A recently filed patent has provided a glimpse of Google's pending voice-activated search engine.

Google Voice Search has been no big secret on the Google Labs website for more than a year, but Patent No. 7027987 was filed Tuesday.

The patent involves "a voice interface for search engines", it stated. "Through the use of a language model, phonetic dictionary and acoustic models, a server generates an n-best hypothesis list or word graph."

Voice-in, text-out searching has been around as a concept at least since IBM promoted it as the way to go beyond the limitations of ever-smaller mobile phones in 1999. Google is not the only company to be working in the area – News.com reports that a voice-activated internet system works with speech-to-text conversion software called Maestro was unveiled in Israel in May last year.

Maestro is said to convert spoken search requests into a list of query-friendly ASCII words, which are relayed to a search engine, with results returned to the searcher audibly.

A Google spokesman told News.com that "prospective product announcements should not be inferred from our patent applications". The Google Voice Search demo is currently not available.