Dragon Systems, one of the four main PC voice-recognition software vendors, has stolen a march on its rivals by being the first to introduce a USB headset microphone. It's a significant development because audio quality is key to consistent and reliable voice recognition. If your PC has a high quality sound card which is unaffected by radio frequency noise from internal components like the CPU, then as long as you use a good-quality microphone you should get close to ideal results. The problem is that many PCs, and especially notebook PCs, are saddled with poor quality audio circuitry. Using a microphone connected via the USB port could be the answer.

USB (Universal Serial Port) is a digital interface - by converting incoming audio into a digital signal using an external processor and then presenting it to the PCs USB port you can avoid a most of the compromises inherent in internal PC audio design. This is exactly the case with Dragon's NaturallyClear USB System H100 microphone headset. Produced for Dragon by Telex Communications, the H100 headset consists of a 11.5 x 5.5 x 2cm box which connects to the USB port at one end and a conventional looking headset at the other. The headset part itself is nothing special - it's lightweight but the boom tends to wobble and isn't as adjustable as some we have used. This particular solution does not incorporate an earpiece speaker so you are forced to use external speakers if you want to hear PC output.

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As this is a USB device it is recommended that you use Windows 98. Our experience using Windows 98 Second Edition was quite straightforward - the microphone successfully hot-plugged and did not require additional drivers. We successfully tested the H100 using Dragon Naturally Speaking Preferred Edition version 4 and Lernout & Hauspie's VoiceExpress Pro version 4. IBM ViaVoice Millennium Edition was useable with the H100 but it was unable to automatically set the audio level. However, with a little fiddling it was possible to set the level manually. IBM told us that they intend to support USB microphones in the next release of their software.

Using a desktop PC fitted with a fairly old but good-quality 16-bit ISA sound card, we were able to record noticeably improved audio quality ratings in the software tested. However, the impact on voice recognition accuracy was not that dramatic. On the other hand, there was a noticeable improvement when using a notebook PC.

Our recommendation would be for desktop PC users to invest in a better sound card but notebook PC users should seriously consider a USB microphone like the H100. One final point, the H100 costs £70 - which is a high price to pay when many current voice recognition packages are supplied with perfectly good analogue microphones.