Yamaha AW4416 Aids the Hearing-Impaired
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BUENA PARK, CA (November 8, 2002) Since 1988, Salt Lake City (UT)-based SONIC Innovations has designed, developed, manufactured and marketed advanced digital hearing aids, and is renowned for using the smallest single-chip DSP platform ever installed in a device for the hearing impaired.
According to SONIC's Bob Ghent, Senior Research Audiologist, with advances in hearing aid technology, there has not been a clinically satisfactory way to test noise reduction algorithms and directional microphones in hearing aids until now. Ghent and his team used the Yamaha AW4416 Digital Audio Workstation to develop an application for testing advanced signal processing features in hearing aids.
"One of the first things we did with the AW4416 was to establish testing norms," says Ghent. "We'd like to see it become a standard for research in our discipline. Many sound field systems utilized in hearing aid research use up to eight loudspeakers driven from an iMac or a G4 running ProTools. That's all fine, but the learning curve is very steep and cost-intensive. We found the AW4416 to be both cost-effective and easy to operate, which makes the system clinically efficient and really helps with interclinic consistency. That is, different clinics and research facilities using the same equipment and same materials so that the results they gather can be compared accurately." Ghent and his colleagues initially tested subjects with normal hearing in order to establish parameters for the system. "Those parameters create a 'base line' against which we can test the hearing-impaired subjects," Ghent explains. "We use recordings of simple, elementary school reading-level sentences so that both children and adults can comprehend them, such as 'The car drove up the hill.' The next step is to create scenarios in both quiet and noisy situations, like on a bus or in a restaurant places that the hearing impaired would have more difficulty due to the competing noise and then play back the sentences for the subjects to decipher." Ghent realized he needed a sound field that would present competing sounds (maskers) from 'all around' the listener much as you would have in a real environment. "The Yamaha AW4416 was the ideal way to go," he explains. "We wanted to have the masking noises uncorrelated. So, instead of sticking up a pair of stereo microphones and getting two tracks of audio and playing that back through four speakers, we wanted four different tracks of maskers presented back through those four speakers. That would simulate more of the 'real world.' We needed to do that for twenty-four lists of sentences, so we needed something where we could store the settings along with the different maskers and be able to recall those easily and we needed, along with multiple tracks multiple outputs." Ghent, also a musician and former director of the Musician's Hearing Institute in Los Angeles, California, completed his graduate degree in Audiology at Brigham Young University (where the original SONIC Innovations hearing aid technology was developed by the Engineering department), plus time at sound reinforcement companies as an audio engineer. "While working in pro audio, I mixed on a Yamaha PM4000M console frequently," he notes, "so when I started researching multi-track recorders, the AW4416 was the only one that had a suitable number of discreet outputs that we could route tracks to. It also had the number of tracks available on the recorder to allow us to do what we call 'Multi-Talker Speech,' where we have recordings of anywhere from 4 16 talkers all talking at once. We can mix those at different levels, different amounts of each talker, and different numbers of talkers into each loudspeaker and send them out as maskers into our test environment. The AW4416 has worked out well, and we've since purchased four more. We've replicated the Salt Lake City installation in the lab at Washington University Medical Center in St. Louis, Missouri, the Cleveland Clinic Foundation in Cleveland, Ohio, and at Brigham Young University in Provo, Utah." With the Yamaha AW4416 Professional Audio Workstation users can record, edit, mix, and master to CD without needing any external equipment other than microphones and/or line sources and a monitor system (headphones will do in a pinch). The AW4416 can be easily expanded to meet even the grandest production requirements with a range of optional I/O interface cards that provide direct connectivity with all types of digital and analog gear. And, whether choosing to record in 16-bit or 24-bit format the sound quality achieved is on a par with the finest professional digital recording gear available anywhere. "Setting up the AW4416 and having it operated properly at other clinics would normally be a tedious process," says Ghent, "because most clinicians don't have a music recording background. We've created our test materials for the AW4416 such that the only things they really have to deal with are the Scene Recall button and the transport buttons. We've been running some fairly sophisticated research with this and the learning curve hasn't been as steep as it could have been otherwise. "What we do at SONIC Innovations with hearing aids and the AW4416 is help hearing-impaired people use the hearing that they have left. There's still no way, with current technology, to put back a person's hearing once they've lost it. We're looking forward to one day being able to do that but for now, once a person loses their hearing it's pretty much gone. And as a musician, I'm fairly sensitive to this issue." For more information on AW4416 Digital Audio Workstation, write Yamaha Corporation of America, Professional Audio Division, P.O. Box 6600, Buena Park, CA 90622; telephone (714) 522-9011; or e-mail infostation@yamaha.com.
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