During a voice interaction session, VoiceInteractionSession#setKeepAwake(boolean keepAwake) allows to decide whether it will keep the device awake while it is running a voice activity. By default, the system holds a wake lock for it while in this state, so that it can work even if the screen is off. Setting this to false removes that wake lock, allowing the CPU to go to sleep and hence does not let this continue to drain the battery.