PEARL of wisdom

This article by Rob Halliday discusses the use of RAYN Growing Systems technology in UCL PEARL and was first published in LSi, March 2023 (www.lsionline.com).

When a government lab wants to model the real world to test the best way of doing something, where does it turn for the expertise in making up scenarios? Why, theatre, of course.

Rob Halliday reports . . .

Go on any given journey on any form of public transport, and it’s fascinating to witness the sheer number of people trying to separate themselves from our world, maybe even isolate themselves, ears clamped with headphones trying to keep the noise out. Ask Professor Nick Tyler of University College London why they choose to do that, and his answer is immediate and unequivocal: “Because we’ve made the real world sound so terrible.” Ask him how we might be able to make that better, and he’ll tell you he’s working on it. Ask him how he’s doing that, and he’ll introduce you to the fascinating building called UCL PEARL . . .

In an area where the ‘other’ realities – virtual reality, augmented reality – are grabbing all the attention, Professor Tyler’s fascination is very much with the actual real world. The trouble is, as a scientist, the real world is a hard place to conduct proper, precise experiments. There are too many variables to really be in control of your testing. His solution is not to turn to VR or AR, both poor substitutes for the experiences of real life.

Instead, at his behest, University College London (UCL) have built a ‘real reality’ but in a controlled way – in effect, a giant laboratory for experimenting with the practicalities of life.

So: you’ve got a new train and need to figure out whether people can get on and off quickly enough to let it run to its proposed schedule. Or new buses that you want to figure out how to improve disabled access for. Or electronic scooters that need to warn people they’re coming, but want to know what would be the best sound for achieving that. This facility, called PEARL, gives you the space, equipment and controlled environment to do just that.

This is a result of “Government realisation in about 2012 that it was going to have to spend billions on infrastructure – but how to spend that best?” Prof Tyler explains. “The Research Council provided funding to establish new labs for this, distributed around the country. Some were new versions of existing labs. This one, which received about £9million plus then an associated contribution of £39m from UCL, was unique in being about the interaction between people and the environment.”

Hence the name: ‘PEARL’ is derived from Person Environment Activity Research Laboratory.

But why are you reading about all that here? Because it turns out that if you want the equipment and skillsets to create alternate worlds, the entertainment industry is a really good place to start – because in effect that’s what we do day-in, day-out on every show we do. “It felt like we were trying to build worlds in here, and that’s what people in theatre do, so it felt like people with experience of that might be interesting people to work with. So we advertised, and met a really interesting set of people as a result.”

Reduced to the simplest possible summary, PEARL is a big warehouse. But it’s a remarkable warehouse, designed, equipped and staffed with the best the entertainment industry has to offer.


All this is happening in Dagenham, in East London. PEARL stands on land once owned by May and Baker, an early and pioneering chemical company; it will soon find itself neighbours with another aspect of the entertainment industry, with a number of new film production sound stages rising rapidly around it. There’s a lot going on around here.

The building was designed by London-based architects Penoyre & Prasad, though, it’s clear, with very precise guidance from Prof Tyler. Earlier in his life he was a professional musician, an oboist. “Musicians are always trying to do it better,” he says.

“There’s an oboe note in the Brahms fiddle concerto that’s difficult to start – but you’re always trying to get as close to the ideal – a start that you don’t realise has started – as you can. It’s the same with the building. I felt we needed a 40m clear span, no columns, which is about how far we can see with good acuity and being able to lose the horizon into our peripheral vision. Everyone kept saying no, but eventually we achieved it. We had to work really hard to achieve silent a/c, but once everyone bought into it, we made it happen. The plant was located at the far end of the building for noise purposes, but the bonus is it will be easy to replace in the future if necessary.”

The building offers a 10m clear height, a volume of 44,000m 3 and 4000m 2 of floorspace – a bigger floor area than Wembley Arena, and with enough length to get a car up to 30mph and then stop it again. Access doors are big enough to bring in buses or trains and there are plans for a retired Boeing 737 to be parked outside and connected through to the main building.

It is UCL’s first net-zero building, aided by high insulation levels and a roof lined with solar PV panels.

Inside, the width of the building is divided roughly into three along its 100m length, one side containing office and workshop space across two levels – this called ‘the Groove’, its name prominently sculpted into the front of it – the other storage for the facility’s equipment. But that still leaves a huge working space down the middle – named ‘The Space’ – which then grows to the full width of the building in its last third. The working space can be gently divided into four zones using black masking and motorised tracks and drapes supplied by theatre specialist J&C Joel, who also looked after installing the points for the many runs of dead-hung truss, and loose rigging equipment including motors, control and truss.

So, a warehouse? But one that doesn’t look or feel like any warehouse you’ve ever been in. It’s hard to know whether it’s the light or the sound that you notice first – or perhaps actually that you don’t notice it. It is incredibly quiet, without the terrible echoes that are a characteristic of most warehouses.

And the light feels somehow natural: you look, and so feel, healthy, rather than the oppressive industrial lighting you’d more usually find.

You also realise it’s very hard to grasp the scale of the place, All these things are, of course, deliberate. “The space is wide enough that with the black drapes at the side, which are slightly rippled, and with the lights being set to not light the drapes, you can’t see the edge in your main vision. Without any other visual references a big tiger model would seem close and scary, but a small tiger model would seem further away rather than just smaller,” Prof Tyler explains. “The aim is to be able to control as much about the space as possible.”

The acoustic has been carefully engineered to have a reverberation time of just one second, giving an acoustically neutral space that you can then manipulate however you like. The lighting is specified to be able to recreate an enormous colour range at anything from just a pitch black – the building is light-tight – to as close to the brightness of daylight as is achievable. Even the floor can be adjusted, with a highly engineered modular system from Babcock that allows floors, steps or slopes of different heights and angles to be set up, and even the flooring material itself to be changed if necessary. The only thing not immediately changeable is temperature, generally kept at a constant 22˚C – though a new building called Cave, just being completed next door, adds that, with the ability to vary from -5 up to +40˚C.

The building provides the background into which you can set up your ‘world’, as quickly and efficiently as possible, just as when putting a show into a good theatre – and, it turns out, using exactly the same sort of infrastructure.


If that infrastructure – the GRP grating walkways that encircle some of the space, the facilities panels all over the building – is familiar, it’s because it’s the work of theatre consultants Charcoalblue and very much follows the style of their contribution to so many other performing arts venues around the world.

They came on board quite late – “the architects realised that there were some very complex technical and infrastructural requirements for the space, given the nature and complexity of the research that would be undertaken there,” recalls Charcoalblue director Jenni Harris. “Certain things were fixed already – the footprint, height, how the space could be divided up, but it was clear it was going to need to fundamentally function and operate like a production centre, with design, fit-ups and turnarounds that we’re all familiar with in theatres – that’s really what intrigued us about the project. I think when the architects first reached out to us, Professor Nick was initially sceptical that we could bring any value to the project, but by the end he trusted us, and in particular our project lead Joe Boxshall, wholly as we helped shape the project.”

The call for some ‘theatrical’ intervention came, Joe Boxshall notes, “because the wife of the lead architect is a set designer, so he is very much linked in to the theatre world.

When Charcoalblue got involved it was a big empty warehouse with the idea of big truss pods that came in and out with everything on them. We suggested that might not be the best solution – if you had something set very precisely, you might not want to move it in order to get to something else, so we moved to the permanent overhead truss plus bits of rigging for other things, plus the catwalks to get at everything approach. The catwalks were perhaps the biggest change – but I think we could achieve that because everyone else was looking to us to solve the problem.”

Boxshall became so fascinated by the project that, along with fellow Charcoalblue consultant Beky Stoddart, he jumped ship to join PEARL as it opened – a shift he admits to finding “refreshing, to get back to actually being hands-on and doing things after two years of working at home during COVID – but also quite an eye-opener; employing a team who would then keep picking apart everything about how we’d designed the space!” Though having the consultants on-site to explain the decisions was probably also helpful!


The infrastructure, specified by Charcoalblue, includes 360 ways of ETC ColorSource ThruPower racks installed in several ‘dimmer’ rooms around the building to provide power to the lights – the core rig is all LED, but the potential for tungsten or other sources is supported – plus a comprehensive lighting data distribution using fibre and ethernet to facilities panels, many of which then include ETC’s one-port DMX nodes to feed data out to the lights. All this lighting infrastructure was supplied and installed by White Light, who also supplied the building’s lighting fixtures.

These fixtures are something quite special, slightly unexpected – and didn’t actually exist when the project started.

If you’ve been to ETC’s London building over the last couple of years you might have seen a little sign inside one window saying just ‘RAYN Growing Systems’. The mysterious name is for what was the last of many remarkable projects instigated by ETC’s founder, the late Fred Foster.

“Fred and I had independently gone to seminars about the application of LEDs in horticulture,” recalls Adam Bennette, long-term technical director at ETC in London before retiring last year. “Fred got really excited by it, which led to RAYN – a project to take the multi-spectral work we’d been doing for ETC’s theatrical products and move it into the horticultural field, with fixtures and controllers that let you manipulate precisely what kind of light a plant receives and for how long. That lets you shape how it grows, how deep its roots grow, when it blossoms – everything about it.”

ETC’s Jeremy Roberts recalls “doing a fos/4 panel show-and-tell for White Light when they said, ‘we’ve got this strange brief for a really wide-spectrum light – maybe your 8-colour system would work for it?’ We talked about it. I knew it wouldn’t achieve it, but . . .”

“Jeremy joined the dots,” Bennette recalls. “He walked a bunch of people into R&D one day, which you’re absolutely not supposed to do, and started showing them what we were doing. We took what were then prototypes of the RAYN Rosa fixture, which started off some fascinating conversations with Nick Tyler. The standard Rosa contains colours that are really only useful for plants; PEARL wanted more human-centric lighting, so we changed the recipe.”

If you love your 8-colour Lustr3s, then prepare to be jealous: PEARL’s fixtures have 11 – violet, indigo, blue, cyan, green, the broadband lime, amber, red/orange, a standard red, a deep red like the Lustr3s and then a 740nm far red that goes beyond even that.

The final installation has 312 of these custom fixtures rigged on fixed trusses that span the width and are distributed along the length of the space, able to be controlled from either a pair of ETC Ion Xe-20 consoles, or the more plant-centric RAYN control system. “We had a tree in here at one point, inside the building,” recalls Steve Mayo, one of those who jumped from theatre (teaching at RADA, and before that head of sound at the Barbican, and head of sound on touring RSC productions) into being PEARL’s acting technical services manager and specialist lead for sound.

“And with the RAYN lights, we made it blossom and flower in the middle of winter.

It was remarkable to watch.” Standing in the space, it feels able to create any mood, from the best rendition of a grey English day I’ve ever encountered in stage lighting, to the deepest saturated colours, up to almost 30,000 lux, but also right down to the very lowest levels. “Nick wants to get down to the milli-lux, maybe even the micro-lux level, in monochromatic colours that emulate sodium streetlights or in intense reds,” Adam Bennette explains. “We can get close – but you’re down into the noise then; that’s really hard to do.” Tyler, as ever, is pragmatic about this reality – but still keen to achieve his objective.

The RAYN fixtures are supplemented by other items from the more familiar end of ETC’s range, with a selection of fos/4 Fresnels and panels, Source Four LED Series 3 Lustr X8 profiles and Irideon FPZ and WLZ fixtures available to be deployed as required.

The visual equipment stock also includes four Barco G60W10 projectors, a Mac Pro and MacBook Pro with DaVinci Resolve and an editor keyboard, cameras from Canon and GoPro, interfaces and monitors from Blackmagic, plus four Gerriets white two-way projection screens. The projectors and screens allow the team to create projected environments – though in these setups the projectors are sometimes having a hard time competing against those RAYN fixtures. PEARL’s video lead Ralph Stokeld and the team are actively investigating LED screens as a technology that might let them better achieve this. In the big stage space at the far end of the building, the team also has a 24 Axis moving camera rig for tracking motion or objects to provide realtime analysis of experiments.


The building’s precisely controlled acoustic – the walls are internally perforated with millions of tiny holes to let sound pass into rockwool – and very low base sound level, down at around -30dB, essentially provides an aural blank canvas to bring any sound into, or to manipulate the acoustic of. PEARL is equipped with tools to achieve just that, with a comprehensive audio system specified by Arup, the project overseen by Arup’s Tom Brickhill and then completed by James Beer as Brickhill moved to Australia.

The challenge – and opportunity – here is that there is no standard configuration of the space and so no pre-definable set-up for the audio system: flexibility was needed, along with audio quality plus the requirement to create both ‘immersive’ audio – here that meaning audio that could envelope people in the space and move sound around them – and to be able to modify the acoustic of the space.

The system to achieve this came from L-Acoustics, with Julien Laval, the company’s applications project manager and consultant liaison, recounting a key human moment that perhaps helped shape that choice: “On a day when Nick was visiting our London demo room, I was able to steal 10 minutes of time with Christian Heil, L-Acoustics’ founder. It wasn’t planned, but it just felt important – they share so much in terms of culture, in background, both with a really high interest in science and in music. For me it was a given that if they were in the same room, able to talk, they’d both recognise the alignment in their work.”

And so it came to pass. The main space is equipped with L-ISA immersive sound technology from L-Acoustics, which includes around 150 L-Acoustics loudspeakers: 100 X8, 24 A15, 20 KS21 and 8 KS28s driven by L-Acoustics amplification, plus the company’s L-ISA Processor and Controller for object-based mixing system.

“In discussions with Tom at Arup, we came up with the concept of having ‘cells’ of loudspeakers in each space you’re using,” recalls Julian Laval. “The basic rule of design for an object-based system like this is that wherever you go in the space you want to be exposed to the coverage of each speaker, so that as an object is moving around it doesn’t disappear and then come back again.”

L-ISA has various ‘tricks’ to maximise the realism of sounds moved in this way – not just moving it from loudspeaker to loudspeaker, but also shifting the delay and the high-frequency roll-off.

PEARL doesn’t (yet?) use the kind of trackers others have deployed to move sound with performers, but as well as using L-Acoustics software, they were early adopters of Dan Higgott’s panLab addition to QLab (see LSi July 2022).

With his history in audio, Steve Mayo of course knew Higgott. “I heard him asking if anyone had a space he could borrow for a day to test his software. I called and said, ‘you have to come and look at this’. He did, and panLab is now a creative partner with us, because it gives us some advantages over the L-Acoustics software – that system always has the idea of a stage around which things move, which isn’t always the case here.”

L-ISA, though, also now offers for varying the room acoustic by using microphones to pick up the sound of the room, manipulate it and feed it back out to the speakers – there are a lot of tricks available for the PEARL team to deploy as necessary.

To prep sound effects in this immersive world, PEARL has a sound studio – ‘The Vibe’ – equipped with what is in effect a miniature version of their main system – 16 L-Acoustics 5XTs plus SB15m sub-bass units, “though I tend to turn the bass off unless I really need it because it breaks through into the workshops next door,” Mayo admits.

This rig is designed to allow an ambisonic loudspeaker setup, based on Arup’s SoundLab, for developing spatial audio environments. A DiGiCo SD9 console sits in the centre of the room, with rigging around the walls that allows the speaker positions to be precisely adjusted as required. Prep work – for both sound and video – often involves the PEARL team just heading out with microphones and cameras to capture whatever is required for an experiment.

For audio, they’ve “found that ambisonics is the best way of capturing and then recreating the sound of the real world,” Mayo notes. “We are currently using a Sennheiser Ambeo microphone and Sound Devices MixPre6 field recorder and have taken first-order ambisonic recordings around central London for use on our e-scooter Acoustic Vehicle Alert System sound project. With PEARL’s large stock of loudspeakers and one second reverb time throughout the space, ambisonic recordings are a really practical way to get the inside of the lab sounding like outside environments.”

The L-Acoustics system was supplied by Adlib, on a competitive tender, with the company also supplying and installing the building’s sound infrastructure and support equipment. This includes Apple Mac Pros running Pro Tools with an Avid MTRX Studio interface or QLab with a Dante Virtual Soundcard.

That connects to Biamp Tesira servers, with RME AVB Tools used to interface between MADI and Milan AVB for the L-ISA processors. “We designed a system where an amplified controller could be connected to any AVB data or fibre point in the building and instantly connect to the audio racks without the need for analogue or AES patch-bays and tie-lines,” explains Adlib’s project manager Andrew Watt. Adlib also designed and built flightcases for all of the equipment, protecting it when not in use or when being moved around the building.

“I was presented with a space that was huge, but acoustically treated,” comments L-Acoustics’ Julien Laval. “For me, that was like, wow! – very interesting.

Not just as a potential project, but also as a partnership or even as a space we could use – selfishly – as a playground for me!”

He’s right, though: it’s a lab that could be used for many things. Where else could loudspeaker manufacturers investigate the behaviour of their products in an arena-sized space, free of all the inherent acoustic issues most arenas have?


Laval is not the only one to have been immediately fascinated with PEARL – it happens to many who hear about it, most who visit it, including Joe Boxshall and Beky Stoddart who jumped at the chance to work there having helped design it.

Boxshall has since moved on, but Stoddart remains as team lead in the ‘backstage’ team which includes lighting and video specialist Ralph Stokeld, technician (and Raspberry Pi/ Python wiz) Shane Gill, and technicians Matt Vile and Ben Paveley, all under the overall direction of acting technical services manager and specialist lead for sound, Steve Mayo. They bring a mix of backgrounds and experience – variously, as sound designers, or lighting designers, or astrophysics students who fell into the college theatre crowd, working on immersive shows by the likes of Punchdrunk – but all seem thrilled to be in this unusual new environment, part performance space, part science lab, where they never quite know what each day is going to bring, and what challenges each new project is going to present them with. That might be creating a set (they still call those days ‘fit-ups’), figuring out lighting, capturing audio or video to create the world, or connecting sensors and coding computers (the Raspberry Pi is their tool of choice, for its ability to be strapped to things under test) to collect the data that the scientists require and thrive on, all with the ‘can do’ attitude of the best entertainment industry practitioners. I think they’re also enjoying working with those scientists and researchers – a whole realm of people that those working backstage never normally get to meet.

They have some backstage space to support their work: ‘The Buzz’ and ‘The Toolbox’, one an electronics/engineering workshop with computers and plotters and 3D printers, the other a construction workshop with big machine tools.

Above them are the open plan office space (‘the Riff’), plus some separate meeting and planning rooms, and ‘the View’ – a balcony next to the offices that gives a full view out over the space.

I describe his team as his ‘theatrical pirates’ to Professor Nick. He smiles, but then notes: “Everyone here is a pirate, to some extent. By coming here, you’re choosing to think about things in a different way.”

I have one last question for him, since it seems to me that people who go to all of the trouble and effort of fighting to get a facility like this built often have an ulterior motive, an experiment that they really want to use it to carry out. What is his? “I want to be able to explore everything about interactions between people in the real world,” he replies after just a moment’s thought. “Right down to, why do they sometimes say ‘hi’ to each other, and if they do, do they feel better?”

It’s a simple yet powerful answer, an experiment too big to carry out in one go. But PEARL is a tool to start unpicking it, one layer at a time.

From the perspective of ‘our’ world of entertainment, it’s fascinating to see how it’s chosen to do that, yet another example of how the technology and skills from our field can now be deployed to provide solutions far beyond traditional entertainment productions.

But it’s also just fascinating to know it’s there.

Everything we do in live entertainment is about one specific version of that human interaction: how an audience reacts to what we create. We instinctively know what works and what doesn’t, but we never get a chance to properly, scientifically test that instinct, to prove or disprove it, to do the experiment. Julien Laval might be excited about testing his speakers there, but why not go beyond that? Why not see how louder or quieter or immersive or not sound, lights flashing or static or colourful or not, actually affects real audiences watching real bands? Amongst so many other things, PEARL would make a great gig lab . . .

Want to do it? Give them a call. I’m sure they’d be happy to help.