Originally Published MPMN May 2007

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Processing Technology Offers Flexibility to Hearing Aid Manufacturers

Daniel Grace

Digital hearing aid technology has become widespread in the last half-decade, with 92% of hearing aids purchased in 2006 being digital, up from 20% in 2000. Still, only around 20% of people who could benefit from hearing aids elect to use them, and the primary reasons for nonuse remain the same as before digital hearing aids: discomfort, aesthetics, and poor audio performance.

AMI Semiconductors (Pocatello, ID; www.amis.com) is attempting to harness digital technology to enable manufacturers to build hearing aids that overcome the common obstacles to comfortable use. The company now offers a series of open programmable integrated digital signal processors (DSPs) that it says will provide high-precision sound through high-precision computing capability.

The Ezairo 5900 series’ precision will also allow manufacturers to efficiently develop more complex algorithms than exist today, says Michael De Mey, senior director of hearing and audio development at the company. “As speech and audio processing algorithms evolve to become more complex and intelligent, the Ezairo 5900 architecture has the processing headroom and flexibility to implement these highly sophisticated algorithms with extremely low group delay,” De May says.

The Ezairo DSP’s 24-bit sound processing also enables the most advanced existing adaptive hearing aid algorithms to perform better, according to the company. These capabilities include adaptive noise reduction, which gives the user better speech intelligibility in noisy situations, and adaptive beam forming, which gives users better directional sound pickup, meaning users can listen where they look without excessive interference from background noise (background noise levels are commonly complained about by today’s hearing aid users).

The Ezairo DSPs achieve 90-dB dynamic range while maintaining low power consumption, 1 mA at full processing power. They utilize adaptive feedback-canceller algorithms, which allows for the manufacture of behind-the-ear (BTE) hearing aids, an increasingly popular format that requires more power than traditional hearing aids. BTE hearing aids address issues of cosmetics and comfort. The hearing aid piece (containing the DSP) is attached over the ear and rests behind it, and a small, transparent tube connector is inserted in the ear. The BTE format is less noticeable to others, and by alleviating the need for a larger piece to be inserted inside the ear, comfort is increased and the occlusion effect, whereby users amplify their own voices when an ear is plugged, is reduced.

The Ezairo 5900 units also include four parallel input channels for microphones, telecoil, and direct audio. The latter will allow manufacturers to eventually offer hearing aids that connect to music players.

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