Nuance Communications has filed a federal lawsuit against Vlingo, charging the startup with infringing on a Nuance patent for speech recognition software being supplied for the Yahoo! oneSearch mobile search service.

Vlingo issued a statement Friday calling the Nuance lawsuit "unfounded" and saying it fits a pattern of "filing frivolous lawsuits in an attempt to stifle competition." Vlingo said it would fight the lawsuit "aggressively."

The suit, filed in the eastern district of Texas on Monday, seeks damages from Vlingo for alleged patent infringement and urges U.S. District Court Judge David Folsom to issue a restraining order to Vlingo to prevent future possible infringement. The amount of damages sought was not specified, according to a copy of the lawsuit.

The lawsuit, signed by attorney Eric Findlay of Tyler, Texas on behalf of Nuance in Burlington, Mass., states that Vlingo has been infringing on a Nuance patent for "adaptation of a speech recognition system across multiple remote sessions with a speaker." Patent number 6,766,295 was received on July 20, 2004. The technology was invented by Hy Muveit and Ashvin Kannan, both of California, and assigned to Nuance, according to a copy of the patent.

The patent abstract describes the Nuance technology as allowing a telephone caller to speak, and when speech samples are obtained, software decides whether the speech is different from a standard model and stores any modifications. In subsequent sessions, the speaker is identified and the modifications are used to recognize the speaker's speech. Further modifications, if needed, are also stored, improving the accuracy of the speech recognition system, according to the patent abstract.

One of the products that uses the technology, as provided by Vlingo, is Yahoo! oneSearch, the lawsuit claims. Vlingo, on its Web site, announced on Tuesday that it is the voice enabler of the mobile search service and had enabled the English language product to also recognize Indian and Singaporean accents. (download PDF).

Vlingo calls the voice-enabling technology a means of allowing searches for Yahoo! oneSearch users (now available on BlackBerry wireless devices), to "say what they want, how they want, and Vlingo captures the results, word for word." Vlingo said it relies on a set of technologies called Adaptive Hierarchical Language Models to allow recognition of regional variants with a language.

In its statement, Vlingo said that the patent Nuance references "has serious limitations in its coverage" and does not apply to technology developed by Vlingo nor the third-party licenses employed by Vlingo. A spokeswoman refused to comment further.