Continuous speech recognition method

In a speech analysis system for recognizing at least one predetermined keyword in a continuous audio signal, each said keyword being characterized by a template having at least one target pattern, said target patterns having an ordered sequence and each target pattern representing a plurality of short-term power spectra spaced apart in real time, an analysis method comprising the steps of

• repeatedly evaluating a set of parameters determining a short-term power spectrum of said audio signal within each of a plurality of equal duration sampling intervals, thereby to generate a continuous time ordered sequence of short-term audio power spectrum frames,
• repeatedly selecting from said sequence of frames, one first frame and at least one later occurring frame to form a multi-frame pattern,
• comparing each thus formed multi-frame pattern with each first target pattern of each keyword template,
• deciding whether each said multi-frame pattern corresponds to a said first target pattern of a keyword template,
• for each multi-frame pattern which, according to said deciding step, corresponds to a said first target pattern of a potential candidate keyword, selecting later occurring spectrum frames to form later occurring multi-frame patterns,
• deciding whether said later occurring multi-frame patterns correspond respectively to successive target patterns of said potential candidate keyword template, and
• identifying a candidate keyword template when said selected multi-frame patterns correspond respectively to the target patterns of a said keyword template.