A privacy preserving sensor apparatus is described herein. The privacy preserving sensor apparatus includes a microphone that is configured to output a signal that is indicative of audio in an environment. The privacy preserving sensor apparatus further includes feature extraction circuitry integrated in the apparatus with the microphone, the feature extraction circuitry configured to extract features from the signal output by the microphone that are usable to detect occurrence of an event in the environment, wherein the signal output by the microphone is unable to be reconstructed based solely upon the features.