REPORT 035
Introduced by Roland Hemming Roland is an independent audio consultant. He has managed and designed a number of stadium projects and was in charge of all audio - except the ceremonies - for the London 2012 Olympic Games.
The London 2012 Olympic Stadium
proaching concert quality, rather than a plain, compliant announcement system. This is of course more expensive but not massively so. In the grand scheme of things audio is very cheap, you get a lot more impact for spending not much more. To accompany a better sound - and video system- you need good content, but there are plenty of production companies capable of producing effective high quality presentation, week after week.
THE TECHNOLOGY
The sheer size of a stadium means that there will be no single audio location running the whole building. It is common to have multiple rack locations, often connected together with fibre, each driving loudspeakers near to them. These racks are often co-located with IT racks so the fibre routes can be shared. Simple stadia will often have racks North, South, East, West - sometimes at two different levels - one set to drive the roof loudspeakers for the bowl and the other for all the concourses. Larger stadia may have upwards of 20 racks. Digital audio networks are frequently used, using redundant loops to make them resilient to failure. Programmable digital signal processors provide the brains of the system routing audio to and from different parts of the building for commentary, announcements, entertainment and emergency messages. Broadcast audio signals also sometime pass through the network to assist programme makers dealing with the long cable runs sometimes required from where the action takes place to where the broadcast trucks are parked. On the loudspeaker side, the bowl requires high performance loudspeakers evenly spread, they need to be arranged so they cover both the lower and upper tribunes. Stadia with balconies may need some local loudspeakers to cover the shadow in coverage caused by the balcony. Any outdoor loudspeakers need to be weather- proof.
Inside the requirements can be simpler, large concourses, toilets, corridors, entry gates and boxes most often need simple box-type, ceiling or horn loudspeakers to
provide the coverage. Some places such as restaurants and special hospitality areas may need higher quality loudspeakers. You also need to consider that you may need local inputs for microphones and music sources. Any ‘production’ inputs need to be shut off in the event of an emer- gency announcement. The same goes for any local audio systems that are separate from the main building PA.
COMPLIANCE
For anyone working with life-safety systems, such as those required in stadia, the bane of our lives is having to comply with the various standards. It is essential that you comply with the standards in order to ensure that your building is safe. But the argument is more complex than that.
When talking about evacuation of stadia you also need to get a few things straight. The audio system is not strictly for evacuating the public. You are expected to carry out a manual evacuation of such a building using marshals. The audio system is there to assist with such an evacuation, not to do it on its own. When a possible emergency arises there is a procedure for investigation, confirmation, coded and warnings to pre-warn staff before proceeding with any evacuation. Most deaths and injuries are caused by crushing and stampeding, it is often safer to tell most people to stay where they are, and only evacuate the part of the building where there is immediate danger. This requires you to be able to address different zones within the building.
Just about everyone outside of the audio and fire industries doesn’t understand the standards, so they rely on us to advise on what we are doing. There are a number of different local, national and international standards and it isn’t always clear when each one applies.
There are some fundamental things you have to do that few would disagree on. The system has to be intelligible, this means being able to be heard above any crowd
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