When One Theatre Becomes Two: Combining the old and the new to deliver exceptional acoustics

The Toronto Centre for the Arts (TCA) underwent renovations led by Diamond Schmitt Architects in 2014, splitting one theatre into two. This is a section through the original hall showing the new configuration, with the Greenwin located in the fly tower and the Lyric located at the original orchestra level.

2. Acoustic strength
Used to quantify the total acoustic energy arriving at a given listener location, acoustic strength (G) is a technical indicator of how loud a space naturally sounds, and it provides another parameter for designers to use to better optimize the space.

3. Reverberation time
Reverberation time (RT) relates to the period it takes for energy to decay in a room by 60 dB. While this is the most well-known acoustic parameter, RT does not provide a complete assessment of the acoustical environment in the space.

4. Early decay time
Early decay time (EDT) is similar to RT, but focuses on the decay of the early sound. EDT is a technical parameter more representative of how humans perceive the reverberance of a given space. For many spaces, EDT and RT are very similar; however, in extremely large volumes, a difference may be observed between the two. While RT is the measure of the reverberance in the space, EDT will provide a better indication of how audiences perceive that reverberance. For example, in a large volume, the RT will be high, but if enough absorption is located in close proximity to the listener, the EDT may be lower. In this case, although the RT is high, the perception of the listener is the space may not be ‘lively’ or reverberant because the EDT is lower.

5. Noise criteria
Noise criteria (NC) is used to rate indoor noise, such as the hum from air-conditioning equipment. For this theatre, the target was to maintain the existing quiet ambient noise levels. With much of the existing equipment being reused, it was critical to ensure all mechanical equipment, including the HVAC system and the new ductwork for the Greenwin Theatre, remained quiet enough to maintain the background noise levels.

6. Sound transmission class
Sound transmission class (STC) is a single-number descriptor indicating how much sound is attenuated across a given partition. The STC rating system was developed as a way to classify various wall, floor, or ceiling assemblies based on how well they performed at minimizing speech transfer. Generally, a higher STC value indicates a partition will provide more attenuation than one with a lower value. However, because STC was developed for speech, it is important to consider the source of the noise being evaluated—especially if it is not speech-based—when developing the appropriate demising partition construction.

The project was split into two phases. The Greenwin Theatre was to be completed within three months to avoid bringing other productions to a complete halt during construction, and the Lyric Theatre followed soon after and was completed in November 2016.

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