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Fine-tuning the acoustics of the Joan Sutherland Theatre

To our audio engineers, sound is both an art and a science

Justin Tam

Imagine you’re at home, settling in with coffee and a book, and you hear the rain trickling against the window. It grows to something louder, a steady pattering. The sound of it makes you feel relaxed, a little calmer. What about the sound makes people feel calm?

When you’re at the opera, you hear the orchestra pulsing from below the stage, the choir roaring on stage and the soprano delivering a beautiful song from centre stage that fills the hall. It sends shivers down your spine—but what in your brain is being triggered to make you feel this?

We can’t see it, but we have always known it: sound affects our emotions; music is sound organised to maximum effect.

In recent years, the neurological changes worked by sound have undergone a flood of studies—including why we get the chills from that beautiful violin solo; how a powerful chorus spikes our dopamine levels.

new paper in Nature Neuroscience revealed music creates the same feelings of happiness and craving that are felt after you go to the gym or eat your favourite bar of chocolate.

Sound affects our emotions; music is sound organised to maximum effect.

The art and science of sound has been very front-of-mind at the Sydney Opera House in recent months. Between May and December 2017, the Joan Sutherland Theatre (affectionately referred to as 'the JST') underwent a $71 million dollar upgrade to improve the venue’s acoustics, functionality and accessibility.

The works are part of the Opera House’s wider $273 million suite of Renewal projects. Improving the acoustics in the room and opening up new possibilities for artists and audiences was integral to Renewal.

What makes good sound?

“It’s easy to think about music as just a sequence of sounds,” says Elizabeth Hellmuth Margulis, a pianist and author specialising in music’s effects on human cognition. “[But] we never just hear music.

“Despite sometimes being thought about as an abstract art form … music carries with it, and is shaped by, nearly all other aspects of human experience: how we speak and move, what we see and know.” For Margulis, there is a dimension of music’s effect that will always remain unmeasurable, mysterious, stubbornly resistant to quantification.

According to acoustic engineers however, the science of sound—know-how and cutting-edge technology, that complex sequence of sliders, knobs and meters—affect a lot more than just how loud or soft something is. They are the technical dimension of creating magic, of engineering mystery.

So what does the orchestra hear?

The magic of good sound starts in the orchestra pit with the musicians. A violinist needs to hear what they’re actually playing—that they’re bowing the right notes at accurate pitch (whether they sound “in tune” or “out of tune”) and rhythm (whether they’re plucking or bowing notes at the right time).

To do this, they also need to hear lower notes from the double bass at the back of the orchestra, and the timpanis thumping along and keeping time in the back row. Naturally, if the musicians can hear themselves and their colleagues, they’ll perform better.

Gunter Engel and Jürgen Reinhold are two of the engineers from Austrian company Müller-BBM that worked on making the JST sound great. “As a musician you adapt to what you hear,” says Engel. “If the room is dry (if there is no natural reverberation), a string player will change the manner of their bowing.”

For woodwinds such as the clarinet, Engel stresses the importance of tonal quality (how ‘rich’ they might be perceived to sound). A good clarinettist may be able to play fast, but it’s often the slow, thoughtful passages that set them apart from an amateur.

By adding extra reverberation (a type of echo) to the hall, sound engineers are able to pick up the subtler textures of sound and bounce it around the hall. The subtle, softer notes that might otherwise fade away like a faint echo are able to be spread through the hall.

Doing this requires the perfect seating arrangement as well as a network of discreet speakers in the pit. “We ask the musicians about how they perceive their own instruments—what their perception of the space in the pit is, especially when we have acoustic enhancements in there. We try to find the perfect settings to make it as natural as possible for them.”

While it’s easy to believe that the instruments are just being ‘amplified’ by computer software, Engel stresses this is a common misconception. “In the pit, we try to improve sound without any noticeable or measurable increase of sound level (decibels, or ‘dB’). We try to bring the impression of a bigger room to the musicians, so they have a better feeling of how it sounds to the audience.”

We try to bring the impression of a bigger room to the musicians, so they have a better feeling of how it sounds to the audience.

What does the audience hear?

And what about the audience? Hearing a bold symphony charge through at full strength is just as crucial as being able to concentrate on the quiet, stirring solo of a single violin. This is a feature Engel calls ‘acoustic transparency’.

“If you consider the orchestra as one big instrument, this instrument should also be acoustically transparent so you can follow each individual instrument and their different lines of music.”

Special microphones inside the pit allow the natural reverb and echo of each instrument to be spread throughout the hall, as if you were hearing the careful bowing of the violin from the front row.

In the Concert Hall, the petal-like acoustic reflectors are designed to stop sound from disappearing straight upwards and into the empty space directly above the stage and above the orchestra. In the JST the real challenge is ensuring that people sitting at the back of the hall have the same experience as those in the front row. To do this, invisible speakers are nested on the stage’s edge, above the proscenium, and at the rear of the hall.

In most sound systems like a home theatre hi-fi or the car, sound is projected across left, centre and right channels; this is tiny compared to an opera theatre. With invisible speakers placed around a theatre, a sound engineer can can create sound effects that can be projected from all directions and moved around to any point in the hall. This technique is known as ‘3D spatial mixing’.

For contemporary music festivals like Vivid LIVE, there’s much more than opera that goes on between the Opera House’s walls. From rocker St. Vincent to electronic music with Oneohtrix Point Never, the ability of the JST to enhance the sound has expanded. “All our speakers around allow us to create additional sound sources which can fix a sound, or move it around in the audience,” says Engel. “On stage, you can create a very precise and transparent sound and add effects on top of this: adding reverb to a single voice, or adding reverb to the room.

“By adding it to the whole room, you can avoid creating a muddy sound. You have possibilities with the sound which are much better than any home hi-fi system.”