Can a concert hall have a perfect acoustic?

Sound engineer Paul Waton and soprano Lesley Garrett discussing theatre acoustics at the Royal Opera House. (Courtesy: Brian Slater)

By James Dacey

Concert hall acoustics was the theme of a fascinating panel debate last night at the Royal Opera House (ROH) in London. Among the speakers was British soprano and presenter Lesley Garrett who shared her views on the acoustics of some of the great concert halls in which she has performed. She was joined by acoustics engineer Trevor Cox, acoustics consultant Helen Butcher and sound engineer Paul Waton, who has recorded a range of classical concerts for the BBC. Insight: the Art and Science of Acoustics was co-hosted by the Institute of Physics, which publishes Physics World.

Cox – who featured in our 2014 podcast about sonic wonders – set the scene by describing some of the fundamental acoustic considerations in designing a concert hall. We heard clips of Cox playing a saxophone in an “anechoic” chamber, followed by the same sax lick performed in an oil tanker – the place with officially the longest echo in the world. Cox’s point was to show the difference between high clarity at the one extreme and intense reverberation at the other. The sound wasn’t quite “right” in both cases. “Concert hall design is about finding a pleasing balance between these two extremes,” he said.

For opera fans, the night was packed with interesting anecdotes and titbits. For instance, Butcher said that those who seek clarity of spoken word would be better to sit near the sides of a theatre to benefit from proximity to reflections off the wall. Alternatively, those seeking the full richness of reverberation should sit high and central – right in the mix of all the vocals and instruments. Cox also explained how positioning an orchestra in a pit below the opera singer cuts out some of the instruments’ higher frequencies, enabling the singer’s voice to pop out above the music in a dramatic way.

From a design point of view, it was interesting to learn about some of the engineering fixes being applied to existing concert halls. One famous example cited by Cox was the acoustic “mushrooms” suspended from the ceiling of the Royal Albert Hall. These fibreglass diffusers were added in the late 1960s to counteract the strong echo caused by its iconic dome. Three modern concert halls that received universal praise from the panel were: Birmingham Symphony Hall (highly adaptable); Boston Symphony Hall (a classic “shoebox” shape with great clarity); and La Philharmonie de Paris (a modern masterpiece combining beautiful design with cutting-edge acoustic technology).

Butcher talked about the work her company, Arup, is doing to the ROH’s Linbury Studio Theatre, which had the opposite problem of the Royal Albert Hall. To improve the “liveness” of this space, the firm plans to add timber panelling to various surfaces to increase reverberation. It will also reduce the steepness of the seating areas to reduce the sound absorbed by audience members’ bodies – something that is a bigger factor than you might think, according to the panel. Meanwhile, the Arup team will electronically enhance the overall sound by distributing the music from places around the hall – a process that does not involve amplification.

You could imagine some purists getting a bit precious about the introduction of this sort of technological enhancement. But Garrett very much supports such innovations. She talked about the changing expectations of audiences now that home sound systems are so sophisticated. “To keep live music vital, we need to embrace new technologies or we risk losing our audiences,” she said.

Garrett added that in general she prefers smaller venues where her voice is not lost in the space. But her favourite acoustic experience of all time was visiting the Ancient Greek theatre at Epidaurus, famed for its acoustics. She recalled how she stood in the acoustic sweet spot and started belting out some songs – much to the joy and surprise of the other tourists!

Towards the end of the evening, the event’s host, broadcaster Samira Ahmed, put the evening’s big question to each of the panellists: Is there such a thing as a perfect concert hall? This is what each of them had to say on the matter (paraphrased):

Helen Butcher
There isn’t a perfect design because music is so varied and each performance has its own requirements. Also, the atmospheric conditions affect the sound and these change all the time.

Trevor Cox
No. Audiences comprise people with different tastes – some prefer clarity, others prefer reverberation.

Paul Waton
As it is my job to record performances, my perfect hall is one that is consistent between when I do my sound tests and when the audience are present. I prefer dry (high clarity) because it gives me more control when recording and mixing.

Lesley Garrett
I believe the words of opera are where the real drama lies and it is vital that the audience can hear what is being communicated. Too much reverberation and you lose the sound.