Operations & Maintenance

Making it better: Improving sound quality in all circumstances

audio

A collaborative approach has been taken to solve challenging passenger audio information installations.

Hear the difference in audio quality before and after the solution was installed.

Information systems across a train network can be exposed to some harsh and unforgiving environments. While your average amplifier or speaker wouldn’t be able to last long outside of a airconditioned studio, tm stagetec systems (TMS) supplies the audio technology equipment in use on the NSW railway networks that must withstand anything from a near 50°C day in Broken Hill to below freezing temperatures in Goulburn.

Not only does the technology have to withstand extreme temperatures, but also the realities of a dense, urban rail network. Mark Lownds, general manager of TMS, noted that there are many requirements that are applied to audio equipment on the Sydney Trains network.

“On the Sydney City Circle underground stations, there’s a lot of brake dust and dirt and while Sydney Trains do a great job cleaning of everything, that created another one of the requirements, they need to high pressure hose down our equipment, without damaging it.”

However, for Lownds, some of the trickiest tests of installing sound equipment is not so much the station environment but the acoustics.

“I think Museum and St James are the harshest acoustic environments because they are just concrete tunnels,” said Lownds.

Two years ago, Sydney Trains began the process of updating the audio public address system in Museum and St James stations. A newer audio system would improve the quality of the announcements and importantly bring Sydney Trains into compliance with its requirements under legislation including the NSW Disability Inclusion Act 2014 and the federal Disability Discrimination Act 1992. In addition, the audio system forms part of the evacuation system so must meet high safety standards.

Meet these requirements, without creating a cacophony in the station would be tricky. On top of that, both Museum and St James are heritage-listed stations, meaning that any change to the aesthetics of the stations would need to be approved by heritage architects.

With these competing requirements, a project to improve the speakers on both underground stations required the input and approval of a variety of stakeholders. Luckily, TMS and Sydney Trains had the experience of working on a similarly contested station upgrade at Waverton that was finalised in 2019.

As Charles Chan, audio and visual services manager at Sydney Trains explained, due to local resistance to announcements from the station a number of voices had to be heard in the sensitive project.

“The project involved the legal and customer services group, and environmental group. The residents formed an advisory group, employed their own lawyer, acoustic engineer, and civil engineer. TMS collaborated with Sydney Trains to resolve the issue. Based on that experience, we developed the solution for St James and Museum, but this time we’re not dealing with a noise pollution issue but a heritage issue.”

Through communication between TMS and Sydney Trains a number of solutions that would meet the requirements for announcements without impacting the heritage value of the station were proposed.

“Initially we started with a system where we said we’d put a speaker along the platform wall however this did not meet the requirements of the heritage architects,” said Chan. “We tried putting a few large speakers along the wall, then, we tried putting the speaker on top of the lighting arm. Finally, we got to a solution where we hid the speaker inside the arm and asked, ‘What do you think?’ and the heritage architect said ‘Yeah, it’s a good idea.’”

The idea for the design is that the speakers would be structured in an array and mounted into the underside of the existing light fittings that extend out from the station wall. Luckily, this solution seemed to fit the requirements of all those who had a say in the project, but not without presenting some challenges.

“We can only design the custom-made speaker housing to fit inside the existing arm – the existing light fittings,” said Chan. “On the one hand you need to provide a good acoustic performance but on the other hand you’re limited by the speaker size you can use, the location you can use. As it’s a fixed location, it’s really hard to design a system to meet all the requirements.”

To ensure that the design would meet the requirements for speech intelligibility TMS produced a 3D audio model of the station.

“We worked with an acoustic consultant as well, an electroacoustic engineer, to do the designs, and did a presentation to Sydney Trains to say, ‘If we could pull this off would this be acceptable?’” said Lownds.

With the design idea agreed upon, TMS began working on the custom design of the unique speakers. However, while the speaker was unique, the system that it plugged into would be the same as the rest of the Sydney Trains network, simplifying future maintenance.

“It was a custom manufactured speaker for the station but just using the same electronics that we use in every station but with a different configuration. The network amplifier module that we’ve used is the same as every other station,” said Lownds.

As part of the design process, drawings had to be found of the existing light fittings had to be found. With none forthcoming, full size physical prototypes were built to test the fitting of the speakers within the light arms. In addition, while they appeared similar, the arms were slightly different in Museum and St James, necessitating a module that could fit in both.

“All up the solution employs more than 100 line arrays across the two stations,” said Lownds. “What we did is design a solution that would fit in both, manufactured in bulk which brings the price down substantially, and then also for maintenance makes it a lot easier because you’ve got one spares pool instead of two.”

Not only did this design satisfy the heritage requirements, but the sound requirements as well, said Lownds.

“With the technology that we’ve used, we’re putting sound only where the passengers are. We’re not exciting this whole, empty room anymore, which means there’s none of that big reverb sound and the speech intelligibility is massively higher than the old system.”

Key to ensuring this project was successful was the collaborative approach taken by TMS and Sydney Trains.

“We talk a lot between TMS and Sydney Trains and at different levels as well,” said Lownds. “Charles and I talk a lot to make sure we’re meeting requirements and then we’ve got our project management team here, that works with the Sydney Trains project team; they’re the one who are actually executing. We also have a dedicated support team here that talks with the operations team at Sydney Trains.”

Leading into commissioning, the system was installed during a shut-down period to be ready for final testing. While all the modelling had shown that the system would deliver so far, there was still a crucial last check.

“At heart, we are an audio company,” said Lownds. “We need to make sure that it sounds good, so the final part is to tweak it by ear, and then we go back a couple of times, for these sites because it was really complicated, during the day, to make sure that all the other systems we have in place are working correctly.”

Inbuilt into the system are smart details to ensure that the announcements play out in the most understandable manner.

“We have an ambient noise sensing at these stations, so if there’s a lot more people there, it will turn itself up. If a train comes in when there’s an announcement playing, the announcement will turn up as it’s making noise, and as the train leaves, it’ll turn back down.”

To make sure that these systems were working properly, final testing was carried out during the day while trains were running in late October. Reflecting on the process the week after, Lownds noted that this was one time where modern technology could almost make the stations feel just as they were when they opened in the 1920s.

“The heritage architect had asked, in the meeting, ‘Are you saying you won’t really see anything?’ ‘You won’t see anything,’ we replied, and straight away he said it’ll actually make it better, closer to how it used to be.”

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