Automatic Calibration of Command-Detection Thresholds

When a voice-activated device or application is first started, the signal levels corresponding to spoken commands are initially unknown, making it difficult to set detection thresholds. The inventive method provides an initial command-detection threshold based on the noise level alone. The first command is detected using this initial threshold. Then the threshold is revised according to the first command sound, and a second command is detected using the revised threshold. After detecting each command, the detection threshold is further refined according to the current noise and command sounds. Methods are also disclosed for optimizing the thresholds, adjusting parameters according to sound, and detecting voiced and unvoiced sounds separately. These capabilities enable many emerging voice-activated products and applications.