If Jack Randorff does his job right at the Republican National Convention, the delegates will never notice he's here. Like a behind-the-scenes speechwriter, his job is to make sure the presenters' words come through loud and clear.
But Jack Randorff isn't a political wordsmith. He's a physicist--and he uses science to transform a potentially noisy, reverberant environment into a sonically viable meeting place.
Only the stock exchange rivals political conventions in their raucous clamor. Hundreds of delegates, gathered in a single space, converse with each other and vocalize their support as they listen to party VIPs speak. What's more, the convention sites are not always selected with serious thought to acoustics - a point made very clear in the 1988 Republican Convention at the Superdome in New Orleans.
Although Randorff was just an outside observer at the time, "it was pretty evident to me that they were going to have some acoustical problems," he says. Sure enough, reverberations were so high that speakers could not avoid listening to their own echoes as they delivered their speeches. "It took 3 days to fix the problem," Randorff says, and ultimately, the sound technicians had to turn off part of the sound system.
The experience took on new significance for Randorff as he planned his first active role in convention acoustics with the 1992 Republican Convention at the Houston Astrodome an acoustically primitive indoor space that the acoustician knew would require lots of work.
Randorff and his associates designed an "acoustical umbrella" that hung 60 feet over the speakers' heads. The rectangular structure created a "shadow zone" that blocked reverberating sound waves from reaching the speakers and their microphones. To cut down on low-frequency sounds, they covered unused seats with very thick mylar - which converted unwanted sound into quiet vibrations of the mylar. They also lined the walls of the mezzanine level with fiberglass, and sprayed a cellulose material under the same area - this helped stop the mezzanine from acting like a guitar and amplifying low-frequency sounds.
This year, in Philadelphia's First Union Center, Randorff was initially worried about a blue-gray slate wall that the organizers were mounting at the back of the stage. While it is a visually beautiful backdrop for the speakers, "you can't get much harder than slate," Randorff says. The slate wall and the monitor speakers on the stage are a potentially troublesome combination. The monitor speakers face the presenters to let them hear themselves. But if these speakers are allowed to face the wall, trouble can occur when sound from the monitor bounces against the slate. The resulting reflections of sound waves can cause the buildup of unwanted sound, making it difficult for the presenters to hear themselves and supplying unwanted noise to microphones on the stage. All of these unwanted sound waves would be perceived as echoes by the delegates and TV audiences.
But Randorff's breathing a sigh of relief, after finding out that the monitors were mounted in the lectern, so that the presenters themselves would be blocking much of the sound and minimizing the amount that reaches the wall.
Another reassurance to Randorff is that he will be working once again with a sound crew that has seen some demanding projects, such as the Three Tenors concert tour which included famous opera singer Luciano Pavarotti. The crew will be employing a "real-time equalization (EQ) system" to ensure that the broadcast sound has an appealing spectrum of low-, middle-, and high-frequency sounds.
At the beginning of the day, before the audience arrives, the sound crew sculpts the desired levels of low- to high-frequency sound that they would like the sound system to broadcast. As the audience fills their seats, and the temperature and humidity change, this spectrum inevitably gets altered, usually for the worse. In real-time EQ, a bank of microphones arranged around the arena monitors the changing sound and compares it to the desired equalization spectrum that the crew had at the beginning of the day. The real-time EQ system then makes electronic adjustments to arrive at the desired sound spectrum.
In general, Randorff says the 21,000 seat First Union Center is a "fairly good choice" for the convention, but he's still making adjustments. He has installed an extensive amount of fiberglass sound-absorbing material in the rectangular ring between the lowermost seating area and the arena floor, where there is an 8 foot gap. Covered with drapery to obscure its presence, this material is expected to reduce troublesome "flutter echoes," short-lasting reverberations which Randorff anticipates will be caused by noise from the audience area.
So when it comes to watching the Republican National Convention, you may not be able to see Jack Randorff, but you'll clearly be able to hear his work.
Contact:
Ben Stein
American Institute of Physics
301-209-3091
bstein@aip.org
Rory McGee
American Institute of Physics
301-209-3088
rmcgee@aip.org
Expert:
Jack Randorff
Founder, Randorff and Associates (acoustical consulting firm)
Also Adjunct Research Professor, Texas Tech University
Director, Center for Applied Acoustical Research and Development, Texas Tech
806-829-2521