Taking arriving and departing passengers on a sonic journey of 6,00km (3,900 miles) down China’s Yangtze river in two minutes, HSBC’s London Gatwick Airport Skybridge project is the world’s largest interactive sound installation at an airport.

The project, dubbed A Living River, celebrates HSBC’s 15-year partnership with the World Wide Fund for Nature (WWF) and The Water Programme, a five-year, $100m programme aiming to provide and protect water sources, inform, educate and drive economic development. Delta Sound played a major role in the installation’s design and installation of the sound system for the 180m-long walkway.

Marketing company J Walter Thompson (JWT) was commissioned by HSBC to provide the project’s soundscape, with JWT’s Tom O’Donnell serving as Creative Director for the project with Delta Sound’s Davey Williamson, whose experience of immersive audio and motion sensors to trigger recordings in real time was invaluable. This has included an immersive 3D show at Berlin’s Tempelhof Airport for Toyota, turning the soundtracks to videos into a surround sound experience, using a custom speaker array.

‘Tom and I went through a number of different options for what we could do for the Skybridge project,’ Williamson says. ‘Could it be a big musical instrument that people could play? Could it be playback, voice messages? But then I came up with the idea of having 160 speakers at the side of the Skybridge at chest height and hung from the I beams directly above the travellators in both directions. This would provide a really good, immersive experience, if the speakers were positioned at frequent intervals.

‘Because of my background in producing content for shows and technical sound design, I knew the possibilities and the way a sound designer would work. I wanted to provide a limitless canvas for them to work with.’

Once Williamson had written a technical brief on the design, how audio could be played back and his suggestions for the use of motion sensors, the sound design went out to tender. The tender was won by Nick Ryan, whose concept for location recordings of the Yangtze River really captured the imagination of HSBC and JWT.

‘Nick wanted to make it as authentic as possible,’ Williamson reports. ‘Providing Skybridge users with a realistic experience of the Yangtze was the most important thing and he was concerned about the positioning of the speakers. He initially didn’t think it would feel immersive enough, but once we’d listened to some mock-up material, he was sold.’

Ryan’s recording concept involved an eight-channel array, based on DPA 4060 omni-directional, miniature microphones and Sound Devices 788T eight-channel field recorders. Mounted on custom telescopic camera tripods, the microphones were arranged in a row 10.5m long, spaced 1.5m apart, with the ‘height’ mics set back by 1.5m. This meant they were positioned exactly the same distance apart as groups of eight loudspeakers on the Skybridge, ensuring that the Yangtze ambience would sound completely natural when replayed at Gatwick. ‘It’s a fantastic way of capturing audio,’ Williamson says. ‘It also meant there were no issues of phase.’

Ryan spent five days recording 100 hours of audio in 35 locations along the length of the river, which would give Gatwick travellers the experience of travelling the entire length of the river as they traversed the Skybridge. He also used a selection of other microphones to capture ambience and spot effects, as well as hydrophones to record the sounds beneath the water, including rocks and bottles tumbling along the river bed.

With the recordings ‘in the can’, back in the UK he worked with Williamson on a 20m offsite mock-up of a section of the installation, to hear how it would sound to Gatwick passengers and to mix the content. Postproduction technologies included Pro Tools, QLab and Apple Logic Pro, various Waves plug-ins and others. The mock-up also gave them the opportunity to work out the best loudspeakers for the finished installation. Davey chose the Bose DS100 SE for the side speakers, because they could run low impedance or 100V line, as well as delivering good bass extension and a defined high end. For the ceiling speakers he chose JBL pendant models, which provided the easiest method of deployment and had very natural dispersion.

’The Bose speaker is a surface mounted product, so I designed a bespoke L bracket, which was manufactured by R Concepts in Shepperton Studios. The speakers almost look like they’re floating in space,’ he says,

With the PA/VA room where the amplifier racks were housed being around 400m from the furthest speaker, Williamson had to run the speakers as high impedance devices. He chose Crown 8 x 300w amplifiers and used 80 amplifier channels, the speakers being linked in pairs. ‘We ended up using around 28km of low smoke, zero halogen speaker cable, which was necessary to comply with the Gatwick Airport standard,’ he continues. ‘The cabling was arranged as eight 25 core multicores, routed from the PA/VA room, over a service road, up an electrical riser tower to a termination panel in a service room at the end of the Skybridge. From there it was distributed out to 80 two core cables, which ran to the speakers.’

The use of Merging Technologies Ovation media server allowed different scenes to be played back at different times of the day, all sequenced to a real-time clock, with bidirectional sharing with Pyramix for on the fly asset editing. Ryan then created a detailed schedule with options available for six ‘time of day’ slots: dawn, morning rush hour, morning, afternoon, afternoon pm rush hour and evening.

‘For example, the market scenes play early in the morning and late in the afternoon. There are some fishermen at work only in the morning or late evening when they’re coming back. Nick’s schedule explained when, how and in what mode each sound would play. But there were also elements like crickets only being heard in the evening. So we made a cricket overlay and we scheduled the sequencer in Ovation to only play that if it was in the evening time slot,’ says Davey. ‘Ultimately, programming took 30-40 days – mostly working 16-18 hours.’

The installation was also designed to interact with the weather in China. A script on a Raspberry Pi mini-computer in the PA/VA room looks at weather data from Yibin in China every ten minutes and reacts by triggering ‘overlay’ sounds of wind, rain or other relevant material as necessary.

Ten further Raspberry Pis were used for the PIR motion sensors, which are located at the second side speaker in each of the five audio zones that span each travelator, as well as multiple other tasks. ‘You can have a sound, such as a moped, coming from behind you and moving in front. This makes it very apparent that your human interaction with the sound installation has made something happen,’ Williamson says. ‘Also, every time someone goes through the first sensor it starts a dim timer which runs for 30 minutes. So if 30 minutes go by without anyone passing the first sensor again, it fades the whole experience out until it’s woken up by someone passing it again.’

The installation covers both the arrivals and departure sides of the Skybridge, with all the loudspeakers and sensors mirrored, but reacting independently.

When it came to installation, the strict rules governing design approval, materials and airside working meant that the Delta team worked under the sponsorship and guidance of Adam Betherick and Michael Bradey at Corporate Connection. ‘They work with HSBC Global, managing and installing their print campaigns across all airports that they have advertising rights to,’ says Williamson. ‘They’ve been working at airports for the past 15 years and they were the bridge between JWT, me and Gatwick Airport Commercial. Adam and Michael were fantastic, they set up the programme of works, got us accredited, told us best practices of working and acted as a site manager and escorts.

‘Once on site we had two days of induction and training before starting installation. Because you can only work while the passengers are clear and have to be off site an hour before the first passenger would go through, time on site could be very limited. I approached it with a demanding ‘live sound’ schedule, working with a carefully handpicked, four-person team. This including Mark Powell, Delta’s technical manager. He was able to manage my designs and specification and all the technical and mechanical parts that were needed to complete things. He also built the server racks for the PA/VA room, which were beautifully done.’

The Skybridge installation has gained widespread international attention, including from mainstream news media, and Davey is obviously pleased that he and Delta were invited to play such a key role.