Abstract: Various methods, systems, and apparatus are disclosed with improved imposter rejection for keyword recognition systems in a wearable device. Speech signals are measured by a microphone and a vibration sensor, the vibration sensor configured to measure vibrations in the body of a wearer of the device. An audio signal from the microphone and a vibration signal from the vibration sensor are input into a classifier to determine whether the wearer of the device spoke the keyword. In some embodiments, high-frequency components of a signal from the microphone may be combined with low-frequency components of a signal from the vibration sensor to generate a combined speech signal. The classifier may use a classification model trained with positive training data of the wearer speaking the keyword and negative training data of a non-wearer speaking the keyword.