Baby cry recognizer

A process for recognizing a baby's cry comprising the steps of:

• filtering out non-voice signals from a received sound signal,
• amplifying said filtered sound signal,
• generating a pulse signal having zero crossings which are aligned with the zero crossings of said detected sound signal,
• obtaining the zero crossing rate of said pulse signal during each of a preselected number of frames in a predetermined length time interval, determining if the zero crossing rate of said pulse signal in more than a first threshold number of said preselected number of frames falls within a particular frequency band, determining if the zero crossing rate of said pulse signal over said entire time interval is at least equal to a second threshold but at most equal to a third threshold, and outputting an indicating signal from said signal recognition circuit if the conditions of both of said determining steps are satisfied.

A process for recognizing a specific audio signal comprising the steps of:

• generating a signal corresponding to a received audio signal,
• in at least some frames of a time interval divided into plurality of frames, determining the number of zero crossings of the generated signal and determining if the number of zero crossings is between a first number of zero crossings and a second number of zero crossings for a first threshold number (C.sub.1) of said frames,
• determining the number of zero crossings of the generated signal for the entire time interval and if the number of zero crossings is between a third number of zero crossings and a fourth number of zero crossings whereby said specific audio signal is detected, and
• activating a device when said specific audio signal is detected.

A signal recognition device comprising:

• (a) pulse generating means for receiving a sound signal and generating a pulse signal having zero crossings corresponding to zero crossings of the received sound signal;
• and
• (b) signal recognizing means connected to the pulse generating means for:
• (i) receiving the generated pulse signal;
• (ii) counting the zero crossings of the generated pulse signals during each of a plurality of preselected time intervals;
• (iii) determining if a first predetermined number of zero crossings occur in a second predetermined number of the plurality of preselected time intervals;
• (iv) determining if the number of zero crossings during all of the plurality of preselected time intervals is within a range between third and fourth predetermined numbers;
• and
• (v) generating recognition indication signal when the signal recognizing means determined that conditions (iii) and (iv) above are met.