This was a great relief to all concerned with the Transformation project, especially after the acoustic blips that had surfaced in parts of The Courtyard. It was possibly a greater relief to Nicholas Edwards—an auditorium designer specialising in room acoustics. Edwards admits that the RST job was one of the most challenging he had ever taken on. ‘"I have done many difficult spaces —including found spaces for the Birmingham Opera—but at the RST, the stakes were particularly high. The RSC is such an important company that the building will define the nature of performance for the next hundred years. There was no margin of error to get it wrong.’

The new thrust theatre form of the Royal Shakespeare Theatre auditorium presented a uniquely important acoustical challenge in an area of room acoustics where there is almost no research or precedent to provide design guidance.  While conventional acoustical thinking has typically focused on the measurements of volume-per-seat and reverberation time, the Royal Shakespeare Theatre required breaking those rules in order to achieve acoustical success while meeting the design directives for the space. 

With a volume-per-seat in excess of 10m3 – a value that exceeds some recommendations for concert halls and is more than double the usual value for a theatre—the conventional approach would have been to design strongly sound-absorptive finishes—killing the acoustic energy within the space.  We stepped away from the traditional acoustics approach in the design of the RST to embrace the underlying physical science of acoustics.  Our approach began from first principles to develop a number of original computer modeling methods and measurements. These models were used to study design proposals and to communicate the how and why to the design team and client.  We studied comparison values achieved in computer models of a number of existing theatres including the Swan, the old RST, the RSC Courtyard, the Globe and the Olivier.

The RSC chose the thrust theatre form because it brings audiences and actors close together in a shared space which Shakespeare would recognize. The Swan Theatre with its 380 seats had proven a very successful form for Shakespeare's plays, and the RSC concept for the new auditorium was to scale this up to 1030 seats. The history of auditorium design is littered with examples of how an acoustical concept that works in a small room does not work in a large room, so while the idea of scaling up is simple from an architectural standpoint, the acoustical reality is quite different. To address this--and the essential need for a temporary venue while the redevelopment work was taking place--the RSC used a different design team and built the Courtyard Theatre as a full-size prototype of their concept.

Performers in the Courtyard Theatre found that they had to “bellow out their lines” compared to when performing in the Swan, and even then the sound in the audience areas was weak. One of the reasons for this acoustical weakness is that the technical theatre requirements for flying and lighting exclude space for an acoustically-reflective ceiling. (There is not even space for the flat soffit of the ”heavens” as found above the stage in the Globe.) As in the Courtyard, the new RST could have no sound-reflective ceiling, and since the proscenium opening of the original theatre was retained, there was no possibility for a sound-reflective upstage wall either. With these significant constraints on the locations for sound-reflective surfaces inherent in the design, we had to make the wall surfaces and balcony fronts work extremely hard. We used our computer modeling to show how we could best use these surfaces, studying the strength and arrival-times of reflected and edge-diffracted sound. We designed these surfaces to reflect sound to the audience located behind the performer.

Creating an intimate space with the audience as close to the performers as possible was a common goal for the design team and it helpfully minimized the direct sound distance.  To further maximize the strength of the direct sound we sought to reduce grazing losses of sound propagation over the audience by using a hard floor rather than a carpeted one. Creating natural-sounding speech was a high acoustical goal.  We did not want the reverberance of a concert hall – even though the theatre has the same volume-per-seat as a concert hall.  We controlled reverberance by making the distant surfaces strongly sound-absorptive. Another goal was to allow the audience to be aware of every laugh or gasp from any part of the theatre creating the community experience. Sound-reflective wood floors under the seating areas and reflective surfaces under the seats (as you would find in a concert hall) promote this. 

In addition, the ventilation systems are designed to be silent (at the threshold of hearing) so that performers can make use of the full dynamic range of sound.  Raising the stage height allowed the rake of the seating to be significantly reduced so a taller sound-reflective surface could be introduced at the step/railing between the front main floor seats and the rearmost ones, and this exposed more of the rear wall surface.  It also improved the upward sightlines from the rear rows under the circle. When the Courtyard opened, the balcony fronts were completely open with no reflective surfaces.  We worked with the theatre consultants and the architects to maximize the area of reflective/diffractive surface without obstructing sightlines in the new RST.

While the Courtyard auditorium walls are at the perimeter of the building, the RST walls are moved in close behind the last row of seats.  This reduces the delay time and increases the strength of the sound reflected from the walls.  There was much debate  during the design process of the curve versus the segment – and with the acoustics demanding a flat, segmented wall line the architects developed an ingenious interplay between the curve of the “drum wall” visible in the foyer and the flats of the acoustic walls behind the seats.

The Royal Shakespeare Theatre has a rich history of leading theatrical thinking.  We are pleased and honored that the acoustic design for the new RST was allowed to follow this innovative path.  And with success measured in proof of performance, the legacy lives on: "I came offstage and the first thing I said to Michael Boyd [the artistic director] was 'it works'," said actor Nick Asbury. "I came in booming. I found I had to drop it down. You can, finally, be subtle."

About the author: Nicholas Edwards, who leads the UK office of Acoustic Dimensions, has been working on the RSC Transformation project since 2000. Photos are by Peter Cook and are used courtesy of the RSC.