Most of us have never faced the prospect of going to a dance but not being able to hear the music. For those of us who can hear music and laugher and speech and noise, sound is something we pretty much take for granted. But for the more than 24 million deaf and hearing impaired people in this country, the story is very different. And many who have been deaf from birth don't know what sound is, or even realize that their own voice makes a sound.

“When he figured out that his voice was causing the floor to vibrate, he started to sing.”

At the Rochester (NY) School for the Deaf, seniors asked school administrators if they could move their special floor to a nearby restaurant so they could have a school dance just like students who can hear. What is their special floor? It's part of a unique audio/video system recently acquired by the Rochester School for the Deaf that transforms energy the deaf and hearing impaired can not experience - sound - into forms they can experience: vibration and light.

The Multisensory Sound Lab electronically processes signals from musical instruments, recordings and other sources, such as the human voice, so that the deaf and hearing impaired can experience all the characteristics of sound, pitch, volume, timbre and rhythm, through feel and sight. The Rochester students special floor is a very special indeed. It consists of interlocking panels that float on foam blocks. A specially modified pair of BAG END S18-E subwoofers, bolted face down on the floor, harmonically transfer electronic signals to the floor, causing it to vibrate. Anyone sitting or standing on the floor perceives low-pitched sounds as slow vibrations and high-pitched sounds as much more rapid vibrations.

The subwoofers, using BAG END's ELF (Extended low frequency) signal processor technology, go down to 8 Hz., well below normal audio range, but enhancing the sensory perception. "High-pitched sounds that are outside the 20-500 Hz range are electronically transposed downward to enhance the vibrotactile experience," Lederman said. "Feedback concerning intensity and rhythm is perceived through the vibrating floor. The speakers are fastened to the floor face down, thus the sealed cabinet transfers the maximum energy directly to the floor," he said.

Two major, companion elements are a LumaSound Light, which displays different pitches and volumes through its bands of lights, and a Visualizer which displays the same pitches and volumes through colorful bar graphs. "The Visualizer is a 1/3-octave spectrum analyzer that displays the harmonic content of sound on a color monitor as vertical bars, changing in location and height depending upon the characteristics of the signal." He said. "The LumaSound Light is a seven-foot tall column made of translucent plastic containing three banks of color lights that respond to different frequency bands and intensities of sound."

The magic of Multisensory Sound Lab is that the physical reproduction of sound is transformed into something that is concrete, tactile and visual. Fred Koch, assistant superintendent at the Rochester School for the Deaf, agrees. "It broadens our students life experience," he said. "For our profoundly deaf children, those vibrations are the only 'sound' they know. The children enjoy sitting on the floor and feeling the vibrations, and the older kids dance on it."

Christine Yoshinaga-Itano, associate professor of communication disorders and speech science at the University of Colorado, has used a Multisensory Sound Lab for several years. "We could try forever and students still might not really understand what sound actually is and what it can do," she said. "The lab makes it obvious to them quickly."

Yoshinaga-Itano related the story of one youngster, A.J. Cook, deaf from birth, when he experienced the lab for the first time. The laser light was bouncing, the column in the corner was flashing lights, and the images on the TV screen were bouncing up and down as A.J. spoke into the microphone. His eyes got bigger and bigger as, for the first time in his six years, he understood that his voice made sounds. "When he figured out that his voice was causing the floor to vibrate, he started to sing," Yoshinaga-Itano said. "It was the first time he understood sound and realized he could produce it. It was like a baby's voice, it was just beautiful.

Rebecca Anderson, an audiologist and speech pathologist at the Bethesda Centre for Speech and Hearing in Boynton Beach, Fla., has had similar experiences. "Sound becomes alive for hearing impaired youngsters," she said. "The multisensory input makes up for the missing auditory information for these children."