Tom Patterson theatre’s unique acoustical considerations

by brittney_cutler_2 | May 23, 2022 8:00 am

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By Payam Ashtiani, P.Eng., and Doron Meinhard, B.Arch.

Along the banks of the picturesque Avon River in Stratford, Ontario, stands a significant new addition to the Canadian cultural landscape. Named for the festival’s founder, the Tom Patterson Theatre (TPT) is the Stratford Festival’s first new performance space in 20 years. Organizers had planned to dedicate it in 2020 to coincide with the 100^th anniversary of Patterson’s birth; however, the pandemic delayed the tribute, and it is now slated to open in time for the 2022 season.

The $72-million project provides a state-of-the-art theatrical experience and replaces a similarly named venue in the same location. Originally constructed within a repurposed curling rink in the 1960s, the previous theatre had cramped seating, limited backstage areas, no space for patrons to mingle before and after the show, and was showing its age.

The new theatre is in many ways its opposite, designed not only as an attractor, and described by The Globe and Mail as having “some of the most beautifully detailed and well-sited public rooms in the country,” but it is also acoustically magnificent.

The horseshoe-shaped auditorium is the jewel set among an array of program spaces that are enclosed by a shimmering curvilinear glass and bronze veil. This organic shape blends into the riverside garden landscape and dissolves the line between indoors and out. The lobby, cafe, members’ lounge, education lab, and a secondary performance space called Lazaridis Hall are all light-filled spaces that face the landscape and river.

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Redesigning the new theatre

Throughout the building, acoustics were a top priority for the festival and its artistic director, Antoni Cimolino. The festival had tried to improve the acoustics in the original theatre, but mechanical noise, lights, and dimmers were an issue.

The new theatre recognized that being able to create moments of silence on stage could bring ‘magic’ to a performance.

The new auditorium is reminiscent of the original room in one respect: the innovative elongated thrust stage of the former TPT has been lovingly replicated and surrounded now by 615 seats in the three-quarter configuration. This unique performance space provides actors with runway-like access into the audience chamber. With only eight rows of seating on each side of the stage, the experience is immersive—with a more intimate connection between performer and audience than in traditional proscenium auditoriums.

With today’s focus on accessibility, the new auditorium is wider and longer than its predecessor and posed significant acoustical challenges. While it brings the audience closer, the acoustics of thrust stages are complicated by an actor facing away from large parts of the audience about half the time. In theatre, speech intelligibility is critical. The possibility of a performer facing away from the audience meant a considerable effort was needed to ensure a base level of speech intelligibility no matter where an actor was positioned. Speech intelligibility is affected by the ambient noise level in the room, and the complex reflection patterns of sound as it travels from the speaker to the listener.

The challenge was to deliver clear, intelligible speech to a location well behind the actor’s back—putting extra pressure on the acoustic performance of the space. While there is a sound system, the priority for the space is for unamplified spoken word, and its ability to reach every patron clearly—particularly when actors are at the other end of the thrust stage and facing away from the audience.

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First, the ambient noise level of the wood-lined room was designed to be quiet enough to allow for sounds to be heard clearly before fading into the background. This involves ensuring the noise from HVAC and other building systems were adequately controlled. The theatre is equipped with state-of-the-art, silent light-emitting diode (LED) lights to avoid any additional sound.

Second, the pattern of reflections had to be carefully designed. For good speech intelligibility, more acoustic energy would have to arrive at the listener in the first 50 milliseconds of sound arrival than after 50 milliseconds. This was achieved by approaching the challenge at two levels: macro and micro. At the macro level, the overall surface materials in the space were optimized to reduce the reverberation and minimize the sound that would linger past 50 milliseconds.

At the micro level, angled reflectors were designed and placed beneath each of the three catwalks above the stage to create a shorter path for reflected sound to reach the audience. Since the distance from the actor to the ceiling to the audience was too long, the reflectors intercepted the sound much sooner and reflected it back. The shape of the reflective surfaces was designed to direct early sound (<50 milliseconds) to the audience locations that needed it the most: behind the actor. If the geometry allows for those reflections to arrive in time, speech intelligibility is enhanced. Even with the actor at one end of the catwalk and facing away, this ensured an audience member on the other side would have a high level of speech intelligibility. Many design iterations for these reflectors were tested in a state-of-the-art sound lab to validate any subjective impressions of what the acoustic models and scientific values would be like to experience.

Finding silence in the curves

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The auditorium is unique because it is acoustically separate from the rest of the building. It is not precisely a box within a box, but rather a hybrid with elements of a separate structure and layering to create a floating shell around the space. The large concave shell over the entire theatre was part of the initial design vision. Traditional acoustic design in theatres avoids concave surfaces, as their effects are not easily analyzed with confidence. There is also the risk of focusing sound unevenly in the room and creating acoustic hotspots that make for suboptimal acoustics. To preserve the esthetic vision while delivering superb acoustics, refined in-house modelling techniques were used to design the acoustics to keep the concave curvature throughout the space. Non-uniform rational basis spline (NURBS) based acoustic analysis tools were used to identify the curve areas that had the potential for focusing, and either change the curvature, or design those areas to be acoustically absorptive. This way, the vision of a large concave shell still meant excellent acoustics. Acoustic bearings were used for structural beams and columns and the inner lining of the auditorium was isolated from concrete by creating a floating liner inside for the finishes.

Usually, there is a base level of quiet in a performance hall. It is akin to how white a canvas an artist needs for a painting. However, the quieter a room gets, the more complicated and expensive the engineering demands become. Typically, live theatre rooms have a noise criterion of NC15 or NC20. For a hall like the new Tom Patterson Theatre, an ambient noise level of not louder than a preferred noise criterion (PNC) of 20 to 25 would typically be recommended. PNC is like NC, except it also has requirements in the lower frequency range. However, the quieter the hall becomes, the more acoustically dynamic the space is. After conducting several demonstrations of different levels of ambient noise, a goal of NC10 was determined as a reasonable target to avoid hearing the noise from mechanical equipment without introducing large amounts of added complexity into the design.

To control the noise, the HVAC system was designed to have a very low supply air speed, and ductwork was fitted with appropriate silencing and acoustic liners. To create a seamless acoustic and esthetic effect, the terminals of the supply ducts were fitted with custom-designed open diffusers that fit naturally into the slatted wood wall/ceiling design. Care had to be taken to ensure the slats did not create aerodynamic turbulence noise as the air exited the ducts into the space.

All the materials in the theatre were carefully selected for their acoustic properties. The right amount and pattern of acoustic reflections is critical in creating a space that works acoustically. For example, the wall and ceiling arcs are unique. The theatre’s side walls have a cohesive walnut wood slat panel curving from the side all the way up to the curved ceiling and are designed to look like a seamless wall or ceiling. This wood slat design is used in two different ways.

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Parts of the wall behind the custom seating are acoustically absorptive. The area above the audience plane has a different backing material, making it reflective to optimize the overall acoustics, and to deal with curvatures that could have been problematic. This provides a seamless look and offers absorption and reflection where needed. The theatre’s double-layered masonry construction not only ensured the acoustical warmth of the venue is preserved, but also controlled sound from the outside.

The design incorporates a carefully configured roof construction to prevent external sources of noise from penetrating the facility and to mitigate rainfall noise on the roof above the auditorium.  To create a greater separation between the stage house and loading area, heavy doors with a sound transmission class (STC) rating of 50 were specified.

Considering acoustical comfort in a multi-use performance facility

The other chapter in the acoustics story is what is happening outside the auditorium, in the lobbies and other public rooms. The building is a dynamic place with many indoor and outdoor activities, so it was important to understand how the facility would be used to determine the acoustic considerations for the rest of the building. The theatre is designed so a variety of events and programming can be held concurrently and to serve a wide range of purposes. Acoustically, however, such multi-use facilities can pose significant challenges because the acoustics will differ depending on the activities taking place. Ignoring this will impact the user experience because bad acoustics can make an audience uncomfortable.

There are many potential noise threats beyond the theatre walls, and the quieter the theatre, the more critical the sound isolation design becomes. Double concrete walls and noise barrier ceiling designs were incorporated to reduce sound transfer between the theatre and the spaces surrounding it. A feature glass panel in the lobby provides guests with an enticing view into the auditorium on entering the building. To ensure sound does not penetrate, 101-mm (4-in.) air gaps separate a pair of 0.25-mm (1-in.) thick laminated glass panes. This, coupled with a wooden door that is closed when a performance begins, eliminates the transmission of sound going into and out of the theatre.

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An elegant, curved glass facade runs the entire length of the building’s north elevation and provides breathtaking views of the water and adjacent parklands. To ensure exterior noise would not be too intrusive, the windows needed thicker and laminated glazing. Glazing is highly reflective acoustically, so there was an added pressure on the acoustic strategy for these rooms to mitigate sound reverberation.

The architects’ experience in designing public gathering spaces across different building types, including academic, institutional, and health care, allowed for a customized response for the Tom Patterson Theatre. The lobby, forum, and cafe wood-slat ceiling system is blanketed with absorption in a specific way: between each wood fin, there is a gap that allows air to contact concealed fabric and insulation that absorb the noise and dampen the room acoustics. This produces a warm, intimate acoustic atmosphere to facilitate ease of conversation.

Lazaridis Hall

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The acoustic plans for the new theatre are also designed to enhance program versatility and the festival’s bottom line. In the larger Festival Theatre, a forum space has no acoustic separation from the lobby, so events cannot be held concurrently with a performance. The goal for the new Tom Patterson Theatre was to create a more versatile forum with an emphasis on programming and scheduling diversity. This meant providing acoustic separation from the adjacent lobby. As the project developed, so too, did the potential for uses of the space in the client’s mind. If enough acoustic separation could be achieved, the space could be used more broadly and concurrently with events in the theatre and the lobby.

Flexibility of the space was top of mind as the forum became Lazaridis Hall. It would provide the option to close off the hall for smaller performances and private events or open the hall to become an extension of the lobby and cafe when needed. Having one continuous space that could also be divided and acoustically sealed, if needed, put the design to the test. Ensuring proper acoustic isolation and integration was key to enhancing the potential of the space.

The acoustical engineers first examined the acoustic separation of folding operable partitions, but these were not available in a curved configuration with a 9-m (30-ft) opening as desired by the festival. A 5-m (16-ft) high reverse engineered sliding door was custom made to provide acoustic robustness, in lieu of a tested rating. A companion and smaller door were also needed for the east side of the room.

Creating a curved sliding door and track to acoustically isolate Lazaridis Hall involved trial and error. Several layers of sound gaskets, sweeps, and stops were added to minimize sound transmission. The hall was also fitted with multiple layers of curtains to reduce transmission and reverberation in the space, as the programming needs shift between speech and musical performances.

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Global recognition for a Canadian landmark

In 1952, Tom Patterson set out to establish a six-week Shakespeare Festival. More than six decades later, the festival has welcomed 28 million theatregoers. Like its namesake, the Tom Patterson Theatre will also create a legacy and become a treasured landmark not only for Stratford but also as a Canadian cultural destination. The facility has already received international acclaim, including a ‘Best of the Best’ award in cultural architecture from the Architecture Master Prize in Los Angeles, California. The project also won Britain’s Civic Trust Award, the only project in Canada recognized by this global competition that celebrates design excellence in the built environment.

The re-imagined Tom Patterson Theatre advances the art and possibility of performance in a building designed to attract, engage, and connect. Light-filled spaces create set pieces for encounters that complement the auditorium’s intimate enclosure. The acoustical design coupled with the architectural design enables guests to take in a performance, mingle, learn, discuss, go behind the scenes, and come together as a community.

Crafted with sustainable and natural materials, this acoustically fine-tuned, Leadership in Energy and

Environmental Design (LEED) Gold registered building embodies the very spirit of the festival to celebrate the arts and allow inspiration to soar.

Authors 

[9]Payam Ashtiani is a professional engineer and a principal at Aercoustics Engineering Ltd., a privately held firm that specializes in fostering innovation in acoustics, vibration, and noise control. With more than 15 years of experience specializing in acoustics, Ashtiani works with architects to solve noise reduction and noise mitigation issues for a wide variety of projects including health care facilities and residential planning. He can be reached at
payama@aercoustics.com.

[10]Doron Meinhard, B.Arch., is associate partner with Hariri Pontarini Architects, a leading practice dedicated to producing works of lasting value. His extensive experience on institutional and cultural buildings includes managing the complex and multi-award-winning Bahá’í Temple of South America. Meinhard has led signature and large-scale projects such as the Richard Ivey Building at Western University and the new Nicol Building for the Sprott School of Business at Carleton University. He can be reached at dmeinhard@hp-arch.com.

Source URL: https://www.constructioncanada.net/tom-patterson-theatres-unique-acoustical-considerations/

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