Voiced interval command interpretation
A method is disclosed for controlling a voice-activated device by interpreting a spoken command as a series of voiced and non-voiced intervals. A responsive action is then performed according to the number of voiced intervals in the command. The method is well-suited to applications having a small number of specific voice-activated response functions. Applications using the inventive method offer numerous advantages over traditional speech recognition systems including speaker universality, language independence, no training or calibration needed, implementation with simple microcontrollers, and extremely low cost. For time-critical applications such as pulsers and measurement devices, where fast reaction is crucial to catch a transient event, the method provides near-instantaneous command response, yet versatile voice control.
1. A method for interpreting a spoken command by detecting voiced intervals and non-voiced intervals in the spoken command, and for performing a type-1 responsive action if the command has exactly one voiced interval, and for performing a type-2 responsive action if the command has two voiced intervals separated by a non-voiced interval, a voiced interval being a time interval containing voiced sound, and a non-voiced interval being a time interval that has no voiced sound therein, said method comprising the steps:
(3a) converting sound waves into an electrical sound signal, and comparing the sound signal to a threshold voltage, a sound being detected when the sound signal exceeds the threshold voltage, and no sound being detected while the sound signal remains below the threshold voltage;
(3b) detecting a first voiced interval when the sound signal exceeds a threshold voltage V1+;
(3c) then, determining when the first voiced interval has ended by waiting until the sound signal remains below a threshold voltage Va+ throughout a time period Ta;
(3d) then, detecting a second voiced interval if the sound signal exceeds a threshold voltage V2+ during a time period Tg;
(3e) then, performing the type-1 responsive action if the sound signal remains below V2+ throughout Tg, and performing the type-2 responsive action if the sound signal exceeds V2+ during Tg.
2. The method of claim 1 which additionally includes performing a type-3 responsive action when the spoken command includes three voiced intervals, said method including the steps of:
(4a) after detecting the second voiced interval, determining when the second voiced interval has ended by waiting until the sound signal remains below a threshold voltage Va2+ throughout a time period Ta2;
(4b) then, performing the type-3 responsive action if the sound signal exceeds a threshold voltage V3+ within a time period Tg3.
3. The method of claim 2 which further includes incrementing a counter when each voiced interval is detected, and then performing the type-1 or type-2 or type-3 responsive action depending on how many counts are in the counter.
4. The method of claim 1 which further includes a step, before detecting the first voiced interval, of ensuring that any prior sounds have ended by waiting until the sound signal remains below a threshold voltage Vs+ for a time period Ts.
5. The method of claim 4 wherein the threshold voltage Vs+ is set to be above a sound signal corresponding to silence but below Va+, and Va+ is set to be above a sound signal corresponding to non-voiced sounds but below V2+, and V2+ is set to be below a sound signal corresponding to the second voiced interval, and V1+ is set to be above V2+ but below a sound signal corresponding to the first voiced interval.
6. The method of claim 1 which further includes amplifying and filtering the sound signal to emphasize sounds in a frequency band corresponding to voiced sounds, and to suppress sounds outside that frequency band.
7. The method of claim 1 which further includes rectifying and then low-pass filtering the sound signal to produce a smoothed unipolar sound signal, and then comparing the smoothed unipolar sound signal to a threshold voltage.
8. The method of claim 1 wherein detecting a sound includes comparing the sound signal to two threshold voltages V1+ and V1−, with V1+ being more positive than V1−, a sound being detected whenever the sound signal is more positive than V1+ or more negative than V1−.
9. The method of claim 1 wherein detecting a sound includes comparing the sound signal to two threshold voltages V1+ and V1−, with V1+ being more positive than V1−, a sound being detected as soon as the sound signal has become more positive than V1+ at least once and more negative than V1− at least once.
10. The method of claim 1 wherein performing a responsive action includes modifying a responsive action.
11. The method of claim 1 wherein performing the type-1 responsive action includes modifying the type-2 responsive action, and performing the type-2 responsive action includes modifying the type-1 responsive action.
12. The method of claim 1 wherein performing a responsive action causes the type-1 and type-2 responsive actions to be interchanged.