This randomized clinical trial will test the effectiveness of a nonpharmacologic intervention to prevent delirium. The Family Automated Voice Reorientation (FAVoR) intervention uses scripted audio messages, recorded by the patient's family and played at hourly intervals during daytime hours, to provide information about the ICU environment to the patient; this ongoing orientation to the ICU environment through recorded messages in a voice familiar to the patient may enable the patient to more accurately interpret the environment and thus reduce risk of delirium. The primary specific aim of the project is to test the effect of the FAVoR intervention on delirium in critically ill, mechanically ventilated adults during hospitalization in the ICU. Secondary aims are to: (1) explore if the effect of FAVoR on delirium is mediated by sleep, (2) explore if selected biobehavioral factors may potentially moderate the effects of FAVoR on delirium, and (3) examine the effects of FAVoR on short term (immediately after ICU discharge) and long term (1 and 6 months after hospital discharge) outcomes, including cognitive function and patient-reported health status. FAVoR holds promise for reducing delirium in critically ill adults, improving sleep in the ICU, and secondarily benefitting cognitive function and health status in ICU survivors.