Among other things, a sensor is configured to sense sound from a gut of a person and to output a corresponding acoustic signal. A signal processor has an input for the acoustic signal and is configured to output corresponding digital acoustic samples. There is a storage device for the digital acoustic samples. A processor is configured to apply the digital acoustic samples to a model to determine an aspect of a state of the person. A device is configured to present information about the determined aspect of the person's state to a user.
