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The purpose built labs are all floated rooms, with acoustic treatment, a large projector and screen, client facilities and use an Ambisonics surround-sound system to replay calibrated simulations using 12 Dynaudio BM5 speakers running off six Quad power amps.

“A shoebox hall is a very good thing because it’s not too wide. A potential problem with the design is when a venue gets to about 2,000 seats and you have to keep it narrow, people can end up too far away from the stage.”

Sugden, led Rob back to design for the performing arts. The first major project for the practice that was a huge project, even by today’s standards, was the Hong Kong Shanghai Bank HQ, which was well under way when Rob started. The team in Hong Kong was Arup’s first dedicated acoustics team to be established outside the UK. He comments: “Our work on the Hong Kong Bank building in 1985 helped launch Arup Acoustics’ presence in Hong Kong and worldwide.” Rob’s first major role as principal acoustician was Bridgewater Hall, Manchester, in 1989. The 2,400-seat home of the Hallé Orchestra in Manchester, widely acknowledged as one of the best concert halls for acoustics in the UK. It is also one of several that Arup Acoustics has isolated from the ground borne noise of adjacent rail tracks or roads. At Bridgewater, the 22,500 ton structure has no rigid connection to its surroundings; instead it is supported on a matrix of steel springs. The undercroft beneath the hall has also become a popular filming location. Most concert hall designs fall into one of two forms. Traditional shoebox-shaped concert halls have their design roots in the 18th and 19th Century rectangular court ballroom form in which the classical orchestral concert was born. The prototypical shoebox room is tall, narrow, with parallel side walls, and most of the audience is formally arrayed in front of the orchestra, such as Musikvereinssaal Vienna, Birmingham Symphony Hall, or Kilden concert hall Kristiansand, a design by Arup Acoustics. Acoustically the reason for the shoebox design is that when listening to music it is important for an audience to hear sound that arrives quite soon after the direct sound to give clarity and intimacy. For orchestral music it is also very important that the sound comes from the sides. So the building needs to have surfaces to the sides which aren’t too far away from where the audience. Rob explains: “A shoebox hall is a very good thing because it’s not too wide. A potential problem with the design is when a venue gets to about 2,000 seats and you have to keep it narrow people can end up too far away from the stage. Birmingham Symphony Hall is a good hall but a few hundred people are stuck away towards the back.” The other form of design is the vineyard. These are, for the most part, a 20th Century development, following an arena concept that wraps the audience around the performers. The result is that the audience is seated closer to the performers, in a less hierarchal arrangement than found in the shoebox model. These rooms are typically wide, with audiences organised in terraces around the orchestra, and whose wall surfaces provide critical early reflections of acoustic energy. The Berlin Philharmonie, St. David’s Hall Cardiff, and Suntory Hall Tokyo are examples. The auditorium is divided into sections with walls created between the sections. They in a sense make up for not having a narrow hall.

At Bridgewater Hall, Rob tried to find a hybrid solution, somewhere between the shoebox and the vineyard. That was a fairly bold thing to do. With a concert hall you only get one go at it. So the prototype is the final thing. Rob adds: “Working with the architects we developed a hybrid design which we think works really well. It has good acoustics and a sense of space as a hall. I feel very much that to get a great auditorium you have got to have this balance between acoustics, architecture and what you might call theatricality and functionality as well as safety and technical systems. If any one of those is too strong you have an imbalance. I could take you to a hall that looks good and sounds terrible or I could take you to ones that sound good and look terrible. There is always a balance to be struck.” Bridgewater Hall was one of the first projects to use computer modelling for acoustics, using a programme called Odeon, which they still use today. The software tool is used for room acoustic design to predict the acoustic quality of interior spaces. For an acoustician the most efficient way to start a design process is to have the architect’s 3D model and import it into the software. They are then in the position of using it to inform either the ground up creation of a building space or putting in sound systems in existing building spaces. At later stages analysis is made to select the final layout of surfaces, choice of material properties and loudspeakers to obtain the optimal spatial coverage and the optimal values for acoustical parameters such as reverberation time (RT), clarity and the Speech Transmission Index (STI) used to measure speech intelligibility. For reverberation time Rob says what he is aiming for. “The longest times you want are for things like choral and organ music. You might want a mid frequency RT time of about 2.5 seconds. For symphonic concerts two seconds, for opera somewhere between 1.5 and 1.9 seconds, for recitals 1.2 to 1.8 depending on the size of the hall. Then going right down for drama you want one second and for conferences 0.8. And ideally for a speech based recording studio you don’t want anything at all. Maybe 0.5 seconds.” Steering sound in particular directions and pinpointing targeted areas and zones are all important factors for consideration when discussing architectural audio. Subtlety and accuracy are key. But it is the ability to disguise audio technology, and be flexible, whilst still satisfying the aural requirements of a space that Rob feels, demands a great deal of time and attention.

AURALISATION A major part of Arup Acoustics current practice is their pioneering use of auralisation (the sound equivalent of visualisation) as a design and demonstration tool. Arup’s SoundLabs in New York, London, Glasgow, Melbourne and Hong

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