This article introduces a novel observational ambulatory monitoring method called the electronically activated recorder (EAR). The EAR is a digital audio recorder that runs on a handheld computer and periodically and unobtrusively records snippets of ambient sounds from participants' momentary environments. In tracking moment-to-moment ambient sounds, it yields acoustic logs of people's days as they naturally unfold. In sampling only a fraction of the time, it protects participants' privacy and makes large observational studies feasible. As a naturalistic observation method, it provides an observer's account of daily life and is optimized for the objective assessment of audible aspects of social environments, behaviors, and interactions (e.g., habitual preferences for social settings, idiosyncratic interaction styles, subtle emotional expressions). This article discusses the EAR method conceptually and methodologically, reviews prior research with it, and identifies three concrete ways in which it can enrich psychosomatic research. Specifically, it can (a) calibrate psychosocial effects on health against frequencies of real-world behavior; (b) provide ecological observational measures of health-related social processes that are independent of self-report; and (c) help with the assessment of subtle and habitual social behaviors that evade self-report but have important health implications. An important avenue for future research lies in merging traditional self-report-based ambulatory monitoring methods with observational approaches such as the EAR to allow for the simultaneous yet methodologically independent assessment of inner, experiential aspects (e.g., loneliness) and outer, observable aspects (e.g., social isolation) of real-world social processes to reveal their unique effects on health.