Designing “Virtual acoustics” rehearsal rooms for orchestra safety

Cameron Hough – chough@marshallday.com

Marshall Day Acoustics, Melbourne, VIC, 3066, Australia

Nick Boulter, Arup
Simon Tait, AmberTech

Popular version of 5aAA3 – The use of electrocoustic enhancement systems in the design of orchestral rehearsal rooms
Presented at the 188th ASA Meeting
Read the abstract at https://eppro01.ativ.me//web/index.php?page=Session&project=ASAICA25&id=3864386

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Rehearsal rooms for orchestras pose many acoustic design challenges. The most fundamental concern is that of safety. Modern musical instruments are loud enough to create a significant risk of long-term hearing damage to the players and conductor. Loudness also takes a toll on musicians from constant exposure to loud sound and musicians feeling that they have to always “hold back” and cannot play their instrument normally.

Unless the rehearsal venue has similar size to a performance venue, increasing cost and embodied materials, rooms are often either too loud to be a safe working environment for the orchestra or suffer from a lack of reverberation and richness which makes it hard for musicians and conductor to work on the color, blend and nuance of the music.

The use of electronic acoustic enhancement systems offers a way to break some of the fundamental “interlocks” between size and loudness of a rehearsal venue and resolve some of these challenges. Beyond just an artificial reverberation system, enhancement systems allow a “virtual acoustic environment” to be created – providing musicians with sound reflections that simulate the experience of playing in a larger room plus a richer – but quieter – room sound. This gives the musicians “breathing room” for their rehearsal.

The recent Australian Chamber Orchestra auditorium at Walsh Bay Arts Precinct, Sydney is an excellent example of how this technology has allowed a safe and comfortable rehearsal environment for the orchestra in a smaller space, without sacrificing musical quality.

Located in a heritage-listed former industrial wharf complex in Sydney Harbour, the ACO’s a 277-seat venue, The Nielson, is an “artist’s studio of sound” which features views of the Sydney Harbour Bridge through its upper floor windows. The ACO plays across all major Australian cities in venues that seat up to 2500 people, so providing the ability to preview how a performance would sound in each touring venue is important to allow the orchestra to adjust for how their performance will change in each room. The orchestra size for each tour varies from small chamber groups up to full symphony orchestra with added wind and brass players. The Nielson must therefore provide a wide range of acoustic conditions at the touch of a button, all while managing musicians’ noise exposure.

Figure 1: View of The Nielson in flat floor mode with seats retracted. Source: Authors

The electro-acoustic enhancement system installed in ‘The Neilson’ is a Yamaha AFC4 system consisting of 16 microphones, various DSP (Digital Signal Processing) modules, 79 amplifier channels and 79 loudspeakers mounted within the walls and ceiling space which allow the room’s apparent width and height, reverberation and timbre to be varied, creating different virtual ”venues” for the orchestra to rehearse and perform in.

To provide support to musicians and control loudness, the physical room’s surface finishes emphasize reflections from the side walls (lateral reflections) and de-emphasize sound reflections from above.

This allows the AFC4 system to “raise the roof” and create the impression of a much larger room without overwhelming the sound, “knitting together” the physical and electronic parts of the room sound.

The Nielson’s walls and ceiling include several sound scattering finishes that blend and “soften” the sound, where the architecture itself was inspired by music.

The lower walls are textured with small indentations, encoding a quote by Beethoven written in Braille.

Figure 2: View of the “wavy wall” with “Braille” acoustic diffusion. Source: Authors

The glazed upper walls along the balcony level are “frozen music”, based on the chord progression of Bach’s Chaconne for solo violin, with each of the 16 window sections “spelling” a chord (the widths of the panes of glass are in proportion to the intervals of the notes in the chord).

Figure 3: Render of the “Chaconne window” glass diffuser. Source: TZG Architects

The ceiling “wells” and “fins” were set out in a sequence where the height of the wells in each portion of the ceiling was proportional to the intervals between notes in three famous musical motifs by Wagner (Tristan und Isolde), Shostakovich (String Quartet No.8) and Richard Strauss (Elektra).

The “virtual acoustics” provided in the Nielson make it more than just a beautiful space, but one of the most flexible orchestra rehearsal rooms in the world that allows the ACO to preview how they will adjust their performance to venues ten times larger than the “real” room – and unlock new performance options for audiences in the room and reach new streaming audiences online. It provides a great example of how technology has allowed “more from less” via the sustainable re-use of an existing heritage building.