Handsets sprout six microphones

AUDIO CHIP specialist, Wolfson, kicks off a new range of silicon microphones today with two offerings which are highly suitable for mobile handsets. We could see as many as six of them inside one handset.

"Some handsets are already using 'digital' microphones," explained Wolfson's Mark Hesketh. "Although I've seen no fundamental shift towards digital." He's being modest because Wolfon's technology is ideal for mobile devices.

The fabless chip designer uses a special mix between CMOS and MEMS to get 5,700 microphones on one wafer with high yields.

As the new WM7110 and WM7120 chips use CMOS production techniques, it presents an easy opportunity to ramp up production and drive costs down.

Wolfson has also chosen to use Silicon Nitrate which Hesketh claims gives enhanced reliability thanks to higher stress and strain resistance.

He wouldn't go as far as saying that MEMs microphones offer better water resistance than the rival ECM technology but he did say they withstanding humidity much more easily.

Wolfson estimates that MEMs mikes currently enjoy around 35 per cent of the total market with mobile phones being by far the biggest users. Its figures also show they should take 50 per cent of the handset market by 2011.

The most interesting claim Hesketh made was that – given the ease which which silicon mikes can be integrated onto the board - handset vendors will start to put arrays of up to six microphones inside one phone.

One reason for this is that the more mikes used, the better noise cancellation works. Additionally handset mikes are normally mounted in the base of the handset. They'd work better if side- mounted and if you use six then covering a couple with your fingers won't matter. How bizarre.

The WM7110 will start sampling next month [November] and the WM7120 in December. Pricing starts at $1.64 per 1,000. µ