Voice search device, voice search method, and non-transitory recording medium

A voice search method comprising:

• converting a search string into a phoneme sequence;
• acquiring durations of respective phonemes included in the phoneme sequence;
• deriving a spoken time length of voice corresponding to the search string based on the durations;
• designating a plurality of designated zones having time lengths in a target voice signal;
• acquiring, using an acoustic model that does not depend on adjacent phonemes, a first group of likelihoods indicating how likely each zone from among the plurality of designated zones is a zone in which voice corresponding to the search string is spoken;
• specifying, based on the first group of likelihoods, a plurality of estimated zones from among the plurality of designated zones, wherein each estimated zone is a zone in which the voice corresponding to the search string is estimated to be spoken, and wherein a number of the estimated zones is less than a number of the plurality of designated zones;
• and
• acquiring, using an acoustic model that depends on adjacent phonemes, a second group of likelihoods indicating how likely each of the plurality of estimated zones is a zone in which the voice corresponding to the search string is spoken.

A non-transitory recording medium having a program recorded thereon that is executable to control a computer to:

• convert a search string into a phoneme sequence;
• acquire durations of respective phonemes included in the phoneme sequence;
• derive a spoken time length of voice corresponding to the search string based on the durations;
• designate a plurality of designated zones having time lengths in a target voice signal;
• acquire, using an acoustic model that does not depend on adjacent phonemes, a first group of likelihoods indicating how likely each zone from among the plurality of designated zones is a zone in which voice corresponding to the search string is spoken;
• specify, based on the first group of likelihoods, a plurality of estimated zones from among the plurality of designated zones, wherein each estimated zone is a zone in which the voice corresponding to the search string is estimated to be spoken, and wherein a number of the estimated zones is less than a number of the plurality of designated zones;
• and
• acquire, using an acoustic model that depends on adjacent phonemes, a second group of likelihoods indicating how likely each of the plurality of estimated zones is a zone in which the voice corresponding to the search string is spoken.