IOP and the Royal Opera House collaborate to sound out theatre acoustics

4 March 2016

The IOP teamed up with the Royal Opera House (ROH) for an evening to discuss “The Art and Science of Acoustics” on 1 March with an expert panel chaired by journalist and broadcaster Samira Ahmed and including opera singer Lesley Garrett, acoustic scientists and practitioners.

IOP and the Royal Opera House

 
At the event, Professor Trevor Cox, professor of acoustic engineering at the University of Salford, demonstrated the difference between a “dry” space, in which sound is stopped very quickly, and a “wet” or “lively” space, in which reverberations continue for a long time, with two recordings of himself playing the saxophone. The first was in an anechoic chamber, which has no reflection of the sound from walls, floor or ceiling, while the second was inside an oil tanker.

Cox explained that the modern science of acoustics had really begun in the 19th century when Wallace Sabine had introduced a parameter called reverberation time – essentially the time taken for a sound to die away to nothing within a space. Up till then, the design of theatres and concert halls had been based on precedence – building on what had worked in the past, with varying success.

Despite this trial-and-error approach, there had been remarkable achievements in good acoustic design, from as far back as the amphitheatre at Epidaurus in the 4th century BC to the Musikvereinssaal in Vienna, built in 1870, he said. In recent years more attention had been paid to the sound reflected from side walls, and shaped surfaces had been built into structures such as the enormous Philharmonie de Paris, opened in 2014.

Sound engineer Paul Waton, who worked for BBC Radio for more than three decades and has specialised in live and recorded classical music performances, described the challenges of working in different spaces and for widely varying events. For an opera, this could involve placing 40 or 50 microphones to achieve the optimal sound, and this was done without any special rehearsals for the engineers. Opera houses were, however, purpose-built for performance and were designed so that singers could be properly heard by the audience without amplification, unlike certain concert halls that were notorious for their poor acoustics.

Helen Butcher, an acoustic consultant with Arup, described working with the ROH on its Open Up project, which includes redevelopment of the Linbury Studio Theatre. This had to take account of the different but overlapping needs of the audience, performers and creators of music, and be designed for performances as varied as opera, ballet and amplified music. The designers are aiming to retain some of the Linbury’s best features, such as its quietness, while improving on others by, for example, replacing meshing around the tiers with more reflective solid wood.

They are also introducing electronically-enhanced sound, which is different from amplification as it does not aim to increase loudness but to distribute sound around a space. Lesley Garrett said she was happy with electronic enhancement in the right context, although in general opera singers performed without amplification. She and the other panel members agreed that people’s expectations of live music were changing as they were used to hearing recordings in high definition. Garrett, pictured with Waton, said: “I think we have to meet that challenge and if it’s subtly done I have no problem with electronic enhancement, if the quality of the music demands it.”

She described how singers need to be able to hear their voices reflected back to them so that they can adjust how they sing. In dry spaces, younger singers could be tempted to over-project their voices, she said. No two live performances were the same because no two audiences were the same, Garrett said, and even factors such as what the audience were wearing or temperature and humidity could dramatically change the acoustic, particularly in an open space. “If a mist comes down it affects the sound immediately – it’s suddenly like wading through treacle,” she said.

The panel took several questions from the audience including whether loop systems for hearing-impaired people could be used to help all audiences hear more clearly, and whether theatre design was such that people in the cheaper seats had a worse sound experience.

Butcher explained that that had not been true in older theatres, while in more modern ones the intention was for the sound quality to be as good as it could be for seats on all levels. This did not mean that the acoustic would be the same in all positions – listeners in the side seats would experience greater clarity while those at the top would hear a richer, more romantic sound, but, she said, “we try to make an excellent acoustic in all parts of the auditorium”.

The evening – part of the ROH’s behind-the-scenes Insights programme – was not the IOP’s first collaboration with the ROH: in 2014 they jointly held an event on “What makes the perfect song?” with Professor Brian Cox.

The IOP’s public engagement manager, Manisha Lalloo said: “After a successful event last time we were delighted to partner with the ROH again, this time taking a look at theatre acoustics. The evening lived up to its name, providing a fascinating insight into the world of acoustics from a fantastic and diverse panel of speakers. I hope our audience have gained a new understanding of how physics can play its part in uniting with design and performance to create a memorable musical experience.”