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In my modest home theater, Sasha Lazard,
a bel canto singer, is listening to the theme song she sang
in the Japanimated fantasy movie "Princess Mononoke," while
toggling back and forth between two settings on the remote.
One, "Bypass," sends the digital information from the CD
directly to the speakers; the other, marked "A," reroutes
it through an intermediary stop -- a state-of-the-art sound
processor called a Sigtech 2000, developed by Cambridge
Signals Technology and now used in ultra-high-tech broadcasting
studios, such as Walt Disney's in Los Angeles.
Each time she presses button A, the music
changes. She looks up agog. "It sounds like I'm someplace
else. It sounds like I'm back in the recording studio."
In fact, by pressing button A she had made my room disappear
-- at least psychoacoustically -- and what remained was
the sound of another place in space and time, the room in
which the recording was made.
Up until the 20th century, music was
heard only in the venue in which it was performed. Whatever
its quality, everyone experienced it in much the same way.
With the commercial development of the record player in
the early 1900s, performers were no longer inseparable from
their performance. What they sang and played in a concert
hall or studio could now be transported to another time
and space. Any room in a home, no matter how small, now
became a concert hall. For example, an entire symphony orchestra
performing Tchaikovsky's "Overture of 1812," as well as
the sound of the auditorium in which it was played, could
now be jammed into a 100-square-foot bedroom. The echoing
vibrations from so many instruments, not to mention the
exploding cannons, will obviously no longer sound the same.
What one would hear is a musical cocktail. One part would
be the originally recorded music, another part would be
the reverberations of the original auditorium. And a third
part would be the sound of the bedroom and its furnishings.
Since the sonic waves from the vibrating room parts, ricocheting
off walls and ceiling, will crash on the listener's ear
only about 1/5,000 of a second after the sonic waves arrive
directly from the speakers, the brain, which had no evolutionary
needs for parsing such minute distinctions in incoming sounds,
will blend the two sounds together in a new and idiosyncratic
aural brew. Unintended instruments, such as walls, cabinets,
table tops, lamps and doors, will join the clarinets, french
horns, drums, violins and cellos in the original orchestra,
at times blurring, if not totally obscuring, them. To hear
the performance without these interfering obstacles, the
only practical option is to get rid of the offending room,
which is the purpose of the Sigtech 2000.
When Ronald Genereux at Cambridge Signals
Technology in Cambridge, Mass., developed the Sigtech 2000,
he took advantage of a curious phenomenon in acoustics:
sound cancellation. If two identical sound waves encounter
each other, and one is inverted -- that is, 180 degrees
out of phase with the other -- they cancel each other out.
A noise and its upside-down clone thus produce no noise.
Such noise cancellation has been used for years in places
where offensive noise occurs uniformly and constantly. A
microphone simply passes it to a processing chip that inverts
it and retransmits it to knockout the unwanted sound. Airplane
manufacturers, for example, have eliminated much of the
engine noise in cockpits in this way.
But canceling unwanted room reflections
that occur over a wide range of frequencies in reaction
to highly variable recorded sound isn't nearly as easy.
Mr. Genereux had worked out the mathematical concepts for
the machine almost a decade before advances in computer
technology made it commercially feasible to build one. What
made it practical was Motorola's mass production of the
dedicated digital-sound-processing chip, or DSP, for the
defense and telecommunications industries in the late 1980s.
Initially, Mr. Genereux used 25 of these DSPs to analyze,
replicate and invert room sounds, but later found that the
job could be done with only five DSPs. Still, even with
the falling price of computing power, the Sigtech 2000 for
CDs and DVDs costs a minimum of $6,300. I couldn't resist.
Cambridge Signals Technology dispatched
Mark Donahue, a field engineer with considerable experience
in room vanishings for recording studios and concert halls,
to my New York apartment, fully equipped, with a cart full
of professional-looking equipment. First, he efficiently
repositioned my tower speakers so they were optimally located
in the room. Next, he connected the Sigtech 2000, a black
box about 18 inches square and 4 inches high, to a portable
computer and to a microphone fixed on a tripod placed where
I usually listened to music. Then, for the next hour, the
Sigtech emitted a preprogrammed set of pings, hisses, thumps
and other test signals, which registered on the computer
screen in jagged lines that looked like a mountain chain
drawn by someone with double vision. One set represented
the sounds coming directly from the speaker; the other,
those reflecting off various room surfaces. From this sort
of sonogram of the room, he identified the most prominent
haunts of the sonic trolls. It took another hour or so to
construct computer programs, or "filters," through which
the Sigtech would add digital data to that already encoded
on my CDs, laser disks and DVDs. This army of inverted clones
generated by the machine's DSPs would zap at least 10 decibels
of unwanted room sounds and, through more digital wizardry,
also restore some of the music that out-of-phase room sounds
had nullified. The filters were then put into the Sigtech's
memory. Mr. Donahue left behind (temporarily) the Sigtech
2000 so I could listen to music, operas and movies at leisure
in a disappeared room.
Some two-dozen volunteers turned up,
including the diva-in-training Ms. Lazard with her recording.
Aside from "Princess Mononoke," the visitors tested a wide
range of DVDs, including Janacek's opera "The Cunning Little
Vixen," Donizetti's "Lucia di Lammermoor" and Woody Allen's
film "Bananas." When the room vanished, they discovered
previously hidden woodwinds, french horns, cellos and other
instuments, as well as auxiliary voices previously camouflaged
by room noise. During Joan Sutherland's rendition of the
mad scene in "Lucia," one guest temporarily managed to break
the illusion of being somewhere else -- the Metropolitan
Opera House in 1982 -- by simply clapping his hands together
once. Sonically, room abnegation proved to be a vast improvement,
but it posed a nagging philosophic problem. What approaches
reality more closely: real music in an artificial "space"
or inauthentic music in a real room?
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