As chairman of a publicly traded company, Stan Larson has stood before a cadre of Wall Street stock and mutual fund managers, trying to convince them why they should invest in a company that supplies ethanol for oxygenated fuels.

The 70-year-old executive, who doesn't hear as well as he used to, would have been intimidated by the youthful crowd and their questions, had he not been wearing one of the newest advances in hearing aids.

"It gave me so much more confidence in front of all these young guys in their 30s," said Larson, who commutes from his Tucson home as chairman of High Plains Corp. of Wichita, Kan.

Like almost everything else in the computer age, hearing aids are going digital.

Computer chips the size of a ladybug are being built into hearing aids. The latest models contain a type of chip known as a digital signal processor that can process 1 million instructions per second - about as fast as a 286 personal computer.

The processing rate allows digital hearing aids to adjust automatically to noise encountered by users. Older analog hearing aids must be adjusted manually and cannot distinguish among background noises.

Even early digital models, known as digitally programmable hearing aids, made adjustments at a rate of only 22 instructions per second.

"The technology has gotten so advanced that we're getting closer to giving them (patients) back their hearing," said Cathy Kurth, a clinical audiologist who has fitted several patients with DSP hearing aids at the Audiology & Hearing Aid Center in Scottsdale.

Kurth, who has been in practice for 20 years, counsels patients to choose DSP or digitally programmable hearing aids, depending on their individual needs.

"You've got choices today, and that's really the point," she said. "We're trying to design a hearing aid around the hearing loss and not the other way around."

Unlike analog hearing aids, digital devices rely on a binary code of ones and zeros. In the DSP model, for example, sound is picked up on a microphone at the top of the device in analog, or wave, form, transformed into ones and zeros by a microchip in the middle of the device, and transformed back into analog form at the bottom for the user to hear.

The process occurs continuously in a matter of milliseconds, allowing digital hearing aids to react quickly, for example, to soften the ear-piercing shattering of breaking glass. "We're trying to create a hearing aid that doesn't get out of their area of (volume) comfort, and you can't do it with analog," Kurth said.

Audiologists estimate that 27 million Americans suffer from hearing loss. After age 40, people lose 1 percent of their hearing each year, and after age 65, one in three needs some type of hearing aid.

But vanity, pride and cost prevent many from correcting the problem.

With the graying of America, however, that may change. Baby boomers now hitting 50 are expected to fuel demand for hearing aids of all kinds.

For those seeking a digital solution, Kurth recommends Senso by Widex, a digital signal processor, or the digitally programmable ReSound by ReSound Corp.

The Senso costs about $4,000 a pair, and the ReSound runs from $3,300 to $3,800. A pair of analog hearing aids, by comparison, runs from $1,200 to $1,800.

Since 1990, Larson has worn a pair of ReSound hearing aids. But two weeks ago, he was fitted with a pair of Sensos.

Both models are a vast improvement over the analog, over-the-ear device Larson originally was fitted with in 1983, he said.

On a scale of one to 10, Larson rated the analog device a three and the ReSound a seven.

"And I'm hoping the Sensos will be a 10," he said.

But another patient said the difference is more dramatic than that.

"That ReSound is for the birds," said Mary Deeter, an 87-year-old who lives in a retirement community. "Every time I went into the dining room, I had to punch it down because of all the background noise.

"But this new one does it automatically."

Kurth said that with the advancements in digital hearing aids, "Someday, we're oing to see hearing aids implanted right on the eardrum."

"And you know what? She'll have me right back here getting one," Larson added.