Passive acoustic monitoring often relies on data collected with various instrumentation, by multiple research groups in different locations, under diverse conditions, and with a variety of data analysis methods. To make the output comparable and to preserve data for long time-series analysis, metadata needs to be reported in a standardized way. This will enable broader metadata studies and the sharing of data in repositories, which will allow for cross fertilization of analyses and hence cost savings for new projects. The Acoustical Society of America Working Group S3-SC1-WG7 “Acoustic Metadata for Passive Acoustic Monitoring” is in the process of defining this standard. We are building upon schemata developed for the metadata database software “Tethys” [Roch et al., Ecol. Inf. 31, 122–126 (2016)]. Instrument deployments and on- or off-effort detections of acoustic signals were defined within this manuscript. The current deployment schema is being implemented in the National Center for Environmental Information Passive Acoustic Monitoring Archive. We have expanded the vocabulary to include mobile platforms, vector sensors, localizations, and calibrations. Exemplary scenarios were developed to test the comprehensiveness of the current standard definitions for these frameworks. We also consider extensibility, making sure that the standard is flexible enough to support new ideas.