Adjustable acoustics fit variety of music
Complex, sometimes unseen acoustical elements
will guide the sound quality of Miami's new John S. and James L.
Knight Concert Hall.
by Fred Tasker / The Miami Herald
August 17, 2006
When an orchestra plays in the Carnival Center's
concert hall, it sends out powerful sound waves not just forward,
the way the instruments are pointing, but in all directions.
And for years, acousticians Russell Johnson and
Tateo Nakajima and their Artec firm have been working on an acoustical
system to blend those waves, seeking the balance of clarity and
complexity so a true, undistorted sound reaches a listener's ears.
''What the audience hears is both the direct
sound and the sound that is reflected from every surface in the
room,'' says Nakajima.
That includes natural surfaces -- walls, floors,
ceiling, seats, even audience members. It also includes ''adjustable
acoustics'' elements that Artec has built into the hall so it can
be used by a hundred-piece orchestra one day, a chamber quartet
The elements include the acoustic canopy, reverberation
chambers, acoustic drapes and an acoustic gap that separates the
audience chamber from the noise of the outer building.
On Friday, the Cleveland Orchestra begins three
days of private rehearsals, playing while Artec's experts fine-tune
The process will continue after the orchestra
finishes on Sunday, right up to the hall's October opening and beyond,
using jazz groups, Latin ensembles, the Master Chorale of South
Florida, the South Beach Chamber Ensemble and others.
Even on opening day the tuning process will be
less than half-done, Nakajima says. ``It takes 12 to 24 months to
adjust a hall.''
Not all concert halls are adjustable. Disney
Concert Hall in Los Angeles has ''fixed'' acoustics, built in by
acoustician Yasuhisa Toyota and adjusted once -- for the Los Angeles
Philharmonic. (The fixed acoustics limit the ability of other groups
to play there.)
In Miami's adjustable system, the reverberation
doors open onto a vast, empty chamber stretching two-thirds around
the room. With a full orchestra playing, the doors are open to let
the sound waves enter the chamber, reverberate inside and come back
out. They arrive at listeners' ears a millisecond later than the
sound waves coming from the orchestra -- long enough to create complexity,
but not to be perceived as an echo.
''Even when the music stops, everybody's holding
their breath, and you still hear its reverberation in the air,''
says Nakajima. 'That's called the `tail.' You only get it in a really
When other groups perform -- a solo pianist or
a rock band -- the hall's acoustics are adjusted.
For the pianist, the acoustic canopy would be lowered, in order
to distribute sound more directly and to create more visual intimacy
in the 66-foot-high room.
When an amplified band plays, the canopy goes
into the ceiling, three big banks of speakers descend above the
stage and heavy, motorized velour drapes descend in front of the
reverb doors to muffle the sound waves. In Miami's concert hall,
two levels of balconies continue around the back of the orchestra.
They can seat a choir of 200, lifting the choir
above the orchestra so they can be better heard. When there's no
choir, the audience can sit there.
''A lot of audiences love it,'' Nakajima says.
``The sound can be excellent. And they can see the conductor's face.''
With an infinite number of settings of the various
acoustical elements, Nakajima says performers usually don't have
to tune the hall to each group.
``They usually settle on just four or five standard
ones -- for solo performance, string quartet, jazz band, 110-piece
orchestra, heavy-metal rock band at full amplification. It's like
giving a painter different-sized canvases.''