The microphone shrinks to a single chip

Microphones haven't radically changed in several decades--but a new digital version could give designers more freedom.

It's time the microphone got an upgrade, according to audio chipmaker Akustica.

The company, which was spun off from a Carnegie Mellon University project in 2001, announced this week the AKU2000, a single-chip microphone that can be produced on standard silicon processes. Ultimately, the chip could lead to better voice quality on Skype phones embedded in laptops, for example, or sharper, more distinct sound on video captured by digital cameras.

A few Asian laptop manufacturers may begin to offer notebooks with the chip in a few months, said Akustica CEO Jim Rock.

"If you are serious about VoIP, you need to offer a digital microphone," he said.

Microphones in laptops, cell phones and MP3 players/voice recorders are largely Electret Condenser Microphones. ECMs are analog devices, which mean they capture real-world sound waves with a membrane and transmit them to an analog-to-digital converter. To prevent signal interference or noise, ECMs have to be insulated from wires and components.

The membrane in the AKU2000 is one of the metal layers of the chip. (Chips are made up of layers of silicon and metal.) An integrated analog-to-digital converter then turns the captured vibrations into a digital signal. The entire microphone is contained on a single chip--a first, according to the company.

With the digital microphone, interference is less of an issue, meaning the chips can be placed more freely inside a notebook or cell phone. Two to four of the chips can be embedded into the bezel of a notebook, for instance. The first notebooks with Akustica's product will likely have two chips. With more microphones, sound quality improves.

"You can focus better on the speaker and get rid of noise," Rock said.

The AKU2000 takes up less space than traditional microphones because additional components for preventing signal interference aren't needed.

The basic chip technology may also be used one day to make accelerometers, be incorporated into car-braking systems or be built into different types of communications chips.

The difficult part, at least for now, is the price, noted Allen Nogee, an analyst at In-Stat. "It is not the cheapest microphone on the market," he said.

Akustica's chip will sell for $3.76 in quantities of 1,000, while conventional microphone chips sell for $1 or less. Still, Rock said the price difference is actually rather slight, because most customers will order more than 1,000.

"We're talking 50,000 and 100,000," he said.

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