line arrays; however these types of arrays generally have reduced high-frequency polar consistency between 5kHz and 10kHz, resulting in listeners near the loudspeakers receiving poor frequency response and reduced intelligibility. This high frequency issue was overcome with the customised Intellivox DSX arrays which incorporated additional high-frequency steering components to allow the arrays to deliver extremely consistent frequency responses over distances ranging from 2m to 30m from each loudspeaker.
‘In the marketplace of ultra-directional arrays, the customised DSX Intellivox arrays now have the lowest extent of side-lobe behaviour at high frequencies,’ he continued. ‘Not only do side lobes add unwanted sound energy to the reverberant sound, they cause echoes from ceilings. The combination of the improved high frequency performance of the customised DSX arrays and the weatherproof rating made them the ideal choice for this project.
Mr Leembruggen also noted that ‘line array loudspeakers have very wide radiation patterns in the horizontal plane at low and mid frequencies due to their narrow size. When using line arrays in a delay-based system, this wide radiation pattern allows direct sound to be radiated behind delayed speakers, causing strong echoes for listeners for listeners in these areas. At the Light Rail platform, we located the delayed Intellivox speakers behind large stone columns located on the edge of the platform, which allowed us to take advantage of the acoustic shielding provided by these columns of the loudspeakers’ rear-radiation. The resulting effect was a complete elimination of the echo problem.
‘The acoustic commissioning of the system was just as important and detailed as the design phase,’ Mr Leembruggen reflected. ‘It is during commissioning that the complete design parameters are confirmed and field adjustments optimised. In the first part of the process, every electronic and loudspeaker element in the signal chain was checked for connectivity, polarity and frequency response correctness. The second part of the process was equalisation, delay and level adjustment, which involved numerous spatial measurements of frequency response based on impulse responses using a WinMLS2004 analyser, and careful equalisation of the average responses using Acoustic Directions proprietary curve-fitting software. The final stage of commissioning utilised an iterative process of further acoustic measurements and listening to music and live and pre-recorded speech.
‘Transport NSW can now make announcements that are easily understood in each external area of Central, and they were very happy with the demo we gave them at the conclusion of the commissioning process,’ he concluded.