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Architect Jack Diamond on the science of concert hall acoustics
By
Holly Gordon

Published

April 14, 2015

Genre

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"It’s not magic."

Jack Diamond is blunt about the science of things. The South African-born Canadian architect has been practising since 1968, completing projects such as the Four Seasons Centre for the Performing Arts in Toronto, la Maison symphonique de Montreal, the Israeli Foreign Ministry and the new Mariinsky II Theatre in St. Petersburg, Russia. He’s currently working on the Buddy Holly Hall of Performing Arts in Lubbock, Texas.

While Diamond is clear that it isn’t all smoke and mirrors (though, architecturally, he may use mirrors), he doesn’t deny the magical quality of music itself.

"Music ... is a love," he admits. "Next to architecture it’s probably the next field and area that I love and find absolutely inspiring ... and whether it’s pop or classical, whatever it is, I think music really does affect one’s emotions."

It’s no coincidence that Diamond’s thesis for his bachelor degree was a concert hall in acoustics. His thesis supervisor was, as Diamond puts it, "one of the great acousticians": Philip Hope Bagenal, who worked on the Sydney Opera House, New York’s Lincoln Centre and the refurbishment of the Royal Albert Hall. The marriage of architecture and music is a crucial union for Diamond.

For CBC Music’s Science Week, we asked Diamond to give us Acoustics 101: the science of sound in concert halls. Want to know how to get a 10 out of 10 on your concert hall architecture? Keep reading.

 

On the physics of sound

"Physics of sound obeys very varied, specific phenomena. Sound travels a bit like light in the sense that the angle of incidence is equal to the angle of reflection. So you can measure where the sound goes. There are lots of ways that one can really understand how sound travels.

"The problem I think often is, in romantic architects who have a predilection for a certain shape: [they] say here's the shape in a kind of preconception of some form or other, and say to the acoustician: 'Now fix it.' [They] are going to get a six out of 10.

"But if you start with the physics of sound, you'll get an eight or nine out of 10, and then you can tune the hall with some minor adjustments. So it isn't magic at all. People think of acoustics as some kind of a black box. It's not."

On designing for sound before shape

"If you can see well, you can begin to hear well. What it means is that you're going to be getting direct sound, not interfered by anything. That's number one. It’s not the only thing, but it's a beginning.

"In fact an acoustician I know has said that you see with your ears and you hear with your eyes, as well. So you need both. That's a start.

"You also need a quiet room. So you’ve got to really exclude sound or noise … so the quieter the hall, the better it sounds. The more nuances that you can perceive."

On the actual physics of it all

"You need to refract low-, medium- and high-frequency sounds. All of them. The full range of sounds. And you need to refract them and blend them so that you get what some acousticians call 'bloom' — there's a wonderful quality to the sound, and it comes through this blend.

"Low, medium and high frequencies are refracted by different surfaces. High frequency is refracted by very finely modulated — like a ground glass or a sandpaper. Medium frequencies are reflected by rather bigger moves like a balcony front. And the low frequency are much much bigger moves, really large shapes will reflect that sound.

"But the most interesting thing is, if you can get ... in addition to the quality of sound, there's the density or the quantity of sound you get, and what you want is the last seat in the theatre and the first seat in the theatre, closest the stage, if it’s at all possible, to have the same density of sound."

 

On the stage as a 'megaphone'

"Now we all know that sound decays as it moves away from its source, gets fainter and fainter. So you need to reinforce it. So not only do you need to get direct sound, but you need to get reflected sound, so the early reflections that come from a singer or an instrument and the direct sound … by the angle of the surface, just like a megaphone, you can direct the sound up into the balconies.

"So you're trying to accomplish a nice blend."

On reverberation, a.k.a. why you can’t have a hall for both choral and chamber music

"The other aspect of this is ... reverberation: it's how long the sound is in the air. Now, you will get, if you go into a recording room, it sounds quite dead. It's because the reverberation time is extremely short. All the walls have absorbent materials to suck up the sound. The sound loses its energy in all the tiny, tiny apertures in cloth or woven fabrics and so forth because speech intelligibility comes from a short reverberation time.

"That works for both chamber music and speech, because chamber music was originally designed to be in a chamber, usually a palace or a castle or something, which had tapestries on the walls, carpets, cushions, furniture. Those all absorb sound, and so the reverberation time is quite short. Symphony music is a medium reverberation time.

"And then choral music or organ music has a very long reverberation time ... so the short reverberation time is under one second. The medium is anywhere between about 1.2 or 1.3 seconds to about two. And then longer reverberation times are those above two, 2.5, three and in some cathedrals four. In fact, I think Salisbury Cathedral is something like 16, I mean it's like an echo hanging in the air.

"I'm a firm believer that you design the hall for the purpose and you make it work for that purpose. And you talk about the limitations, you know. You wouldn’t design a hall for long, choral organ music and chamber music. It can't be done. And it's no good pretending it can be."

Really, it’s not magic

"You can think about it this way: if you throw a ball against a curtain, ball probably falls flat. Throw it against a concrete wall, and the ball will bounce back. The thing is that the curtain has absorbed the energy of the ball. The concrete wall makes no movement at all, so the energy in throwing the ball is contained in the bounce back.

"You don't want the sound bouncing back from the back wall, is an example. That would interfere with sound coming to you. So you often make that rear wall an absorbent one. Around about the stage, near where the performers are, your very, very rigid surfaces, which will be sure to reflect the sound out into the hall. It's really the principle of a megaphone: it concentrates the sound and directs it."

On getting a 10/10

"The aesthetic [of a hall] is really driven by the acoustic. Now, of course you can do it in different ways. In the classical halls, all the decoration, you know, the mouldings of angels or grapes ... and so on as you found in baroque halls, those surfaces are actually doing a job. They were really acoustically important for that medium range, and so it can be done stylistically differently, but the principle of moulding the surface to get the right refraction is a way that leads you to the aesthetic.

"It’s a bit like a sculptor with a block of stone. You first block it out. Then you chip away and then you polish. So we've blocked out the shape of the [Buddy Holly Hall] to accommodate the 2,200 seats that will suit that range of functions we know. We will now begin to design the details of the materials. The detail shapes of the wall and it’s texture. That’s next.

"I think the most enduring aesthetics come from a principle that I have and that is that you make a virtue of a necessity. That creates authenticity and very enduring design."