It's Muddy In The Acoustic Minefield
The Age
Friday March 17, 2000
Stadiums are notorious for their acoustic problems. By nature, they are big and have plenty of flat surfaces, - windows, floors, doors and even chairs - that can reflect sound.
Colonial Stadium, with its glass-fronted corporate boxes, not to mention the roof, is a breeding ground for echoes.
And, according to Associate Professor Stephen Ingham, a lecturer in acoustics at the University of Wollongong, correcting these echoes is a ``technical minefield".
``In a large stadium, it's to do with reflections, it's sound reflecting off flat surfaces," he said. ``Usually in the design of a stadium a lot of effort is put into ensuring there are not many flat, hard walls."
Barbra Streisand is particular about the sound quality of her performances. To improve acoustics for her show, London's Wembley arena was carpeted, and heavy black fabric was draped in another venue.
For Melbourne, Streisand's sound engineer, Bruce Jackson, draped material over empty seats and hung heavy wool serge from the roof.
Mr Jackson enlisted Sydney mathematician David McGrath to design a computer model of Colonial Stadium to track the path of sound and identify where the wool was needed to mop up echoes.
But other factors had to be considered. ``In stadiums there are extra problems because of the enormous distances involved," Professor Ingham said. There was a long distance between Streisand and some of her audience and this would have created a physical delay in the sound.
Hence the loudspeakers. ``You have loudspeakers with delays built in so the experience is in sync with what you see," Professor Ingham said. And there were also special delay speakers set up to boost high frequencies that disappeared over distance.
``Most of the sound that you hear is relayed over loudspeakers, very little is live sound," he said. ``If there are substantial reflecting surfaces it will apply to the amplified sound as well as the live sound."
OPINION 17: Alan Attwood
© 2000 The Age